Skeetchestn
Indian Band:
Research
and Development in
Riparian
Zone Management
March 2005
Prepared by: John Karakatsoulis, Satwinder
Paul, Rod Osborne, Chris Ortner and Mike
Anderson
The
purpose of the project, �Research and Development in Riparian Zone Management�
was to conduct research into low impact forest harvesting techniques in the
riparian zone within Skeetchestn traditional territory, focusing on the social
and economic viability of alternate timber harvesting techniques. The objective
is to develop techniques that could increase opportunities for the Skeetchestn
Indian Band to specialize in low impact harvesting in the riparian zone and to
gather practical knowledge on First Nation cultural values. Economic
comparisons are made between current standard (clearcut) harvesting methods and
low impact systems on both biological and economic (employment) outcomes.
Skeetchestn
Indian Band has defined Cultural Resource Management zones (CRMZs) as existing
in the 100 metre buffer zone adjacent to S4 to S6 streams (as classified by the
Forest Practises Code) and other water bodies where clearcut logging is
permitted. Low impact harvesting is defined as removal of a percentage of the forest
cover rather than clearcut logging. Skeetchestn has used different logging
equipment and different levels of forest cover removal to determine impact on
lesser vegetation and economic return to participating communities. The results
of the study will provide socio-economic knowledge to apply to future logging
considerations, as well as provide empirical data on cultural values for
sharing with forest licensees operating in traditional territories.
Research
variables were defined in a formal research plan developed through subcontract
by the
Integral
to the success of the project was the integration of current forest licensee priorities,
and their cooperation was essential to the project. Given the short time frames
involved, it was not possible to generate new, unique cutting areas. Areas
already in consideration for harvest were used for the project, with the
cooperation of Weyerhaeuser
To
provide and account for aboriginal values for the purposes of this study, the
Skeetchestn Indian Band carried out Cultural Heritage Overview and Archaeology
Overview Assessments. The information obtained from these assessments was used
to determine presence of plant, wildlife and other significant attributes that
are of social and cultural concern to the Skeetchestn Indian Band.
The
study area consisted of four individual sites; Heller Creek,
Preliminary
results have shown that understory vegetation cover is significantly reduced
regardless of the harvesting treatments used or site location. However,
long-term monitoring is needed to determine whether any of the post-harvest
treatments will recover to pre-treatment levels. The sole immediate impact of
canopy removal was on Trapper�s Tea, which showed significant declines. At
least 5 years of monitoring will be required to establish trends on most
species.
A
socio-economic analysis was conducted to determine the economic feasibility of
alternative harvesting practices and the overall impact that harvesting
practices may have on local employment and income. Logging costs for horse
logging and small-scale machinery were higher than conventional logging costs
by 160% ($24.68) and 247% ($38.14), respectively.
With
small-scale and horse logging over 95% of logging costs are retained within the
local economy, with labour costs for small-scale and horse logging accounting
for at least 82% of all logging costs, while only 34% of total costs were
attributed to labour under conventional harvesting. Increased employment in
greater labour intensive harvesting activities contributes to the local area
through job creation, local spending, and income taxes.
As a
result of the project, Skeetchestn has increased their ability to participate
in the forest economy, through building of technical forestry skill both in the
field, and with Geographic Information and Mapping Systems. Other benefits of
the project relate to relationship building with the
1.3.6 Timber
Harvesting within the Area
2.2.1 Riparian
Management In British Columbia
2.2.2 Riparian
Management In Other Jurisdictions
2.2.3 Buffer
Strips as a Management Approach
2.2.4 Partial
Retention as a Management Approach
2.3.2 Regeneration
of Conifers following Riparian Harvesting
2.3.12 Large Woody
Debris (LWD)
2.3.14 Effects of
Cattle Grazing
2.4.2 Fisheries
and Riparian Values
3.3
Research Plan and Design Limitations
3.4.3 Site
#3 � Greenstone Mountain
3.4.4 Site
#4 � Chartrand Lake
3.6.2 Pre
harvest Stand Characteristics
3.6.3 Post
Harvest Stand Characteristics
3.8.3 Conventional
Large-scale Mechanical
4.1
Pre-harvesting Vegetation and Soil Assessments
4.1.3 Site
#3 - Greenstone Mountain
4.1.4 Site
#4 - Chartrand Lake
4.2
Post-harvest Vegetation and Soil Assessments
4.3
Socioeconomic Impact Assessment
5.2
Literature Review Findings
6.2
Training of Staff and Information Management
List of
Figures
Figure 1.0. Ecological functioning of riparian areas
Figure 2.0. Graphical depiction of the riparian management area.
Figure 3.0. Graphical depiction of field assessment process.
Figure 4.0. Soil sampling unit for determining soil bulk density.
Figure 5.0. Site #1 � Heller Creek percent cover changes of
Ledum glandulosum .
Figure 6.0. Soil bulk density (g/cm3) pre- and post
harvesting .
Figure 7.0. Site #2 � Tunkwa Lake percent cover of Equisetum
species .
Figure 8.0. Site #2 � Tunkwa Lake soil bulk density.
List of
Maps
Map 1. Overview of Research and Development in Riparian Zone
Management study area.
Map 2. Site #1 - Heller Creek.
Map 3. Location of the treatment plots in Site #1 -
Heller Creek.
Map 5. Location of the treatment plots in Site #2 - Tunkwa
Lake.
Map 6. Site #3 � Greenstone Mountain.
Map 7. Site #4 � Chartrand Lake North
Map 8. Site #4 � Chartrand Lake South
List of
Photographs
Photo 1. Skeetchestn horse logging operation
Photo 2. Berfor Forcat 2000 skidding within Site #1 - Heller
Creek.
Photo 3. Conventional feller buncher and skidder working
within Site #1 - Heller Creek.
Photo 4. General view of the Site #1 - Heller Creek
prior to treatments.
Photo 5. Site #1 � Heller Creek�s understory is
dominated by Ledum glandulosum
Photo 6. Site #1 � Heller Creek, major soil horizons.
Photo 7. Site #1 � Heller Creek soil profile (Orthic Gleysol).
Photo 8. Site #2 � Tunkwa Lake general overview prior to
harvest treatments.
Photo 9. Site #2 � Tunkwa Lake dominated by Equisetem
(horsetail) .
Photo 10. Site #2 � Tunkwa Lake soil profile (Orthic Humic Gleysol).
Photo 11. Site #3 � Chartrand Lake general over prior to
harvest treatments.
Photo 12. Site #4 � Chartrand Lake understory dominated
by Equisetum (horsetail).
Photo 13. Site #1 - Heller Creek understory following
harvesting treatments.
Photo 14. Site #2 � Tunkwa Lake understory
characteristics following harvesting.
List of
Tables
Table 1.0. Stream classifications as set forth by the MOF, June
1995.
Table 2.0. Washington State stream classification and riparian
management.
Table 3.0. Classification of Oregon State streams
Table 4.0. Summary of buffer strip widths ranges and averages
for various functions
Table 5.0. Recovery period of Hydrologic responses to various
treatments.
Table 6.0. Biogeoclimatic information for Site #1 - Heller
Creek.
Table 7.0. Biogeoclimatic information for Site #2 � Tunkwa Lake
Table 8.0. Biogeoclimatic information for Site #3 � Greenstone
Mountain
Table 9.0. Biogeoclimatic information for Site #4 � Chartrand
Lake
Table 10.0. Harvesting methods used for various treatments.
Table 11.0. Average Pre-harvest Stand Characteristics of Site #1
� Heller Creek
Table 12.0. Fifteen highest cover rates Site #1 � Heller Creek
Table 13.0. Fifteen highest frequency rates for Site #1 � Heller
Creek
Table 14.0. Average Pre-harvest Stand Characteristics of Site #2
� Tunkwa Lake
Table
15.0.Fifteen highest cover rates for Site #2 � Tunkwa Lake
Table 16.0. Fifteen highest frequency rates Site #2 � Tunkwa Lake
Table 17.0. Average Pre-harvest Stand Characteristics of Site #3
� Greenstone Mountain
Table 18.0. Fifteen highest cover rates for Site #3 � Greenstone
Mountain
Table 19.0. Fifteen highest frequency rates for Site #3 �
Greenstone Mountain
Table 20.0. Average Pre-harvest Stand Characteristics of Site #4
� Chartrand Lake
Table 21.0. Fifteen highest cover rates for Site #4 � Chartrand
Lake
Table 22.0. Fifteen highest frequency rates for Site #4 �
Chartrand Lake
Table 23.0. percent cover, frequency and height pre- and
post harvesting at Heller Creek .
Table 24.0. frequency, percent cover, and height pre- and
post harvesting at Heller Creek.
Table 25.0. Fifteen highest cover rates for Site #2 (2003) �
Tunkwa Lake
Table 26.0. Fifteen highest frequency rates for Site #2 (2003) �
Tunkwa Lake
Table 27.0. Summary of Labour and Harvesting Activity Costs.
Table 28.0. Literature Research on Productivity Findings in
British Columbia
Table 29.0. Comparison of Harvesting Costs
List of
Appendices
Appendix 1. Summary of Pre-harvest Overstory
Vegetation Assessments
Appendix 2. Summary of Post-harvest Overstory
Vegetation Assessments
Appendix 3. Summary of Pre and Post-harvest Understory
Vegetation Assessments
Appendix 4. An Evaluation of various Harvesting
Techniques
Appendix 5. Skeetchestn Cultural Resource Management
Zones
1
Introduction
1.1
Purpose
The
Skeetchestn Indian Band is researching opportunities for integrating low impact
forest harvesting techniques as an alternative to conventional harvesting in
riparian areas within their traditional territory. To address the concerns
around current logging practices and legislation of S5 and S6 (see Table 1.0
for definitions of classifications of S5 and S6) headwater streams and the
maintenance of ecological integrity within riparian areas, the Skeetchestn
Indian Band has developed a protocol for a 100 meter special management
zone. This zone is defined by the Band as Cultural Resource Management
Zones (CRMZ�s), and are established adjacent to all streams, wetlands and water
bodies within their traditional territory. While not wanting to exclude
harvesting from CRMZ�s, Skeetchestn Indian Band will integrate management of timber,
water, wildlife, indigenous plants, and fisheries values with scientific
methodology and traditional knowledge. The Band sees changes in
harvesting and legislation as a means to convey their traditional ecological,
cultural and social interests and values into forest development operations,
management and legislation. At the same time this will increase the
employment opportunities for band members and a greater retention of provincial
investments and income revenues within the community.
The purpose
of this research project is to measure the vegetation ecology and
socio-economic impacts of horse, small-scale mechanical and conventional
harvesting systems. The Skeetchestn Indian Band and the research team realize
that there are other significant attributes that are affected by riparian
harvesting therefore an in-depth literature review was conducted to recognize
their significance in riparian ecology and management. This two year project
was designed to provide literature research on riparian ecology, riparian
management, impact assessments, harvesting techniques, socio-economic analysis
and First Nations values. A research methodology was developed to
evaluate preliminary research on four individual harvesting experimental sites.
This methodology consisted of 7 treatments. The harvesting treatments were
conventional clearcut, conventional select, small-scale clearcut, small-scale
select, horse logging clearcut, horse logging select and control. Treatments
were replicated to increase experimental reliability.
It was
the objective of this project to establish areas of 100% removal to represent
current (clearcut) harvesting practices and to implement areas of alternative
harvesting through selection cutting (50% removal). Timber values and characteristic
sampling were conducted congruently with pre-harvest and post harvest
vegetation assessments. Treatments plots were laid out as 0.25 ha squares
(0.16 ha for site #3) in the summers of 2003 for sites #1 and #2 and 2004 for
sites #3 and #4. Each site consisted of 14 treatment plots (7 treatments
replicated twice) in which 15 sample plots were established for pre and post
vegetation assessments. Soil samples were also taken for both pre and
post harvest years to determine the impact on soil bulk density which is an
indicator of soil compaction. All harvesting was conducted in winters of
2003 -2004 for sites #1 and #2 and planned for 2004-2005 for sites #3 and #4.
Due to unforeseen warm weather patterns, horse logging of site #4 will be
postponed to the winter of 2006. It was the intention of the study to
harvest only over frozen and snow covered grounds. Unsuitable condition
that deviated from the logging plan was the reason for delaying harvesting
until 2006.
A
socio-economic analysis was used to monitor harvesting operations to determine
harvesting productivity and costs, thus enabling an assessment of the
operational suitability of using low impact systems as an alternative to
conventional harvesting for riparian areas. Three harvested areas ranged from
8.1 to 14.0 ha and were used to evaluate man hours contributed, total labour
costs, maintenance cost and total logging cost on per m3
basis. Involvement in the project included input and cooperation from the
Skeetchestn Indian Band, University College of the Cariboo, West Fraser Mills
Ltd., Weyerhaeuser Ltd., British Columbia Ministry of Forests, and Ministry of
Sustainable Resource Management, with facilitation by Cirque Resource
Associates Ltd. This project is funded by the Economic Measures Fund
through the British Columbia Treaty Negotiation Office, with in kind
contributions from partners.
1.2
Background
The
impetus for this research project is based deeply in the social, ecological and
cultural values of the Skeetchestn Indian Band. The Band relies on the
resources of the Deadman Watershed and over time this watershed has been
subjected to a �disproportionate amount of human impact.� The local community
has concerns around the decreased health of fish and wildlife species and
forest vegetation in their traditional territory and believe that this
decreased health is an indicator of a broader ecosystem dysfunction that can be
attributed to forestry practices, tourism, mining, urban and agricultural
development. These concerns have lead to the development of a community vision
and a framework for ecosystem stewardship in the Deadman Watershed and the
traditional territory of the Skeetchestn Indian Band. Riparian management
has become critical to Skeetchestn Band as the 100 meter buffer in the CRMZ is
considered to have the highest concentration of First Nation values for plants,
wildlife, and archaeological features. These areas have been significantly
disrupted through conventional logging methods and restoration of these areas through
re-evaluating harvesting methods is seen as means to return functionality and
health to the watershed. The band is specifically interested in assessing
how to conduct economically viable harvesting operations within riparian areas
and at the same time maintain the integrity of the Deadman Watershed and its
riparian ecosystems.
Alternative
low impact forest harvesting practices have been identified by the community as
a viable option for sustainable use and management of non-timber forest products
and economic development. The band has high seasonal and un-employment rates,
therefore they want to develop more labour intensive, ecologically sensitive
harvesting practices to increase local employment. Horse logging and
small-scale mechanical harvesting methods are seen as a way of providing
employment as well as providing environmentally sound alternatives to
conventional harvesting. The community also believes that partial harvesting
with low impact logging systems provides the best opportunity for managing for
the distribution of species, age classes and succession levels in a specific
riparian harvest area as well as ensuring connectivity between critical habitat
areas.
This project also provides the opportunity for the
community to demonstrate the importance of integrating traditional practices
and incorporating traditional ecological knowledge in forestry management
practices in riparian areas. Other values of this project also include
development of partnership opportunities with industry, government agencies and
the University College of the Cariboo to demonstrate low impact logging and
promote application of scientifically based new riparian area management
systems. Other targeted outcomes include building capacity and development
of skills of band members in technical and professional disciplines including
archaeology, forest and vegetation surveying, Geographical Information Systems
(GIS) and forest operations.
1.3
Study Area
The Deadman River drains a land base of approximately
1500 km2 into the Thompson River, 50km west of Kamloops B.C. The
watershed is located within the Kamloops and 100 Mile Forest Districts of the
Kamloops and Cariboo Forest Regions, respectively (Speed and Henderson 1998).
This watershed encompasses six biogeoclimatic zones; Bunchgrass (BG), Ponderosa
Pine (PP), Interior Douglas Fir (IDF), Montane Spruce (MS), Sub-Boreal Pine
Spruce (SBPS), and Engelmann Spruce Sub-alpine Fir (ESSF) zones (ARC
Environmental Ltd. 1998). Elevations within the watershed range from
606m-1728m.
Currently
forest harvesting is occurring within the MS zone of the watershed. The MS
biogeoclimatic zone is located between the IDF and ESSF zones at an elevation
of 1300-1650 meters. Weather within this zone is characteristic of cold winters
with shorter, relatively warm summers. Forest stands are generally dominated by
young to moderate aged lodgepole pine stands due to the affects of the areas
higher fire frequency. The MS zone provides habitat for numerous forest
dwelling species and provides habitat for deer and moose during summer and fall
seasons (Ministry of Forests (MOF) 2001b).
Within the Deadman Watershed there are numerous
smaller watersheds. They can be divided into 12 sub basins;
�
Joe Ross Creek
�
Vidette Lake
�
Upper Deadman River
�
Upper Criss Creek
�
Mow Creek
�
Heller Creek
�
Upper Residual Creek
�
Tobacco Creek
�
Gorge Creek
�
Barricade Creek
�
Lower Criss Creek
�
Clemes Creek
(Moore 2001)
The
upper headwater tributaries of the Deadman River are located within the MS zone
at elevations that range from 1,400-1,500m. However, the headwaters of Criss
Creek originate from the ESSF zone at an elevation of up to 1,750m (ARC Environmental
Ltd. 1998). The Deadman River is characteristic of low gradients within its
upper reaches with steeper gradients in lower reaches near its confluence with
the Thompson River (Young et al. 1992).
1.3.1 Geology
The areas surrounding the Deadman watershed are
comprised of volcanic extrusive bedrock with minor sedimentary portions. It
consists of the Nicola and Kamloops bedrock group, being characteristic of
andesite, basalt, rhyolite, associated tuff and breccia, limestone and
agrillite (Young et al. 1992).
Surficial geology of the lower portions of the Deadman
Valley includes various landforms. The valley bottoms consist of fluvial and
fluvioglacial deposits, surrounded by colluvial and morainal deposits at higher
elevations (Young et al. 1992).
The area around Vidette Lake within the Deadman
Watershed is underlain by mafic volcanic rocks of the Upper Triassic Nicola
Group. This area is exposed through the erosion of flat lying Miocene
sedimentary rocks and plateau basalts of the Chilcotin group. The uppermost
Chilcotin Group strata is comprised of an extensive layer of plateau basalts of
the Chasm Formation, underlain by fluviatile and lacustrine sedimentary strata
and volcanic ash of the Deadman River Formation which occupies the northwest
trending Miocene channel (Geological Survey Branch 2002).
The Deadman River Formation within the Deadman River
Valley is comprised of 350 meters of ash, sandstone, siltstone, shale and diatomite.
Fluvial paleoenvironment is found within deeply incised north and west tending
valleys (Read 1988).
1.3.2 Soils
Soils
of the Deadman Watershed are generally characteristic of Eutric Brunisols at
lower elevations, Gray Luvisols at higher elevations and Dark Brown Chernozems
at low elevation grasslands (Young et al. 1992). Soils within the
Deadman River Valley are generally fine textured and are extremely susceptible
to erosion and contribute high quantities of sediment into surrounding watercourses
(Olmsted et al. 1992).
1.3.3 Climate
The
area surrounding Kamloops receives an average annual rainfall of 260.5 mm. The
Kamloops area generally sees 2202 growing degree days (>5oC) and
an average of 145 freeze free days. Temperatures of the valley are
characteristic of mean July temperatures of 20.9oC and mean January
temperatures of �6oC. Average snowfall accumulation equals
approximately 77.1� and the lower elevations of the Kamloops area are
around 346m (Young et al. 1992).
1.3.4 Fish
and Wildlife
The
Deadman River and its tributaries provide valuable habitat for a variety of
salmonid species. Within the Deadman River, pink (Oncorhynchus gorbuscha),
coho (O.kisutch), steelhead (O.mykiss) and chinook (O.tshawaytscha)
salmon can be found up to the Snohoosh Dam. It is also suggested that the
Deadman River is the most important tributary to the Thompson River for coho
and steelhead production. However, in recent years there has been a substantial
drop in the escapement numbers of salmonid species, leading to a self-imposed
fishing closure by the Skeetchestn Indian Band. Declines have been attributed
to the 1 in 500-year flood experienced by the Deadman River in 1990 (ARC
Environmental Ltd. 1998) and to the possibility that reductions in upstream
nutrient components such as macroinvertebrates and small organic debris have
impaired proper watershed functioning. The Kamloops Land and Resource
Management Plan (KLRMP) (1995) has defined areas of the Deadman watershed as
critical winter range habitat for both deer and moose..
1.3.5 Land
Uses
Land uses within the Deadman River watershed include
primarily agriculture, forestry and recreation (ARC Environmental Ltd. 1998).
Currently there are six forestry service campgrounds within the Deadman
watershed, they include; Vidette, Bog, Deadman, Windy, Skookum and Snohoosh
Lakes. Provincial parks within the watershed include Bonaparte, Porcupine
Meadows, Tsintsunko Lake parks. The area also includes the Skookum Hoodoos
Protected Area (Speed and Henderson 1998). Other recreational users of the area
include: snowmobiling, camping, fishing, hunting, hiking and mountain biking
(Speed and Henderson 1998).
Forest licensees working within the watershed include;
Ministry of Forests Small Business Forest Enterprise Program, West Fraser Mills
Ltd, Sk7ain Ventures Ltd., Ainsworth Lumber Co., Tolko Industries Ltd. and
Weyerhaeuser Canada Ltd.
1.3.6 Timber
Harvesting within the Area
Within the Kamloops Forest Region Timber Supply Area
(TSA), only 9.27% of harvesting is done as a selection silvicultural system.
Most harvesting is done as clear cutting or clear cutting with reserves,
totalling 84% of the total harvest (MOF 2000a). Revenues paid in 1999/2000 from
stumpage within the Kamloops Forest Region totalled over $180 million. The
productive forested land base of the Kamloops Forest Region is 4,306,000
hectares (MOF 2000a). The Deadman River watershed has 14,950 ha of riparian
habitat. 12.2% of this area has already been either clearcut (871 ha, 5.8%) or
selectively harvested (954 ha, 6.4%) (Ministry of Water, Land and Air
Protection (MWLAP) 2000). According to the MOF (2000a), one opportunity to
overcome challenges currently faced in the forest industry is to work with
First Nations to advance economic opportunities for aboriginal people in the
forest sector.
2
Literature
Review
2.1
Riparian Ecology
There are
many definitions that surround the term �Riparian Area�. Most definitions
describe a riparian area as the land that is adjacent to creeks, rivers and
wetlands including lakes, marshes and bogs. Riparian areas provide a transition
zone or interface between the aquatic and terrestrial ecosystems (Burton 1998,
Hennan 1998, MOF 1998b, Bunnell et al. 1995, Stevens et al. 1995,
Belt et al. 1992). Particularly, they act as the transition between
water dominated low-lying topographic areas and the surrounding upland,
generally forest dominated, ecosystems. These areas are generally described as
having a plant community that is distinct from those that occupy the drier
well-drained area of the upland environment. Riparian areas are also routinely
referred to as �Riparian Zones� and �Riparian Ecosystems� and may be used
synonymously. In many definitions within the scientific community even
wildlife, fish and birds are considered an equal attribute to the components
that make up a riparian area (Bunnell et al. 1999).
Riparian areas are of important ecological
significance as they act as a synergistic network of interactions between the
terrestrial and aquatic environments (Koning 1999). While these areas make up
only 10% of the land base within British Columbia (MOF 1998b), they are
considered the most important aspect of forested ecosystems due to their
ability to produce the highest diversity of plant life and attract the greatest
number of wildlife species (Cockle and Richardson 2003, Gyug 2000, Haag and
Dickinson 2000, Whitaker and Montevecchi 1999). However, research has shown
that riparian areas have diminished by as much as 66% in the United States from
historical levels (Innis et al. 2000). This is of importance as
riparian areas maintain part if not all the life stages of approximately
55%-75% of British Columbia�s rare, threatened or endangered species
(Richardson 2000, Bunnell et al. 1999, MOF 1998b). In British Columbia
there are 51 vertebrates that are obligatory and 157 opportunistic users of
riparian areas (MWALP 2000a). According to Knutson and Naef (1997), similar
numbers have been determined for other areas of western North America, as
approximately 85% of Washington�s terrestrial vertebrate species use riparian
habitat for essential life processes and 46 of Oregon�s vertebrate species
possess an obligatory life stage within riparian areas.
Riparian areas also provide a multitude of other
attributes essential to the ecological processes of the natural environment
(Figure 1.0). According to Koning (1999), these attributes can be grouped
into two main functions; aquatic functions and terrestrial functions. Aquatic
functions include; 1) contributing large woody debris (LWD) to maintain channel
morphology and create habitat for fish and invertebrates, 2) regulation of
water temperature through stream shading, 3) contributing to instream
biological production through small organic debris, 4) buffering the stream
from fine sediments by intercepting surface flow, 5) regulating instream
sediment storage and transport. Terrestrial functions include; 1) providing
wildlife habitat features, including coarse woody debris (CWD), wildlife trees,
nest and perch sites, and summer and winter dennings, and 2) providing summer
and winter forage for terrestrial fauna.
Other attributes of riparian ecosystems are those of
importance from an anthropogenic viewpoint and include; cultural, economic,
diversity and water. Cultural values include; technological, food, ceremonial,
recreational, tourism, medicinal and spiritual purposes. Economic values
include; trapping, timber extraction, livestock grazing and sport fishing.
Diversity includes; fish, wildlife and plants. Water includes its quality,
quantity and reliability (MOF 2002a).
Figure 1.0. Ecological functioning of riparian areas
(Taken from Koning (1999)).
2.2
Riparian Management
2.2.1 Riparian
Management In British Columbia
The management of riparian areas has received much
attention over the last decade in terms of water quality, specifically for its
potential impact on fish populations and habitat (Cockle and Richardson 2003,
Richardson 2000, Waterhouse and Harestad 1999, Hayes et al. 1996).
However, due to poor management practices and incomplete information on the
effects on other components, research is now progressing to provide greater
information on wildlife and bird habitat (Gyug 2000), aesthetics, overall
ecosystem functioning (Waterhouse and Harestad 1999) and the cumulative
downstream effects not prevalent in past research (Richardson et al.
2002, Richardson 2000).
In 1995 the MOF constructed a new classification
system to deal with concerns arising around the management of riparian areas.
However it is felt that this system was produced mainly to ensure that water
quality in community watersheds and fish habitat would be protected from the
effects of forest harvesting. The MOF used a classification system that included
seven categories of stream characteristics with a varying amount of protection
allotted to each (Table 1.0).
Table
1.0. Stream classifications as set forth by the MOF, June 1995.
|
Riparian
Class |
Average channel Width (m) |
Reserve zone width (m) |
Management zone width (m) |
Total width (m) |
|
S1
Large rivers |
>100 |
0 |
100 |
100 |
|
S1
(except large rivers) |
>20 |
50 |
20 |
70 |
|
S2 |
>5<20 |
30 |
20 |
50 |
|
S3 |
1.5<5 |
20 |
20 |
40 |
|
S4 |
<1.5 |
0 |
30 |
30 |
|
S5 |
>3 |
0 |
30 |
30 |
|
S6 |
<3 |
0 |
20 |
20 |
|
|
Fish
bearing stream or community watershed |
|
|
Non-fish
bearing and not in a community watershed |
(Modified from
Forest Practices Code 1998)
Currently there is great concern that the present system
under protects the values of small headwater streams of British Columbia (Gomi et
al. 2002, Haag and Dickinson 2000). In particular, those streams classified
as S4, S5 and S6 streams under the MOF Guidelines. Streams of S5 and S6
classification are those that are determined to be non-fish bearing, and not
considered to be within a community watershed. S5 streams are those that have a
bankfull width greater than 3m while S6 streams are those with a bankfull width
less than 3m (Riparian Management Area Guidelines 1995). Streams of S4
classification are those that are less than 1.5m in width and are either in a
community watershed or are fish bearing.
Harvesting within these headwater streams currently
accounts for 70% of all harvesting in riparian areas yet harvesting guidelines
for these streams provide the least level of protection (Bradley 1997). These
streams are also known as Class C (Bradley 1997), first and zero-order streams
(Hudson and D�Anjou 2001, Bradley 1997). This is inherently important to
watershed management as headwater streams make up over 50% of the total channel
length within watersheds (Benda et al. 2002, Richardson 2000, Beschta
and Platts 1986).
According to Gomi et al. (2002) harvesting activities
that occur in smaller headwater streams are being inconsistently regulated.
They also suggest that the management of these streams has been based on
limited scientific research. Gomi et al. (2002) suggests that this is
due to the absence of fish species within the streams. Another factor may
include the fact that riparian habitat of small streams is narrower and less
distinct than that associated with large streams or rivers (Knutson and Naef
1997). The influence exerted by the riparian area on the aquatic system is
greater in smaller streams than larger ones (Knutson and Naef 1997), and
therefore requires equal protection.
Management of these streams is controversial at best
due to the management requirements under the Forest Practices Code Act (FPC).
All streams within the province require a riparian management area that
consists of a riparian reserve zone and/or a riparian management zone (Riparian
Management Area Guidelines 1995). Under the current code, S4-S6 streams
are required only a riparian management zone and not a riparian reserve zone
that is required for those streams of S1-S3 classification (Figure 2.0).
Riparian reserve zones and riparian management zones are defined as;
�Riparian
Reserve Zone: that portion, if any, of the riparian management area located
adjacent to a stream, wetland or lake. Harvesting of trees is not permitted
normally in the reserve zone unless approved by government in specific
circumstances.�
�Riparian
Management Zone: that portion of the riparian management area that is outside
of any riparian reserve zone or if there is no riparian reserve zone, that area
located adjacent to a stream. Harvesting of trees is permitted in the
management zone.�
(Forest
Practices Code 1998)
Figure 2.0. Graphical depiction of the
riparian management area, riparian reserve zone and the riparian management
zone (Taken from Riparian Management Areas Guidelines 1995).
The lack of riparian reserve zone is of great concern
because the riparian management zone requirements only suggest the best
management practices for these streams and does not provide the same protection
that the riparian reserve zone legislation does (Forest Practices Code 1998).
Within the Riparian Management Area Guidebook (1995), the MOF states best
management practices for these streams. Best management practices for S5 and S6
streams suggest that riparian management should;
� maintain
important wildlife habitat and, where needed, a source of LWD and root networks
for bank and channel stability, and overall shading for stream temperature
control�.
(Riparian Management Area Guidebook 1995)
These are recommended practices only and are not
legally binding (Forest Practices Code 1998). That is to say that forest
licensees are not legally obligated to follow these practices (Muchow and
Richardson 2000). This lack of legislative regulation is of great concern as
these smaller streams contribute greatly to the overall length of stream
networks and are receiving the lowest legislative protection against harvesting
(Gomi et al. 2002, Muchow and Richardson 2000).
Even with the fact that these streams may be
ephemeral, they are an important part of protecting quality of downstream
resources (Gomi et al. 2002). Headwater steams are crucial for the
transport of organic matter, sediments, water and nutrients to larger downstream
reaches. Headwater streams produce a greater amount of coarse particulate
organic matter (CPOM) than downstream reaches and obtain their nutrients
primarily through onsite riparian vegetation (Gomi et al. 2002, Belt and
O�Laughlin 1994).
An investigation by the Forest Practices Board (1998)
determined that only 39% of S6 streams had the recommended amount of vegetation
along the stream bank or within the riparian management area. They attribute
this to the forest industry leaving a larger amount of vegetation along a few
streams, while leaving smaller amounts vegetation retention along most other S6
streams. They also attribute this to clear cutting and cross-stream yarding
which has been shown to increase large woody debris left in streams and reduce
standing riparian vegetation.
Based on the findings of the investigation,
recommendations have been set as follows;
�Government,
working with the forest industry, should provide standards, guidance and
training to improve stream inventories, identification and classification. A
clear definition of a �stream� is also essential.
Government
should develop more specific requirements and recommendations for retention of
trees and vegetation in riparian management zones, to meet objectives for biodiversity
and habitat management.
Government
and the forest industry should work together to improve planning and practices
around small streams, particularly to prevent the transport of debris in
non-fish streams.�
(Forest Practices Board 1998)
It is now becoming apparent that stream orders may be
an inappropriate way to classify hydrologic and biological processes (Gomi et
al. 2002, Bunnell et al. 1999). Even the Department of Fisheries and
Oceans (DFO) shows concern over the fact that non-fish bearing streams are
receiving little or no protection under the FPC. DFO is concerned that current
forest practices within S4-S6 streams may be contributing to the harmful
alteration and disturbance of fish habitat and therefore may be in
contravention of the Fisheries Act. To rectify this, DFO recommends that S5 and
S6 streams that are tributaries to fish bearing streams or sensitive spawning
areas and S4 streams should have vegetation retention of the riparian
management zone of close to 100% unless other more appropriate management
issues provide greater ecological significance (J.
Guerin. pers. comm).
According
to the Ministry of Sustainable Resource Management (MSRM) (2002), concerns have
been recently raised with regards to how adequate the legislation under the FPC
protects riparian areas, particularly non-fish bearing (S5 and S6
classification) streams and smaller fish bearing streams (S4 classification).
The MSRM (2002) has therefore established objectives and strategies for a
greater increase in protection of these areas. They include;
�Manage
streams less than 1.5m in width with fish (S4), throughout the plan area, by
applying a 20m reserve zone and a 20m management zone�
Manage
streams greater than 3m in width with no fish (S5)�� by applying a 10m reserve
and a 20m management zone�
Manage
larger S6 streams (greater than 1.5m bankfull width up to 3m)��by applying a
10m reserve zone and a 10m management zone�
For
smaller S6 streams (less than 1.5m bankfull width), use best management
practices from the Riparian Management Area Guidebook, September 1995�.
(MSRM 2002)
These
objectives of the MSRM therefore imply that only those guidelines for small S6
streams under the best management practices are an appropriate protective
measure. They therefore suggest that the FPC is inadequate for the protection
of all other S4, S5 and large S6 streams.
According
to Hogan (2002), the FPC also limits overprotects S1-S3 streams in regards to
LWD supply while under-protecting smaller S4-S6 streams. He suggests that these
inappropriate levels of protection restrict access to timber around larger
streams while smaller streams receive little attention or protection for
non-timber resources.
2.2.2 Riparian
Management In Other Jurisdictions
Riparian
Management in the United States varies significantly from state to state. The
primary focus of most states is to provide regulations which sets forth guidelines
for minimum riparian zone width, minimum residual trees for the riparian zone,
and other guidelines for modifying management practices within the riparian
zone (Blinn and Kilgore 2001).
Riparian
management in Washington State falls under the direction of the Department of
Natural Resources. Riparian areas are regulated under forest practices rules
and are termed Riparian Management Zones (RMZ's) (MOF 1995, Belt and O�Laughlin
1994). Under this management protocol, riparian streams are classified into
five categories. They include; Type 1-waters including shorelines, Type
2-waters with important fish, wildlife or human use. Type 3-those with moderate
fish, wildlife or human use. Type 4-not Type 1,2, or 3 and that are >2 feet
(0.6m) wide and Type 5-intermittent streams, temporary ponds and seepage areas
(Table 2.0).
RMZ's
are only required for Type 1, 2 and 3 waters (MOF 1995, Belt et al.1992)
and are variable widths ranging from 1.5-33m in western Washington (Belt et
al. 1992) and 10m-100m in eastern Washington, depending on stream width.
These streams also require that all unmerchantable timber be left and the
combination of that timber and merchantable trees provide a minimum of 50%
shade. If the stream is characteristic of 7-day average temperatures in excess
of 60oF (15.6oC), 75% stream shading must be retained
(Belt et al. 1992).
Washington
State�s RMZ�s are also required to maintain Riparian Leave Areas (RLA�s), a set
number of trees/300m. The number of trees/300m is based on stream width, type,
material, size of cut block and percent harvest within the RMZ (Belt et al.
1992). RMZ�s are also required on Type 4 streams for the preservation of small
trees and other vegetation to help prevent debris torrents (MOF 1995). RMZ's
are primarily focused on maintaining a supply of large organic debris for
western Washington streams. Concerns in eastern Washington are more oriented
toward wildlife habitat.
Table
2.0. Washington State stream classification and riparian management (Modified from
Belt and O�Laughlin 1994).
|
Stream Class |
Buffer Strip
Requirements |
||
|
Width |
Shade or Canopy |
Leave Trees |
|
|
Type 1, 2, and 3 |
variable by stream width (5 to 100
feet) |
50%; 75% if temperature
>60oF |
# /1,000 feet dependent on stream width
and bed material |
|
Type 4 |
None |
None |
25trees/1,000 feet |
|
Type 5 |
None |
None |
- |
In
Oregon State, streams are classified into three size classes and three beneficial
use classes (see Table 3.0). Type F streams are those that contain fish and may
be used for domestic water uses, Type D are non-fish bearing and are used for
domestic water purposes, while all other streams are classified as Type N
streams (Oregon Administrative Rules (OAR) 2003).
Classification
of the three classes of stream size is based on rates of flow rather than
stream widths (Robison et al. 1999). Large streams have a flow greater
than 2.3 m3/s, medium streams 0.45-2.3 m3/s and small streams
have a flow of less than 0.45m3/s (OAR 2003).
Table
3.0. Classification of Oregon State streams (Modified from MOF 1995).
|
Stream Size |
Type of Use |
||
|
Fish Use (F) |
Domestic Use (D) |
Neither F or D (N) |
|
|
Large |
100 feet (30m) |
70 feet (21m) |
70 feet (21m) |
|
Medium |
70 feet (21m) |
50 feet (15m) |
50 feet (15m) |
|
Small |
50 feet (15m) |
20 feet (6m) |
varies |
These
Riparian Management Areas (RMA�s) are not reserves but rather areas that restrict
management practices unless otherwise approved. The only streams that have a
reserve area are those streams that are classified as large streams. These
reserves require a 6m strip in which no harvesting in permitted. The
requirements for vegetation retention within RMA�s vary according to stream
type, size and geographical region. There are seven geographical regions within
Oregon (MOF 1995).
Vegetation
retention for all Type F and D streams and large and medium Type N streams
include the retention of all understory vegetation within 10 feet of the high
water level, all trees within 20 feet of the high water level, all trees
leaning over the channel and all downed wood and snags that are not safety or
fire hazards. In addition vegetation retention must retain a minimum of 30
conifers/300m along large Type D and Type N streams and 10 conifers/300m along
medium Type D and Type N streams (OAR 2003).
Smaller
Type N streams are not required to have any merchantable timber retained
(Robison et al.1999). However in certain geographic regions of Oregon
understory and unmerchantable trees must be retained if the perennial channels
have an upstream drainage of 160 (South Coast), 330 (Interior), and 580 acres
(Siskiyou) and all perennial streams in the Eastern Cascades and Blue Mountains
(Robison et al.1999).
2.2.3 Buffer
Strips as a Management Approach
Managing for the protection of riparian areas has been
predominantly implemented through the presence and retention of fixed width buffer
strips around streams (Cockle and Richardson 2003, Hayes et al.1996),
wetlands and lakes (Burton 1998, Belt and O�Laughlin 1994, Castelle et al.
1992). Buffer strips are areas of protected land adjacent to stream channels
that provide a certain level of protection against anthropogenic activities
(Whitaker and Montevecchi 1999, Burton 1998, O�Laughlin and Belt 1995). There
are many functions of riparian buffers. They contribute to the maintenance of
hydrologic, hydraulic and ecological integrity of the stream channel and
associated vegetation and soils, protect aquatic and riparian plants and
animals against upstream pollution, and protects fish and wildlife by supplying
food, cover and thermal protection (Belt et al. 1992).
Buffer strips have been studied for their contribution
in maintaining high quality rivers in regards to fish habitat and water quality
but little attention has been paid to small non-fish bearing headwater streams
(Richardson et al. 2002). Although buffer strips can afford some
protection against the impacts of timber harvesting, these areas of intact land
also have the potential to become disconnected from other forests of similar
structure surrounded by young forest types, creating fragmentation (Waterhouse
and Harested 1999).
If buffer strips are implemented into riparian
management they are often too narrow to provide protection (Richardson et
al. 2002) and may be prone to windthrow (Burton 1998, Moore 1977). It is
also suggested that if buffer strips are widened to increase protection, they
may take away form the amount of harvestable timber that is available for
forest licensees, resulting in a loss of timber resources, and creating a point
if contention (Gomi et al. 2002, Bunnell et al. 1999, Burton
1998). Spatial analysis suggests that if buffer strips of one tree height were
required on all perennial streams, 30% of the land base in British Columbia
would be excluded from timber supply (Burton 1998) and it is for this reason
that small streams are exempt from protection. While areas of the interior of
British Columbia do not possess the same magnitude of small order streams as
coastal regions, analysis of the interior shows similar tends. The Skeetchestn
Indian Band along with Integrated Wood Services mapped out a 100 meter buffer
zone around all water features in the Deadman Watershed. It was determined that
20.67% of the land base would be protected under the buffer zone (M. Anderson
pers. comm).
Within the scientific community, there is a general
consensus that appropriate buffer widths should be based on several variables,
including; existing wetland functions and values, sensitivity to disturbance,
buffer characteristics, land use impacts, and desired buffer functions
(Castelle et al. 1992). Due to the fact that riparian areas have such
variable patterns of gradients, they cannot be directly linked to one
particular width of stream protection or buffer width (Bunnell et al.
1999, Burton 1998). Bunnell et al. (1999) suggests that by setting specific
boundaries or required buffer widths, mangers are suggesting the extent of
conductivity with the adjacent upland areas and the appropriate width of
management area is easily delineated. However, according to Miller et al.
(1997), different buffer widths can provide protection for various functions.
They suggest that water temperature can be moderated with buffer widths as
little as 10m. Sediment removal, nutrient removal and the protection of species
diversity have shown to be accomplished by retaining buffer strips of 50, 80
and 90m respectively. However, according to Belt and O�Laughlin (1994), the
appropriate buffer strip width will change from site to site based on
infiltration rates and slope and suggests that buffer strips are more efficient
at controlling overland sediment flows than channelized flows. Research has
shown that channelized flow can move over 300m while overland flow is usually
limited to less than 100m (Belt et al. 1992).
Knutson and Naef (1997) conducted a comprehensive
literature review on buffer widths and summarized their findings in Table 4.0
for various riparian habitat functions. There appears to be great variability
in the recommended buffer widths between researchers, particularly for wildlife
habitat. However, wildlife habitat summaries included all recommended widths
for invertebrates, fish, birds and mammals.
Table 4.0. Summary of buffer strip widths
ranges and averages for various functions (Modified from Knutson and Naef
(1997)).
|
Riparian
habitat function |
Range of reported widths (m) |
Average of reported widths (m) |
|
Temperature
control |
11-46 |
27 |
|
Large
woody Debris (LWD) |
30-61 |
45 |
|
Sediment
filtration |
8-91 |
42 |
|
Pollution
filtration |
4-183 |
24 |
|
Erosion
control |
30-38 |
34 |
|
Microclimate
maintenance |
61-160 |
126 |
|
Wildlife
habitat |
8-300 |
88 |
Another concern regarding buffer strips is that of
creating an edge effect (Burton 1998). Edge effect can be defined as the boundary
between two distinct biological communities. In reference to riparian areas, it
is the boundary that is created between the riparian vegetation and the
vegetation and attributes of the upland area (MOF 1998c). Edge effect becomes
more prevalent as buffer strips are created as long and narrow strips of land
that lose the influence of the surrounding interior forest (Cockle and
Richardson 2003). Harvesting changes this area of transition from a gradation
to an abrupt boundary. This abrupt boundary can have severe effects on the
population dynamics, through changes in dispersal and predation rates. Over
time edge effects can have severe impacts on the composition of vegetation
communities (Miller et al. 1997). This can occur from blowdown, loss of
lichens, alteration of understory vegetation and increased mortality of shade
tolerant plant species (Miller et al. 1997). Investigation into the
effects of increased edges along riparian areas has been minimally researched
and requires further investigation into its effect on biodiversity,
particularly small organisms (Richardson et al. 2002).
Richardson et al. (2002) has begun research to
look at alternatives to fixed width buffer strips as a form of riparian
management. While fixed buffer widths are beneficial for administration
simplicity (Belt et al. 1992), variable width alternatives would be
advantageous as current buffers provide either too much or not enough
protection (Belt and O�Laughlin 1994). However, according to Knutson and Naef
(1997), there is currently insufficient information to recommend variable width
that can adequately protect the high variability of riparian width, land uses,
and fish and wildlife communities.
The appropriate buffer width for riparian areas varies
according to the protection requirements for different functions.
Research has shown that the effectiveness of buffer strips increase as buffer
width increases in regards to removing sediments, nutrients, bacteria, and
other pollutants from surface water runoff (Knutson and Naef 1997). However,
research has shown that the efficiency of sediment removal is disproportionate
to the increased widths of buffers. Knutson and Naef (1997), suggest that
sensitive or priority species may benefit from these incremental increases.
Huryn
(2000), suggests that based on a review of literature, buffer widths should be
>30 m to protect the community dynamics of insects within small headwater
streams. Huryn (2000) suggests that buffer strips of narrow widths such as the
7.6m width used in 0-order streams in Maine are inadequate for mitigating the
effects of harvesting activities for insect communities.
However, buffer strips alone have shown to be insufficient
in regulating stream temperature, as stream temperature is also a function of
stream width, air temperature, groundwater temperature and slope. According to
Teti (2000), stream temperature is a function of reduced shading levels rather
than a function of harvesting. Therefore it appears that the effectiveness of
stream shading is based on buffer design rather than buffer width, and the more
closely a buffer provides shade in proportion to natural shade levels, the more
effective the buffer (Teti 2000, Belt and O�Laughlin 1994).
Research is now looking at the effects of partial
cutting as opposed to buffer strips within riparian areas to determine what
protection this system can provide. While any cutting within riparian areas
will alter communities beyond their natural parameters, partial cutting
treatments provide greater protection than small headwater streams currently
receive. This may also relieve some of the contention that has arisen in
concern between full reserve zones and timber extraction.
2.2.4 Partial
Retention as a Management Approach
Partial retention of vegetation adjacent to smaller
streams has increased in recent years since the imposition of the FPC in 1995.
This legislation has lead to an increase in the use of alternative
silvicultural systems other than clear cutting. However, there are minimal
results available on these silvicultural systems within riparian areas. One
research report within British Columbia does however provide insight into the
condition of small fish bearing (S4) streams following various riparian
management practices.
Chatwin et al. (2001) conducted an
investigation into 2989 cutblock across British Columbia and determined that 81
blocks contained an S4 stream or S5 and S6 streams that were direct tributaries
to an S4. Of the streams, 68% had some type of unharvested riparian reserve,
22% were clearcut and 10% had a partial retention treatment. Study blocks were
located in the Merritt (5 blocks), Kamloops (8), Salmon Arm (4), Clearwater
(6), 100 Mile House (38) and Williams Lake (20) Forest Districts.
The partial retention treatment varied from 71%
retention (% stem/ha) directly adjacent to the streams to approximately 25%
tree retention 20-30m from the streams, with cumulative tree retention of
approximately 50%. According to Chatwin et al. (2001), partial retention
treatments possess the highest stream impacts as 33% of streams had moderate
impacts due to windthrow and high impacts due to livestock. Boundary and fixed
reserves had the least impact on streams with 4.8 and 7.7% streams having
moderate to high impacts. Chatwin et al. (2001) also found partial
cutting to have moderate to high risk of canopy shade loss. They determined
shade loss in 42% of partial retention blocks compared to 36% in variable width
reserves, 17% in boundary reserves, 31% in fixed-width buffer reserves and 73%
in clearcut treatments.
According to Chatwin et al. (2001) partial
retention has implications as a forestry management practice within riparian
areas. It was determined that partial retention had the highest proportion of
concerns regarding stream channel stability, windthrow incidence and loss of
stream shading. Clear cutting appeared to be a sufficient management practice
in regards stream channel stability, and windthrow but appeared to promote high
shade loss. Chatwin et al. (2001) suggests that boundary reserves and
fixed-width buffers provide the most stream protection as they provide the best
combination of stream channel stability, shading and windthrow resistance.
However, this method may provide increased biological protection but again
raises issues of a loss in available timber for harvesting. It should also be
noted that while the study results suggests partial retention has many
management implications, channel stability is also a factor of cattle use and
must be evaluated and managed in conjunction with harvesting treatments.
2.3
Impact Assessment
Removing vegetation from the riparian zone through timber
harvesting can cause severe and sometimes indirect effects to the functioning
of an ecosystem and cumulative effects many kilometres downstream (Hayes et
al. 1996). Due to riparian areas being situated within topographic
depressional areas, they receive water, soil and organic debris that are
affected by upslope land uses (Knutson and Naef 1997). This is particularly
true when areas are clearcut to the stream banks, impairing their role of
providing the linkage between biological and physical characteristics of the
terrestrial and aquatic ecosystems (Koning 1999).
Harvesting can have different impacts on headwater
streams due to the high diversity among the size of streams and their gradient,
thus affecting the incidence of radiation, current velocity and sediment
deposition (Bunnell et al. 1999). When harvesting diminishes the
vegetation within these ecosystems, riparian areas also lose their ability to
influence and moderate the surrounding environments, thus affecting wildlife,
water quality and fish habitat. However, different harvesting techniques can
affect the magnitude of these detrimental impacts. Studies have also shown that
riparian management techniques are required to ensure that water quality
concerns do not affect downstream resources (Hudson and D�Anjou 2001).
Alternatives to clear cutting other than buffer strips
can include variable retention of merchantable trees or retention of
non-merchantable trees within the cutting area. The retention of small groups
and individual trees can provide structural complexity, which has been shown to
be an important part of forest ecosystem maintenance. These alternative systems
tend to have management goals that are broader than solely economic gains and
place equal value on all forest resources (MOF 2000b). The retention
of small groups and individual trees can provide islands that are
characteristic of mature forests and provide an area of refuge for many
organisms until the site conditions within the cut block become inhabitable
again (MOF 2000b).
The
overall impacts of forestry on riparian areas, through vegetation removal, road
construction and soil disturbance can include but are not limited to:
�
Alteration of site vegetation
�
Fish and wildlife impacts
�
Water quality and hydrologic (relating to water flow) effects
�
Stream temperature increases and a more severe microclimate
�
Soil destabilization, erosion, and sedimentation
�
Loss of large woody debris
�
Increased windthrow
�
Cattle grazing
2.3.1 Vegetation
Plant diversity is generally highest in riparian
areas. This is due to the gradient of moisture that extends between the
influencing water source and the upland area. Plant biomass therefore increases
with proximity to the water source (MOF 1998b). Riparian areas are generally
dominated by plant species that are both shade tolerant and shade intolerant.
Due to the occurrence of flooding, riparian areas at the fringe of the water
source generally consist of species that are shade intolerant as crown closure
is generally less in these areas. As the gradient of moisture lessens from the
water source to the uplands, shade tolerant species become more pronounced due
to reduced flooding and increased crown closure (Bunnell et al. 1995).
Therefore herbaceous shrubs and deciduous species compliment water-loving
plants as they diverge from the central water channel to upland areas
(MOF1998a).
Riparian
vegetation creates a complex rooting system that is usually shallower than
vegetation found in upland areas due to the higher water table. These shallow
but extensive root systems provide protection against soil erosion, reducing
the amount of sediment being deposited into streams and providing an
appropriate level of stream bank stability and contribute to the maintenance of
water quality and velocity (Stevens et al. 1995, Beschta and Platts
1986).
Riparian vegetation also contributes greatly to the
recruitment of organic material in the system as it provides leaves, twigs and
insects that provide energy to various components of the aquatic environment.
Riparian areas also contribute large woody debris that provides habitat
structure for numerous aquatic organisms while aiding in maintaining stream
bank stability (MSRM 2002, Bunnell et al. 1995).
When clear cutting occurs within riparian areas,
modification of vegetation layers can occur. For example, clear cutting
generally eliminates the moss layer found on the forest floor and replaces it
with increased herbaceous cover (Gyug 2000). That increase in shrub cover can
occur following the opening of the canopy through clear cutting or partial
cutting.
2.3.2 Regeneration
of Conifers following Riparian Harvesting
Regeneration
of vegetation following harvesting is primarily through the rapid growth of
deciduous shrub species. Due to forest management practices within riparian
areas generally being lumped with upland harvesting techniques, many streams
are harvested to the banks. Because this promotes a flourish of fast growing
shrubs that usually give way to the growth of hardwood species, conifers are
often poorly represented within the overstory of regenerating riparian stands
(Beach and Halpern 2001). This is of importance as conifers are a source of LWD
that provides structural integrity to streams for a longer period of time as
opposed to hardwoods due to differences in size, structure an decomposition
rates.
A
major concern with the regeneration of conifer species is the lack of seed
availability for natural regeneration following harvesting. If riparian areas
are clearcut along with upland areas, the seed bank available to provide seeds
for regeneration is often too small or too distant from the stream bank. Due to
harvesting practices within the riparian areas of small headwater streams, few
riparian areas experience sufficient seed rain for successful conifer
regeneration (Beach and Halpern 2001). The method of selectively logging can
provide increased seed dispersal in immediate or close proximity to riparian
areas.
Research
conducted by Beach and Halpern (2001) suggest that regeneration of conifer
species is greatest for areas in which seed trees are within a 80m proximity. They
also found no regeneration occurred in areas that were in excess of 170m from a
seed source. These results suggest that selective harvesting which removes
individual trees or groups of trees retains an increased seed bank that is
better capable of regenerating harvested areas to conifer stands. Beach and
Halpern (2001) also determined that over 50% of conifer regeneration occurs on
coarse woody debris. This suggests that conifers are required within riparian
areas for perpetual regeneration of stands.
Natural
regeneration may also be of concern due to the fact that species such as
Douglas-fir are relatively shade-intolerant especially when regeneration occurs
under deciduous species. Douglas-fir have shown to rarely establish in stands
were shrub cover exceeds 10% (Beach and Halpern 2001). However, MOF (1998a)
studies conducted on 31 partially cut stands within the IDF dk3, xm and xw of
the Cariboo Forest Region determined that Douglas-fir regeneration was abundant
in all stands. Areas were harvested using 13-89% basal removal. Twenty eight of
the blocks studied all met MOF stocking standards. The three that did not meet
stocking objectives were due to those sites that had steep, southerly slopes
with low crown closure (MOF 1998a). This study suggests that natural
regeneration is sufficient to meet the stocking standards set forth by the MOF
regardless of the amount of basal area removed under partial cutting systems
(MOF 1998a).
Other
species such as spruce (Picea) and sub-alpine fir (Abies laciocarpa)
have shown varying regeneration success. In a study within the ESSF of the
Cariboo Forest Region, it was determined that the natural regeneration of
spruce had no relationship to the area of opening harvested, while
subalpine-fir was determined to have a greater regeneration success within
small (0.03ha) or medium (0.13ha) openings as compared to large openings
(1.0ha) (MOF 2000c). However, seven years after harvesting, regenerating spruce
and sub-alpine fir were insufficient in height to meeting local stocking
standards.
Artificial
regeneration through planting may be an alternative method for regenerating
partially cut riparian areas. MOF (1997) conducted studies into the artificial
regeneration of conifer species within the ESSFwc3. Lodgepole pine, interior
Douglas-fir and sub-alpine fir were planted under five treatments; protected
sites, natural raised sites, rotten wood, mechanized scarification and standard
grid planting. Results determined that seedling diameter and leader growth of
all species increased as opening sized increased and elevation decreased. Lower
amounts of terminal damage were also noted within large openings. Results also
suggest the pine has superior growth but spruce provide better tree form due to
slower growth characteristics and lower mortality in higher elevation sites
(MOF 1997).
2.3.3 Fisheries
Riparian areas are an imperative aspect of retaining
viable fish populations. It is the forest management practices within the
riparian zone that can have the greatest effect on fish habitat (Beach and
Halpern 2001). Fish have evolved life history strategies that depend on natural
conditions found within freshwater streams. Fish have developed behaviours for
breeding, feeding, resting, and avoidance of predation that are adapted to
natural rates of stream flow, erosion and sedimentation, and inputs of organic
materials including food sources and large woody debris (Knutson and Naef
1997).
Four ways
in which riparian areas aid in ecosystem function in regards to fisheries
include:
� Physical
and biological filtration: buffering impacts of activities
such as logging outside the riparian area by absorbing nutrients and silt
produced by those activities;
� Amelioration:
reducing variability of physical or chemical characteristics such as water
temperatures;
� Biological
production: providing the bulk of the aquatic food chain base
through terrestrial organic matter and food organisms (insects), specially in
small, shaded streams
�
Structural protection and renewal: stabilizing
banks, minimizing erosion and stream sedimentation, and providing sources of
logs, gravel, etc. that provides critical structural elements and variation in
stream characteristics
There
are many ways in which forestry can impact a productive fisheries stream
directly or indirectly from upstream inputs. Some of the negative impacts may be
cumulative and include increased sedimentation, temperature changes, loss of
LWD, and changes in hydrology.
Research
conducted by Chatwin et al. (2001) evaluated 81 harvested areas in 6
forest regions of British Columbia that encompassed or were adjacent to S4
streams to determine the impact of various riparian silvicultural treatments.
Treatments included boundary reserves, fixed and variable width buffers,
partial cuts and clearcuts.
2.3.4 Wildlife
Riparian
areas are of great importance to wildlife throughout British Columbia,
primarily due to the attraction of available free flowing and standing water
(Waterhouse and Harestad 1999). The variation in plant structure and diversity
is also an important attractant of wildlife to riparian ecosystems (MOF 1998b)
as the diverse structure provides a source of nutrition while providing rearing
and concealment habitat and travel corridors (Bunnell et al. 1999,
Knutson and Naef 1997, Stevens et al. 1995). Most wildlife species use
riparian ecosystems at some stage in their lifecycle and are obligatory, while
others are only dependent on these areas for opportunistic reasons (Stevens et
al. 1995). The assemblages of species that rely on riparian ecosystems for
various life processes include; birds, fish, amphibians, invertebrates and
large and small mammals.
Riparian areas generally have a higher number of
wildlife species inhabiting them compared to upland areas due to the presence of
free flowing water, greater cover and thus the greater abundance of forage for
forest dwelling species. Riparian areas generally consist of both coniferous
and deciduous species, therefore providing a greater number of niches than
limited structured ecosystems (Bunnell et al. 1999).
Due to the greater complexity and biomass of the
riparian area, cover is generally greatest in this area. This dense cover
allows mammals an environment in which they can hide and take refuge from
predation. The greater abundance of shrub species in riparian areas due to
wetter conditions and greater sunlight provide an important attribute for
mammal populations (Bunnell et al. 1999). Research conducted in southern
British Columbia has shown that even insectivorous bat activity is more
abundant in riparian areas due to greater prey availability and drinking sites
(Richardson 2000, Grindal et al. 1999).
According to Bunnell et al. (1999), riparian
areas provide primary habitat for 13 species of rodents that are generally not
found in upland forests. Riparian areas within British Columbia are also
crucial for mountain beaver (Aplodontia rufa), as they are found no
where else in Canada and are also limited to the Pacific Northwest of the
United States. Ungulates also use riparian areas as a source of concealment and
shade while obtaining water and forage as the availability of winter forage is
always greater in late-successional stands than in young stands or clearcuts
(Bunnell et al. 1999)
With most studies looking at the effects of upland
harvesting on wildlife species, few have looked at the impact that harvesting
may have in riparian areas (Cockle and Richardson 2003). This is an important
area that requires greater research, as riparian areas possess a greater
abundance of hardwoods than upslope areas. These hardwoods provide cavity
nesting for birds and forage for a variety of wildlife (Bunnell et al.
1999, Knutson and Naef 1997). Research has also shown that the abundance and
diversity of birds that are associated with shrub species can be directly
related to harvesting (Bunnell et al. 1999). Bunnell et al.
(1999) found that shrub-associated species tended to increase relative to
increased volume removal (basal area) of timber. The research of Bunnell et
al. (1999) suggests that bird species are influenced least by the selective
harvesting of lodgepole pine compared to partial removal or clear cutting.
However, the study also shows that elk benefited from clear cutting to stream
banks, as they are intermediate grazers and are attracted to increased shrub
production.
According to the results of Cockle and Richardson
(2003), small mammals, such as shrews (Sorex) and red-backed voles (Clethrionomys
gapperi), tend to decline in species richness after clear cutting even
though certain species increased in abundance. Implementing buffer strips
around streams also appears to be an effective method of conserving habitat as
Cockle and Richardson (2003) determined that small rodent abundance was
greater in these areas than adjacent clearcuts, and similar to those sites that
remained unlogged. These areas may also prove to be important for the
recolonization of regenerating cutblocks (Cockle and Richardson 2003). However,
according to Hannon et al. (2002) voles were as likely to inhabit cut
blocks with at least 10% retention, as they were to inhabit buffer strips left
in riparian zones.
According to Bunnell et al. (1999),
alternatively designed silvicultural techniques may provide a means of ensuring
sustainable populations exist within our forested ecosystems. They suggest that
the retention of large living trees, snags, and large woody debris can aid in
proper ecosystem functioning while ensuring the characteristics of a mutli-aged
management regime. However, Bunnell et al. (1999) also suggests that any
one silvicultural treatment, whether retention or clear cutting will result in
winners and losers among vertebrate populations.
Research conducted by Richardson et al. (2002)
looked at changes in small mammals between clearcuts and buffer strip protected
riparian areas. They determined that species richness was greater in buffer
strips and controls than clearcut areas. Species diversity also declined with
increased alteration by clear cutting and buffer strips. Richardson et al.
(2002) therefore suggests that while buffer strips appear to have less of an
impact on small mammals than clear cutting, changes within species structure
and dynamics are still present within buffer strips.
Sullivan et al. (2000) conducted studies on
small mammal use of Douglas-fir �Lodgepole pine stands within south-central
British Columbia under different silvicultural treatments. They determined that
red-backed voles were found in higher abundance within old growth stands than
young clearcuts or seed tree stands. In contrast, meadow voles (Microtus
pennsylvanicus) were more abundant in seed tree treatments, and five other
species of Rodentia were found to be more abundant in both seed tree and
recent clearcuts. Deer mice (Peromyscus maniculatus), long-tailed voles
(Microtus lingicaudus) and short tail weasels (Mustela erminea)
all had similar means among all treatments. Sullivan et al. (2000),
therefore suggests that seed tree systems are therefore more appropriate for
providing natural stand structure and biodiversity than clear cutting
treatments.
A study of the effects of group selection on small
mammals was conducted within the ESSF of the Cariboo Forest Region (MOF 1997).
Treatments included openings of various sizes; 0.03ha, 0.13ha and 1.0ha, each with
30% volume removal and an unharvested control. It was determined that there was
no significant difference between the four treatments in terms of species
abundance, diversity and evenness. While there was no difference in treatment
use, small mammals showed a preference for the forested areas within the
various treatments. It therefore appears that partial cutting that create small
openings have minor, if any effects on small mammal dynamics two years after
harvesting.
The upper Deadman River and Criss Creek valleys
provide a wide range of winter habitat for moose populations including riparian
shrub habitat and wetland complexes (Lemke 1998). Riparian areas (riparian
willow habitat and spruce/sedge meadows) within the Deadman and Criss Creek
areas also provide optimum area for moose calving habitat (Lemke 1998) as they
provide secluded shelter, high browse availability and close proximity to
water. Lemke (1998) also suggests that mature conifers that border riparian and
wetlands provide crucial thermal cover throughout the year. Lemke�s (1998)
research in the Upper Deadman River area on moose habitat suggests that
harvesting should be conducted in a manner to minimize damage to understory
vegetation. She also suggests that buffer zones of 300meters be established
around all riparian and wetland complexes greater than one hectare, 200m for
high forage sites, and riparian /wetland edges should retain 75% of its
vegetation.
Research has also been conducted into the effects of
partial cutting on the abundance of mule deer populations (Armleder et al.
1998). Interior Douglas�fir within the Cariboo Forest Region, British Columbia
was harvested in a single-tree selection system in which 20% of the volume was
removed. Armleder et al.�s (1998) results determined that there was no
significant difference between mule deer abundance of undisturbed stands and
those 20% harvested following track assessments for the winters of 1984-1991.
Results suggest that single-tree selection systems may be an appropriate method
to harvest interior Douglas-fir at low volumes without having adverse effects
on the winter requirements of mule deer populations.
2.3.5 Birds
Riparian areas provide birds with a variety of habitat
with distinct attributes for perching and resting and provide snags that ensure
ample nesting cavities are available (MOF 1998b). Studies have shown that the
abundance of 75% of all perching birds increases within riparian areas as they
use hardwoods and shrubs as habitat in preference to conifers (Bunnell et
al. 1999).
According to Hannon et al. (2002), a study
comparing buffer width and species composition determined that buffer strips of
20m showed a decrease in the number of bird species inhabiting them as compared
to wider buffer strips. They suggest that this may be due to an inability to
hold territories within the confined space of the strips. However, the work of
Darveau et al. (1996) showed that riparian buffer strips increased
between 30 and 70% in abundance and composition following adjacent harvesting,
but suggest that this was due to dispersal of nesting individuals from the
clearcut rather than the quality of habitat. Initial increases dropped to
pre-harvest levels within two years.
Hannon et al. (2002) suggest that buffer strips
may need to be 200m in width to maintain the communities of small passerine
bird species. However, they feel that 200m buffer strips are not sufficient to
maintain the communities of larger raptor, woodpeckers species or carnivores. This
is supported by Whitaker and Montevecchi (1999) who feel that even buffer
strips >100m will not support unaltered bird assemblages. Hannon et al.
(2002) also suggest that buffer strips of < 100m may promote �edge habitat�.
Whitaker and Montevecchi (1999) also determined that even buffers of 40-50m
contained <50% of the bird densities found in adjacent interior forest
habitats. Research conducted by Vander Haegen and Degraff (1996) also suggests
that small buffer strips contribute to increased nest predation of passerine
bird species. Vander Haegen and Degraff (1996) found that riparian areas in
unharvested stands (control) have a 15% predation rate while harvested riparian
areas with buffer strips of 20-40m and 60-80m had increased predation at 31%
and 23%, respectively. Hannon et al. (2002) suggests that riparian
buffers are insufficient and inappropriate for managing intact vertebrate
communities that would be found in older growth forests.
Research has also been conducted into the effects of
partial cutting on predation of bird nests. Steventon et al. (1999)
conducted research into how the removal of 30 and 60% of vegetation affects
predation rates of artificial nests. It was determined that a 30% partial cut
had no effect on predation rates compared to uncut areas, but data form the 60%
partial cut suggest only a moderate increase in predation. They therefore
suggest that their results support other studies that indicate that a 30%
removal still retains mature forest characteristics (Steventon et al. 1999).
Studies from within the ESSF zone of the Cariboo
Forest Region found similar results to Steventon et al. (1999). MOF
(1997) found that following group selection silvicultural trials and fives year
post harvest studies, no significant changes in species abundance, richness or
diversity have been observed. Again suggesting that a 30% volume removal has
minimal impacts on bird species dynamics and maintains bird communities at
levels found in mature stands.
2.3.6 Amphibians
Riparian
ecosystems are extremely important to the lifecycle of amphibians as these
species use water as a medium in which to lay their eggs. Adults also rely on
these areas to provide mating sites and foraging areas (Knutson and Naef 1997).
Two species of the seven amphibians found within British Columbia are at risk
and are found on the red or blue provincial list of British Columbia (Bunnell et
al. 1999). In Washington 80% of amphibian species are obligates of stream
or wetland-related habitats (Knutson and Naef 1997). Due to their reliance on
water, amphibians are highly susceptible to changes in stream temperature and
increases in sedimentation can impede respiration and interrupt food supply
(Bunnell et al. 1999). Amphibians may even play a more integral part in
ecosystem functioning then previously thought as they contribute up to four
times the biomass in riparian ecosystems than salmonids (Stevens et al.
1995, Petranka et al. 1993).
Amphibians can also be adversely affected by
harvesting of riparian areas. The three main effects of harvesting on
amphibians inhabiting headwater streams include;
� changes in cover,
aeration, and flow patterns associated with downed wood in streams;
� changes in incident
radiation, which modifies both periphyton production (through photosynthesis)
and stream temperature; and
� changes in
sedimentation rate
(Bunnell
et al. 1999)
In the
research of Richardson et al. (2002), there appeared to be no immediate
(one-year post-harvest) effect on community structure of aquatic breeding
species between controls, buffer strips or clearcuts. However terrestrial
breeding species showed lower densities and tended to be smaller in size than
those of the buffer strips. Richardson et al. (2002) also determined
that buffer strips appeared to be movement corridors following harvesting.
Contradictory to the findings of Richardson et al. (2002), Petranka et
al. (1993) found dramatic changes in salamander densities as results showed
500% greater salamander densities in mature forests than within recently
clearcut stands. Petranka et al. (1993) also suggests that up to 80% of
salamanders are lost following clear cutting and that their study indicates
that in would take approximately 50-70 years for structure to regain
pre-harvest conditions.
2.3.7 Invertebrates
Forest
harvesting has been shown to alter the population dynamics of many
macroinvertebrates. Studies conducted by Muchow and Richardson (2000) within
the Malcolm Knapp Research Forest in British Columbia indicate that even
ephemeral streams that dry up during the summer may contribute an equal
proportion of macroinvertebrates as larger persistent streams. They found that
intermittent streams also had an emergence of stoneflies (Plecoptera),
twice that found in continuous streams over the course of the study. This study
provides evidences of the value of small ephemeral streams in their ability to
produce invertebrates that provide a food source for downstream predators such
as salmonid species. Therefore these riparian areas along ephemeral streams are
an integral part of ecosystem functioning (Muchow and Richardson 2000,
Richardson 2000).
It is
suggested that small headwater streams are major sites for the accumulation of
leaf litter that is then processed to organic particles by the feeding activity
of invertebrates (Huryn 2000). Shedders are the dominant functional group of
macroinvertebrates in small headwater streams as compared to the filterers and
gatherers of down stream networks. These shredders provide coarse particulate
organic matter (CPOM), an important input to downstream reaches (Gomi et
al. 2002). The research of Richardson et al. (2002), who looked at
the effects of riparian buffer widths on invertebrates, found that changes in
invertebrate communities appeared to drastic for some species while others had
very little changes in community structure following harvesting. Richardson
(2000) also suggests that large riparian trees may be important in the
aggregation of mating insects.
Research
conducted by Heise (2000), used artificial substrate to measure the effects of
timber harvesting within three creeks of the Sicamous Creek watershed, British
Columbia. Heise (2000) determined that macroinvertebrate abundance decreased in
streams adjacent to clearcut harvesting compared to unharvested control
streams. He also noted a change in population structure, with the abundances of
stoneflies, flatworms and diptera, all showing declining numbers within the harvested
stream. However, Batzer et al. (2000) had opposing results from his
study of 12 small wetlands in Georgia that had been harvested and replanted
between 1975 and 1997. He found that there was a direct correlation between
smaller streamside vegetation and increased terrestrial invertebrate
diversities and numbers. He also found increases in other variables such as
water pH, light levels and herbaceous plant cover and biomass. Batzer et al.
(2000) therefore suggests that harvesting near small wetlands can alter
ecological interactions for up to 15 years following vegetation removal.
According to Huryn (2000), protecting of the
biodiversity of stream invertebrate communities at undisturbed levels within
smaller headwater streams is an essential management practice that is required
for maintaining ecosystem functions within drainage networks. Changes though
large clearcut harvesting to the edge of stream banks can affect
macroinvertebrates through alteration of light levels, sediment input, larval
habitat, adult habitat, larval food, summer water temperatures, and inputs of
leaf detritus (Huryn 2000).
In a five year study conducted by Erman and Mahoney (1983),
on streams with and without buffer strips in California, it was determined that
narrow buffer strips had higher macroinvertebrate diversity than those streams
with no buffer protection. Diversity in unbuffered streams dropped 12.5%
following logging and remained at those levels for five years while narrowed
buffered streams dropped 25.2% following harvesting but improved to 9.1% after
a five year period (Erman and Mahoney 1983).
2.3.8 Water
Quality
The
quality of water is extremely important within riparian areas, as it is one of
the major determining factors of life for plants, wildlife, fish and humans
(Stevens et al. 1995). Due to the high abundance of plant material and
diversity within riparian areas, these areas can act as a sponge. These areas
aid in the infiltration and percolation of surface water into the ground,
providing a storage for water that is slowly released into the surrounding area
over time (MOF 1998b, Miller et al. 1997) Riparian areas also filter out
harmful compounds such as nitrogen and phosphorous that may have a detrimental
affect on the aquatic system (Bunnell et al. 1995).
Harvesting
can adversely affect stream quality due to altering the amount and timing of
sediment production. Sedimentation can occur due to the exposure of mineral
soil due to logging activities (Grace and Carter 2000) or due to wind blowdown
of trees that are rooted within or on the stream bank of riparian areas (Hudson
and D�Anjou 2001, Moore 1997). In experiments in Demo Creek located on the Sunshine
Coast, British Columbia, Hudson and D�Anjou (2001) found that not only did
blowdown in riparian areas create sedimentation into the channel but also that
the exposed roots and mineral soil will continue to erode and create
sedimentation during later periods. This is also suggested by Moore (1997), who
determined that while sediment pulses may not be of direct importance of these
streams themselves, sediment pulses have a greater effect on downstream reaches
that provide domestic water supply or fish habitat. It should also be noted
that in silvicultural treatments which shortens the rotation period, harvesting
frequency is increased and therefore can accelerate erosion losses and
potentially decrease water quality (Grace and Carter 2000).
2.3.8.1 Hydrologic
Effects
Riparian
vegetation along with upland vegetation moderates stream flow within watersheds
(Knutson and Naef 1997). Plant roots can aid in increasing the soil porosity
while vegetation interrupts the surface flow of water and promotes onsite
infiltration which can then be released over time through subsurface flow
(Knutson and Naef 1997), thus decreasing sudden water pulses following rainfall
and snow melt events.
Many studies have shown alterations of
streamflow due to various forest harvesting practices such as clear cutting
(Hicks et al. 1991, Keppeler and Ziemer 1990). These alterations of
streamflow are due to changes in the rate of interception, evaporation and
transpiration following the removal of riparian vegetation (Hicks et al.
1991, Keppeler and Ziemer 1990). Alterations may be seen in the form of
increased, decreased or temporal changes of streamflow. When decreases in
streamflow occur during different periods of the year, they can directly affect
fisheries values. This is due to the fact that even small reductions in stream
flow can cause increases in stream temperature and promote stress, disease and
increased competition among fishes (Hicks et al. 1991).
Increases in streamflow can also be seen as
a benefit of forest harvesting. However, 90% of streamflow increases generally
occur in October to March and therefore do not aid in rectifying any low flow
levels indicative of summer periods (Keppeler and Ziemer 1990).
While research conducted by Hicks et
al. (1991) suggests that logging may actually decrease summer streamflows,
they did determine that the practice of patch cutting might actually regulate
streamflow at pre-harvest levels or even provide increases in streamflow during
the summer. This is supported by research conducted by Keppeler and Ziemer
(1990), who evaluated streamflow data from a Californian creek for a 21-year
period. They also determined that selective harvesting can increase summer and
annual streamflow levels. However studies have shown that a removal of less than
25% basal area tend to show no detectable increase in water yield (Hornbeck and
Kochenderfer 2000). Similar research
conducted by Hudson (2001) found peak flow of harvested areas was greatest in
variable retention treatments of 18% canopy retention compared to shelterwood
treatments of 49% retention.
Recovery
of hydrologic responses is also a great concern. Keppeler and Ziemer (1990)
found that reductions in summer flow still persisted five years after selective
logging and is expected to be from increased transpiration of water by residual
vegetation. Knutson and Naef (1997) also suggest that partial cutting can alter
hydrologic effects for up to 10 years (Table 5.0)
Table 5.0. Recovery period of Hydrologic
responses to various treatments.
|
Hydrologic Response Variable |
Treatment |
Recovery Period |
|
Water yield � Summer |
Clear-cut |
2-3 years |
|
Water yield � Annual |
Partial-cut (25%-33%) |
10 years |
|
Water yield � Annual |
Clear-cut |
- |
Modified
from Knutson and Naef (1997)
2.3.8.2 Water
Temperature
Harvesting can also affect the temperatures of
instream water and surrounding soils (Mellina et al. 2002, Beschta and Taylor
1988, Beschta and Platts 1986). Literature suggests that increases in stream
temperature are predominantly due to the removal of riparian vegetation rather
than the harvesting of the surrounding watershed (Mellina et al. 2002,
Teti 2000, Teti 1998, Knutson and Naef 1997). However, the effectiveness of
buffer strips is directly related to how well shading of the stream is
maintained at natural levels. It also appears that fixed buffer widths such as
those set forth in the Riparian Management Areas Guidebook (1995) are less
effective than buffers designed to reduce angular canopy density or sun
penetration. Literature also suggests that temperature increases in small
headwater streams is minimal but may be of importance as the cumulative effects
can have a dramatic change upon entering a S5 stream.
While most literature suggests that stream
temperatures increase following the removal of riparian vegetation, the time
required for a stream to recover to pre-disturbance levels is still under
debate. According to Teti (2000) and Teti (1998), the recovery period of stream
temperature increases can be affected by topography, microsite conditions,
riparian species and stream morphology. Some studies have suggested that
thermal recovery after harvesting may take up to 7 years for coastal regions
and up to 20 years for high elevation areas like the Oregon Cascades (Teti
2000). Johnson and Jones (2002) found that recovery to pre-harvest conditions
took 15 years following either patch cuts or clear cutting. Other studies
suggest that thermal recovery should be based on the regeneration of vegetation
rather than a set period of time (Beschta and Taylor (1999). Studies conducted
by Beschta and Taylor (1988) also determined that following harvesting, the
temperatures of a stream in Oregon increased 6oC over a 30-year
period. They suggest riparian vegetation regrowth would take approximately 15
years before a linear decrease in stream temperatures would occur and that the
first 5 years growth would not be enough to affect the high maximum stream
temperatures. Water temperatures increased directly, and from water flowing
over the surface of warmer land eventually reaching streams and further
increases water temperatures (Beschta and Taylor 1988).
Recovery
of increased temperature following the flow through clearcut blocks is in
debate on how long it takes to regain is pre-cutblock temperatures. According
to Andrus (1993), a study conducted in Oregon in 1993, established thermographs
90, 180 and 360m downstream in shaded reaches. Results determined that water
temperatures within cutblocks were 1-5oF higher than expected under
undisturbed canopies. These temperatures decreased as they flowed through
undisturbed downstream areas on four of six reaches. Recovery of increased temperatures
occurred at its greatest rate in the first 180m down stream (Robison et al.1999).
In a study conducted within the Brush
Creek watershed, Robison et al. (1999), found that temperatures
increased 3.8oC after flowing through a clearcut (no streamside
vegetation) due to increased exposure to solar radiation. Temperatures
recovered to within 0.3oC after flowing through 834ft (254m) of
unaltered canopy cover. This recovery is attributed to groundwater
exchange and mixing. Robison et al. (1999) suggests this recovery is
site specific and would depend on the presence of well-connected terraces as
those streams that flow over bedrock would be influenced little by groundwater
and recovery would not be as quick. Influxes of groundwater into the stream channel
can aid in regulating temperature fluctuations, providing thermal stability
(Poole et al. 2001).
Hornbeck
and Kochenderfer (2000) also found that once stream areas are again shaded by
shrubs and regrowing trees, stream temperatures decrease and exhibit fairly
uniform annual and seasonal variations through the remaining successional
stages, or until another disturbance reduces or eliminates streamside shade.
Another reason for variations in recovery period
are heat losses to the air within the surrounding riparian areas. Robison et
al. (1999) suggests losses to air would be insignificant as peak
temperatures in riparian areas are often hotter than the heated stream
temperatures. Based on studies conducted by Robison et al. (1999), is
was determined that the rate of recovery ranged form 0.9-2.1oC per
300m of streams and all seven streams recovered to temperatures of 17.8oC
(64oF) within 150-360m downstream of clearcuts. 17.8oC
(64oF) is the maximum temperature allowed following harvesting in
non-fish bearing streams within Oregon.
A study on stream temperature responses to forest
harvest conducted in the western Cascades, Oregon, also found that temperatures
increase following vegetation removal (Johnson and Jones 2000). According to
Johnson and Jones (2000) similar temperatures (summer maximum 23.9oC)
were found for clearcut and partial cutting treatments for 16 years following
harvesting. Unharvested stream temperatures showed a mean summer maximum temperature
of 16.7oC. Temperatures within the first four years after clear
cutting and patch cuts were 5.4-6.4oC and 1.6-2.0oC
greater than the control.
According to Story and Moore (2002), who conducted
research on stream temperature recovery in the Stuart-Takla Fish-Forestry
Interaction Project in British Columbia�s central interior, determined that
stream temperatures showed recovery of temperature within 200m of entering
undisturbed vegetation. Temperatures increased an average of 4-5oC
after flowing into the partial clearcut. Streams not only showed a recovery but
in some instances temperatures returned to temperatures lower than preheated
levels. They suggest groundwater mixing, bed infiltration of heated water and
heat exchange with cool canopy cover in afternoons and evenings as reasons for
temperature recovery but suggest that these attributes are highly variable in
time and space, but do suggest harvesting in headwater streams may be of little
importance to cumulative down stream effects.
While it appears that thermal recovery not uncommon
following harvesting, the debate on recovery times is complex. Recovery time is
varied by the amount of downstream dissipation that occurs with the distance
required to dissipate heat gains being site specific and dependent on the
interactions of the following attributes; topographic shade, upland vegetation,
precipitation, air temperature, wind speed, angle of radiation, cloud cover,
relative humidity, groundwater temperature and discharge and tributary temperature
and discharge (Poole et al. 2001).
2.3.9 Microclimate
Due to the complexity of plant life, riparian
ecosystems provide dense vegetation that blocks direct radiation from
penetrating the floor of the riparian area. This shields direct sunlight and
aids in maintaining a constant temperature within the understory (Mellina et
al. 2002, Knutson and Naef 1997). This in turn ensures that soil
temperature and moisture levels are regulated to provide a moist cool
environment for amphibians, ungulates and other large mammal species (Knutson
and Naef 1997) while producing lush overhanging vegetation that further helps
maintain water temperatures (Mellina et al. 2002, MOF1998a).
The Itcha-Ilgachuz Alternative Silvicultural systems project,
conducted in the MS zone of the Cariboo Forest Region, British Columbia
evaluated the effects on microclimate following various harvesting regimes (MOF
2001a). The harvesting regimes included; group shelterwood system at 50%
removal (20-30m dia. openings), clearcut and controls. The study determined
that clearcut microclimates had a greater proportion (49%) of nights below 0oC
compared to partial cutting at 37%. Frost also occurred 18% of the nights in
clearcuts compared to 5% in the partial cutting treatments. Summer temperatures
were also warmer within clearcuts but edges showed a 1-2oC decrease
than the center of openings. All results suggest greater winter characteristics
within clearcuts can be detrimental to seedlings. However, greater shading may
mean reduced growth in partial cutting as opposed to clearcuts during the
growing season.
A similar study on the effects of opening size on
microclimate determined that only minor temperature changes occurred between
opening sizes except that larger openings tended to be 1-2oC warmer
than smaller opening at a soil depth of 15cm (MOF 1997). Similar results
were also found by Johnson and Jones (2000) in which temperature under forest
canopy was determined to be 5oC lower than those found within forest
gaps. This suggests that larger opening sizes are prone to greater soil
temperatures, increased growing degree-days and therefore larger openings would
become snow free earlier in the season and increase the growing season (MOF
1997).
Hagan and Whitman (2000) conducted studies on
microclimate by comparing temperatures with a 22m buffer strip adjacent to a
clearcut and an undisturbed site. They determined that daily average
temperatures were 5-10oF in clearcuts compared to intact forests.
However they determined that air temperatures dropped dramatically just within
riparian buffer edge. Temperatures within the buffer strip were <2oF
higher than temperatures of intact forests. Based on their results it appears
that buffer strips of 22m are capable of maintaining microclimate similar to
undisturbed forest.
2.3.10 Soils
Soil is a very integral component of the forested and
riparian ecosystems for the many functions in which it provides. Soil provides
gases, moisture, nutrients and a rooting medium while providing filtered water
to aquatic systems (Sutherland 2003). Maintaining the integrity of soils is
crucial to ensure proper functioning, as damaged soils can take many years to
return to their pre-disturbed state. The major components of soils include mineral
and organic particles that are surrounded by pore spaces containing either
water or air (Sutherland 2003). It is the texture and moisture content of
these components that determine how severe the degradation from harvesting may
be (MacDonald 1999).
Harvesting practices can degrade soil through;
compaction and puddling, displacement, surface soil erosion, and mass wasting.
The two most important forms of degradation of forest soils are through
compaction and rutting (Sutherland 2003, Grace and Carter 2000). Compaction
occurs when forest machinery compresses the soil beyond its ability to resist
the load pressure. Different sites vary in their ability to resist disturbance
based on terrain, slope, climate, hydrology, and soil horizons, texture and
depth. When compaction occurs in can increase bulk density, convert macropores
to micropores, and reduce the infiltration capacity (Keppeler and Ziemer 1990).
While compaction can reduce infiltration rates,
scarification of the forest floor through skidding and machine travel can
remove surface materials allowing for better infiltration and reduced surface
runoff (Grace and Carter 2000). However, Grace and Carter (2000) also suggest
that this scarification can lead to increased erosion due to rain splash and surface
runoff during higher period of precipitation.
The main practice to limit soil degradation is to
limit the amount and timing of travel on soils. The chances of degradation are
determined by assessing the hazards to determine how sensitive the site is to
soil disturbances (MacDonald 1999). Seasonal logging can also limit the amount
of soil disturbance as a thin snow crust or deep snow can protect the ground
from compaction and other adverse affects (MacDonald 1999).
Due to the impacts of harvesting on soils, research
has been conducted into how different silvicultural systems can mitigate
detrimental impacts. The Date Creek study conducted trials to determine site
disturbances from harvesting. Treatments consisted of no harvest, light harvest
(30% removal of volume in either single tree or group selection), heavy removal
(60% removal of volume as irregular shelterwood) and clear cutting in which all
merchantable timber was removed (Coates et al. 1997). Site disturbance
was determined to be consistent between treatments with approximately 10% of
disturbance being compacted soils with 50% of that being less than 10cm. Soil
bulk density was also consistent between treatments at an increase of 10% from
that of undisturbed sites. Soil surface conditions were considered
undisturbed for 80.4% of the clearcut treatment, 79.4% for shelterwood, 79.3%
of patch cut and 75.5% for the green tree treatment. In all treatments the
majority of site disturbance was through excavator tracks. The treatment of
shelterwood left the largest woody debris with the small dimensions of woody
debris being left in the patch cut. Road densities were found to be at 6.3 %
within the treatment areas, similar to the control cutblock with 6.5%.
Conventional hand falling and processing with line
skidders (Clarke 664) was compared to that of a mechanical feller-buncher
(tracked Cat 325)/grapple skidder (John Deere 748G) harvesting system. On an
area basis the impacts of both systems showed similar disturbances of 51%, with
the mechanical system being slightly higher in rutting depths and compacted
bulk densities at a depth of 200-300mm. Overall both treatments showed that
increases to bulk density were non-detrimental to the majority of the
area. Excessive compaction and puddling was noted on both sites within
wetter areas (Wulfsohn et al. 1999).
Research has also been conducted within the Roberts
Creek Study Forest, north of Vancouver. Research was conducted in two phases.
Phase one occurred between March 1996 and April 1997. Silvicultural treatments
included; clearcut with reserves (1 tree per ha), dispersed retention of
Douglas-fir and red cedar (95 per ha) and removal of trees (11% of stand
volume) in narrow parallel corridors. Phase two occurred between the fall of
1998 and summer of 1999. Silvicultural systems included; variable retention,
retaining trees both in groups and individually, strip shelterwood removing
trees in strips between 50 and 100 meters in width and removal of trees (18% of
stand volume) in narrow parallel corridors. Results showed that soil
disturbance from hand falling and cable yarding was low between all harvested
blocks. But that the clearcut of phase 1 showed slightly high ground
disturbance than the dispersed retention treatment (D�Anjou 2002)
2.3.11 Sedimentation
A study conducted by Kreutzweiser and Capell (2001),
looked at the impacts of different silvicultural treatments to determine their
effects on fine sediment deposition. The three treatments included;
selection-cut of 40% removal, shelterwood-cut of 50% removal and diameter-limit
cut of 85% removal. Kreutzweiser and Capell (2001) determined post-sediment
increases following logging, they were, 435.3 g/m2 (selection
harvest treatment), 99.9 g/m2 (shelterwood) and 477.0 g/m2
(diameter limit harvest). While sediment increases appear to be very high for
the selection harvest treatment it was determined that most of the increase was
due to the construction of secondary roads and not the disturbance caused be
the treatment itself. Kreutzweiser and Capell (2001) therefore suggest that the
greatest sediment increase was attributed to high ground disturbance and
rutting due to skidder activities within the riparian areas of the diameter
limit treatment.
Kreutzweiser and Capell (2001), also determined that
the felling, delimbing, and skidding activities within the shelterwood could be
done up to the edges of the stream without impacting sediment load. They
therefore suggest that riparian buffer strips are not required for select
harvesting of up to 50% in regards to sediment increases.
In a study conducted by Grace and Carter (2000), an
Alabama stream was monitored to determine the effects of clear cutting on
surface runoff and sedimentation supply. They determined that sediment production
was higher for the treatment area than for undisturbed controls. Harvesting
accounted for an average 360% increase in sediment within treatment areas (0.14
tons/ha compared to 0.03 tons/ha). Runoff was determined also to be greatest
for the harvested area in 14 of 17 sampling events. The mean runoff yield
increased from 2.1mm to 6.3mm following harvesting, with some increases being
as high as 1200%.
2.3.12 Large Woody Debris
(LWD)
Large woody debris (LWD), log pieces that are >10cm
in diameter and >1m in length, are an important attribute to the proper
functioning of a riparian area as they contribute to alterations in channel
morphology and are an important component of aquatic ecology (Lassettre and
Harris 2001, Belt and O�Laughlin 1994, Beschta and Platt 1986). LWD is of great
importance as it represents centers for biological interaction and energy
exchange (Arsenault 2002). LWD is introduced to streams through blowdown, stem
snapping, bank erosion and landslides (Millard 2001). This LWD tends to
obstruct the stream channel as �log jams� and trap sediment that provides
habitat for macroinvertebrates and fish (MSRM 2002, Moore 1997) and promotes
natural tree regeneration through nurse logs (Arsenault 2002, Lassettre and
Harris 2001). Smaller headwater streams are generally characteristic of
providing a large portion of LWD that can settle within the stream and provide
stability and prevent erosion.
Current legislation that allows clear cutting to the
banks of S5 and S6 streams may promote an increase in the amount of LWD
entering the system in coastal streams (Millard 2001). However, studies on
woody debris determined that logging slash might not necessarily be transported
out of a particular reach. The transport of LWD is dependent on the transportability
of the stream compared to the resistance of debris to transport and Millard�s
(2001) results on a study of 42 streams in the Anderson River watershed of
British Columbia suggest that lower gradient streams may transport greater
amounts of LWD as they are smoother and have less form and are less likely to
encounter resistance.
With the majority of streams in British Columbia�s
interior being lower gradient streams, LWD is therefore more likely to be
transported downstream and alter fish habitat in a detrimental way through
scarification and sedimentation. Clear cutting adjacent to smaller interior
streams may therefore not provide similar amounts of LWD that is seen in steep
coastal streams. When LWD are reduced though clear cutting and downstream
transport, low instream recruitment of the wood can create a greater chance of
erosion and sediment transport (Lassettre and Harris 2001) along with
disrupting the habitat of instream organisms such as amphibians and
invertebrates. Large woody debris that fall within riparian areas but outside
the stream channel also provide habitat for species of small mammals, including
bats (MSRM 2002), while providing soil-moisture retention, soil stability,
contributing to soil structure and nutrient pools (Arsenault 2002). Clear
cutting is also thought to place LWD and wildlife trees below levels that would
naturally be found within ecosystems (Gyug 2002). Therefore due to the value of
small streams to the recruitment of LWD, management strategies that are based on
stream size alone may not meet the best riparian management
objectives.
Buffer strips have also been shown to have an equal
proportion of LWD to those of unharvested riparian areas and have recruitment
levels equal to natural levels in undisturbed forests (Hayes et al.
1996). Conifers are also the dominant form of structure for pools as smaller
deciduous species are prone to higher decay rates and downstream transport
(Hayes et al. 1996).
Research conducted by Hogan (2002) on the
relationships of LWD, channel morphology and watershed management determined
that the volume of LWD supply was dependent on biogeoclimatic zone. However,
Hogan (2002) found that the proportion and spacing of LWD stored in logjams was
similar within all biogeoclimatic zones. This suggests that logjams are not
affected by stream size but rather accumulation of LWD at log jams due to
different rates of input.
2.3.13 Windthrow
The success of silvicultural treatments is directly
dependant on how much of the stand is subject to windthrow following harvesting
(Whitaker and Montevecchi 1999, Coates 1997). There are many factors that
affect the success of different harvesting regimes. They can include; stand
characteristics such as age, species and dimensions, stand history in regards
to fire and harvesting, site condition and climate and wind conditions (Coates
1997, Moore 1977, Stathers et al. 1994). The amount of timber lost to
blow down is very important to the forest industry as it diminishes the
availability of timber for harvest and if salvaged, can be expensive and often
dangerous to retrieve (Moore 1977).
According to Huggard et al. (1999), there are
two mechanisms of wind condition that lead to windthrow; direct blow down by
strong winds and structural failure due to harmonic oscillations generated by
moderate wind speeds. They suggest that trees next to large openings are
subject to sudden strong direct winds and are therefore blown over directly,
while trees within small opening or individual tree selection areas will be
more prone to structural failure from moderate winds. It therefore appears that
in areas of strong short duration winds, uniform and small openings may be a
more appropriate management technique. However, success of silvicultural
treatments is site specific in regards to windthrow.
While it appears that wind can a be a primary
determinant of windthrow, Moore (1977) suggests that wind alone is not the
cause of blowdown but rather the interactions of location, local climate, aspect
and slope, soil depth and texture, species composition and rooting and stream
characteristics.
Windthrow within five treatments were monitored within
the Sicamous Creek area of British Columbia. Treatments included; 10ha
clearcuts, 1ha patch cuts, 0.1ha patch cuts, individual tree selection and
undisturbed controls (Huggard et al. 1999). The four cutting
treatments were all conducted to remove 33% of the timber volume. Huggard et
al. (1999) determined that harvesting significantly increased the
occurrence of windthrow in comparison to uncut controls following a 2.7 year
post monitoring period. A greater portion of windthrow occurred in the
individual tree selection treatment due to the increased exposure of residual
stand and reduced crown contact. However, windthrow within all systems was
determined to be equivalent in volume but variable in distribution. They
suggest that the overall distribution of windthrow within the individual tree
selection may be more beneficial for a wider array of organisms than areas of
concentrated windthrow, although salvage operations may be more appropriate for
dense piles near the edge of clearcuts (Huggard et al. 1999).
Similar analysis on the effects of harvesting was
conducted at Date Creek in northwestern British Columbia. Windthrow damage was
assessed following two partial cutting treatments, 30% (light) and 60% (heavy)
volume removal through single tree harvesting and group selections up to 0.5ha
(Coates 1997). Coates� (1997) results determined that windthrow within the
partial cutting areas were 2.2%, 1.1% higher than unlogged areas. Results
suggest little difference in windthrow between light and heavy treatments.
Windthrow of the light and heavy treatments was
primarily due to the uprooting of trees, accounting for 84.4%. This is due to
direct blowdown as suggested by Huggard et al. (1999). Stem snapping
accounted for 15.6% of windthrow (Coates 1997), which would be due to the
harmonic oscillations of moderate winds (Huggard et al. 1999). Coates
(1997) suggests that partial cutting with a windthrow rate of less than 10% is
successful and that as a stand matures it becomes more susceptible to windthrow
due to increased levels of decay.
In another study based on a review of buffer strips in
59 Vancouver Island watersheds, Moore (1977) found that blowdown may be
attributed to other factors than just the sudden exposure to wind following
harvesting. Moore (1977) and Stathers et al. (1994) suggest that
following harvesting, wind velocities also increase and create greater
turbulence due to reduced friction in surrounding clearcuts and are therefore
not only subject to increased exposure to wind but also to other increases in
wind characteristics. Moore (1977) also suggests that precipitation and soils
impact the susceptibility of windthrow. He suggests that heavy rainfall can
reduce holding strength due to saturated soils and that roots within finer
textured soils are shallower and more prone to blowdown.
In a study conducted within the Blackbear Creek
drainage, British Columbia that included small (0.03ha), medium (0.13ha), large
(1.0ha) and an uncut control determined windthrow to be greatest in large areas
followed by medium, small and uncut treatments. Percentage of blow down was
determined to be 4.2, 4.1, 3.2 and 2.6%, respectively (MOF 1997).
Beese (2001) conducted studies within the
Montane Alternative Silvicultural systems to evaluate wind damage under
clearcut (69ha), patch cut (1.5ha), green tree retention (25sph) and
shelterwood systems (70%basal area removal) for montane coastal B.C. forests
for six years following harvesting. He determined that green tree retention
windthrow totalled 29% of leave trees (8sph).Shelterwood that retained 25%
basal area showed the greatest number of blowdown at 10% (21sph). Edge trees of
all treatments were less impacted by windthrow within the patch cuts. Patch cut
and clearcut lost 6 and 9sph respectively.
Rollerson and McGourlick (2001), who conducted surveys
on windthrow within 58 buffer strips on Vancouver Island, determined that on
average 21% of the strip was subject to blowdown and found the average distance
of penetration into the buffer to be 12 meters. They suggest that
two-sided buffer strips are about 100% more vulnerable than one-sided strips
and the penetration of windthrow is about 24meters. However, their study
suggests that buffer strips that are feathered are subjected to the least
windthrow (7%) and that the untreated buffer showed an 18% windthrow
rate. They suggest that these feathered strips are less susceptible as
they have had the most vulnerable trees removed around the edges, in contrast
to uniform cutting or the retention of small trees. Their research also
suggests that increases in buffer width decrease windthrow rates up to a
maximum of 25-30m buffer width for one-sided buffers and up to 40m for
two-sided buffers.
According to Knutson and Naef (1997), the Washington
Department of Fish and Wildlife suggests adding 30 m to the outer edge of the
windward side of riparian buffer strips where there is high blowdown potential.
Stathers et al. (1994) also suggests many techniques that can be
employed to mitigate the effects of windthrow following harvesting. They
include:
�
Edge feathering can be used to reduce the drag force on boundary trees.
Trees within the edge buffer should be removed in the following order of
preference:
1.
Unsound trees, especially if they have a large crown. These include
diseased, deformed, forked, scarred, mistletoe infested, and root rot infested
trees.
2.
Trees with asymmetric or stilt roots.
3.
Trees growing on unstable substrates, e.g., rocky knolls, large
boulders, nurse logs, poorly drained depressions.
4.
Tall non-veteran trees, especially with the above features or with
disproportionately large crowns.
� Residual trees
should be left in the following order of preference:
1. Sound, well-rooted veterans (e.g. snag-top cedars)
or deciduous trees.
2. Sound trees (strong roots and good
taper) with relatively small, open crowns.
3. Sound snags, when safety is not compromised.
�
Stem removal should not exceed 15-20% of the trees in a strip 20-30 m in
from the edge of the stand.
�
Excessive thinning will increase windthrow susceptibility. Edge thinning
is not recommended in single-storied, high-density stands.
�
Topping and/or pruning (delimbing) of vulnerable trees along opening
boundaries may be necessary to protect and maintain critical areas such as
streamside buffers, ungulate ranges, forage areas, and other critical wildlife
habitat.
�
Reducing the crown by 20-30% appears to be adequate to reduce the risk
of windthrow for most trees.
(Stathers et al. 1994)
2.3.14 Effects of Cattle
Grazing
Within
British Columbia, eighty percent of all grazing lands are forested rangeland
owned by the crown. It is this forested rangeland that provides the forage base
of grasses and forbs that is consumed by cattle and desired by the livestock
industry. Riparian areas are a very important source of forage production
within these forested rangelands (Powell et al. 2000). Similar to a
variety of wildlife species, cattle tend to congregate in riparian areas
(Belsky et al.1999). There are many reasons for this attraction. They
can include the lush vegetation and grass species for food sources, shade and
water availability (Hennan 1998). However, the presence of cattle within
riparian areas can cause adverse affects on the riparian system. They can
reduce bank slope and stability, reduce vegetation cover, alter stream channel
characteristics, effect plant community structure (Powell et al. 2000)
and water quality and quantity (Knutson and Naef 1997).
Cattle
grazing can also cause many other alterations to riparian areas that may
include;
�
Reduction or elimination of the regeneration of woody vegetation.
�
Alteration of plant species composition (e.g., xeric species and highly competitive
exotic species invade, perennials are replaced by annuals, and
trees/willows/sedges are replaced by brush and bare soil).
�
Reduction on overall riparian vegetation.
�
Reduction in overall plant vigor.
�
Bank and instream deformation and erosion from loss of protective
vegetation, and increases soil compaction and churning by hoof action, which
lead to reduced water quality and changes in bank and channel integrity.
�
Stream channel widening, shallowing, trenching, or braiding because of
increased stream bank erosion.
�
Inability of riparian habitat to trap and filter sediments and
pollutants, leading to increased sedimentation and pollution from fecal matter
of livestock.
�
Increased stream temperatures as a result of lost cover provided by both
woody and herbaceous plants.
�
Loss of nutrient inputs, especially invertebrate food sources, to
streams.
�
Decrease in water table, with subsequent loss of riparian vegetation and
stream flow.
�
Increased magnitude of high and low stream flow events.
�
Reduction in shrub and ground-nesting habitat for songbirds and other
wildlife.
�
Declines of amphibians, small mammals, and other ground-dwelling animals
that need herbaceous and woody vegetation for food and cover.
�
Increased songbird nest predation and brown-headed cowbird parasitism
due to loss of shielding vegetation.
�
Loss of structural and compositional diversity of plant communities,
thereby reducing overall wildlife diversity.
�
Reduction of forage available for wild ungulates and other herbivores.
(Knutson and Naef 1997)
In
British Columbia, riparian health is assessed based on its characteristics of
�proper functioning condition�. Proper functioning condition (PFC) refers to
the ability of the riparian area to filter runoff, store and safely release
water, and its ability to withstand normal peak flood events without
experiencing accelerated soil loss, channel movement, or bank movement (FPB
2002). If a riparian area lacks one of these attributes it is considered to be
either �at risk� or �non-functional� due to its inability to perform certain
functions to the functioning of riparian areas.
The
FPB (2002), assessed 341 sites subject to cattle grazing within the Kamloops,
Penticton, Horsefly and Cranbrook Forest Districts to assess their condition.
The assessment consisted of 204 streams and 187 wetlands, with the majority of
sites being found within the IDF and MS biogeoclimatic zones. Methods included
an assessment of 10 riparian characteristics along 100m transects rather than
the standard PFC checklist used by MOF. Results showed that approximately 12%
of riparian areas are subject to extensive cattle use with other areas
being lightly utilized. FPB (2002) determined that 71% of riparian areas are
considered to be properly functioning, while at risk sites and non-functioning
riparian areas were determined to be 16 and 13%, respectively. However it
should be noted that the somewhat drier zones of the province such as the IDF
and MS had a higher proportion (30-40%) of at risk and non-functioning riparian
areas. The Kamloops Forest District also showed higher proportions of
non-functioning areas than the average for all four districts.
Cattle
can alter soils within riparian areas through compaction (Belsky et al.1999).
According to Krzic et al. (1999) and Newman et al. (1999), this
compaction can alter the penetration resistance of soils and increase soil bulk
density. This increased penetration resistance can create hydrophobicity of the
soil and surface ponding thus causing conifers to become water deprived
underground while their root collar is submersed in water. However, while
Newman et al.�s (1999) studies showed changes in compaction and bulk
density are higher on grazed sites they noted that these increases are far
below any limiting threshold for conifer root growth.
In
similar studies near Tunkwa Lake, British Columbia, Bromersma et al. (2000),
determined that a one-month stocking rate of 0.69AUM/ha was not a sufficient
enough grazing pressure to significantly alter the soil bulk density of the
study sites. However, they did determine that over an eight-year monitoring
period, soil bulk density did increase 6% when compared to control exclosures.
Soil penetration resistance was increased over most of the soil profile
following the eight years of grazing, thus indicating a greater availability of
rain water for plant growth on ungrazed sites compared to exclosures. Again
there results suggest that soil penetration resistance was above thresholds to
be considered root restricting.
Belsky
et al. (1999) review of literature on cattle grazing in riparian areas
found that a major concern is that upland riparian vegetation is removed
through livestock while areas adjacent to streams are compacted thus
interrupting the infiltration of rainwater.
There are numerous ways to mitigate any detrimental
effects that cattle may have on riparian areas. These include; increasing the
density and cover percentage of riparian vegetation and promoting plants to
maintain root systems thus stabilizing stream banks and reducing sediments
(McInnis 1996).
Improper
management of livestock grazing in riparian habitat is likely to have
significant negative consequences for fish and wildlife (Knutson and Naef
1997). Riparian areas are site specific and therefore no one cattle grazing
strategy will work for all sites. According to Knutson and Naef (1997) the proper
implementation of a grazing strategy will; 1) incorporate sufficient rest
periods to allow plant regrowth, vigor, and energy storage; 2) retain
sufficient vegetation during high flow periods to protect stream banks,
dissipate stream energy, and trap sediments; and 3) control grazing times and
intensity to prevent damage to stream banks from trampling and over-utilization
of vegetation.
Kauffman
and Krueger (1994) also suggest that well-supervised grazing management within
riparian areas, when used in conjunction with resting and restoration of
severely damaged areas, can result in decreased stream bank erosion and
floodplain losses, increased forage production for both livestock and wildlife,
and increases in fish and wildlife resources.
2.4
First Nations Values
Forest
management is slowly recognizing the values of forests for their non-timber
resources and uses. These non-timber values are therefore now considered part
of integrated forest management (Kulshreshtha 1995). Timber resources are continually
competed for as they provide an array of monetary values as well as biological,
spiritual and cultural values. It is therefore imperative to evaluate the cost
and benefits to each user of forest resources. Economic values can be in terms
of production, consumption or exchange of goods (Kulshreshtha 1995). Timber
uses of forest resources can include woodlands operations, logging activities
and primary and secondary wood processing. The non-timber uses of forested
resources can include grazing activity, collection of specialty forest products
and the production of vegetative foods (Kulshreshtha 1995), as well as
spiritual and cultural values.
British
Columbia First Nations place high values on forested ecosystems for reasons
other than timber values. Non-timber values that are important to First Nations
groups are those that are related to their spiritual and ceremonial values,
fisheries, plant and riparian values, and wildlife values. Wildlife values can
include sustenance while plant values can include those for food, building
materials, medicinal, technological, spiritual and ceremonial uses (Moore
2001).
The
tie with nature is pronounced in their ceremonial process that is conducted
prior to harvesting non-timber products such as forage plants (Blackstock 2002,
Teit and Steedman 1930). The spiritual value of plants is therefore evident as
they have been used indiscriminately and it is believed that nature�s resources
represent a spiritual power that can adversely affect their lives if not treated
with respect. It is evident that there is spiritual value in plants species
through the eyes of first nations people. It is this connection of different
values that makes it difficult for indigenous peoples to separate culture,
language and spirituality from the land base (Fortier 2002).
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