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C.V
Forest
Development
Research
PROGRAM
Manning Diversified Forest Products Research Trust Fund MDFP 7/95
Effects of Natural and Clearcut Disturbances on Small Mammal and Bird Diversity in Conifer Dominated Boreal Forest
/dbertci
ENVIRONMENTAL PROTECTION
Manning Diversified Forest Products Research Trust Fund MDFP 7/95
Effects of Natural and Clearcut Disturbances on Small Mammal and Bird Diversity in Conifer Dominated Boreal Forest
Project Update 1996/97
April 1997
By Lisa Verbisky and Ainsly Sykes University of Alberta Edmonton, Alberta Canada
Pub. No. T/387 ISBN: 0-7732-9993-9
- Disclaimer -
The study on which this report is based was funded by the Manning Diversified Forest Products Research Trust Fund (MDFP) which is a component of Alberta's Environmental Protection and Enhancement Fund (EPEF). The views, statements and conclusions expressed, and the recommendations made in this report are entirely those of the author(s) and should not be construed as the statements conclusions, or opinions of members of the Manning Diversified Forest Products Research Trust Fund or of the Government of Alberta and its EPE Fund.
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https://archive.org/details/effectsofnatural1996verb
Effects of Natural and Clearcut Disturbance on Small Mammal and Bird Diversity in Three Age Classes of Conifer Dominated Boreal Mixedwood Forest
- Progress Report - March 31, 1997
by
Lisa Verbisky and Ainsley Sykes
Summary
Data was collected during the 1996 field season, but due to a lack of funding, we were unable to sample for small mammal abundance and species richness. The $25,000 from the 1996 Manning Diversified Trust Fund went towards technician salaries. This report includes analysis of 1996 data and preliminary discussion of results. Funding has been secured for the 1997 field season and thus sampling will begin in late April to early May. Data collection will continue as per the 1996 field season, but will also include sampling for small mammals.
I) Rationale
Disturbance is a natural part of the boreal forest and plays an important role in determining ecosystem structure, composition and function (DesGranges and Rondeau 1992). Variation in disturbance size, intensity and frequency creates a mosaic of habitats which supports a variety of wildlife (Telfer 1992). -Before fire suppression, the boreal forest was dominated by a fire- disturbance regime to which each species is adapted (Wein 1991; Telfer 1992). Presently, large sectors of Alberta's boreal forest are subjected to large scale timber harvesting. Fire suppression and clearcut harvesting practices are changing the type of disturbance dominating the landscape. The effect on wildlife and vegetation diversity is not known.
To reduce potential changes in biodiversity arising from timber harvesting, it has been proposed that forest companies use harvest techniques that mimic natural disturbance processes (Titterington et al. 1979; DesGranges and Rondeau 1992; Hunter 1993, Thompson 1992). Both fires and harvesting alter stand structure and composition (DesGranges & Rondeau 1 992), but it is not known whether structural and compositional differences exist between these two disturbance regimes and, if extant, how they may affect wildlife.
In past studies, effects of clearcutting have been compared to undisturbed forests. Not surprisingly, vast differences in vegetation and wildlife diversity were found between clearcut disturbed and undisturbed forests. Studies investigating the effects of clearcut harvesting on wildlife communities found that after harvesting, the number and species richness of birds increases over time and often will increase to levels higher than in mature forests (Kavanagh et al. 1985; DesGranges & Rondeau 1992). In a study on small mammals, Kirkland (1977) found that in coniferous forests, clearcut harvesting initially resulted in an increase in abundance, diversity, and density of small mammals, followed by a decrease with succession. Although Ramirez and Homocker (1981) stated that timber harvesting may simulate fires by providing a
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variety of habitats for small mammals as succession occurs, their failure to actually compare harvest and bum sites renders this conclusion speculative.
Fox (1983) reviewed a number of papers on post- fire succession of wildlife communities for North American boreal forests. Under this disturbance regime, he also found an increasing trend in bird species diversity and richness with succession to a mature forest stage. Numbers of birds increased to the shrub stage to levels higher than mature forests, but were lower in the sapling stages. After fire disturbance, small mammal abundance was greatest in the early stages of succession relative to mature forest, but was lower in the shrub and sapling stages.
Thus, based on previous, although separate, investigations, there appear to be few differences in the patterns of abundance and diversity of birds and small mammals on harvest versus fire disturbed sites. To confirm this, biodiversity studies must incorporate comparisons of vegetation and wildlife abundance in burned and logged sites to determine if the use of harvest techniques to mimic natural disturbance processes is a sound approach to sustaining biodiversity. Indeed, Thompson (1992) states that "the most important research priority in forest/wildlife is... is the biodiversity associated with post-logging forest the same as would be expected under a natural disturbance regime?" and advocates further investigation into succession after fires. The purpose of this study is to determine any differences in wildlife and vegetation diversity between harvest and fire disturbed sites in spruce dominated mixedwood forest in order to make recommendations to forest companies to maintain vegetation and wildlife diversity.
II) Objectives
1 ) Identify any vegetation variables that distinguish clearcut and fire disturbed sites in three age classes of white spruce dominated boreal forest.
2) Compare relative abundance, species richness and species composition of birds and small mammals in three age classes of clearcut and fire disturbed sites of white spruce dominated boreal forest.
Ill) Experimental Design and Methods
1) Study Area and Layout
This study is being conducted in harvest and fire disturbed sites in three age classes of white spruce dominated boreal forest. The study area (47 km2) is located in the region northwest of the town of Manning (58°, 1 17°), 92 km north of Peace River, Alberta, Canada (Figure 1).
Three age classes of bums and cutblocks were selected; 3 years, 16 years, and 27 years.
The design consists of a total of 24 sites with four bum and four cutblock sites within each age class (Figure 2). Three age classes were chosen in order to determine if convergence in vegetation and wildlife occurs between fire and clearcut disturbed sites over time, but each age class has its own reason for being selected. The three year age class was chosen to determine what occurs immediately after disturbance. The 16 year age class was selected because at approximately this age, coniferous trees have reached a height of 3.0 m when logging companies can harvest adjacent leaves in a two pass system (Alberta Environmental Protection 1994). The
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Figure 1 . Location of study sites. All bum and harvest sites are located within the Manning Ranger District.
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A) Fire disturbed Sites
B) Harvest disturbed sites
1993
1980
1969
Figure 2. Schematic diagram of harvest and bum sites selected for study in each of three age classes (n=4). A) Bum sites and B) cutblocks selected for sampling. Multiple sites were located on large bums. Dates indicate origin year of disturbance.
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27 year age class was chosen for two reasons. We believe convergence between fire and harvest disturbed sites may have occurred by this age and it is the earliest date at which clearcut harvesting replaced selective logging in this area (Pers. Comm.).
Harvest strategies in this region target old stands, use a 1 10 year rotation age and use clearcutting as the primary method of harvesting. Harvesting typically follows a two pass cutting regime resulting in an orthogonal patchwork of cut and uncut blocks (Alberta Environmental Protection 1994). The mean cutblock size harvested by Manning Diversified Forest Products (MDFP) in 1994/95 was 9.3 ha and in 1995/96 will be 17.4 ha. Cutblocks are generally harvested in the winter and scarified and replanted in the summer months. For our sampling purposes, harvest sites between 14.7 and 31.2 ha situated on the edge of a cut/leave pattern were chosen. This layout represents realistic past and future harvesting practices, yet reduces the influence of nearby cutblocks. In order to be considered part of a cut/leave pattern, a cutblock had to be located within 1000 m of another cutblock on one side, but have sufficient forested landscape between to allow for further harvesting. The remaining three sides of the cutblock had to be adjacent to a minimum of 1000 m of undisturbed landscape. To ensure independence, sample sites had to be a minimum of 1000 m apart.
Even before effective fire suppression was implemented in northern Alberta in the early 1 980's, small fires largely dominated the fire disturbance regime in Alberta (Murphy 1985). In the Peace River Forest District, which encompasses the study area, 87 % of all fires between 1960 and 1980 were less than 40.0 ha in size (determined from fire records obtained from the Provincial Forest Fire Centre). Small fire disturbances best represent the predominant fire regime in our study area. Due to difficulties in accurately locating and accessing small fire disturbances, 15 ha sites will be selected in fingers of larger bums for each age class. Fingers were defined as having three edges adjacent to 1000 m of undisturbed landscape. Bum sites located in fingers of larger fires most closely represent a small fire disturbance.
Although fires cross all vegetation boundaries (Sousa 1984), only fingers that were previously merchantable timber (large diamter white spruce dominated, aspen/white spruce mix or white spruce/pine mix) were selected for study. Using sites with similar pre-disturbance vegetation will allow for meaningful comparisons between fire and harvest disturbed sites, particularly for comparison of vegetation variables. As for cutblock sites, bum sites had to be a minimum of 1000 m apart to ensure independence.
METHODS:
1) Avian Census
Avian species richness and relative abundance were sampled using the point-count technique (Ralph et. al. 1993). Two census stations were located in each cutblock and bum site; the stations were located 250 m apart to minimize double-counting individuals. All stations were positioned a minimum of 100 m from the stand edge to avoid counting individuals residing in the undisturbed forest effects (Hansson 1983). Each station was visited 3 times in 1996. Censuses were conducted from sunrise until 10:00 am from late May to early July (peak breeding season). Birds were recorded within and beyond 50 m of the observer for a period of 5 minutes. At least one singing male had to be recorded over the three point counts for the species to be recorded as present in a stand. Species richness was recorded as the total number of different species present.
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The census with the highest number of a species was used to represent the abundance of that species.
Species richness and abundance, both within and beyond 50 m, were calculated for each census station. In addition, the total species richness and abundance (regardless of distance) were calculated for each census station. Kruskal- Wallis analyses were performed on these species richness and abundance at each census station to compare between clearcuts and bums within each age group.
2) Vegetation Sampling Down Woody Material
Down woody material was divided into three groups for sampling based on diameter of material; down woody material <5 cm (DWM<5), >5 cm (DWM>5), and >10 cm (DWM >10). DWM<5 and DWM>5 were sampled along lm transect lines. Frequency was recorded for both size classes. For DWM >10, frequency was sampled along 5 m transects and diameter, length and decay class was recorded for each log. For all three size classes, the number of transects varied among stand types and age classes in order to accommodate different vegetation types.
Live Trees and Snags
To sample density and characteristics of live trees and snags, the point quarter sampling method was used (Krebs 1989). Along a 300 m transect, sample points were located at a certain distance. The distance between points was modified for each stand age and stand type (bum or cutblock). This was necessary due to the wide variety of tree and snag densities in this study design. At each point, the distance to the nearest live tree and snag was measured. Characteristics of trees measured included tree height, tree diameter, tree species and cavity presence. The same variables were measured for snags, except stage of decay was also recorded. Because this technique is not limited by a sampling boundary, it maintained relatively large sample sizes despite sparsely distributed vegetation. This was particularly important in newly disturbed study sites and for collecting data on specific tree characteristics.
RESULTS Bird Census
Fifty-three avian species were detected across the six habitat types. White-throated Sparrow, Chipping Sparrow, Alder Flycatcher and Tennessee Warbler were the most abundant species.
1993 clearcut vs burn:
Species richness and abundance were higher in the bum within 50m of the census point (x2 = 4.141, d.f =1, p=0.042 and x2 = 4.094, d.f.=l, p=0.043, respectively) and higher in the clearcut beyond 50m (x2 = 4.639, d.f =1, p=0.031 and y}= 5.448, d.f.=l, p=0.02, respectively). However, there was no difference between clearcuts and bums for the combined species richness or
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abundance at the census point (%2 = 1.693, d.f.=l, p=0. 193 and %2= 1.712, d.f =1, p=0.191, respectively).
The most noticeable difference in species composition was the absence of the Tennessee warbler in the 1993 bum as this species was abundant in all other clearcuts and bums.
1980 clearcut vs burn:
Species richness within 50m, beyond 50m and for both combined were higher in the clearcut than the bum (%2 = 4.962, d.f.=T, p=0.026, 6.38, d.f.=T, p=0.03, y2= 14.765, d.f.=l,
p=0.003 respectively). Abundance within 50m was also higher in the clearcut than bum (%2 = 5.775, d.f.=l, p=0.016), however, there was no difference in abundance beyond 50m or for the combined total abundance (x2 = 1.688, d.f.^l, p^O.194, %2= 2.466, d.f.=l , p=0.116).
1969 clearcut vs burn:
Species richness and abundance within 50m were higher in the clearcut than the bum (%2 = 9.343, d.f.=l, p=Q.Q02 and y2 = 10.274, d.f =1, p=0.001 respectively). There was no difference between the clearcut and bum in species richness and abundance beyond 50m (x2 = 0.046, d.f =1, p=0.83 and y^= 0.045, d.f.=l, p=0.831 respectively). There was no difference between the clearcut and bum in the combined total species richness (x2 = 2.538, d.f.=l, p=0.1 1 1), however, there was a higher combined abundance in the clearcut in comparison to the bum (x2 = 4.347, d.f.=l, p=0.037).
Vegetation
1) Down Woody'Material
a) Down Woody Material <5 cm in diameter
As for the remaining vegetation data, sampling size varied across bums versus clearcuts and across the three age classes. The number of sampling stations in each stand type was as follows: 36 in 1993 bums and 14 in 1993 cuts, 29 in 1980 bums and 17 in 1980 cuts, and eight in both 1969 bums and cuts.
For down woody material <5 cm in diameter (DWM<5), there was a trend for frequency to decrease for time since distrubance for harvested sites and to increase for time since disturbance for bums (Figure 3). Average frequency of DWM<5 was almost 5 times higher in 93 cuts than 93 bums (x2o,05,i=21.04). Any initial differences disappeared, with almost equal frequency of DWM<5 in 80 cuts and bums (x2o.o5,i=0.24). When time since disturbance reached 28 years, frequency of DWM<5 was 1 .7 times greater in bums than in clearcuts, but this was not a significant difference (x2o,05,i=2.07).
7
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Stand Type
Figure 3. Average frequency of down woody material <5cm in diameter across six stand types. b) Down Woody Material >5 cm in diameter
The trends were not as sharp for down woody material greater than 5 cm in diameter (DWM>5), but DWM>5 did decrease in frequency from time since disturbance for bums and showed a slight U-shape trend for harvested sites (Figure 4).
Stand Type
Figure 4. Average frequency of down woody material >5cm in diameter across six stand types.
In 1993, frequency of DWM>5 was 4 times greater in bums than cuts, but there was no significant difference (x2o,05,i=0.30). The overall frequency of DWM>5 decreases for both bums and cuts in 1980, but the difference increased with bums having 10 times more DWM>5 than
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cuts. However, diffemces between cuts and bums were not detectable (x2q.05,i=Q-47). In 1969, there was little difference in frequecny between cuts and bums (x2o.q5,i=0-0@52).
c) Down Woody Material >10 cm in diameter
To determine if any initial differences in frequency of down woody material >10 cm in diameter (DWM>10) between bums and cuts disappeared as time from disturbance increased, data was analysed using chi square analysis for trends among proportions (Zar 1996, p. 562). Although initial differences in frequency of DWM>10 were slightly greater 3 years after disturbance than 27 years after disturbance (Figure 5), the proportion of DWM>10 between cuts and bums was similar for all three age classes (x2o.05,2=l-68).
3.5
1993 1993 1980 1980 1969 1969
Bum Cut Burn Cut Bum Cut
Stand Type
Figure 5. Average frequency of DWM>10 cm in diameter across six stand types.
For 1993 cuts and bums, there were no differences in the frequency of decay stage (x2o.05,5=0-43 , Figure 6a). As time from disturbance increased, there was a significant difference in stage of decay with a higher frequency for lower decay stages in both the 1980 and 1969 bums (X2o.o5,5= 11-21, X20.05,6= 15.08, respectively; Figure 6b and c).
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7
a) Stage of Decay for 1993 sites
b) Stage of Decay for 1980 sites
c) Stage of Decay for 1969 sites
Figure 6. Average frequency of DWM>10 for each of seven stages of decay for bums and harvest sites a) 3 years after disturbance b) 16 years after disturbance and c) 27 years after disturbance.
Volume of DWM>10 cm generally increased as time from disturbance increased for both bums and cuts (Figure 7). To determine if any initial differences in volume of DWM>10 between
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bums and cuts disappeared as time from disturbance increased, data was analysed using chi square analysis for trends among proportions (Zar 1996, p. 562). Although initial differences in colume of DWM>10 were slightly greater 3 years after disturbance than 27 years after disturbance (Figure 7), the proportion of DWM>10 between cuts and bums was similar for all three age classes (x2o,05,2=0.185).
Figure 7. Volume of DWM>10 cm in each stand type across three age classes.
d) Stumps
The low number of stumps detected in any of the stand types made meaningful analysis impossible. As suspected, there were a greater number of stumps in the 93 cuts as compared to the 93 bums, but these differences disappear after 16 years of time since disturbance (Figure 7). There were almost twice as many stumps in the 1969 bums as there were in the 1969 cuts. Sampling for stumps will be increased in 1997 to accommodate the low frequency of stumps.
bum cut burn cut burn cut Stand Type
Figure 7. Frequency of stumps across bums and cutblocks for 1993, 1980 and 1969.
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2) Snags
a) Snag Density
Number of snags sampled varied with stand treatment and stand age. Snag densities were highest in bum sites disturbed in 1993 (287.3 snags/ha; Figure 10), but snag density decreased sharply in 1980 and 1969 bum sites to 19.4 and 16.7 snags/ha, respectively. In harvested sites, snag densities were lowest in 1993 and 1980 cuts (2.2 and 2.0 snags/ha, respectively), but more than doubled in 1996 cuts (5.0 snag/ha).
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69 Bum 69 Cut 80 Burn 80 Cut 93 Burn 93 Cut Stand Type
b) Snag Characteristics 1993 Bums vs. Cuts-
Average diameter of snags in 1993 harvest sites (24.07 cm) was greater than snags in 1993 bums (17.68 cm; F=46.05, df=l,2, p=0.0001), but the height of snags was greater in bums (16.93 m) compared to cuts (1 1.0 m; ANOVA; F=61.92, df=l,2, p=0.0001). No snags with cavities were found in 1993 cuts and only 1 .4 % of snags had cavities in 1993 bums (Figure 1 1). The majority of snags originated from white spruce trees in both bum (40.3 %) and harvest (64.8 %) sites. The remaining snags consisted solely of aspen in bums (23.6%), whereas 22.2 % of snags in 1993 cuts were aspen and the remainder of snags were divided among balsam poplar (7.4 %), black spmce (3.7%) and alder trees (1.9 %; Figure 12a).
1980 Bums vs. Cuts
Snag diameter was similar between cuts (24.75 cm) and bums (23.06 cm) disturbed in 1980 (F=1.78, df=l,2, p=0.184), but snags in bums (14.82 m) averaged twice the height of snags in cuts (7.27 m; F=64.39, df=l,2, p=0.0001). The greatest percentage of snags with cavities was found in the 1980 harvest sites with 24.65 % of snags having cavities compared to only 0.9% of snags with a cavity in the 1980 bums (Figure 11). As with the 1993 distuirbed sites, the greatest percentage of snags were white spmce in bums (44.8 %) and cuts (50.0 %; Figure 12b). The remainder of the snags originated from pine (in bums only), aspen, birch, balsam poplar, and black spmce.
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1969 Bums vs. Cuts
Similar to 1980 snags, there was little difference between snag diameter in 1993 cuts and bums (21.22 and 21.04 cm, respectively; F=2.74, df=l,2, p=0.101) and snag height was greater in the bums (13.86 m) than cuts (9.94 m; F=1 3. 1 9, df=l,2, p=0.0005). As with the 1980 disturbed sites, harvest sites had a greater percentage of snags with cavities (14.2 %) as compared to the bum sites which had no snags with cavities (Figure 11). Most snags were white spruce in both bums (78.1 %) and cuts (60.3 %; Figure 12c). The remaining snags included pine, aspen, balsam poplar (in cuts only), and black spruce.
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69 Burn 69 Cut 80 Burn 80 Cut 93 Burn 93 Cut Stand Type
Figure 1 1 . Average percentage of snags with cavities across all six stand types.
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Average Percent Average Percent Average Percent
of Species of Species of Species
70
D 93 Burn I ■ 93 Cut |
Burn i Cut
JL
(/>
c) Species of Snag for 1969
Figure 12. Percentage of snag species for cuts and bums a) 3 years after disturbance b) 16 years after disturbance and c) 27 years after disturbance
b) Species of Snag for 1980
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3) Live Trees
a) Tree Density
The number of trees sampled varied with stand type and included only trees >10 cm DBH that were part of the canopy layer. Density of trees >10 cm DBH equalled zero in the 1993 and 1980 bums. In the 1969 bum , tree density reached 13.4 trees/ha (Figure 13). For the harvest sites, live tree density increased from 0.9 trees/ha in 1993 cuts, 1 1.9 trees/ha in 1980 cuts and 47.8 trees/ha in 1969 cuts. Of all the trees sampled only two trees with cavities were found. Percent of trees with cavities was 2.9 % in the 1980 cuts.
Burn Cut Burn Cut Burn Cut Stand Type
Figure 13. Live tree density (>10 cm DBH) in harvest and bum sites across the three stand ages. b) Tree characteristics
Becuase no trees >10 cm DBH were sampled for 1993 and 1980 bums, analysis could not be done to compare bum to cut sites within age classes. For 1993 cuts, average tree diameter was 25.9 cm and average height was 19.8 m. Both average tree diameter (16.1 cm) and height (1 1.4 m) decreased in 1980 bums. For 1969 sites, both tree diameter was greater in cuts than bums (14.5 cm and 13.0 cm, respectively; F=6.13, df=l,2, p=0.015) and height (12.9 m and 10.8 m, respectively; F=42.53, df=l,2, p=0.0001) was greater in cuts than bums.
In regenerating 1969 cuts and bums, the greatest percentage of tree species was aspen (50.0 % and 47.6 %, respectively; Figure 14). This differed from the 1993 where 51.1 % of trees were white spruce and in 1980 cuts where live trees were distributed mainly among poplar (32.2 %), aspen (30.9 %) and birch (26.5 %). Pine and fir trees were found only in the older stands with 27.0% pine treesin bums and 9.4 % in cuts and 1 .6 % fir trees in both 69 cuts and bums. Percent of Black spruce in 69 bums (14.3 %) was twice that in 69 cuts (7.8 %), followed by 6.4 % in 93 cuts and 2.9 % in 80 cuts.
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60
50
069 Bum ■ 69 Cut
□ 80 Cut
□ 93 Cut
0
Sw Pine Aspen Birch
Stand Type
Poplar Fir BIS
Figure 14. Average percent species for trees (>10 cm DBH) in 1969 bums and 1969, 1980 and 1993 cuts. No live trees were sampled in 1980 and 1969 bums.
Discussion
Because only one year of data has been collected and only half of the stands were sampled for vegetation, this discussion is based on a small sample size with no replication between years. Therefore, any conclusions are to be considered preliminary.
Birds
Prior to suppression, fire played a major role in the disturbance regime of the boreal forest, thereby, influencing the habitat available to birds (Telfer 1992); clearcutting and fire are two disturbance regimes (human-induced and natural, respectively) which influence the habitat structure and diversity available today.
The paucity of canopy trees and vertical heterogeneity in the vegetation may account for lower avian species richness and abundance in the recent clearcuts (3 years old) in comparison to bums of a similar age. Availability of nest, perch and singing sites, and food resources will influence species richness and abundance. Beyond 50m, the higher species richness and abundance in the clearcut may be an artifact of sampling design. The clearcut stands were small and often species in nearby woodlots accounted for a high proportion of the species detected beyond 50m; this will bias the results toward species that are in actuality resident in surrounding woodlots and not within the clearcut per se. The bums were larger and therefore this bias was less likely to exist.
The Tennessee Warbler was an abundant species in our study area and was conspicuously absent from the 1993 bum sites. Tennessee Warblers are primarily foliage gleaners (Ehrlich et al. 1988) and the lack of live trees remaining in the bum would result in a paucity of food resources.
Habitat complexity and heterogeneity have been shown to be important determinants for many bird species (e.g. Lynch and Whigham 1986). The quicker regeneration of clearcuts in
17
comparison to bums may account for the trend toward higher species richness and abundance in the clearcuts (both 16 and 27 years). Increased vertical heterogeneity will provide increased potential nest sites and food resources for many species. More detailed vegetation data are required to try to gain insight into the factors influencing avian species richness and abundance in the clearcuts and bums.
This study was prompted partly by concerns about the impact of forest practices of bird species and the potential to mimic natural disturbances. Avian census data spanning a longer time period and detailed vegetation data are necessary to address these concerns.
Vegetation
In terms of down woody material, there were few difference between cuts and bums within age classes. The biggest differences appear to be in the stage of decay of DWM. DWM reaches later stages of decay more quickly in bums than harvest sites. This may be due to the nature of the DWM at time of disturbance. In bums, the CDM was burned hard whereas the debris left at the harvest site was often broken pieces of wood. The exposed inner core of the wood could make the wood more susceptible to decay.
There was a large difference in the density of snags between cuts and bums at the 1993 disturbance sites with bums having a much greater density of snags. However, this difference disappears quickly as snags fall over. By 1980, there was little difference in the density of snags between cuts and bums. By 1969, a slight increase in the density of snags indicates that live trees started to die within the stand and therefore contribute to the snag density.
It appears from the higher density of live trees in cuts versus bums indicates that trees regenerate more quickly in cuts than bums. This might be caused by lower levels of light due to the high density of snags in the early stages after fire disturbance.
Summary of 1996 Budget:
supervisor/technician @ $25 00/month for 6 months $15,000
field technician @ $2000/month for 5 months $10,000
Total $25,000
Acknowledgements
We would like to thank those people of the Wildlife Management Division from the Department of Environmental Protection for their insight for the need of this study, and for their advice and direction during the initial stages of this project. Our appreciation also goes out to everyone at the Manning Forest Ranger Station for providing the use of their office and for always taking the time to answer our many questions.
We thank the Manning Diversified Trust Fund, the Alberta Sports, Recreation, Parks and Wildlife Foundation and the Canadian Circumpolar Institute for providing financial support and Manning Diversified Forest Products for showing flexibility and openmindedness which helped make this project possible.
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DesGranges, J. and Rondeau G. 1992. Forest bird response to natural perturbations and
silvicultural practices: Does logging mimic nature? In: Kuhnke, D.H., editor. 1992. Birds in the boreal forest. Proceedings of a workshop held March 10-12, 1992, Prince Albert, Saskatchewan. For. Cent. Northwest Reg., North. For. Cent., Edmonton, Alberta.
Ehrlich, P.R., Dobkin, D.S., and Wheye, D. 1988. The birders’ handbook: a field guide to the natural history of North American birds. Simon and Schuster Inc. Toronto, ON. 785pp.
Fox, J.F. 1983. Post-fire succession of small-mammals and bird communities. In: The role of fire in Northern Circumpolar Ecosystems. Eds. R.W. Wein & D.A. MacLean.
Hansson, L. 1983. Bird numbers across edges between mature conifer forest and clearcuts in Central Sweden. Omis Scandinavia 14:97-103.
Hunter, M.L. Jr. 1993. Natural fire regimes as spatial models for managing boreal forests. Biological Conservation 65: 115-120.
Kavanagh, R.P., Shields, J.M., Recher, H.F. and Rohan-Jones, W.G. 1985. Bird populations of a logged and unlogged forest mosaic at Eden, New South Wales. In Birds of Eucalypt forests and woodlands: ecology, conservation, management. Eds. A. Keast, H.F. Recher, H. Ford and D. Saunders. Royal Australasian Ornithologists Union and Surrey Beatty & Sons.
Kent, M. and Coker, P. 1992. Vegetation description and analysis; a practical approach. Broca Raton: CRC Press; London: Belhaven Press. Pp. 28-76.
Kirkland, G.L. Jr. 1977. Responses of small mammals to the clearcutting of Northern Appalachian Forests. Journal of Mammalogy 58(4): 699-609.
Krebs, C.J. 1989. Estimating abundance: distance methods and removal meighods. In: Ecological methodology. HarperCollins Puyblishers. New York, NY. Chapter 4. Pp. 125-169.
Lair, H. 1990. The calls of the red squirrel: a contextual analysis of function. Behaviour 115: 254- 282.
Murphy, P.J. 1985. History of forest and prairie fire control policy in Alberta. Faculty of Agriculture and Forestry, University of Alberta.
Murphy, P.J. and Tymstra, C. 1986. The 1950 Chinchaga river fire in the Peace River district of British Columbia/Alberta: Preliminary results of simulating forward spread distances.
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Ralph, C J., Geupel, G.R., Pyle, P., Martin, T.E. and DeSante, D.F. 1992. Field methods for
monitoring landbirds. USDA Forest Service, Redwood Sciences Laboratory, 1700 Bayview Drive, Areata, California 95521. Pp. 38-44.
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