Boreal Shield Research Articles

Impact of forest harvesting on trophic structure of eastern Canadian Boreal Shield lakes: insights from stable isotope analyses.

Perturbations on ecosystems can have profound immediate effects and can, accordingly, greatly alter the natural community. Land-use such as forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. The objective of this study was to evaluate the impact of forest harvesting on trophic structure in eastern Canadian Boreal Shield lakes. We measured carbon and nitrogen stable isotopes values for aquatic primary producers, terrestrial detritus, benthic macroinvertebrates, zooplankton and brook trout (Salvelinus fontinalis) over a three-year period in eight eastern Boreal Shield lakes. Four lakes were studied before, one and two years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. Stable isotope mixing models showed leaf-litter to be the main food source for benthic primary consumers in both perturbed and unperturbed lakes, suggesting no logging impact on allochthonous subsidies to the littoral food web. Brook trout derived their food mainly from benthic predatory macroinvertebrates in unperturbed lakes. However, in perturbed lakes one year after harvesting, zooplankton appeared to be the main contributor to brook trout diet. This change in brook trout diet was mitigated two years after harvesting. Size-related diet shift were also observed for brook trout, indicating a diet shift related to size. Our study suggests that carbon from terrestrial habitat may be a significant contribution to the food web of oligotrophic Canadian Boreal Shield lakes. Forest harvesting did not have an impact on the diet of benthic primary consumers. On the other hand, brook trout diet composition was affected by logging with greater zooplankton contribution in perturbed lakes, possibly induced by darker-colored environment in these lakes one year after logging.

Sulfide and mercury species profiles in two Ontario boreal shield lakes

The cycling of sulfur in freshwater environments plays an important role in the cycling of metals. In this study, acid volatile sulfides were measured at nanomolar levels using a purge-and-trap preconcentration, followed by methylene blue derivatization with HPLC separation and UV–Vis detection. The limit of detection using the preconcentration step was 7.5ngL−1 or 0.23nM sulfide. Profiles of sulfide and methylmercury were generated for two Ontario lakes. Sulfide concentrations were inversely related to dissolved oxygen concentrations and significant levels of anoxia had developed in both lakes. In both Plastic Lake and Lake 658, mercury concentrations also increased below the oxycline. Lake 658 showed a strong positive correlation between sulfide and methylmercury (CMeHg=2×10−6⋅Csulfide+0.198; r=0.96, p=1.2×10−5), at the time of sampling.

A dynamic-bioenergetics model to assess depth selection and reproductive growth by lake trout (Salvelinus namaycush)

We coupled dynamic optimization and bioenergetics models to assess the assumption that lake trout (Salvelinus namaycush) depth distribution is structured by temperature, food availability, and predation risk to maximize reproductive mass by autumn spawning. Because the model uses empirical daily thermal-depth profiles recorded in a small boreal shield lake (lake 373 at the Experimental Lakes Area, northwestern Ontario) during 2 years of contrasting thermal stratification patterns, we also assessed how climate-mediated changes in lakes may affect the vertical distribution, growth, and fitness of lake trout, a cold-water top predator. The depths of acoustic-tagged lake trout were recorded concurrently with thermal-depth profiles and were compared to model output, enabling an assessment of model performance in relation to the observed fish behavior and contrasting thermal conditions. The depths and temperatures occupied by simulated fish most closely resembled those of the tagged fish when risk of predation was included in the model, indicating the model may incorporate the most important underlying mechanisms that determine lake trout depth. Annual differences suggest less use of shallow (warm), productive habitats, resulting in markedly less reproductive mass, during the year with the warm stratification pattern. Mass for reproduction may be lower in warmer conditions because of reduced reproductive investment, yet survival may be inadvertently higher because risky surface waters may be avoided more often in warmer, shallower, and metabolically costly conditions. At a minimum our study suggests that lake trout reproductive mass and fitness may be expected to change under the anticipated longer and warmer stratification patterns.

Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions

Peatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7 ± (std. dev.) 36.2 kg C m-2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2 ± 6.9 g C m-2 yr-1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days > 0 °C, and photosynthetically active radiation integrated over days > 0 °C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.

Detecting regional differences in within-wildfire burn patterns in western boreal Canada

Under the auspices of ecosystem-based management (EBM), using historical range of variation (HRV) knowledge to help guide forest management decision-making is becoming commonplace. In support of this evolution, we hypothesized that historical fire-scale wildfire burn patterns in western boreal Canada could be differentiated by major ecological zones. We tested 10 fine-scale burn pattern metrics for 129 natural wildfires across more than 100 million ha of western boreal Canada against existing Canadian and provincial ecological classification schemes. The results showed some evidence of two historic disturbance regimes. Fires in the Foothills and Rocky Mountain ecoregions tended to have more disturbed patches, a smaller dominant disturbed patch, and less area in partially disturbed island remnants relative to fires in the Boreal Forest and Boreal Shield. However, several key metrics such as event shape and total remnant area were zone-invariant. Fire regime parameters such as fire size and frequency may not be linked to more detailed fire behaviour parameters such as remnant patterns. The moderate, yet highly variable levels of remnant pattern variation we found across the study area represents a natural, and potentially universal source of structural and compositional diversity for the boreal that may be critical to its sustainability.

Fire, humans, and climate: modeling distribution dynamics of boreal forest waterbirds

Understanding the effects of landscape change and environmental variability on ecological processes is important for evaluating resource management policies, such as the emulation of natural forest disturbances. We analyzed time series of detection/nondetection data using hierarchical models in a Bayesian multi-model inference framework to decompose the dynamics of species distributions into responses to environmental variability, spatial variation in habitat conditions, and population dynamics and interspecific interactions, while correcting for observation errors and variation in sampling regimes. We modeled distribution dynamics of 14 waterbird species (broadly defined, including wetland and riparian species) using data from two different breeding bird surveys collected in the Boreal Shield ecozone within Ontario, Canada. Temporal variation in species occupancy (2000-2006) was primarily driven by climatic variability. Only two species showed evidence of consistent temporal trends in distribution: Ring-necked Duck (Aythya collaris) decreased, and Red-winged Blackbird (Agelaius phoeniceus) increased. The models had good predictive ability on independent data over time (1997-1999). Spatial variation in species occupancy was strongly related to the distribution of specific land cover types and habitat disturbance: Fire and forest harvesting influenced occupancy more than did roads, settlements, or mines. Bioclimatic and habitat heterogeneity indices and geographic coordinates exerted negligible influence on most species distributions. Estimated habitat suitability indices had good predictive ability on spatially independent data (Hudson Bay Lowlands ecozone). Additionally, we detected effects of interspecific interactions. Species responses to fire and forest harvesting were similar for 13 of 14 species; thus, forest-harvesting practices in Ontario generally appeared to emulate the effects of fire for waterbirds over timescales of 10-20 years. Extrapolating to all 84 waterbird species breeding on the Ontario Boreal Shield, however, suggested that up to 30 species may instead have altered (short-term) distribution dynamics due to forestry practices. Hence, natural disturbances are critical components of the ecology of the boreal forest and forest practices which aim to approximate them may succeed in allowing the maintenance of the associated species, but improved monitoring and modeling of large-scale boreal forest bird distribution dynamics will be necessary to resolve existing uncertainties, especially on less-common species.

Linking temporal changes in crayfish communities to environmental changes in boreal Shield lakes in south-central Ontario

When aquatic ecosystems are among those most intensely affected by local and regional environmental change, it is crucial that stressors are identified to set priorities for future research and mitigation. Studies relating changes in important or sensitive assemblages to environmental changes provide a means to quantify potential stress on aquatic biota. Crayfish are ideal taxa for this type of study because they influence ecosystem structure and function and are sensitive to biotic and abiotic changes. We used historical and contemporary crayfish abundance and select environmental data for 100 inland lakes in central Ontario, to identify factors that are correlated with community membership and species distributions at each time and to elucidate environmental factors that can be directly linked to changes in relative abundance between the two time periods. Our results show that declines in lake calcium, invasions of warm-water centrarchids, and anthropogenic shoreline development have increased in their relative influence over time. These stressors may be affecting other freshwater biota directly, or indirectly through food web changes or altered abiotic interactions among the environmental changes.

Evaluating the relationship between mean catch per unit effort and abundance for littoral cyprinids in small boreal shield lakes

Catch per unit effort (CPUE) is commonly used as a relative measure of littoral fish abundance; however, few studies have examined this relationship for boreal shield lakes. We used non-linear regression to generate relationships between mark-recapture abundance estimates and mean CPUE derived from 7 years of standardized fishing using baited minnow traps for two common cyprinid species; pearl dace (Margariscus margarita) and fathead minnows (Pimephales promelas), in littoral areas of two small boreal lakes. We produced significant, positive CPUE-abundance relationships for pearl dace and fathead minnows. Pearl dace were less variable in daily CPUE during the course of the study, suggesting they may require less sampling effort than fathead minnows to precisely estimate their population size. Density estimates derived from our estimates of abundance were consistent with those from similar boreal shield lakes, providing confidence in our method to estimate abundance. Finally, we developed relationships to estimate population size from long-term monitoring data collected on these same cyprinid species using two types of small mesh trap nets. Non-linear relationships were developed between mean trap net CPUE and abundance estimates derived from minnow traps for fathead minnows, but not pearl dace. These relationships should permit population estimates from mean CPUE data collected using similar capture methods in similar lakes.

Burned Area Detection in the Canadian Boreal Forest Using MODIS Imagery

The boreal forest biome is one of the largest on earth,covering 17% of total land area.The major ecosystems within the boreal zone contain more than 30% of terrestrial carbon stores,thus representing a major component of the global carbon budget.Wildfires are a main disturbance factor in the Canadian boreal forests,which play an important role in boreal ecosystems.In this paper,we mapped the forest burned area in Saskatchewan and Alberta of Canada during 2004-2011,using two data sets of Moderate Resolution Imaging Spectroradiometer(MODIS) Land Surface Temperature(LST) and Enhanced Vegetation Index(EVI) imagery at 1 km resolution.The MODIS global disturbance index algorithm(MGDI) was used to detect the forest burned area.It is based on the consistent radiometric relationship between annual maximum LST and the maximum EVI value that occurs after the LST during the same year at every pixel.The performance of the algorithm was evaluated by comparing the results with the MODIS MCD45A1 products and the inventory data from Forestry Bureau of Canada.The results show that the majority of fire events is captured by the MGDI techniques,and the burned area estimated by the fires pixels is better in good agreement with the inventory data than MODIS products.Compared with the Canadian Forestry Bureau data,the average relative error of our algorithm results is only 8.03%,while the MODIS product results is up to 70.53%.The results estimated that the average burned forest area is about 763 600 ha annually,which is about 3.36% of the total forest in this region.A mean annual burned forest is 468 300 ha for Saskatchewan and 295 300ha for Alberta respectively.The Canadian boreal forest fires show a significant interannual variation and severity,the burned scar mainly appeared in the years of 2006,2008 and 2010-2011.Forest burned area mainly concentrated in the ecotone of the Boreal Shield,Taiga Shield,Taiga plains and the Wood Buffalo National Park located at the northeast of Boreal Plains.

Temporal changes in mercury concentrations of large-bodied fishes in the boreal shield ecoregion of northern Ontario, Canada

Much of the mercury (Hg) in freshwater fish of the boreal shield ecoregion is believed to originate from atmospheric deposition. As such, declines in fish Hg concentrations would be expected in response to recent declines in atmospheric Hg deposition in this ecoregion. We compared recent (2005–2010) and historic (1974–1981) muscle total mercury concentrations ([THg], standardized to a fish body mass of 1kg) in seven fish species (five piscivores, two benthivores) from 73 lakes in northern Ontario (Canada) using a paired-comparisons approach. The rate of bioaccumulation (i.e., slopes of loge[THg] vs loge total length relationship) increased for walleye (Sander vitreus) but did not change significantly for any other species. There was no significant decline in mean [THg] between recent and historic time periods for any species. In fact, recent mean [THg] were slightly higher (<0.08ppm) than historic mean [THg] for all species, and this difference was significant for northern pike (Esox lucius). The magnitude of the temporal change in northern pike declined significantly from south to north over the study area but there were no discernible geographic patterns in the temporal change in [THg] for any other species. This study shows that [THg] of most large-bodied fish species in boreal shield lakes are not declining in response to the decline in atmospheric Hg deposition.

Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 17:107-117 (2012) - DOI: https://doi.org/10.3354/ab00465 Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis Patricia Glaz1,*, Pascal Sirois2, Christian Nozais1 1Département de biologie et centre d’études nordiques, Université du Québec à Rimouski, Rimouski, Québec G5L 3A1, Canada 2Laboratoire des sciences aquatiques, Département des sciences fondamentales, Université du Québec à Chicoutimi, Chicoutimi, Québec G7H 2B1, Canada *Email: patricia.glaz@uqar.ca ABSTRACT: Allochthonous inputs can be an important contribution of organic matter in lake ecosystems. Yet, our understanding of the patterns of energy dependence of littoral invertebrates and fish is poor. We measured carbon (δ13C) and nitrogen (δ15N) stable isotope values for primary producers, terrestrial detritus, benthic macroinvertebrates, zooplankton and brook trout Salvelinus fontinalis in 8 oligotrophic Canadian Boreal Shield lakes to determine food sources that support benthic consumers and brook trout. Mixing models used to determine animal diets from stable isotope analysis showed leaf litter to be the principal food source for benthic primary consumers in 6 out of 8 lakes. Brook trout derived its carbon mainly from benthic predatory macroinvertebrates in all lakes, with a contribution ranging from 60 to 90%. Zooplankton also contributed to brook trout diet in 3 of 8 lakes, ranging from 28 to 37%. δ15N increased from primary producers to consumers at different trophic positions in all lakes. Nitrogen isotopic signatures of brook trout became more positive with increasing fish length, indicating a change in fish foraging strategy related to size. Our study (1) suggests that carbon from terrestrial habitat (leaf litter) may contribute significantly to the food web of oligotrophic Canadian Boreal Shield lakes and (2) highlights the importance of carbon originating from benthic habitats in supporting brook trout in these lakes. KEY WORDS: Allochthonous subsidies · Benthic macroinvertebrates · Zooplankton · Brook trout · Diet breadth · Size-related diet shift · Stable isotopes · Boreal lakes Full text in pdf format PreviousNextCite this article as: Glaz P, Sirois P, Nozais C (2012) Determination of food sources for benthic invertebrates and brook trout Salvelinus fontinalis in Canadian Boreal Shield lakes using stable isotope analysis. Aquat Biol 17:107-117. https://doi.org/10.3354/ab00465 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 17, No. 2. Online publication date: November 06, 2012 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2012 Inter-Research.

NDVI variation and its relation to climate in Canadian ecozones

Parks Canada began the Northern Satellite Monitoring Program in 1997, with the objective of tracking large‐scale vegetation variation in Canadian ecosystems and helping land managers to develop appropriate management practices in response to climate change. Under this program, a sequence of 10‐day composite Advanced Very High Resolution Radiometer (AVHRR)‐derived Normalized Difference Vegetation Index (NDVI) data from 1985 to 2007 was examined to study seasonal and inter‐annual relationships between vegetation and climate data over Canadian ecosystems using statistical and wavelet analysis. Statistical analysis showed that temperature was the principal driver for seasonal variability in greenness, explaining more than 70 percent of seasonal variation in vegetation for most Canadian ecozones. In comparison with temperature, the relationships between NDVI and precipitation were weaker but still significant. Maximum annual NDVI showed increasing trends in Canadian ecozones during the study period, although increasing rates were spatially heterogeneous. Wavelet analysis confirmed that inter‐annual variation in NDVI was different at two ecozones in Canada. NDVI variation in the Northern Arctic was significant at scales of 3–4 years from 1997 to 2001, which was associated with temperature and precipitation variation. Comparatively, NDVI variation in the Boreal Shield was significant at scales of 5–8 years from 1991 to 1999, but did not correspond with climate variation.

Using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to examine the impact of harvest and fire on carbon dynamics in selected forest types of the Canadian Boreal shield

The objective of the study was to assess the responsiveness of the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to management scenarios that included three rotation lengths (50, 100 and 250 years) under harvest and fire disturbances in six forest types (poplar deep soil, black spruce deep soil, jack pine deep and shallow soils, hardwood mixedwood and other conifer lowland). Outputs from five carbon (C) pools were considered: merchantable stemwood (stump height of 30 cm, minimum DBH of 9 cm and a minimum top diameter of 7 cm), deadwood, soil C, total ecosystem C and cumulative total ecosystem C emissions. Yield curves strongly affected the predicted size of all five pools. Longer rotation lengths led to larger pools with the relative differences between rotation lengths varying with stand types. Pools associated with poplar were usually the largest while those of jack pine on shallow sites were generally the smallest. When compared to the starting point of the simulations, cumulative total ecosystem C and C emissions increased with the 100- and 250-year harvest rotations (HARV100 and HARV250, respectively) and declined with the 50-year harvest rotation (HARV50). Fire disturbances resulted in stable pools of cumulative ecosystem C and declines in C emissions. CBM-CFS3 provided realistic pool values but the authors suggest further development of the model depiction of ecosystem processes, especially with respect to the treatment of respiration. In general, the authors recommend that forest management planners consider using an integrated approach that links multiple proven and accepted models under appropriate model linking software.

Hybrid poplar yields in Québec: Implications for a sustainable forest zoning management system

In the province of Québec, approximately 12 000 ha of fast-growing poplar plantations are managed by industrials, while small private landowners have planted only 1000 ha. Most of these poplar plantations are established on clearcut forest sites (approx. 11 000 ha). What are the yields of these hybrid poplar plantations? In this article, available yield data are presented and discussed in the context of a sustainable forest zoning management system. In southern Québec, three factors are highly correlated to yield for clones of various parentages: NO3supply rate in riparian soils, elevation (or climate) and soil P availability in abandoned farmland soils. Many Québec forest sites, particularly in the boreal shield ecozone, have acidic soils and harsh climate, with low mineralization rates. They generally cannot fulfill the very high nutrient requirements of hybrid poplars. Within a forest zoning management system, hybrid poplar plantations and agroforestry should be located in priority in southern Québec landscapes, with low remaining natural forest cover, and where intensive agriculture is the dominant land-use. This strategy will increase biodiversity and the provision of ecosystem services. Elsewhere, intensive trembling aspen regeneration silviculture could be a sustainable alternative to forest conversion into hybrid poplar plantations.

Influence of the 11 year solar cycle on annual streamflow maxima in Southern Canada

Summary The re-occurrence pattern of major extremes in hydrology, such as the timing and intensity of river floods, is related to a variety of natural and anthropogenic factors. In this study, the particular temporal regional influence of ∼11 year solar radiation cyclicities on the maximum annual streamflow (MAS) records from six stations from four eco-zones in Southern Canada were investigated. Wavelet analysis decomposition and re-composition techniques were applied to extract the ∼11 year signals in the hydrological records. An ∼11 year cyclicity is evident in all eco-zones but it is superimposed by non-periodic variability in the 2 to 18 year wavebands that are due to El Nino/Southern Oscillation and North Atlantic Oscillation related precipitation variability or random components in the records. The ∼11 year MAS cyclicity is strong in the Mountain ecozone (Rocky Mountains) and less strong in the Boreal Shield. In these eco-zones, it was found that years that experienced major floods were most likely to occur during low sunspot number years, in the spring time approximately 6–7 years after the last solar maximum. The results of the wavelet analysis demonstrate that major floods are more likely to occur during sunspot cycles with relatively low sunspot numbers after the last maximum.

Changes since the onset of acid deposition among calcium-sensitive cladoceran taxa within softwater lakes of Ontario, Canada

Aqueous calcium (Ca) concentrations are currently decreasing in many softwater lakes on the Boreal Shield. As the onset of these declines often pre-date direct monitoring programs, indirect techniques are required to examine the impacts of reduced Ca availability on aquatic communities with relatively high Ca demands such as the Cladocera (Class: Branchiopoda). Among the Cladocera, the family Daphniidae has been identified as a taxonomic group potentially useful for inferring past Ca concentrations due to their high Ca demands and preservation in lake sediments. Here, we use a “top/bottom” paleolimnological analysis to compare present-day cladoceran communities preserved in the surface sediments of 36 softwater lakes in south-central Ontario, Canada, which are potentially vulnerable to Ca decline (i.e. small headwater systems with present-day lakewater [Ca] < 3 mg L−1), with the communities present in lake sediments deposited prior to the onset of regional acid deposition. To distinguish the potential impacts of lake acidification from those of Ca availability (as Ca and pH trends are strongly correlated in this region), the study lakes were chosen to be evenly distributed about a present-day lakewater pH of 6 and Ca concentration of 1.5 mg L−1 (threshold values). Despite the importance of pH as an explanatory variable for the present-day assemblages, a comparison of the sedimentary remains from the two time periods indicate there have been large declines since pre-industrial times in the relative abundances of Ca-rich Daphnia spp. (particularly of the Daphnia longispina species complex), regardless of present-day pH, accompanied by increases in the Ca-poor species Holopedium glacialis. These observations suggest that recent declines in Ca concentration may have already fallen below baseline conditions, with marked implications for ecosystem function due to the differential responses among cladoceran taxa.

Modeling Large Fire Frequency and Burned Area in Canadian Terrestrial Ecosystems with Poisson Models

Large wildland fires are major disturbances that strongly influence the carbon cycling and vegetation dynamics of Canadian boreal ecosystems. Although large wildland fires have recently received much scrutiny in scientific study, it is still a challenge for researchers to predict large fire frequency and burned area. Here, we use monthly climate and elevation data to quantify the frequency of large fires using a Poisson model, and we calculate the probability of burned area exceeding a certain size using a compound Poisson process. We find that the Poisson model simulates large fire occurrence well during the fire season (May through August) using monthly climate, and the threshold probability calculated by the compound Poisson model agrees well with historical records. Threshold probabilities are significantly different among different Canadian ecozones, with the Boreal Shield ecozone always showing the highest probability. The fire prediction model described in this study and the derived information will facilitate future quantification of fire risks and help improve fire management in the region.

Water level thresholds of benthic macroinvertebrate richness, structure, and function of boreal lake stony littoral habitats

We investigated the role of water level fluctuation on benthic macroinvertebrate communities of stony littoral habitats located in the Boreal Shield Ecozone. Using the reference condition approach (RCA), regression analysis, nonmetric multidimensional scaling (NMDS), and analysis of variance (ANOVA), we analyzed the benthic macroinvertebrate community structure of 20 natural lakes and 28 hydroelectric reservoirs to determine if they are structured by change in water level (amplitude). Along a gradient of amplitude intensity, we found that taxa richness decreases with increasing amplitude (r2 = 0.47–0.60). Littoral benthic macroinvertebrate community structure is significantly different in reservoirs that experience amplitudes &gt; 2.0 m. Out of 28 reservoirs, 13 fell outside the 95.5% confidence ellipse determined by 20 reference lakes. Functional mobility group and functional feeding group composition are also altered with increasing amplitude (nonparametric ANOVA, P &lt; 0.05). Further, a change in benthic macroinvertebrate functional composition occurs after a change in taxa richness. Interestingly, reservoirs that experienced amplitudes &lt; 2.0 m had benthic macroinvertebrate communities whose structural and functional composition is similar to lakes experiencing natural water level fluctuations.

Characterization of woodland caribou (Rangifer tarandus caribou) calving habitat in the boreal plains and boreal shield ecozones of Manitoba and Saskatchewan

As recovery plans are being developed or implemented for boreal caribou, it is becoming important to further examine the spatial and temporal characteristics of areas used at calving and to identify site and landscape attributes that may be selected by the animals. In order to do this, we analyzed the movement and habitat use pattern of 31 animals in the boreal plains and boreal shield ecozones. GPS telemetry data were obtained from 12 female boreal caribou from the Kississing-Naosap herd in Manitoba between 2002 and 2005, and 19 females from the Smoothstone-Wapawekka herd in Saskatchewan between 2005 and 2007. Based on movement rates, LOESS curves were used to identify eight distinct seasons for both herds. Reduced movement rates, involving a rate of 50 m/h or less for a minimum of a week, were used to identify 20 calving sites in the Smoothstone-Wapawekka herd, 13 calving sites in the Kississing-Naosap herd, and their associated preand post-calving areas. Vegetation characteristics at the site and landscape scales were examined using Forest Resource Inventory, roads, trails, fire and cutblocks data. Paired-logistic regression was used to assess calving habitat selection at the site scale and generalized estimating equations were used for the landscape scale analysis. Selection was seen to occur at the landscape scale for calving areas in both herds however, no identifiable trends were seen to occur at the site scale based on vegetation characteristics. The predictive maps of calving and potential calving habitat generated for both herds are providing key management information for the protection of boreal caribou during the calving season.

Food web position of burbot relative to lake trout, northern pike, and lake whitefish in four sub-Arctic boreal lakes

Summary We assessed the food web position of burbot Lota lota relative to co-occurring large-bodied fishes in four northern (62°40′N, 114°10′W) boreal shield lakes of similar size (305–547 ha) using a stable isotope approach. Trophic position (inferred from δ15N) was positively correlated to body mass in burbot, lake trout Salvelinus namaycush, and northern pike Esox lucius, but negatively correlated to body mass in lake whitefish Coregonus clupeaformis. Carbon source (inferred from δ13C) was positively correlated to body mass in lake whitefish, but not related to body mass in any of the other three species. In all lakes, burbot had δ15N and δ13C signatures very similar to those of lake trout. Both burbot and lake trout were more δ15N-enriched than northern pike (P < 0.001). Lake trout had lower δ13C than northern pike and lake whitefish (P = 0.0023) but not burbot. Our results confirm that burbot occupy a position near the top of the food chain in boreal lakes and may play an important role in structuring the limnetic fish community.