Spatial pattern of the shrub layer across the subarctic landscape of Churchill Manitoba

Abstract

The shrub layer provides important habitat for wildlife throughout the harsh environment of the arctic tundra landscape. Studies have shown that the shrub layer is expanding in tundra landscapes and changing habitat conditions due to climate warming. My research goal was to determine the spatial pattern of the shrub layer across the tundra and forest-tundra ecotone landscapes. Data were collected in 1x1 m contiguous quadrats along two 500 m long transects in open tundra and across the forest-tundra ecotone. Within each quadrat, I identified shrub species, recorded their cover and height, and also sampled explanatory variables (soil pH and microtopography). I used wavelet analysis to determine the locations of significant patches and gaps in the shrub layer. Results indicate that distance to a natural or created edge, and microtopography were the environmental variables that best explained the spatial pattern of shrubs across tundra and forest-tundra ecotone landscapes. Throughout both habitat types, shrub height and diversity increased closer to lakeshore edges. The pattern of the shrub layer in the tundra showed gradual changes with relatively uniform distributions of prostrate shrub species. The ecotone displayed a pattern of abrupt changes in shrub habitat with fine-scale variation in shrub diversity and height. The heterogeneity of the shrub layer in subarctic regions will likely continue to change with further climate change.