Canadian Forest Service Publications
Incorporating interspecific competition into species-distribution mapping by upward scaling of small-scale model projections to the landscape. Baah-Acheamfour, M., Bourque, C. P. A., Meng, F. R., & Swift, D. E. (2017). PloS one, 12(2), e0171487.
Issued by: Canadian Wood Fibre Centre
Catalog ID: 40409
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There are a number of overarching questions and debate in the scientific community concerning the importance of biotic interactions in species distribution models at large spatial scales. In this paper, we present a framework for revising the potential distribution of tree species native to the Western Ecoregion of Nova Scotia, Canada, by integrating the long-term effects of interspecific competition into an existing abiotic-factor-based definition of potential species distribution (PSD). The PSD model is developed by combining spatially explicit data of individualistic species’ response to normalized incident photosynthetically active radiation, soil water content, and growing degree days. A revised PSD model adds biomass output simulated over a 100-year timeframe with a robust forest gap model and scaled up to the landscape using a forestland classification technique. To demonstrate the method, we applied the calculation to the natural range of 16 target tree species as found in 1,240 provincial forest-inventory plots. The revised PSD model, with the long-term effects of interspecific competition accounted for, predicted that eastern hemlock (Tsuga canadensis), American beech (Fagus grandifolia), white birch (Betula papyrifera), red oak (Quercus rubra), sugar maple (Acer saccharum), and trembling aspen (Populus tremuloides) would experience a significant decline in their original distribution compared with balsam fir (Abies balsamea), black spruce (Picea mariana), red spruce (Picea rubens), red maple (Acer rubrum L.), and yellow birch (Betula alleghaniensis). True model accuracy improved from 64.2% with original PSD evaluations to 81.7% with revised PSD. Kappa statistics slightly increased from 0.26 (fair) to 0.41 (moderate) for original and revised PSDs, respectively.
Plain Language Summary
There are still many questions about the importance of biotic (living) interactions modeled at larger scales. We explore the potential distribution of tree species native to Nova Scotia, Canada by using the potential species distribution (PSD) model. The PSD model combines data using various characteristics related to tree growth. The model was later revised to include more criteria. The results of the revised model showed that the potential distribution of 16 common tree species in the area was largely based on the individual species’ response to climate and competition between different species. The impact of measuring competition for a species’ potential distribution was relatively low for late developing species with high shade tolerance (e.g., balsam fir, black spruce, red spruce, sugar maple, yellow birch) compared with early developing and shade-intolerant species (e.g., eastern hemlock, American beech, white birch, red oak, red maple, trembling aspen). PSD model accuracy improved with the added criteria from the revised model, and the updates will be used in future work.