Chillán

Using shifting species distribution models to inform rainfall runoff models

Spatial patterns of land cover affect the spatial heterogeneity of hydrological processes. However, rainfall-runoff models typically model weather and climate effects on streamflows, treating land cover as a static parameter. Climate change is predicted to affect the distribution of tree species and forests in mountain regions. Climate change effects may be especially acute in mountain environments, forming ‘sky islands’, as warming temperatures drive montane and alpine ecosystems upslope, resulting in tree mortality at the lower margins of their distribution. Understanding how the distribution of forests might respond, expand, or compress is important for forest and water management. I use species distribution models (SDM) to describe spatial extent of vegetation in conjunction with field data from Chile’s Nevados de Chillán watershed identifying forest (e.g. Nothofagus), shrub and grass communities (e.g. Adesmia, Nassauvia). SDM are built from topographic surrogates (e.g. elevation as a surrogate for temperature) and predict future distributions using anticipated climate change conditions. Stream runoff and snowmelt are then estimated using a rainfall-runoff model under current and future species distributions to identify changes to the timing and quantity of runoff as new plant communities displace disturbed forests. The rainfall runoff model can then be used to examine other ecological disturbances such as the influence of volcanic ash on snowmelt and water supply.