Canadian Forest Service Publications
Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America. 2014. Creed, I.F.; Spargo, A.T.; Jones, J.A.; Buttle, J.M.; Adams, M.B.; Beall, F.D.; Booth, E.G.; Campbell, J.; Clow, D.; Elder, K.; Green, M.B.; Grimm, N.B.; Miniat, C.; Ramlal, P.; Saha, A.;Sebestyen, S.; Spittlehouse, D., Sterling, S.; Williams, M.W.; Winkler, R.; Yao, H. Global Change Biology 20:3191-3208.
Available from: Great Lakes Forestry Centre
Catalog ID: 35780
CFS Availability: PDF (request by e-mail)
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Climate warming is projected to affect forest water yields but the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this question, we examined the variability in historical water yields at long-term experimental catchments across Canada and the United States over 5-year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation (d) was defined as a catchment's change in actual ET divided by P [AET/P; evaporative index (EI)] coincident with a shift from a cool to a warm period – a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of interannual variation in potential ET divided by P (PET/P; dryness index) to interannual variation in the EI – high elasticity indicates low d despite large range in drying index (i.e., resilient water yields), low elasticity indicates high d despite small range in drying index (i.e., nonresilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics are limited, we were able to identify some characteristics of response among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer forests included catchments with lowest elasticity and stable to larger water yields. Deciduous forests included catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/deciduous forests included catchments with highest elasticity and stable water yields. Forest type appeared to influence the resilience of catchment water yields to climate warming, with conifer and deciduous catchments more susceptible to climate warming than the more diverse mixed forest catchments.
Plain Language Summary
Climate warming is projected to affect forest water yields, but the effects are expected to vary. This is important because substantial changes in water yields could place communities that depend on these water resources at risk. We investigated how forest type and age affect water yield resilience to climate warming. We examined the variability in historical water yields over 5-year cool and warm periods at long-term experimental catchments across Canada and the US. One of these sites was the Turkey Watershed, for which the CFS provides support. Forest type appeared to influence the resilience of catchment water yields to climate warming: conifer and deciduous catchments appear to be more susceptible to changes in water yields due to climate warming than the more diverse mixed forest catchments. This is important to forest managers because they may wish to prioritize planning for forested catchments that are hydrologically more resilient to climate change.
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