How Does Tree Density Affect Water Loss of Peatlands? A Mesocosm Experiment

摘要: Raised bogs have accumulated more atmospheric carbon than any other terrestrial ecosystem on Earth. Climate-induced expansion of trees and shrubs may turn these ecosystems from net sinks into sources when associated with reduced water tables. Increasing loss through tree evapotranspiration could potentially deepen tables, thus stimulating peat decomposition release. Bridging the gap between modelling field studies, we conducted a three-year mesocosm experiment subjecting natural bog vegetation to three birch densities, studied changes in subsurface temperature, balance components, leaf area index composition. We found deepest table mesocosms low density. Mesocosms high density remained wettest (i.e. highest tables) whereas control treatment without had intermediate These differences are attributed mostly evapotranspiration. Although our results cannot be directly scaled up level, systematic effect suggests that as become colonized by trees, time, transpiration effects drying becoming increasingly offset shading during later phases encroachment. density-dependent important implications for structure functioning peatbogs.