Studies of the Effects of Biophysical Factors on Surface Temperature over Arid Riparian Ecosystems in Northwest China

Abstract

Forests play an important role in the global carbon cycle and modification of local climate through the biochemical and biophysical processes.However， the biophysical effects of afforestation in arid regions on local surface temperature have received little attentions over the past 30 years.Therefore， in this study， we combined in situ eddy covariance flux measurements from a neighboring pair of forested and the background desert sites with the decomposed temperature metric （DTM） method to systematically analyze the impacts of arid forests on surface temperature （Ts）.Results showed that despite absorbing more net radiation （35.4 W·m-2） than the desert， the riparian forests tended to cool Ts （-1.28 ℃） on annual basis.Meanwhile， this cool effect shows a significant seasonality.Specifically， afforestation may lead to a net cooling effect （ΔTs ranging from -3.6 to -0.6 ℃） from March to October， and a slightly warming effect in other months （ΔTs =0.5 ℃）.The DTM method revealed that evapotranspiration played a dominant role in cooling surface temperature， while surface albedo and incoming longwave radiation acted together to increase forest surface temperature.Therefore， this study not only improves our understanding of interaction between arid ecosystem and climate， but also has important reference for assessing ecological service function of in arid ecosystem.

Keywords

• riparian forest
• arid regions
• surface temperature
• biophysical processes
• net radiation