Seasonal and Depth Dynamics of Soil Moisture Affect Trees on the Tibetan Plateau

Abstract

The soil moisture (SM) influences tree growth with climate change. However, the spatial and temporal dynamics of tree water use strategies in climate-sensitive areas remain uncertain. Therefore, we collected the tree-ring oxygen isotope (δ18OTR) chronologies and divided the wet–dry gradients according to the precipitation on the Tibetan Plateau (TP). Further, the relationship between the δ18OTR and environmental factors was analyzed across different gradients. We found the following: (1) The SM during the growing season was the most important factor for δ18OTR. (2) The response of the δ18OTR to the SM had a lag in arid areas than in humid areas. (3) Trees absorbed the SM on the surface in humid areas (r = −0.49 to −0.41, p r = −0.48 to −0.29, p 18OTR in complex environmental contexts. Trees with single water use strategies should be given more attention to keep ecosystems healthy.

Keywords

• Tibetan Plateau (TP)
• tree-ring oxygen isotope (δ¹⁸O_TR)
• water use strategies
• soil moisture
• wet–dry gradients