Variations of deep water uptake and water use efficiency indicated divergence in tree growth stability

Insights into forest growth stability in response to intensified climate change and disturbances is critical to maintain the continued flow and stability of forest services. However, the underlying drivers for tree growth stability remain poorly understood. In this study, we quantified the spatiotemporal pattern in tree growth stability of Chinese pine (Pinus tabulaeformis) plantations and its relationship to diverse driving factors (climate, stand structure, ecophysiological traits, soil properties, and topography) across a great climatic gradient in northern China in the period of 1979–2018. We calculated the coefficient of variation of tree ring chronology (TRIcv) to characterize tree growth stability and revealed that the TRIcv increased significantly with increasing multiyear mean aridity index (MAI) and vapor pressure deficit (VPD) spatially. Temporally, TRIcv displayed increasing trend in 25 of 40 study sites. Constrained redundancy analysis revealed that TRIcv was strongly mediated by water availability, water uptake from different soil layers, wood density, tree height, leaf stable carbon isotope discrimination (δ13C), and leaf nutrients. The ratio of water uptake from 60 to 80 cm soil layer and leaf δ13C were the two most important ecohydrological-related factors determining TRIcv, highlighting that the water uptake strategy and leaf water use efficiency play critical role in reshaping the tree growth stability of Chinese pine to cope with the intensifying climate change.