资源环境科技发展态势分析平台

Understanding the responses of tree growth and intrinsic water-use efficiency (iWUE) to anthropogenic CO2 increase and climate warming provides important benchmarks for evaluating future forest dynamics under different scenarios of warming and CO2 changes. Relative to the short period of instrumental data of the past few decades, long-term tree-ring width and stable carbon isotopic (delta C-13) data are invaluable in fully comprehending their interactions during the entire industrial era, since similar to 1850. Here, we present a tree-ring width chronology (1856 to 2015) and delta C-13 series (1876-2015) of Pinus massoniana for Yongtai county of Fujian province, in humid subtropical China, a 'green island' relative to other dry subtropical areas of the world. Tree growth was limited by precipitation of the hydrological year (previous November to current October) (r = 0.568, p < 0.001), and the stable carbon isotope discrimination (Delta C-13) was strongly correlated with relative humidity in September-October (r = -0.677, p < 0.001) of the current growing season. We found that the iWUE increased by 40.9% since 1876. Specifically, we found that the c(i):c(a) ratio decreased during the study period whereas intercellular CO2 concentration (c(i)) increased. The negative relationship between basal area increment (BAI) and iWUE indicated that increasing iWUE may not lead to long-term enhancement of tree growth. Our results indicated a drought-induced limitation to tree growth in response to rising CO2, and that trees may mitigate the negative effects of a decrease in water availability through a reduction in stomatal conductance.