基于稳定同位素的中亚热带典型造林树种水分利用对降水格局变化的响应机制

我国人工林面积广大，尤其是在中亚热带地区，发挥着极其重要的生态和社会功能。随着全球气候变化的加剧，季节性洪涝和干旱等极端气候事件频发，这可能会改变该地区人工林树木的水分利用来源和效率，影响生态系统的结构和功能。然而，该地区常见人工林树种将采取何种适应策略，其调控机制是什么，目前仍不十分清楚。为此，本项目拟在江西省中部典型退化红壤丘陵区建立的人工林长期观测样地，选取马尾松、湿地松、枫香和木荷4种典型造林树种为研究对象，基于稳定氢、氧、碳同位素技术，通过野外季节观测和室内降水模拟试验，分析该区域降水-土壤水-浅层地下水同位素组成特征及运移规律，揭示主要造林树种水分来源和水分利用效率的差异，探讨不同功能型造林树种水分利用对季节性降水和极端降水事件响应的功能可塑性调控机制。这将有助于深入认识全球降水格局变化背景下中亚热带不同造林树种的水分利用策略，为我国南方人工林的经营管理提供科学依据。

The area of artificial forests is vast in China, especially in the middle subtropical zones, which plays an extremely important ecological and social functions. The extreme climate events such as seasonal flood and drought will become more intense and frequent as the global climate changes, which may shift the water source depths and water use efficiency of the trees in the subtropical plantations and influence the structure and function of the ecosystem. However, the adaptation strategies and adjustment mechanisms for the common afforestation tree species in this region remain unclear. In this project, we intend to use the stable hydrogen, oxygen and carbon isotopes (δD, δ18O and δ13C) to study the response mechanisms of water use to changes in precipitation patterns for four common afforestation tree species including Pinus massoniana (an evergreen conifer tree species）、Pinus elliottii (an evergreen conifer tree species)、Liquidambar formosana (a deciduous broadleaved tree species) and Schima superba (an evergreen broadleaved tree species) through situ seasonal monitoring and simulation precipitation experiments in the long-term observation sample plots of plantations in a typical degraded red-soil hilly region of Central Jiangxi Province. Our main aims are as follows: 1) to determine the hydrogen and oxygen isotope compositions of different water sources including precipitations, soil waters and shallow groundwaters in this regions; 2) to reveal the differences in water sources and water use efficiency for the different afforestation tree species; 3) to explore the control mechanisms of plasticity adjustment of the afforestation tree species for the water use in response to changes in seasonal precipitations and extreme precipitation events. This study would contribute to better understand the water use strategies for the afforestation tree species under the global precipitation pattern changes, which may provide a scientific basis for the management of plantation in southern China.