青藏高原典型生态系统优势植物水分利用来源 .doc

water sources of dominant species in three alpine ecosystems on the Tibetan Plateau，China De-Yu Duan1,2 Hua Ouyang1, Ming-Hua Song1, Qi-Wu Hu1,2 (1 Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences. Beijing 100101, China 2Graduate University of Chinese Academy of Sciences. Beijing 100039, China) Received: 10 Jan. 2007 Accepted: 28 Feb. 2007 Handling editor: Jian-Xin Sun Corresponding author: Hua Ouyang +86 10 6488 9697 ohua@igsnrr.ac.cn Category: Ecology Abstract: Plant water sources were estimated by two or three compartment linear mixing models using δD and δ18O values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystem (forest, shrub and desert ecosystems) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ18O values of N.tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater raised with an increase of precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environment conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully unde