关键词: 水分来源, 稳定氢同位素, 林分退化, 杨树, 液流

Abstract: To estimate the effects of photodegradation on the decomposition of plant litter in arid areas of central Asia, three types of litter (Haloxylon ammodendron， Phragmites australis leaves and Triticum aestivum straw) were selected as test objects, and by using litterbag method, a decomposition experiment with UV exclusion and natural light was conducted along a precipitation gradient in the hinterland and southern periphery of Gurbantonggut Desert and the Turpan, Xinjiang of Northwest China. At the three sites, UV exclusion decreased the litter decomposition rate, but the contribution of photodegradation magnitude to the litter decomposition differed because of the different drought extent. UV exclusion reduced the N release from the litter, and the N release dynamics differed with litter type. H. ammodendron and P. australis leaves exhibited N releaseaccumulationrelease pattern, while T. aestivum straw showed N releaseaccumulation pattern. UV exclusion reduced the litter’s hemicellulose loss, but had little effects on the litter’s cellulose and lignin contents. Our study suggested that photodegradation played an important role in the litter decomposition in temperate deserts, and the effect magnitude was dependent on the specific environmental condition and litter quality.

Key words: Populus simonii, water source, tree dieback., stable hydrogen isotope, sap flow