中文摘要：

为估算光降解在中亚干旱区地表凋落物分解中的作用，本研究利用凋落物分解袋法，以梭梭叶、芦苇叶和麦秆为研究对象，沿自然降水梯度，在古尔班通古特沙漠腹地、沙漠边缘和吐鲁番进行遮除紫外辐射和自然光照处理的分解试验。结果表明：1）紫外遮除处理降低了3个分解点的凋落物分解速率，但光降解对分解贡献率变化和分解点干燥程度的变化并不一致；2）紫外遮除处理降低了各分解点的凋落物氮素释放。凋落物分解过程中的氮释放动态因凋落物类型而异，芦苇和梭梭叶分解中的氮素变化在各分解点均表现为释放累积释放的变化过程，而麦秆则表现为“释放累积”的过程；3）紫外遮除处理降低了半纤维素损失，对纤维素没有显著影响，木质素在分解过程中的变化对处理没有响应。本研究表明，光降解在温带荒漠区凋落物分解中起着重要的作用，其作用强度受分解点环境和凋落物质量的影响。

英文摘要：

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.