全球变化对陆地生态系统枯落物分解的影响

了解枯落物分解对大大二氧化碳浓度增高，气候变暖和降水变化的反应，对深入理解陆地生态系统土壤有机物形成和碳的固化能力（Carbonh sequestration)十分重要。通过分析业已发表的文献，实验室根系分解实验和美国西北部针叶林叶片的分解实验，旨在评估大气二氧化碳浓度增高，气候变暖和降水化对陆地生态系统枯落物分解的可能影响，大气二氧化碳浓度增高可通过降低枯落物质量和增加草原生态系统土壤水分间接地影响枯落物分离，根据17项研究结果，大气二氧化碳浓度加倍可导致木本和草本枯落物平均氮含量降低19．6％和9．4％；木质素／氮化值增高36．3％和5．5％，枯落物质地的降低通常导致枯落物分解减慢。气候变暖一般加速枯落物的分解，但是用于表示这种促进作用的Q10随着温度的增高而降低，全球降水变化对陆地生态系统枯落物分解的影响不但取决于现有水分条件而且还以决于降水变的程度。以美国西北部地的针叶林为例，降水改变对森林生态系统枯落物分解的影响将是 多元的，有的增加，有的降低，而有的相对不变，最后，指出了今后 在方该领域有待加强的几个研究方面。

Effects of global change on litter decomposition in terrestrial ecosystems

Understanding the response of litter decomposition to elevated CO 2 atmospheric concentration,global warming,and change in precipitation is of crucial importance in understanding soil organic matter formation and carbon sequestration in terrestrial ecosystems.In this review,we use published results,laboratory incubation results of decomposing roots,and leaf litter decomposition data in the coniferous forests of the Pacific Northwest of USA to assess the potential effects of global change(e.g.,elevated CO 2 atmospheric concentration,global warming,and precipitation change)on litter decomposition in terrestrial ecosystems.Elevated CO 2 concentration influences litter decomposition indirectly by decreasing litter substrate quality and increasing soil moisture content in dry grassland ecosystems.According to 17 publishied studies,doubled ambient CO 2 concentration decreased the average N concentration of tree litters and herbaceous litters by 19.6% and 9.4%,respectively.The average lignin:N ratio of tree litters and herbaceous litters increased 36.3% and 5.5%,respectively,due to CO 2 enrichment.Such substrate quality changes should generally lead to a reduction in the decomposition rate of litters.Global warming directly increases litter decomposition,however,the Q 10 value used to express this stimulatory effect decreased with increasing temperature.The degree that global precipitation change influences litter decomposition will depend on the potential magnitude of this change as well as the current moisture conditions.Even within a single region like Pacific Northwest of USA the responses of litter decomposition to altered rainfall can be divergent,with some sites increasing,others decreasing,and others remaining relatively unchanged.Several research areas are identified for reducing the uncertainites in the effects of global change on litter decomposition in terrestrial ecosystems.