Effects of grazing and rainfall variability on root and shoot decomposition in a semi-arid grassland
Effects of grazing and rainfall variability on root and shoot decomposition in a semi-arid grassland
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DOI：
10.1016/j.apsoil.2008.08.002
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发表时间：
2009-01-01
影响因子：
4.8
通讯作者：
Brueck, Holger
中科院分区：
文献类型：
--
作者：
Giese, Marcus;Gao, Ying Zhi;Brueck, Holger
过度放牧日益影响内蒙古大面积的半干旱草原。采用凋落物袋法研究了长期放牧围封区（UG 79）、冬季中度放牧区（WG）和长期重度放牧区（HG）放牧对植物地上部和根系分解的影响。我们分离的影响，当地的环境因素和凋落物质量改变放牧。生长季节的平均和非常低的降水量，使我们能够研究年际降水变化对decomposition. grazing诱导的差异，在环境因素的三个研究草地网站没有影响腐烂率的地上部和根系干物质。不同放牧地凋落物质量的差异也不能通过根系分解动态反映出来。在网站HG的枝条腐烂加速不能明确地与凋落物质量参数。芽腐烂率或多或少是恒定的，即使在非常干燥的条件下。这表明光降解（太阳UV-B辐射），以控制在这个半干旱生态系统的地上分解的可能性。通过对根系分解的回归分析，发现土壤含水量是解释根系分解的最佳参数，在地上部和根系的分解过程中，一般没有检测到N的固定。这是可能的，当根分解强烈减少在干旱时期，芽分解变得相对更重要的养分循环。需要一个单独的分析，以描述在这个半干旱草原的C和N循环的地上部和根系的腐烂动力学。放牧通过植物物质分解对C和N通量的影响可能与季节性降雨模式具有很强的相互作用。(C)2008 Elsevier B. V.保留所有权利。
Overgrazing increasingly affects large areas of Inner Mongolian semi-arid grasslands. Consequences for ecosystem functions and, in particular, for the decomposition as a key process of ecosystem carbon (C) and nitrogen (N) cycling are still unclear.We studied the effects of grazing on shoot and root decomposition with the litter bag method in a long-term grazing exclosure (UG79), a moderate winter grazed (WG) and a long-term heavily grazed site (HG). We separated the effects of local environmental factors and litter quality as altered by grazing. Growing seasons of average and very low precipitation allowed us to study the effect of inter annual rainfall variability on decomposition.Grazing-induced differences in environmental factors of the three studied grassland sites had no effect on decay rates of shoot and root dry mass. Also differences in litter quality among the grazing sites were not reflected by root decomposition dynamics. The accelerated shoot decay at site HG could not clearly be linked to litter quality parameters. Shoot decay rates were more or less constant, even under very dry conditions. This indicates the possibility of photodegradation (solar UV-B radiation) to control aboveground decomposition in this semi-arid ecosystem. By selecting the best predictors of root decomposition from regression analysis, we found that soil water content was the best parameter explaining the dynamics.Net N immobilization was generally not detected during the decay process of shoot and root. It is likely, when root decomposition is strongly reduced in dry periods, shoot decomposition becomes relatively more important for nutrient cycling. A separate analysis of shoot and root decay dynamics is required in order to describe C and N cycling in this semi-arid grassland. The grazing impact on C and N fluxes through decomposition of plant material likely exhibits a strong interaction with seasonal rainfall pattern. (C) 2008 Elsevier B.V. All rights reserved.