摘要:受全球变化的影响生物多样性的丧失日益严重，及时了解凋落物物种多样性及其组成如何直接或者通过调节微生物群落来间接影响凋落物分解已经成为生态学领域的热点问题之一。在呼伦贝尔典型草原区，羊草（Leymus chinensis）为原生群落建群种，茵陈蒿（Artemisia capillaris）、麻花头（Serratula centauroides）、二裂委陵菜（Potentilla bifurca）在退化及恢复群落中的多度均较大，本研究以此4种植物的凋落物为研究对象，在两倍于当前大气CO₂浓度（800 μmol/mol）条件下，通过嵌套实验设计来研究凋落物多样性（凋落物组成）对凋落物质量、C、N残余率和残余C/N的影响，并深入分析凋落物初始性质以及土壤革兰氏阳性菌（G⁺）、革兰氏阴性菌（G^-）、细菌（B）、真菌（F）及土壤总微生物磷脂脂肪酸（Phospholipid Fatty Acid，PLFA）含量和F/B对凋落物分解的影响。结果表明：（1）凋落物多样性及组成对凋落物质量、C、N残余率以及残余C/N均具有显著影响；凋落物组成对G⁺ PLFAs含量具有显著影响；（2）冗余分析（Redundancy Analysis，RDA）结果表明凋落物组成对凋落物分解和土壤微生物群落相关指标的影响高于凋落物多样性；（3）结构方程模型（Structural Equation Model，SEM）结果表明凋落物初始木质素含量和初始C/N均对凋落物分解具有显著影响，其中凋落物初始木质素含量起主导作用，其还可通过对土壤真菌PLFAs含量的影响来间接影响凋落物N残余率和残余C/N。所得结果可为大气CO₂浓度升高条件下退化草原生态系统的物质循环特征的预测乃至草原生态系统功能的合理评估提供数据支持。



Abstract:The loss of species diversity is increasingly rapid due to global change. Therefore, understanding how litter species diversity and its composition affect litter decomposition directly or indirectly via mediating soil microbial community has been a hot topic in the field of ecology. In the typical steppe in Hulun Buir, Leymus chinensis is a dominant species in the natural communities, and plants of Artemisia capillaris, Serratula centauroides, and Potentilla bifurca show high abundance in the degraded or recovering communities. In this study, we selected the litter of these four species as study materials, and set up a nested design by nesting litter composition within the factor of litter diversity under the conditions of doubling ambient atmospheric CO₂ concentration. We tried to explore the effects of litter diversity and its composition on litter mass, C, N remaining rate and remaining C/N, and analyze how the litter initial characteristics and the phospholipid fatty acid (PLFA) contents of gram-positive bacteria (G⁺), gram-negative bacteria (G^-), bacteria (B), fungi (F), the soil total microorganisms and F/B impacted the litter decomposition. The results were shown in the following. (1) The factor of litter diversity and its composition had significant effects on mass, C, N remaining rate, and remaining C/N. The litter composition had a significant effect on G⁺ PLFAs content. (2) The result of redundancy analysis showed that litter composition had greater impact than litter diversity on variables involved in litter decomposition and soil microbial community. (3) The result of structural equation model (SEM) indicated that both litter initial lignin content and initial C/N had significant effects on the litter decomposition parameters, and that litter initial lignin content played a more important role. The litter initial lignin content had significant indirect effect on the litter N remaining rate and remaining C/N by changing fungi PLFAs content. These results would provide data support for the prediction of the substance cycling characteristics in the degraded grassland ecosystem and for a better assessment of grassland ecosystem function in the context of global climate change.





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