黄土丘陵森林带微生物介导的叶片枯落物分解以及对土壤有机碳的贡献

Microbial-mediated leaf-litter decomposition is a key process connecting soil and plant carbon pool. It plays an important role in carbon cycling in terrestrial ecosystem. The project will focus on the typical forest vegetation phyllosphere microorganisms-regulated litter decomposition and the soil organic carbon sequestration on the Loess hilly regions. Based on the combination of the in-site field decomposing-bag and traditional lab analysis, as well as 13C isotope tracing, biomarker, and molecular biotechnology, the interaction among leaf-litter decomposition, phyllosphere microorganisms and soil organic carbon will be investigated. The main focus of the study are: (1) to analysis the variations in leaf-litter stoichiometry (C:N:P) and carbohydrates; (2) to study the structure and diversity of the phyllosphere microorganism; (3) and to further explore the mechanisms of the effect of litter decompositions and microbial biomarkers to the soil organic carbon accumulation during decomposing process. Our aim is: to illustrate the contributions of various forest leaf-litter decompositions to carbon sequestrations; to clarify the proceeding of phyllosphere microorganisms and their roles in carbon cycling. Therefore, shed lights on the mechanisms of the interactions between forest leaf-litters and soil ecosystem, as well as the soil organic carbon sequestrating process originating from aboveground litter decompositions.

叶片枯落物在微生物作用下的分解过程是联系土壤碳库和植物碳库的重要环节，对陆地生态系统碳循环具有重要影响。本研究围绕黄土丘陵区典型森林植被叶际微生物介导的枯落物分解过程与土壤有机碳固定的互作机理这一科学问题，通过野外分解袋与室内提取分析相结合的方法，采用13C稳定同位素、生物标志物、分子生物学等技术，研究叶片枯落物、叶际微生物和土壤有机碳在叶片分解过程中的相互关系。重点研究：（1）叶片枯落物中不同碳水化合物及碳、氮、磷化学计量比变化；（2）叶际微生物群落结构和多样性演变特征；（3）地表叶片枯落物和微生物标志物对土壤有机碳固持的作用机制。旨在阐明不同森林植物叶片分解及对土壤有机碳积累的贡献；探明枯落物分解过程中叶际微生物群落演变及其介导的碳循环过程；丰富森林生态系统中植被叶片与土壤生态系统相互作用机制；为森林生态系统中来自地上部分的土壤有机碳积累提供科学依据。

叶片枯落物对陆地生态系统碳循环具有重要影响，也是联系土壤碳库和植物碳库的重要环节。本项目重点围绕森林植被叶际细菌和真菌群落参与的枯落物分解过程与土壤有机碳固定的互作机理这一科学问题，通过野外分解袋与室内提取分析相结合的方法，采用生物标志物、分子生物学等技术，重点研究了枯落物不同碳组分、叶际微生物和土壤有机碳含量在分解过程中的协同变化。主要结论有以下几点（1）森林树种塑造独特的土壤细菌和真菌群落，它们的群落特征在不同树种间差异明显，叶际的主导细菌的相对丰度基本是叶下土壤的两倍；（2）叶际伴生真菌群落中，子囊菌门和担子菌门是最大的优势门，微生物群落与凋落物化学养分和结构性碳水化合物呈显著正相关，碳水化合物和氨基酸代谢在枯落物分解到中后期时达到最强；（3）叶际微生物随分解时间变化的很快 （细菌显著，真菌不显著），但是这种变化并没有明显的垂直传递性，枯落叶下面的土壤微生物群落结构随时间变化不显著。