半干旱区沙地樟子松人工林凋落物混合分解与光降解效应

Litter decomposition is crucial for soil organic matter formation, nutrient release rate and ecosystem carbon balance. Litter species diversity can significantly influence carbon and nutrient turnover rates; however, no general or predictable pattern has emerged and mechanisms for diversity effects need confirmation. Moreover, photodegradation may play an important role in litter decomposition in semi-arid ecosystems, but the relative contribution of photodegradation and microbial degradation and their coupling mechanism are still unclear. In this proposed project, we will invistegate mixture decomposition and photodegradation processes of litters from pine needles and understory species leaves in a Mongolian pine plantation in the semi-arid sandy region of Northeast China using field microcosms. We will measure mass loss, nutrient dynamics, the concentrations of secondary compounds (lignin and tannin), and the changes of extracellular enzyme activities and microbial community structure during litter decomposition. We attempt to clarify the mixture effect of litter decomposition and its control mechanism, reveal the relative contributions and their interactions of the photodegradation and microbial degradation of litter decomposition, and specify the role of understory vegetation on decomposition and nutrient return of Mongolian pine needles. The results from this project will provide new insights into comprehensive understanding of how biodiversity interacts with decomposition processes, managing understory vegetation and litters in the Mongolian pine plantations as well promotoing the development of forest ecology.

凋落物分解对土壤有机质形成、养分释放速率和生态系统碳平衡具有重要意义。凋落物物种多样性显著影响有机碳和养分的周转速率，然而，目前缺乏普遍的或可预测的格局，多样性的相互作用机制需要进一步探讨；光降解可能在半干旱生态系统凋落物分解中发挥着重要作用，但光降解和微生物降解的相对贡献及其耦合机制仍不清楚。本项目以我国东北半干旱区沙地重要造林树种樟子松人工林为对象，采用田间微宇宙方法，开展樟子松针叶与林下主要植物叶凋落物的混合分解及其光降解过程研究，通过测定凋落物分解质量损失、养分动态，以及木质素、单宁等主要化合物含量、胞外酶活性及微生物群落结构的变化，阐明凋落物分解过程中的混合效应及其控制机理，揭示光降解与微生物降解对凋落物分解的相对贡献及其相互作用，明确林下植被在樟子松针叶分解及其养分归还中的作用，为沙地樟子松人工林林下植被和凋落物管理提供科学依据，促进森林生态学的发展。

凋落物分解是生态系统关键生态过程，对土壤有机质形成、养分释放和生态系统碳平衡具有重要意义。凋落物物种多样性对凋落物分解的相互作用机制、光降解在半干旱生态系统凋落物分解的相对贡献及其与微生物过程的耦合机制仍不清楚。本项目以我国东北半干旱区沙地重要造林树种樟子松人工林为对象，采用田间微宇宙方法和室内培养方法，开展了樟子松针叶与林下主要植物叶凋落物的混合分解及其光降解过程研究，通过测定凋落物分解质量损失、养分动态，以及木质素、单宁等主要化合物含量、酶活性及微生物群落结构的变化，阐明了凋落物分解过程中的混合效应及其控制机理，揭示了光降解与微生物降解对凋落物分解的相对贡献，明确了林下植被在樟子松针叶分解的作用，发现凋落物在分解过程中释放的养分较少，研究结果为沙地樟子松人工林林下植被和凋落物管理提供了科学依据；同时，本研究从凋落物分解角度，为认识全球氮沉降背景下生物多样性与森林生态系统功能关系提供了依据。