氮磷养分添加对热带森林土壤有机碳的影响及其微生物机理

Tropical forest play a key role in global carbon (C) cycling. Since most of tropical forests are phosphorus (P)-limited system, the continuous nitrogen (N) deposition would aggravate its P limitation, which would further affect soil carbon sequestration. Although N deposition have received widespread attention in previous decades, most of these studies were conducted in temperate or boreal forests, with rare reports in tropical forests, where P availability also played an important role in various ecosystem processes. Moreover, the underlying mechanisms of N and P availability on soil C sequestration still remain unclear. In this proposal, we will investigate the effect of N and P addition on plant biomass, soil organic C pools and its stabilization, soil respiration, soil microbial community composition, lignin decomposition and hydrolytic and oxidase enzyme activity in tropical forests of South China. We want to distinguish the effect of N and P availability and their interactions on above processes in tropical forest soils, and elucidate the microbial and enzymatic mechanisms controlling the effect of N and P availability on soil carbon pool in tropical forests. The results from this project would help to accurately understand and simulate future soil carbon budget and long-term carbon sequestration potential in tropical forest, and also would help to understand coupled C, N and P cycles and its biochemical regulatory mechanism in tropical forests.

热带森林土壤碳库在全球碳循环中发挥着关键的作用。由于热带森林普遍是磷限制的系统，持续的氮沉降将加剧森林的磷限制，进而影响土壤有机碳固存。但当前的研究对于氮磷养分影响热带森林土壤有机碳的关注较少，其作用机理也不清楚。而且，这些研究都集中在氮沉降，很少关注磷的作用。本项目拟在我国华南的典型热带季雨林地区，研究氮磷养分添加对森林植物生物量、土壤呼吸及其组分、土壤有机碳储量、土壤有机碳稳定性和木质素分解的影响；通过测定土壤微生物群落结构组成、水解酶和氧化酶、漆酶活性等的变化，探讨氮磷添加对土壤碳过程的影响；通过研究同位素标记的木质素的分解过程，了解氮磷养分对木质素分解的影响；综合以上研究，阐明氮磷养分有效性对土壤碳库及其稳定性的影响，并揭示其微生物和酶学机理。该研究不仅能为准确模拟热带森林碳收支动态变化和长期固碳能力提供科学依据，也有助于了解热带森林生态系统碳氮磷循环的耦合过程及其机制。

热带森林土壤碳库在全球碳循环中发挥着关键的作用。由于热带森林普遍是磷限制的系统，持续的氮沉降将加剧森林的磷限制，进而影响土壤有机碳固存。本项目在我国华南的典型热带季雨林地区，研究氮磷养分添加对森林植物凋落物分解、土壤有机碳储量、土壤有机碳稳定性和不同组分有机碳分解的影响，测定土壤微生物群落结构组成、水解酶和氧化酶活性的变化，并对比氮磷养分提高对以上过程的影响。本项研究发现高氮低磷的热带森林环境会有利于土壤有机碳的固存，但氮磷养分影响土壤有机质累积的机制是不同的：高氮可以降低土壤细菌的活性，从而减缓土壤有机质和凋落物的分解，而低磷则限制了土壤中真菌的活性，降低了氧化酶的活性，不利于土壤中难分解有机质的分解。本研究阐明了氮磷养分有效性对土壤碳库及其稳定性的影响，揭示了其微生物和酶学机理，表明未来高氮低磷的环境有利于热带森林土壤有机碳固持能力的提高。在本项目资助下，负责人已经发表10篇有关生态系统碳循环过程的第一或通讯作者的SCI论文，其中包括Plant Soil, Functional Ecology, National Science Review等土壤学和生态学领域的主流期刊，此外负责人也获评国家林草局科技创新青年拔尖人才称号，并培养博士研究生1名，硕士研究生1名（将于2021毕业）。