西南喀斯特区域水热梯度带土壤碳氮磷耦合关系及其变化机制

Karst area in Southwest China is identified as extremely fragile ecosystems, and has been observed extensive rocky desertification. Increased vegetation growth has been reported via series of ecological engineering projects, however, the soil function that support the sustainable vegetation development is negligibly promoted. At the same time, the region is faced with regional climate change characterized by extreme drought and flood disasters. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. These changes are predicted to threaten vegetation restoration, and exacerbate processes leading to land degradation. In the present study, the vegetation and soil carbon (C), nitrogen (N), phosphorus (P) and its stoichiometric ratio in two different restoration types (natural recovery and artificial restoration) will be investigated along a climate gradient in the karst region of southwestern China. Rate of nutrient input via biological and geochemical processes will be quantified, and the function of climate on biogeochemical cycles will be analyzed. Vegetation community, soil C, N and P forms, and microbial activity will be surveyed, so as to evaluate the direct and indirect effects of climate and restoration type on the coupling of soil nutrient cycles, and eventually reveal the coupling/uncoupling mechanism of soil nutrient cycles under climatic change. The results will provide scientific basis for addressing climate change and the ecological recovery in the karst region southwestern China.

我国西南喀斯特区域生态环境脆弱，石漠化严重，系列生态工程实施后，植被初步绿化，但土壤支撑功能提升缓慢。同时该区域面临着以极端干旱和洪涝灾害为主要特征的区域气候变化，处于恢复初期的土壤碳、氮、磷耦合循环和植被恢复的可持续性面临挑战。针对以上问题，本研究基于区域样带试验，以两种不同恢复模式生态系统（自然恢复、人工恢复）为研究对象，分析土壤和植被碳、氮、磷及其化学计量比随区域水热梯度的变化；量化生态系统地球化学过程和生物过程的养分输入速率，探明区域水热条件对生态系统养分生物地球化学耦合过程的影响；分析植被、土壤养分组分和微生物等生态系统关键结构功能指标变化，解析气候因子和恢复模式对土壤养分耦合关系的直接和间接影响，揭示喀斯特生态系统土壤碳氮磷耦合关系及其随区域水热梯度的变化机制，应对未来气候变化对喀斯生态系统的可能影响，为退化生态系统可持续恢复提供理论依据。

我国西南喀斯特区域生态环境脆弱，石漠化严重，系列生态工程实施后，植被初步绿化，但土壤支撑功能提升缓慢。同时该区域面临着以极端干旱和洪涝灾害为主要特征的区域气候变化，处于恢复初期的土壤碳、氮、磷耦合循环和植被恢复的可持续性面临挑战。针对以上问题，本研究基于区域样带试验研究发现不论在喀斯特还是非喀斯特，植被恢复后的森林生态系统显著提高了土壤碳氮养分。随着降水量增加和温度升高导致喀斯特区域土壤养分流失加剧，土壤C含量有相对降低的趋势，而N、P含量有相对增加的趋势。AMF多样性随温度和降雨增加而增加，在年降雨量和年均温较高区域，灌丛和次生林土壤AMF多样性高于耕地，低水热水平区AMF多样性对植被恢复的响应则相反。AMF和固氮菌相互作用的共线网络结构在高水热水平区域更紧密，网络也更复杂。研究结果揭示了喀斯特生态系统土壤碳氮磷耦合关系及其随区域水热梯度的变化机制，应对未来气候变化对喀斯生态系统的可能影响，为退化生态系统可持续恢复提供理论依据