景观位置对山地森林土壤有机碳库来源、转化和稳定性的影响

Soil is the largest carbon pool in terrestrial ecosystems. Information on soil organic carbon (SOC) sources, transformation and stability is essential to evaluate carbon dynamics and sequestration potential of soil ecosystem. The inherent spatial heterogeneity of SOC complicates the accurate estimation of soil carbon pool. While most researches on spatial heterogeneity in SOC have focused on carbon storage, few has examined the heterogeneity in soil carbon processes. Environment factors such as vegetation, soil moisture and temperature, texture, and nutrient level vary significantly on different landscape positions (terrain factors including slope, aspect and slope position). This will not only causes the spatial heterogeneity in carbon storage, but also generate spatial heterogeneity in SOC sources, transformation and stability. In this study, we are going to sample soils from different landscape positions in a subtropical forest. First, physical fractionation, chemical fractionation and carbon mineralization characters will be analyzed to characterize SOC stability. Second, biomarkers, (including lignin, lipid, amino sugar, neutral sugar), which are from different source and have varying stability, will be detected to investigate carbon sources and transformation. Results may help us reveal the effects of landscape position on carbon cycling and its inherent mechanism, enhance our understanding on the spatial heterogeneity of carbon dynamics in mountain forest landscape, and provide important parameters for simulating mountain soil carbon cycle.

土壤是陆地生态系统最大的碳库，阐明土壤有机碳（SOC）的来源、转化和稳定机制是评估土壤碳动态及其固碳潜力的关键。SOC在空间分布上的异质性不利于景观内土壤碳动态的准确评估。现有SOC空间异质性研究多集中在碳储量上，而对碳循环过程的异质性了解不足。山地森林不同景观位置（坡度、坡向、坡位等）承载了植被、水分、温度、土壤质地和养分等多个环境因素的变化，在引起SOC储量空间变化的同时，也将导致SOC来源、转化和稳定特征的空间差异。本研究选取中亚热带八大公山国家自然保护区内不同景观位置的土壤，(1) 利用SOC物理、化学分组和长期矿化特征，揭示SOC的稳定特征及机制；(2) 通过土壤中生物标识物（木质素、脂类物质、氨基糖和中性糖），追踪碳源的输入输出以及分解转化情况，以明确景观位置对碳循环的影响及内在机理。本研究将有助于加深对山地森林土壤碳过程空间异质性的理解，为精确模拟山地土壤碳循环提供数据支持。

土壤是陆地生态系统最大的碳库，阐明土壤有机碳（SOC）的稳定机制和循环转化特征是评估土壤碳动态及其固碳潜力的关键。山地森林不同景观位置承载了植被、水分、温度、土壤质地和养分等多个环境因素的变化，在引起SOC储量空间变化的同时，也将导致SOC转化和稳定特征的空间差异。本研究选取中亚热带山地森林不同景观位置的土壤进行研究，结果表明景观位置虽不影响土壤碳储量，但对土壤碳循环过程影响显著。具体表现为：（1）流域内存在土壤碳（主要为轻组碳组分）侵蚀，但并未在沟谷沉积，而向更远的地方迁移；（2）沟谷SOC稳定性高于山梁，主要受土壤矿质颗粒的保护作用；（3）沟谷土壤碳排放低于山梁，且对温度、水分变化敏感性低，沟谷区域更有利于SOC的长期固持。以上结果表明亚热带山地森林碳循环过程受到植被分布、水文过程等多因素影响，并揭示了山地森林土壤碳循环过程的空间异质性，为精确模拟山地土壤碳循环提供数据支持。