黄土丘陵区退耕植被土壤C、N、P化学计量特征对土壤固碳的调控机制

土壤碳、氮、磷是营养元素生物地球化学循环的核心组成部分，三者平衡和耦合关系对土壤碳吸存和排放起着关键的调控作用，认识退耕还林区土壤生态化学计量学特征可为研究退耕林区土壤固碳机制提供新思路。本项目以陕北黄土丘陵区退耕还林地为研究对象，研究不同退耕年限自然恢复和人工恢复土壤C、N、P生态化学计量学特征及其演变规律，以明确两种恢复方式下土壤碳、氮、磷的交互作用和制约关系；并进一步分析土壤C、N、P生态化学计量特征演化与土壤碳组分、微生物碳氮磷、酶活性、凋落物碳氮磷输入的响应关系，探讨土壤C、N、P生态化学计量学特征在不同恢复方式下对土壤碳库变化及相关因素的调控作用，为进一步揭示退耕地植被恢复对土壤碳源汇调节机制提供新依据，可为脆弱生态系统恢复、重建及可持续发展理论提供支撑。

Soil carbon, nitrogen and phosphorus elements are the core part of the biogeochemical cycle of nutrient elements, where their balance and coupling relationship play a regulation role to the soil carbon sequestration and emission. That realization of the ecological stoichiometry characteristics can provide a new insight for understanding mechanism of soil carbon sequestration in the regoin of returning cropland to forest. This project focused on returning cropland of Loess Hilly Region in Shaan Bei, and the objective was to first study the ecological stoichiometry characteristics and evolution law of soil carbon, nitrogen and phosphorus in the soil of natural recovery and artificial restore under different stand ages, define the interaction and restriction relationship between soil carbon、nitrogen and phosphorus, and to analysis the response of the evolution law of the C:N:P stoichiometry to soil carbon fractions, microbial carbon, nitrogen and phosphorus, enzyme activity, and the input of litter-carbon, nitrogen and phosphorus. The control effects of C:N:P stoichiometry on the changes of carbon pools and related factors will be discussed in different recovery mode. It is important to reveal regulation mechanism of soil carbon sequestration under conversion of cropland to forest and provide theoretical foundation and support for ecosystem restoration, reconstruction and the sustainable development in Loess Hilly Region.