不同林龄杉木林土壤有机碳稳定性对氮沉降的响应机制

The increasing atmospheric nitrogen deposition will change forest soil organic carbon dynamics, but the mechanism is unclear. In addition, less is known about the effects of nitrogen deposition on soil organic carbon content and stability in different ages of forest stands or the cause for the difference. In the present study, we take Chinese fir plantation in Gaojingmiao forest farm (located in Xuancheng City, Anhui Province) as the experimental site and use field observation，laboratory analysis and incubation to study: (1) Response of soil organic carbon content to nitrogen deposition in Chinese fir plantation; (2) Response of soil organic carbon stability (including physical protection, chemical stabilization and biochemical stabilization) to nitrogen deposition in Chinese fir plantation; (3) Difference of the two processes mentioned above between different ages of forest stands. We expect to clarify the mechanism of soil organic carbon stability response to nitrogen deposition in Chinese fir plantations of different stand ages. The results will enrich the basic theory of soil carbon cycling in plantations, provide basic research for quantitatively assessing carbon stocks of forest ecosystem under nitrogen deposition conditions and support the management of forest ecosystems and sustainable development.

不断加剧的大气氮沉降影响森林土壤有机碳动态变化，但其影响机制尚不清楚，且不同林龄的森林土壤有机碳含量及稳定性对氮沉降的响应差异及造成差异的原因还不明确。本研究拟选取安徽省宣城市的高井庙林场中的杉木人工林作为试验样地，综合采用野外观测、室内分析和恒温培养等方法，对比研究：(1)杉木林土壤有机碳含量对氮沉降的响应；(2)杉木林土壤有机碳稳定性（包括物理稳定性、化学稳定性、生物化学稳定性）对氮沉降的响应；(3)上述作用过程在不同林龄间的差异性。以期阐明不同林龄杉木林土壤有机碳稳定性对氮沉降的响应机制。研究结果将丰富人工林土壤碳循环的基础理论，为定量评估氮沉降背景下人工林生态系统的碳库功能提供研究基础，为人工林生态系统经营管理和可持续发展提供科学支撑。

土壤碳库是陆地生态系统最大的碳库，增强土壤碳库的稳定性是提高陆地生态系统固碳效率的有效途径。森林生态系统碳储量大，不同林龄的森林土壤有机碳含量及稳定性有所差异。本研究选取安徽省宣城市的高井庙林场中的三种林龄的杉木人工林（包括幼龄林，中龄林和老龄林）作为试验样地，采用湿筛和密度浮选 相结合的方法测定了不同剖面层次土壤的有机碳组分，同时用磷脂脂肪酸方法测定了土壤微生物群落结构。结合土壤理化性质，分析了不同林龄杉木林土壤有机碳稳定性机制。研究结果丰富了人工林土壤碳循环的基础理论，为人工林生态系统经营管理和可持续发展提供科学支撑。