基于过程模型的松栎混交林固碳能力的间伐效应研究

如何增加森林碳汇，已成为林业应对气候变化亟待解决的问题。间伐措施到底能不能促进森林固碳能力，使森林生态系统服务效益协调统一，仍存在争议。本项目以秦岭山地松栎混交林为研究对象，通过野外监测和基于过程的模型模拟相结合的研究方法，在陕西省宁西林业局桦树坪林场，选择林分条件（坡度、坡向、土壤条件等）基本一致，建立一组长时间序列样地（对照、间伐后1年，间伐后6年，间伐后9年）共计12个，测定年净初级生产力、土壤异养呼吸、生态水文和淋溶碳通量。改进基于过程的生态模型的热传递、冠层截留和可溶性碳淋溶过程，量化间伐措施对松栎混交林固碳能力的影响。成果将阐明间伐如何及多大程度上影响松栎混交林生态系统碳循环的关键生物地球化学过程，揭示间伐对混交林固碳能力的影响机理，明确现行抚育间伐措施对混交林固碳能力的短期和长期影响。成果有望加深碳循环的经营调控机制的认识，对我国森林碳汇经营的理论和实践具有重要的参考价值。

It is essential to increase forest carbon sequestration to mitigate climate change for forest managers and policy makers. Thinning is a necessary procedure for sustainable forest management. However, it is still not clear whether thinning could increase carbon sequestration or not. We choose a chronosequence of thinning treatment (control, thinning after 1 year, thinning after 6 years, and thinning after 9 years) in pin-oak mixed forests at the Huashuping Forest Farm of Ningxi Forestry Bureau in Shaanxi Province. We will investigate key carbon processes such as net primary productivity, heterotrophic respiration, eco-hydrology, and dissolved carbon flux in the filed. More importantly, we will improve a process-based ecosystem model by modifying the processes that could be affected by thinning operations but not be fully represented currently. These processes include heat transfer (for soil temperature), canopy interception (for soil water balance), and dissolved carbon flux (usually missing). Finally, this research will quantify and access the effects of existing thinning operations on carbon sequestration of the mixed forests using the model. The results will clarify how and to what extent thinning affects the key ecological and biogeochemical processes of the carbon cycle in pine-oak mixed forests. We will reveal the mechanisms of the effect of thinning on carbon sequestration of mixed forests. The results also will helpful in better estimation of carbon benefits or losses due to thinning. The outcomes of this project could deepen the understanding of management regulations on the carbon cycle and be of practical values for the theory and practices of carbon management in China.