森林生态系统碳氮循环功能耦合研究综述

Review on coupling of interactive functions between carbon and nitrogen cycles in forest ecosystems

在大气CO2浓度升高和氮沉降增加等全球变化背景下,森林生态系统减缓CO2浓度升高的作用及其对全球变化的响应和反馈存在诸多不确定性。森林生态系统碳氮循环相互作用及功能耦合规律的研究是揭示这些不确定性的基础,也是反映森林生态系统生物产量与养分之间作用规律,涉及林地持久生产力(sustainability of long-term site productivity)的生态学机理问题。森林生态系统碳氮循环的耦合作用表现在林冠层光合作用的碳固定过程,森林植物组织呼吸、土壤凋落物与土壤有机质分解、地下部分根系周转与呼吸等碳释放过程,这些过程存在反馈机理和非线性作用,最终决定森林生态系统的碳平衡。着重在生态系统尺度上,综述了碳氮循环耦合作用研究的一些进展与存在的问题,对今后研究方向进行了展望。

There are many uncertainties in the role of forest ecosystems in slowing down the increases of atmospheric carbon dioxide concentration and their responses to and feedbacks on the global change associated with the increasing CO2 concentration in the atmosphere and the global increase in nitrogen deposition. Research on the interactions and coupling of carbon and nitrogen cycling in forest ecosystems can pinpoint and thus reduce these uncertainties. Such studies also improve the understanding of the relationships between the productivity and nutrient cycling in forest ecosystems and mechanisms for sustaining the long-term site productivity. The coupling between carbon and nitrogen cycles in forest ecosystems includes photosynthetic processes, autotrophic respiration process, decomposition process of litter and soil organic matter, fine root turnover process, and heterotrophic respiration process. Both positive and negative feedback mechanisms and nonlinear relationships are involved in these processes, which ultimately determine the carbon balance in forest ecosystems. This paper reviews the current literature on the coupling functions between carbon and nitrogen cycles, and describes recent advances, existing shortcomings and limitations of research in this area. The directions for future research in this area are also discussed.