氮素影响陆地生态系统碳循环过程的模型表达方法

氮素是植物生长所必需的重要营养元素。人类活动引起的大气氮沉降增加对陆地生态系统碳循环过程具有重要影响。准确地定量表达氮素对陆地生态系统碳循环过程的影响是预测未来全球碳循环变化的关键环节。论文系统地归纳总结了国内外多个知名生物地球化学模型中氮素影响光合作用、呼吸作用、同化物分配等碳循环过程的数学表达方法,分析了不同碳循环过程中模型表达方法的不确定性及其原因。指出未来模型的发展需在加强机理研究的基础上,发展能反映氮饱和现象、能显式表达氮素与光合速率关系的光合作用过程算法,发展能显式表达氮素与植物体根、茎和叶呼吸速率关系的维持呼吸算法以及发展显式表达氮素对同化物分配过程影响的动态同化物分配方案。指出当今大部分主流模型在模拟氮素对光合作用影响时没有考虑氮饱和现象,因此利用模型预测未来陆地生态系统对氮素增加的响应时可能会高估氮沉降对光合速率的影响。研究综述可为准确评价陆地生态系统碳氮相互作用和发展碳氮耦合模型提供参考。

The Modeling Algorithms for the Effects of Nitrogen on Terrestrial Vegetation Carbon Cycle Process

Nitrogen is an important nutrient element for plant growth. Nitrogen deposition is increasing with the increasing human activities, and this will influence terrestrial ecosystem carbon cycle greatly. Expressing accurately and quantitatively the effects of nitrogen on carbon cycle is the key factor to predict the global carbon balance change. This paper systematically summarizes the mathematical algorithms for the effects of nitrogen on photosynthesis and respiration, assimilates allocation processes in the state-of-the-art biogeochemical models, and analyses the sources of uncertainties in the algorithms used in each process. The future trends of model approaches are: development of new algorithms for photosynthetic process which reflects nitrogen saturation phenomenon and describes explicitly the relationship between nitrogen and photosynthetic rate; development of new algorithms for respiration process which reflects the relationships between nitrogen and the respiration rate for each part of the plant components (such as root, stem and leaf); and development of dynamic assimilates allocation algorithms on the basis of mechanism research. Because most of the current models do not include the nitrogen saturation phenomenon in their photosynthesis algorithms, these models will overestimate the effects of nitrogen deposition on photosynthetic rate when used to predict the future global carbon balance. Our research results will benefit to further carbon and nitrogen interaction researches and to provide references for carbon and nitrogen coupled model researches.