氮输入对植物光合固碳的影响研究进展

植物光合固碳(C)是生物固C的重要途径和生态系统C循环中的重要环节。在全球环境变化背景下,研究氮(N)输入对植物光合固C的影响,对于更好的认识C、N循环过程及生态系统对全球变化的响应过程等具有重要意义。N输入是否能够增加植物固C取决于生态系统类型以及生态系统的N饱和度;草原和湿地生态系统N输入的临界负荷值较高,干旱、半干旱荒漠地区较低;N输入可能改变植物光合固C在各器官的分配,主要由植物生理、自身生长节律和环境养分等决定。由于物种和生态系统类型的差异,N输入对植物固C的影响仍具有很大的不确定性,目前缺乏准确、定量表达N输入对生态系统光合和C同化物分配影响的数学表达方法和过程算法。未来应着重加强N输入下C同化物分配的生物地球化学模型和N、P富集下植物光合固C耦合模型研究,并应用同位素标记和分子生物学技术,从生态系统角度综合探讨N输入下植物光合固C的分配和转化特征。

Reviews on effects of nitrogen addition on plant photosynthetic carbon fixation

Plant photosynthetic carbon fixation is the important pathway in biological CO₂ fixation, and plays an important role in the process of ecosystems carbon cycle. It is quite meaningful to understand the effect of nitrogen enrichment on the plants photosynthetic carbon fixation. The response of carbon sequestration capacity to nitrogen addition depends on the type and nitrogen saturation of the ecosystems. The nitrogen critical load is higher in grassland and wetland ecosystems, and lower in arid and semi-arid desert ecosystem. The distribution of carbon assimilates in plant organs possibly are altered by the nitrogen addition, which depends mainly on plant physiology, growth rhythm and environmental nutrients condition. Because of the diversity of plant species and ecosystems, the effects of nitrogen enrichment on plant photosynthetic carbon fixation are uncertain. The process models for accurately and quantitatively expressing the effects of nitrogen enrichment on fixation and distribution of photosynthetic carbon in plants are still very limited. We suggest to focus on the biogeochemical models of the effects of nitrogen enrichment on distribution of carbon assimilation, and the coupled model of carbon fixation in plants under both nitrogen and phosphorus enhancement. Further more, by using isotope labeling and molecular biology techniques, we need to determine the effects of nitrogen enrichment on fixation and distribution of photosynthetic carbon from ecosystem viewpoint.