外源氮输入对喀斯特生态系统碳固定的影响综述

A Review of the Potential Impact of Exogenous Nitrogen Input on Carbon Fixation in Karst Ecosystems

外源氮输入是驱动陆地生态系统持续碳固定的关键控制因子。论文基于国内外研究进展,结合喀斯特生态系统碳氮循环特点,探讨了生态系统对外源氮输入的可能响应。喀斯特地区基岩广泛出露,降雨过程中水分和沉降氮素在基岩和土壤间的再分配使得土壤实际接收的沉降氮量增加。同时外源氮输入有助于促进喀斯特退化生态系统植被生产力提高,凋落物归还量增加,加上石灰土的高钙环境对新输入有机碳具有重要的稳定和保护作用,这些特点有利于促进生态系统碳固定。下一步的研究应从关键带视角深入解析喀斯特生态系统碳循环过程对外源氮输入的响应趋势及机制。

The input of exogenous nitrogen(N)plays a key role in driving carbon(C)sequestration in karst grassland ecosystems.Based on the research progress at home and abroad,combined with the characteristics of carbon and nitrogen cycle in karst ecosys⁃tem,this paper discusses the possible responses of karst ecosystem to nitrogen deposition and symbiotic nitrogen fixation.In the karst area,the soil layer is shallow,the binary structure is developed,and the hydrological process is rapid.The runoff and soil sol⁃uble matter(including subsided nitrogen)easily enter the groundwater system through the fissures and underground pipelines.It means that the ecosystem has limited interception capacity for nitrogen deposition;on the other hand,the bedrock in the karst area is widely exposed,and the redistribution of water and sedimentary nitrogen between the bedrock and the soil during the rainfall process increases the amount of settled nitrogen actually received by the soil.At the same time,karst degraded ecosystems are gen⁃erally restricted by nitrogen.The increase of nitrogen deposition and biological nitrogen fixation can promote the improvement of veg⁃etation productivity,the increase of plant litter return,and the high calcium environment of lime soil has important stability and protection for newly imported organic carbon.This process may promote ecosystem carbon sequestration.However,under the back⁃ground of increased nitrogen input,the current response to the karst special fragile ecosystem is still not fully understood.