内蒙古典型草原土壤不同剖面深度CO_2通量格局及其驱动因子

Temporal patterns and driving factors of CO_2 flux at different soil depth profiles on typical steppe,Inner Mongolia

土壤CO2的释放能够显著增加大气中CO2的浓度,增强温室效应,从而对全球气候和环境变化产生重要影响。但是,不同的土壤层对CO2通量的贡献量有很大的差异。文章通过挖坑法结合红外气体分析法研究了内蒙古草原典型针茅(Stipa krylovii)群落和羊草(Leymus chinensis)群落不同剖面深度土壤CO2通量格局以及影响CO2通量的驱动因素。结果表明,表层土壤移走后,土壤CO2通量的变化可分为瞬时、短期、长期三种格局。新剖面上最初的0～21min内释放的CO2通量均大于初始土壤表层CO2通量,而且两者比值随土壤深度增加而增大,也随土壤CO2生产能力增强而增大。2～4d后,新剖面CO2通量持续下降至低于初始土壤表层CO2通量的水平,形成短期稳定状态。更长时间后,新剖面则逐渐表现出与初始土壤剖面表层相近的CO2通量特征。我们认为,(1)在新剖面形成时的CO2通量瞬时和短期格局主要受土壤中存留的原始CO2的浓度及其扩散过程控制,(2)长期格局则由资源水平和环境条件共同决定的土壤CO2生产能力主导。文章进一步揭示了建立包含垂直分层的SOC分解和CO2扩散过程的生态系统模型的必要性。

The release of soil CO2 can significantly increase atmospheric CO2 concentration and enhance greenhouse effect, leading to great impact on global climate change and environmental change. Nevertheless, there are great differences on contributions of CO2 flux at different soil depth profiles. This paper studies the temporal dynamics and driving factors of CO2 flux at different soil depths with trenching method together with an infrared gas analyzer （IRGA） in Stipa krylovii community and Leymus chinensis community. The result shows that the change of CO2 flux has three stages after removing top soil, namely, instantaneous change, short-term change and long-term change. The release of CO2 flux of new soil profile is more than that of original soil topsoil in the first 0-21min; meanwhile, the ratio of them increases with the soil profile deepens and the soil CO2 production enhances. After 2 to 4 days, the CO2 flux of new profile continues to decrease until it reaches the level of topsoil, and eventually arrives at short-term steady state. After a longer period, the CO2 flux of new profile gradually becomes similar to CO2 flux characteristics of topsoil. We claimed that （1） The instantaneous pattern and short-term pattern of CO2 are mainly controlled by CO2 concentration of soil and diffusion processes after forming the new profile, and （2） The long-term pattern is controlled by CO2 production, which is determined by resources availability and environmental condition. This paper further demonstrated the necessity to build an ecosystem model with vertical stratification of SOM decomposition and CO2 diffusion process.