雪被和土壤水分对典型半干旱草原土壤冻融过程中CO_2和N_2O排放的影响  

Effects of snow cover and soil moisture on CO_2 and N_2O fluxes from typical semiarid grassland soil subjected to freeze-thaw cycles

作　　者：伍星[1] 刘慧峰[1,2] 张令能[1] 傅伯杰[1] 李宗善[1] 汪庆兵[3] 刘国华[1] 

机构地区：[1]中国科学院生态环境研究中心城市与区域生态国家重点实验室,北京100085 [2]中国科学院大学,北京100049 [3]中国林业科学研究院亚热带林业研究所,富阳311400

出　　处：《生态学报》2014年第19期5484-5493,共10页Acta Ecologica Sinica

基　　金：中国科学院战略性先导科技专项(XDA05060103);国家重点基础研究发展计划项目(2012CB417103);国家自然科学基金项目(41105117)

摘　　要：土壤冻融期间的温室气体排放量会显著增加,并在全年总排放量中占有重要的份额。但目前开展的土壤冻融循环模拟实验大多是在土壤冻结之前调节土壤水分含量,而忽视了雪被在整个土壤冻融过程中的作用,因此导致室内模拟研究的结果与野外原位观测的结果差异较大。为探索开展室内模拟土壤冻融实验的优化方案,采用人工浇水和覆雪两种方式调节土壤水分含量,研究了雪被和土壤水分对内蒙古典型半干旱草原土壤冻融过程中CO2和N2O排放的影响。结果表明,浇水和覆雪两种处理对冻融循环过程中土壤CO2排放影响的差异不显著,CO2排放量在消融期都会明显增加并随着冻融循环次数的增加而逐渐减小。当土壤孔隙含水率达50%左右时,浇水处理中的N2O排放量在第1次土壤冻融循环中最高并随冻融循环次数增加而降低,但在覆雪处理中,N2O在第1次冻融循环中的排放较小,而在后两次冻融循环中的排放量更为显著。造成两种处理N2O排放规律出现显著不同的原因可能是土壤剖面水分动态变化过程和微生物性状等方面的差异。土壤冻融过程中CO2和N2O排放量随土壤含水量升高而增加,但N2O在土壤含水量较低时排放不明显,这表明可能只有当土壤含水量达到一定阈值时,冻融作用才会对N2O的排放产生显著影响。这些结果显示,雪被和土壤水分显著影响土壤冻融过程中的CO2和N2O排放,室内模拟土壤冻融实验应进一步优化。Soil freeze-thaw cycle is very common in the regions at mid-high latitude and high altitude. Soil physical properties, chemical composition and microbial activities could be affected significantly during this cycle. Increases in ouse gas fluxes have been frequently reported during soil freezing and thawing, both in laboratory and field experiments. Moreover, some studies indicated that the accumulative fluxes during soil freezing and thawing could contribute a lot to the annual budget, especially of N20. However, many soil incubation studies have introduced experimental artifacts that diminish the realism and relevance of the freeze-thaw cycle. Most of past laboratory studies adjusted soil moisture before soil freezing, so that the effect of snow cover and water from melting snow was not considered during soil freeze-thaw cycles. In order to simulate field conditions more closely in the laboratory, the effects of snow cover and soil moisture on CO2 and N2O fluxes during freeze-thaw cycles were evaluated for a typical semi-arid grassland soil. Three different soil moisture levels were established either prior to soil freezing or by adding fresh snow to the soil surface after freezing. Our results showed that the dynamics of soil CO2 fluxes during three freeze-thaw cycles under snow cover and watering treatments were not significantly different. Soil CO2 emissions were generally enhanced during the first freeze-thaw cycle, and gradually decreased with successive cycles. However, snow cover had significant effect on soil N2O fluxes during freeze-thaw cycles when the soil water-filled pore space （WFPS） were around 50%. The highest emissions of N2O were observed during the first freeze-thaw cycle in watering treatment, while in snow cover treatment a repetition of the freeze-thaw cycles resulted in a further increase of N2O emissions. The reasons for the significant differences in N2O performance between two treatments might be the different soil water dynamics and microbial properties along the soil profile. CO2

关 键 词：雪被 土壤水分 冻融循环 温室气体 半干旱草原 

分 类 号：S151.9[农业科学—土壤学]