土壤水分波动对高寒草甸生态系统CO_2和N_2O排放的影响

Effect of soil moisture fluctuations on CO_2 and N_2O emission in alpine meadow ecosystem

受地形和气候的影响,高寒草地土壤经历着频繁的土壤水分波动过程,为探索土壤水分波动对青藏高原高寒草甸生态系统CO_2和N_2O排放的影响,采用原状土柱模拟土壤由高含水量(60 cm3·cm-3)到低含水量(30 cm3·cm-3)再到高含水量(60 cm3·cm-3)的波动过程,各阶段持续时间相应为38、57和46 d,并以恒定含水量(60 cm3·cm-3)为对照,研究了高寒草甸生态系统CO_2和N_2O的释放量及其与土壤温湿度、土壤铵态氮(NH4+-N)、硝态氮(NO3--N)和可溶性有机碳(DOC)的关系。结果表明,土壤水分波动增加了高寒草甸生态系统CO_2排放通量。在土壤水分波动过程中,CO_2排放通量与土壤温度呈正指数关系;在开始的高含水量阶段,CO_2排放与DOC含量有显著正相关关系(P<0.05),但在低含水量阶段,相关性不明显(P>0.05);土壤水分波动显著降低了N_2O的排放(P<0.05)。恒湿对照的N_2O通量与其土壤NH4+-N含量呈极显著负相关关系(P<0.01),土壤水分波动处理的N_2O通量与土壤NH4+-N和NO3--N含量相关性均不显著(P>0.05)。

Under the influence of topography and climate,plateau grassland soil experiences frequent soil moisture fluctuations. To explore the influence of soil moisture fluctuations on CO_2 and N_2O emission from alpine meadows in the Qinghai-Tibet Plateau,we used an undisturbed soil column to simulate soil water content fluctuation from a high(60 cm3·cm-3) to low value(30 cm3·cm-3),and to a high(60 cm3·cm-3) again; this duration of each phase was 38,57,and 46 days. A soil column with constant HYPERLINK "javascript:; "humidity level(soil humidity 60 cm3·cm-3) was considered the control. The results showed that: 1) soil moisture fluctuations significantly increased CO_2 emission. A significant relationship was observed between CO_2 emission and soil temperature; additionally,CO_2 emission correlated positively with soil dissolved organic carbon(DOC) concentration in the first high soil-water content phase.2) Moisture fluctuations significantly decreased N_2O emission. In the control treatment,there was a strong significant negative correlation between N_2O emission and NH4+-N; however,no close relation between N_2O emission and NH4+-N level was observed throughout the moisture fluctuation process.