温度对青藏高原热融湖塘沉积物甲烷产量的影响

Effect of temperature on methane production in sediments of thermokarst lakes/ponds on the Qinghai-Tibet Plateau

气候变暖导致多年冻土退化,加快热融湖塘的形成和扩张,进而增加多年冻土区的碳释放。热融湖塘沉积物理化特征与甲烷产量有着重要关系,而这一关系的明确有助于揭示青藏高原热融湖塘甲烷释放对气候变化的响应。本研究选择青藏高原中东部8个热融湖塘为研究对象,通过室内培养实验探究不同温度(5℃、10℃和15℃)下两种主要植被类型区热融湖塘甲烷产量及其与沉积物理化性质的关系。结果表明:培养周期内(50天),甲烷产量最大值出现在10℃培养条件下高寒沼泽草甸区的MD-3样品,产量高达167.63μg·g^(-1)沉积物;最小值出现在15℃培养下高寒沼泽草甸区的AD-2样品,产量为0.01μg·g^(-1)沉积物。从理化性质与甲烷产量的关系来看,热融湖塘深度和氨氮含量都与甲烷产量显著正相关(P<0.05),而pH值(7.08~8.40)与甲烷产量显著负相关(P<0.05),如玛多地区氨氮高、pH低,其热融湖塘沉积物的甲烷产量远大于安多地区。另外,温度敏感性指数Q_(10)值的分析结果表明,温度升高对61.11%的甲烷产量有促进作用,对18.06%的甲烷产量有抑制影响,说明温度是影响热融湖塘沉积物甲烷产量的重要因素。本研究分析了不同培养温度下两种主要植被类型区热融湖塘沉积物的甲烷产量差异及其影响因素,为认识热融湖塘温室气体的排放潜力及模拟提供了科学数据。

Climate warming has caused the permafrost degradation,accelerating the formation and expansion of thermokarst lakes or ponds,and further increasing carbon release from permafrost regions.The physio-chemical variables of sediments play a critical role on methane(CH_(4))production in the thermokarst lakes and ponds.Quantifying CH_(4) production from the sediment of thermokarst lakes and ponds will improve our understanding on the response of methane emissions to climate change over the Qinghai-Tibet Plateau.In this study,based on sediment samples collected from eight thermokarst lakes or ponds in the central and eastern Qinghai-Tibet Plateau,we intended to investigate the relationship between the physio-chemical variables of sediment and CH_(4) production under laboratory incubation at 5℃,10℃,and 15℃,respectively.The results showed that during the 50 days incubation period,the maximum CH_(4) production(167.63μg·g^(-1) sediment)was found in MD-3 samples in an alpine wet meadow at the incubation temperature of 10℃.The minimum value(0.01μg·g^(-1) sediment)was recorded in the AD-2 sample that under a wet meadow at the incubation temperature of 15℃.The CH_(4) production rates were higher in the sediments with relatively deeper thermokarst lakes and ponds,higher ammonia nitrogen content and lower the pH values.Meanwhile,the methane production of thermokarst lakes and ponds sediments was much higher than those in the Anduo area due to the high ammonia nitrogen and low pH values in the thermokarst lakes or ponds in the Maduo area.Temperature sensitivity of methane production(Q_(10))of 5~10℃,10~15℃ and 5~15℃ revealed that the increasing temperature has a promoting effect on 61.11% of total CH_(4) production and an inhibiting effect on 18.06% of total CH_(4) production.The results indicated that temperature was an important factor determining CH_(4) production in the sediment of thermokarst lakes or ponds.This study investigated the effects of temperature on CH_(4) production and their possible influencing factors from the sediments of thermokarst lakes or ponds,and thus provide a scientific basis for evaluating the potential and modeling of greenhouse gas emissions from thermokarst lakes or ponds.