土壤含水率和含盐量对盐渍土甲烷吸收能力的影响

Effects of soil moisture and salinity on methane uptake in salt-affected soils

甲烷(CH_(4))是一种强效温室气体,准确认识特定类型土壤CH_(4)源汇特征及影响因子调控作用,对于提升土壤CH_(4)吸收潜力以减缓全球气候变化具有重要意义。该研究以盐渍土为研究对象,在土壤室内培养试验中,设置了3个土壤含水率处理,分别为田间持水率(Field Capacity,FC)的50%(50%FC),75%FC和100%FC,并在每个含水率下设置了6个含盐量处理,电导率分别为0.3、1.0、2.0、3.2、4.9和6.2 dS/m,研究不同土壤含水率和含盐量条件下盐渍土CH_(4)吸收特征。在田间测坑试验中,观测了0.3、1.0和5.0 dS/m 3种含盐量土壤的CH_(4)吸收特征及其对水分动态的响应。室内土壤培养试验结果表明,100%FC下6种盐分水平土壤CH_(4)累积吸收量分别是75%FC下的1.08~1.39倍和50%FC的1.27~1.72倍,表明在田间持水率范围内,含水率升高促进了土壤CH_(4)吸收;在3种含水率下,土壤CH_(4)累积吸收量均随着处理含盐量升高而降低,6.2 dS/m最高含盐量处理的CH_(4)累积吸收量相比0.3 dS/m最低含盐量处理显著降低了42.6%、52.3%和55.1%(P<0.05);相比50%FC,100%FC含水率下高含盐量对土壤CH_(4)吸收具有更强的抑制作用,土壤含水率和含盐量对CH_(4)吸收的影响存在显著的交互作用。田间测坑试验在野外田间条件下进一步验证了室内培养试验的结果,试验观测期内所有含盐量处理土壤CH_(4)吸收速率均与土壤含水率呈显著正相关关系(P<0.01);1.0和5.0 dS/m含盐量处理的累积CH_(4)吸收量分别为0.3 dS/m非盐渍土处理的82.6%和59.8%,高含盐量抑制了土壤对CH_(4)的吸收。研究结果表明盐渍土是CH_(4)的汇,并受到土壤含水率和含盐量显著影响,在盐渍土开发利用中应考虑通过合理的水盐调控以提高土壤CH_(4)汇的能力。

Methane(CH_(4))is the second most important greenhouse gas,after Carbon Dioxide(CO_(2)).The concentration of CH_(4)in the atmosphere is still rising more rapidly than ever before.Among them,most CH_(4)sinks are widely distributed in water-unsaturated lands.It is a high demand to clarify the CH_(4)uptake characteristics in the different types of soils in response to certain environmental factors.The soil CH_(4)uptake potential can then be improved to mitigate global warming.In this study,a soil laboratory incubation experiment was conducted to investigate the CH_(4)uptake rates of the salt-affected soil at the different moisture(50%,75%,and 100%of Field Capacity(FC),and Salinity Levels(LS1:0.3 dS/m,LS2:1.0 dS/m,LS3:2.0 dS/m,LS4:3.2 dS/m,and LS5:4.9 dS/m,and LS6:6.2 dS/m).A field plot experiment was also carried out to verify the reproducibility of the laboratory incubation under natural conditions.The soil CH_(4)uptake was characterized by three soil salinity levels(PS1:0.3 dS/m,PS2:1.0 dS/m,and PS3:5.0 dS/m),and their responses to the soil moisture dynamics.The soil laboratory incubation results showed that the cumulative CH_(4)uptake of soils(including all six salinity levels)under 100%FC was 1.08-1.39 times those of the 75%FC,and 1.27-1.72 times those of the 50%FC,respectively.It infers that the capacity of soil CH_(4)uptake increased with the increase of soil moisture within the range of field water-holding capacity.By contrast,the cumulative soil CH_(4)uptake decreased under all three soil moisture levels,as the soil salinity increased from 0.3 to 6.2 dS/m.Specifically,the cumulative CH_(4)uptake of the highest salinity LS6 was significantly reduced by 42.6%,52.3%,and 55.1%under three soil moisture levels,respectively,compared with the non-saline soil of LS1.The soil moisture with the 100%FC aggravated the soil CH_(4)uptake capacity along the salinity gradient from 0.3 to 6.2 dS/m,compared with the 50%FC.There was a significant interaction between the soil moisture and salinity on the soil CH_(4)uptake.The laboratory incubation was validated by the field plot experiment under natural environments.The soil CH_(4)uptake rates were significantly positively correlated with the soil moisture for all three soil salinity levels(P<0.01).Compared with soil PS1,both PS2 and PS3 salinity levels led to a significant decrease in the cumulative CH_(4)uptake,indicating that the high salinity significantly inhibited the soil CH_(4)uptake.The laboratory incubation and field experiments indicated that the salt-affected soil was a CH_(4)sink,where the CH_(4)uptake capacity depended mainly on the soil moisture and salinity.Consequently,a sub-goal of the water-salt regulation can be formulated to improve the CH_(4)sink capacity for the high agricultural productivity in salt-affected soils.