土壤含水率和含盐量对盐渍土甲烷吸收能力的影响

甲烷（CH4）是一种强效温室气体，准确认识特定类型土壤CH4源汇特征及影响因子调控作用，对于提升土壤CH4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CH4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CH4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CH4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CH4吸收；在3种含水率下，土壤CH4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CH4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CH4吸收具有更强的抑制作用，土壤含水率和含盐量对CH4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CH4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CH4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CH4的吸收。研究结果表明盐渍土是CH4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CH4汇的能力。

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

Abstract: Methane (CH4) is the second most important greenhouse gas, after Carbon Dioxide (CO2). The concentration of CH4 in the atmosphere is still rising more rapidly than ever before. Among them, most CH4 sinks are widely distributed in water-unsaturated lands. It is a high demand to clarify the CH4 uptake characteristics in the different types of soils in response to certain environmental factors. The soil CH4 uptake potential can then be improved to mitigate global warming. In this study, a soil laboratory incubation experiment was conducted to investigate the CH4 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 CH4 uptake was characterized by three soil salinity levels (PS1: non-saline, 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 CH4 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 CH4 uptake increased with the increase of soil moisture within the range of field water-holding capacity. By contrast, the cumulative soil CH4 uptake decreased under all three soil moisture levels, as the soil salinity increased from 0.3 to 6.2 dS/m. Specifically, the cumulative CH4 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 CH4 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 CH4 uptake. The laboratory incubation was validated by the field plot experiment under natural environments. The soil CH4 uptake rates were significantly positively correlated with the soil moisture for all three soil salinity levels (P<0.01). Compared with the non-saline soil PS1, both PS2 and PS3 salinity levels led to a significant increase in the cumulative CH4 uptake by 17.4% and 40.2%, respectively, indicating that the high salinity significantly inhibited the soil CH4 uptake. The laboratory incubation and field experiments indicated that the salt-affected soil was a CH4 sink, where the CH4 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 CH4 sink capacity for the high agricultural productivity in salt-affected soils.