沼泽湿地开垦后土壤水热条件变化与碳、氮动态

三江平原沼泽湿地的垦殖对土壤环境产生了一定的影响.沼泽湿地开垦前,6～9月湿地表层土壤(10cm)温度均值为12.72℃±4.12℃,明显低于垦后农田(16.71℃±3.81℃).湿地垦殖后土壤温度的增高及氧化-还原条件的改变,促进土壤有机质的分解和土壤呼吸通量的增大, 垦后农田8～9月土壤平均呼吸通量[(946.36±195.78)mg·(m²·h)^-1]是天然沼泽湿地[(153.75±82.59)mg·(m²·h)^-1]的6倍.土壤有机碳及氮素含量随湿地开垦及开垦年限的增加而降低,沼泽湿地开垦初期5～7a,土壤有机碳及其它营养元素的含量变化幅度较大,持续耕作15～20a后,土壤有机碳损失曲线趋于相对稳定值.土壤有机质输入量的减少及分解作用加强导致土壤持水量降低,其变化趋势与土壤有机碳损失趋势相一致.

The Changes of the Soil Hydrothermal Condition and the Dynamics of C, N after the Mire Tillage

The wetlands gain increasing attention to its crucial ecological and environmental function. The tillage of the mires in the Sanjiang Plain has played the important role in regulation of the region ecological balance and climate. Prior to tillage, the mean soil temperature of the topsoil (10 cm) in mire from June to September was 12.72 degrees C +/- 4.12 degrees C, distinctly lower than that of the tilled soil, which was 16.71 degrees C +/- 3.81 degrees C. However, the daily mean evaporation of 4.87 mm +/- 3.78 mm in the mire was larger than that of the tilled soil with mean soil temperature of 2.66 mm +/- 3.78 mm from May to September. The alteration of the oxidization-reduction condition and the augment of the soil temperature led to the increases of soil organic matter (SOM) decomposition ratio and the soil respiration flux, the mean soil respiration (CO2) flux [(946.36 +/- 195.78) mg x (m2 x h)(-1)] was 6 times larger than that of the mire [(153.75 +/- 82.59) mg x (m2 x h)(-1)] from August to September. At the initial stage (5-7a) of the mire tillage, the SOM and the nutrients levels change significantly, but after the 15-20a of continuous cultivation, the SOM loss curve came to a relative stable value. The lessen of the input and strength of the decomposition rate of SOM resulted in the accretion of soil bulk capacity and specific gravity, its changing trend was similar to the changing of the soil organic carbon (SOC) loss.