水热对三峡水库消落带退耕稻田土壤有机碳矿化的影响

采用模拟培养的方法,研究了不同水热条件对三峡水库消落带退耕稻田土壤有机碳(SOC)矿化的影响。试验共设3个培养温度(10、20和30℃)和4个水分梯度(40%田间持水量(WHC)、70%WHC、100%WHC和浅层淹水)。结果表明:1在66天培养期内,各培养温度(10~30℃)下,70%WHC、100%WHC和浅层淹水处理之间的SOC累积矿化量均无明显差异,其中10℃培养时40%WHC处理下的累积矿化量要显著低于70%WHC和100%WHC水分处理(P0.05),但与浅层淹水无明显差异,而20℃和30℃培养时40%WHC处理下的累积矿化量则要显著低于其他水分处理,表明相较于70%WHC的水分处理,40%WHC水分处理会抑制消落带退耕稻田SOC矿化,而高水分(100%WHC和浅层淹水)对SOC矿化则无明显促进和抑制作用。2在相同水分条件下,消落带退耕稻田SOC累积矿化量均随培养温度升高而增加。3高温下各水分处理之间的温度敏感性无显著差异,而低温下水分对温度敏感性有显著影响,低温浅层淹水处理下的Q10为2.33,显著高于40%WHC处理,与70%WHC和100%WHC处理之间无明显差异。且随着温度升高,浅层淹水下消落带退耕稻田SOC矿化的温度敏感性显著降低,而在土壤含水量≤100%WHC下则无明显变化。温度和水分均能显著影响SOC矿化,但二者无明显的交互效应。4双库一级矿化动力学模型拟合结果表明,水分和温度通过影响消落带退耕稻田土壤易分解有机碳含量和难分解有机碳的矿化速率,从而影响SOC矿化。

Effects of Soil Moisture and Temperature on Organic Carbon Mineralization of Abandoned Paddy Soil in the Hydro- fluctuation Belt of the Three Gorges Reservoir

An incubation experiment was conducted in the laboratory to investigate the effects of soil moisture and temperature on soil organic carbon (SOC) mineralization of abandoned purple paddy soil in the hydro-fluctuation belt of the Three Gorges Reservoir. Three incubation temperatures (10, 20 and 30℃) and four moisture levels (40% water holding capacity (WHC), 70%WHC, 100%WHC and shallow submerged condition) were designed in the experiment. The results showed that: 1) During the entire incubation period (66 d), there were no significant differences in SOC cumulative mineralization amounts among 70%WHC, 100%WHC and shallow submerged conditions at the three temperatures (10–30℃). At 10℃ incubation, SOC cumulative mineralization amount at 40%WHC treatment was significantly lower than those of 70%WHC and 100%WHC treatments (P<0.05), but there was no significant difference between shallow submerged and 40%WHC conditions. SOC cumulative mineralization amounts of 40%WHC treatments at 20℃ and 30℃ incubation were significantly lower than those of other treatments. So, it indicated that compared to 70%WHC treatment, 40% WHC treatment had negative-effects on SOC cumulative mineralization of abandoned paddy soil, but high moisture (100%WHC and shallow submerged condition) had no significant promoting or inhibiting effects to SOC mineralization. 2) Under the same soil moisture condition, SOC cumulative mineralization amounts of abandoned paddy soil in the hydro-fluctuation belt increased as temperature increasing. 3) Under higher temperature, the temperature sensitivity had no significant difference in treatments under different soil moisture conditions, but soil moisture significantly influenced temperature sensitivity under lower temperature. TheQ10under shallow submerged condition was 2.33, significantly higher than 40%WHC treatment, but had no significant difference with 70%WHC or 100%WHC treatment. With the increase of temperature, temperature sensitivity was significantly decreased under shallow submerged condition, but it changed inconspicuously when soil moisture content was less than 100%WHC treatment. Both temperature and moisture could affect SOC mineralization significantly, but they had no significant interaction effects. 4) Two-pool first-order model indicated that temperature and soil moisture influenced SOC mineralization through influencing the content of labile SOC fraction and the mineralization rate of recalcitrant SOC fraction.