水热变化对三峡水库消落带紫色土有机碳矿化的影响

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

通过野外采样和室内模拟培养试验,研究水热变化对三峡水库消落带紫色土有机碳(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和淹水].在66 d培养期内,SOC累积矿化量表现为100%WHC处理下的最大,但与淹水之间差异不显著(P>0.05).10℃和20℃时,100%WHC和淹水下的SOC累积矿化量与70%WHC无明显差异,但要显著高于40%WHC,而30℃时100%WHC和淹水下的累积矿化量则要显著高于70%WHC和40%WHC(P<0.05),这表明相较于70%WHC的水分处理,高水分(100%WHC和淹水)对SOC矿化无抑制效应甚至在高温(30℃)下有促进作用.在相同水分条件下,消落带紫色土SOC累积矿化量均随培养温度升高而增加.另外,方差分析可知,温度和水分均能显著影响消落带紫色土SOC的累积矿化量,且二者有明显交互效应(P<0.05).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紫色土易分解有机碳含量和难分解有机碳的矿化速率,致使各处理之间SOC累积矿化量存在差异,其中高温条件下水分影响最为突出.随着温度的升高,低水分(40%WHC)下消落带紫色土SOC矿化的温度敏感性显著下降,而在土壤含水量≥70%WHC下则无明显变化.

Soil sampling in the field and an incubation experiment in the laboratory was conducted to investigate the effects of soil moisture and temperature on soil organic carbon（ SOC） mineralization of purple 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 submerged condition） were used in the experiment. In the entire incubation period（ 66 d）,the SOC cumulative mineralization reached the maximum at 100% WHC,but there was no significant difference between 100% WHC and submerged condition（ P〉 0. 05）. At 10℃ and 20℃,the SOC cumulative mineralization at 100% WHC and under submerged condition was not significantly different from that at 70% WHC treatment,but significantly higher than that at 40% WHC treatment.While the cumulative mineralization of organic carbon at 100% WHC and under submerged condition was significantly higher than that at 70% WHC and 40% WHC when the temperature was 30℃（ P〈0. 05）. The results indicated that compared with 70% WHC treatment,the higher moisture content（ 100% WHC and submerged condition） had no negative effects but rather promotion effects on the mineralization of SOC at high temperature（ 30℃）. Under the same soil moisture conditions,the SOC cumulative mineralization of purple soil in the hydro-fluctuation belt increased as temperature increased. Moreover,the analysis of variance showed that SOC cumulative mineralization was significantly affected by temperature and soil moisture,and there was a significant interaction with temperature and soil moisture（ P〈0. 05）. Fitting of two-pool first-order model was performed to indicate that temperature and soil moisture influenced the contents of labile SOC fraction and the mineralization rates of recalcitrant SOC fraction,which led to the differences of SOC cumulative mineralization under the different treatments. With the increasing temperature, the temperature sensitivity was significantly decreased in the 40% WHC treatment,but there was no obvious difference when the soil moisture content was not less than 70% WHC.