干湿交替对武夷山不同海拔土壤碳矿化的影响

Effects of drying-wetting cycles on soil organic carbon mineralization along an elevation gradient in Wuyi Mountain

干湿交替(DW)对土壤有机碳矿化作用、养分循环和微生物生长代谢有着重要的影响。本文选择武夷山不同海拔0~10 cm的表层土壤作为研究对象,分别在5、15和25℃温度下培养,模拟DW循环,并设置恒湿处理(CW)作为对照,研究干湿循环对不同海拔土壤碳矿化作用的影响。结果表明:与CW处理相比,土壤变干时显著减少土壤有机碳矿化速率。重新变湿后,土壤有机碳的脉冲效应被观察,且变湿的脉冲效应随着DW数的增加而逐渐降低。重复的DW处理土壤累积碳矿化量显著低于CW处理,表明湿润引起的激发碳矿化量不足以抵消干旱期间减少量。DW处理的温度敏感性Q10显著低于CW处理。在DW循环中,湿度敏感性k值随海拔的升高而增加,表明高海拔土壤矿化更强的水分依赖性。DW处理微生物生物量碳含量高于CW处理,而冷水和热水浸提的可溶性有机碳含量则低于CW处理。

Drying-wetting （DW） cycles have important influence on soil carbon mineralization, nutrient cycle, and microbial growth and metabolism. Soil samples （0-10 cm layer） were taken from three different elevations in Wuyi Mountain, and were incubated under temperature of 5, 15 and 25 ℃ in the laboratory, respectively. DW and constant water content （CW） treatments were set to examine the effects of drying-wetting on soil carbon mineralization. The results showed that, compared to CW treatment, carbon mineralization significantly decreased when the soil became dry. When the dry soils were rewetted, a flush of mineralized C was observed. Such pulse effect of rewetting gradually decreased with the increases of DW cycles. The cumulative soil carbon mineralization of DW treatment was significantly lower than that of CW treatment, indicating that the amount of pulse mineralized C in rewetting of dry soil was not enough to compensate for the reduction of mineralized C during the drought period. The temperature sensitivity （ Q10 ） in the DW treatment was significantly lower than that in the CW treatment. In DW treatment, the moisture sensitivity （k） increased with the elevation, indicating that soil mineralization was more dependent on moisture in high elevation than in low elevation. Microbial biomass carbon content of DW treatment was higher than that of CW treatment, while dissolved organic carbon content of cold and hot water extraction was lower than that of CW treatment.