川西高寒山地灌丛草甸不同海拔土壤有机碳矿化的季节动态

为探明高寒山地灌丛草甸不同海拔土壤碳矿化潜力,选取折多山3800 m、4000 m、4200 m 3个海拔梯度的灌丛草甸,采用室内培养法测定不同季节土壤累积矿化量和矿化速率,运用一级动力学方程对土壤碳矿化过程进行拟合,并分析不同海拔土壤活性碳组分季节变化及累积矿化量与土壤环境因子的关系。结果表明:土壤累积矿化量及活性碳组分均呈现出0—20 cm土层显著高于20—40 cm土层,且夏季最高的季节变化,而海拔变化趋势不一致,但大体呈现出3800 m灰化土最大。土壤碳矿化速率随着培养时间的推移逐渐降低慢慢趋于平缓,且前21 d降低幅度显著高于后21 d。各海拔C_0和C_0/SOC均夏季最高,表明高寒灌丛草甸夏季土壤固碳能力最低,且3800 m灰化土固碳能力最低。土壤碳矿化与土壤全氮、有机碳、活性碳显著相关,且微生物量碳更能直接影响土壤碳矿化。土壤碳矿化季节性变化受土壤理化性质和环境因素综合影响,这些因子共同作用使得土壤有机碳库各组分发生复杂变化,所以对于高寒灌丛草甸地区植被多样性的保护及夏季牧场的合理控制至关重要。

Seasonal dynamics of soil organic carbon mineralization for alpine shrub meadow at different elevations, western Sichuan

To explore soil mineralization potential at different elevations in alpine shrub meadow, we selected alpine shrub meadow soils at 3 elevation gradients (3800 m, 4000 m, and 4200 m) in Zheduo Mountains and investigated the carbon mineralization characteristics and carbon mineralization rate by using indoor analysis methods. We used simultaneous reaction model to describe carbon mineralization kinetics and estimated organic carbon mineralization parameters. The relations between soil cumulative mineralization amounts and their influencing factors were also analysis. Results showed that soil cumulative mineralization amounts and activated carbon contents were significantly higher in 0-20 cm soil layer than 20-40 cm soil layer and both of them were largest in summer; There was no consistent change of soil cumulative mineralization amounts and activated carbon contents among different elevations, but the podzolic soil (at 3800 m elevation) was the largest. The soil carbon mineralization rate gradually decreased with the duration of cultivation time, and the decrease rate in initial 21 days were significantly higher than later stage. C₀ and C₀/SOC value were significantly higher in summer, indicating that the carbon sequestration capacity of summer was relatively lower than that of other seasons and the podzolic soil was lowest. Soil carbon mineralization was significantly correlated with soil total nitrogen, soil organic carbon and soil activated carbon. Moreover, microbial biomass carbon could directly affect organic carbon mineralization. The seasonal variation of soil carbon mineralization amounts was affected by the combination of soil physical and chemical properties and environmental factors. These factors worked together to make complex changes in the components of soil organic carbon pool. Therefore, the protection of vegetation and the rational control of summer pastures were essential in alpine shrub meadows.