黄土高原四种人工植物群落土壤呼吸季节变化及其影响因子

以黄土高原侧柏、柠条、沙棘和油松人工植物群落为对象,土壤呼吸日动态和季节变化及其与环境因子之间的关系,结果表明:4种植物群落土壤呼吸速率具有典型的日变化和季节变化模式, 4种群落中,以侧柏6月土壤呼吸日变幅最大,沙棘6月土壤呼吸日变幅最小,大部分群落不同月份最大土壤呼吸与最小土壤呼吸倍数在1.1～1.6之间.4种群落中,以柠条土壤呼吸季节变幅最大,侧柏最小,最大土壤呼吸与最小土壤呼吸的倍数为1.5～2.2倍之间.同一植物类型土壤呼吸具有明显的季节变化特征,其具体变化趋势因植物类型而异.4种植物群落土壤呼吸速率与土壤和大气温度以及土壤含水量的关系在不同季节表现为不同的关系,其中侧柏和柠条土壤呼吸与土壤温度均呈乘幂关系,与大气温度为指数关系.沙棘土壤呼吸与土壤温度和大气温度均为乘幂关系,油松土壤呼吸与土壤温度和大气温度均为线性关系.这表明土壤呼吸与土壤和大气温度之间的关系及其紧密程度因植被类型而异.综合分析表明,同一气候区相同环境因子对不同植物群落土壤呼吸的影响作用不同,且因其自身具有明显的季节变化,从而导致对土壤呼吸的调控作用也具有明显的季节变异模式.

Seasonal changes in soil respiration and the driving factors of four woody plant communities in the Loess Plateau

Soil respiration is one of the most important components in global carbon cycles. Soil respiration is a sensitive integrator of many soil processes that control soil metabolism and reflects human influences on carbon cycles. In order to quantify soil respiration dynamics and its controling factors, we conducted a set of relevant experiments in four woody plant communities in Wu Qi, Shaanxi Province, a Loess Plateau region in Northwestern China. We measured soil respiration, soil water content, soil temperature, and air temperature from June to September in 2006. Soil respiration of the four plant communities all displayed typical diurnal and seasonal dynamic patterns.The Hippophae rhamnoides community had the minimum diurnal range while the Platycladus orientalis community had the maximum range in soil respiration. We found a large seasonal variability for all the four communities with a high to low ratio of 1.1~1.6. The seasonal range of soil respiration was highest in Caragana korshinskii community and lowest in Platycladus orientalis community. The relation between soil respiration and soil temperature can be described as a power function for Platycladus orientalis and Caragana korshinskii communities, but the relation between soil respiration and air temperature can be described as an exponential function. The relationships between soil respiration rates and soil or air temperature were described as a power function in Hippophae rhamnoides community but a liner function for Pinus tabulaefomis community. The close relationships between soil respiration and temperature were community-dependent, and the environmental effects on soil respiration differed among plant community types. We concluded that environmental changes would alter the seasonal soil respiration patterns for different plant communities.