温度和水分对黄土丘陵区3种典型土地利用方式下土壤释放CO2潜力的影响

摘要

为探讨影响土壤释放CO2潜力的因素,本研究采集黄土丘陵区3种典型土地利用方式下(苹果园、退牧草地、辽东栎林地)的原状土壤样品,室内进行不同温度和水分梯度的培养试验,测定培养过程中土壤释放CO2的速率以及土壤的理化性质,并分析其对土壤释放CO2潜力的影响.结果表明:影响土壤释放CO2速率的主要因素是温度,指数模型Ra=aebT可以很好地预测土壤呼吸速率随温度的变化情况.含水率对土壤呼吸速率影响不大,但含水率对Q10值的影响明显,较高或较低的水分情况下都会降低土壤呼吸速率随温度变化的敏感程度.3种土地利用方式下,土壤释放CO2的速率表现为:林地土壤＞草地土壤＞果园土壤.土壤理化性质中,有机碳对土壤呼吸的影响最大,其次为有机氮；此外微生物量碳很可能是间接影响土壤CO2释放速率的一个因素.%The most important greenhouse gases in the atmosphere are CO;, Criand N2O, which in total contribute approximately 80% to greenhouse effect. Soil respiration generally accounts for one half of total CO2 emission into the atmosphere, adding to greenhouse effect. In addition to other factors, soil respiration is highly related with temperature, moisture and soil type. However, few studies have investigated soil respiration under different land use types in the hill-gully area of the Loess Plateau. The objective of this experiment was to determine the effect of temperature, moisture and other related factors on soil respiration. For that purpose, undisturbed soil samples were collected from different land use types in the hill-gully area of the Loess Plateau. The study covered three land use types - 15-year old apple orchard land at Changwu, Shaanxi Province; 6-year old retrieving grass land at Guyuan, Ningxia Hui Autonomous Region; and 140-year old forest land at Fu County, Shaanxi Province. We used the S-distribution method to collect soil samples and the infrared absorption CO2 analyzer to measure soil respiration. CO2 release rate was analyzed in the laboratory using undisturbed soil samples under four temperatures of 5 °C, 15 °C,25 °C. And 35 °C;and five moisture contents of wilting water holding capacity, natural water holding capacity, fracture capillary water holding capacity, field capacity, and saturated water holding capacity. The aim was to determine the correct relationship among the factors and soil respiration rate. Factors that influenced soil CO2 release potential under different land use types in the Loess hilly-gully area were then determined. The results showed that under different land use types in the loess hilly region, the rates of soil respiration under different moisture contents were mainly driven by temperature variation. The "Ra=aehT" exponential model precisely forecasted the changes in respiration rate as affected by temperature. Though, soil moisture slightly influenced soil respiration rate, it greatly affected Q10, which indicated the sensitivity of soil respiration to temperature. Both high and low moisture contents inhibited the sensitivity of soil respiration. Whilethe rates of soil respiration substantially differed, it generally tracked the following order: forest land soil > grass land soil > orchard soil. Organic carbon significantly contributed to the variation in soil CO; release, followed by organic nitrogen. Furthermore, micro-bial biomass carbon might indirectly affect rate of soil respiration.