青藏高原高寒草甸生态系统土壤有机碳动态模拟研究

利用高寒草甸区植被、土壤和气候等资料,借助Century模型研究了青藏高原高寒草甸生态系统土壤有机碳的动态。以2003年7月-2005年7月逐月气象观测资料为输入变量,模拟了自然条件下高寒矮嵩草草甸0～20cm土壤微生物呼吸CO₂-C通量季节变化。模拟值与观测值进行的回归分析显示,二者具有较好的一致性(R²=0.89,P＜0.05)。土壤有机碳动态模拟表明:1)自然条件下高寒草甸土壤有机碳在经历了一个快速积累过程后,积累速率逐渐趋于缓和,最终达到并接近稳定状态。稳定状态下0～20cm土壤总有机碳库约7597.50～7694.10gC/m²。其中活性、缓性和惰性土壤有机碳组分占土壤总有机碳储量的2.80%,58.50%和38.70%。2)过去45年(1960-2005)高寒草甸土壤有机碳呈振幅较为稳定的波动变化,但这种变化主要是土壤有机碳各组分波动变化的结果。气候波动对土壤有机碳影响主要与温度变化引起的惰性土壤有机碳库的变化有关,二者呈显著负相关(r=-0.548,P＜0.01)。降水量对土壤有机碳及有机碳各组分的影响不显著。

Modeling dynamics of soil organic carbon in an alpine meadow ecosystem on Qinghai-Tibetan Plateau using the Century model

A widely used model, Century, was used to simulate the seasonal dynamics of carbon fluxes from soil microbe respiration in alpine Kobresia humilis meadow at Haibei research station, CAS. Monthly maximum and minimum air temperatures and precipitation derived from meteorological data at Menyuan weather station in Qinghai province were used to drive the model. Carbon, nitrogen and cellulose contents were used to initialize the Century model, and all parameters related to the model were based on data from published documents. The observed versus simulated CO_2-C efflux gave R~2＝0.89 (P＜0.05) with all months included in the analysis. The 0 to 20 cm SOC level at equilibrium was about 7,597.50-7,694.10 g C/m~2, with the active, slow and passive SOC pool sizes about 2.80%, 58.50% and 38.70% of the total SOC, respectively. The following simulation resulted in stable fluctuation change in SOC, which was mainly caused by fluctuations of its fractions. The impacts of climate changes on soil SOC was mainly related to soil passive SOC, and a negative correlation existed between mean annual air temperature and passive SOC pool size, with the partial correlation coefficient of -0.548 (P＜0.01). Precipitations had no effects on SOC or its fractions over the entire simulation period of about 45 years.