基于自然植被的延河流域农田生态系统土壤固碳潜力评估

以延河流域自然植被土壤有机碳为对照,对该区现有农田生态系统土壤固碳潜力进行评估。结果表明:影响自然植被土壤有机碳密度空间分布的环境因子有年均降雨季节变化、坡度和年均温度季节变化;而影响农田生态系统土壤有机碳密度分布的环境因素则包括年均蒸发量、年均最高温度与坡向;有机碳空间分布规律方面,延河流域南部土壤有机碳密度要明显高于北部,并且呈由北向南逐渐递增的趋势;情景模拟分析表明,延河流域坡度25°以上、15°~25°以及15°以下不同类型的耕地退耕后分别可以实现的固碳效益为90.41×104t、58.52×104t、57.55×104t,而整个延河流域的农田生态系统如果全部实行退耕还林(草),其固碳潜力在206.48×104t左右。可以看出,以土地利用调整为核心的区域固碳策略对环境改善具有重要意义。

The evaluation of carbon sequestration potential in farmland ecosystem in Yanhe River catchment using natural ecosystem as a reference

The Yanhe River catchment was chosen as a case study to evaluate quantitatively the carbon sequestration potential of farmland systems and its spatial change. The results showed that the SOM density in natural ecosystem is mainly affected by annual mean rainfall seasonality, annual mean temperature and slope grade while the SOM density in farmland ecosystem by annual average evaporation, annual average temperature in July and slope position. Using the established models for SOM density in natural ecosystem and farmland ecosystem, predictive distribution maps of the SOM density in natural ecosystem and farmland ecosystem are produced under GIS environment (ARCGIS 9.3). Then the predictive distribution map of the SOM density in natural ecosystem minus that of the SOM density in farmland ecosystem to evaluate the carbon sequestration potential of farmland ecosystem in Yanhe River catchment. The results indicate that the SOM density in the catchment increases gradually from northwest to southeast and the total carbon sequestration potential is about 206.48×10⁴ t. This indicates that the carbon sequestration potential of farmland system in Yanhe River catchment is huge, and this conclusion has great implication for making strategy of regional carbon sequestration and evaluation of ecological benefit of land use.