中文摘要：

在全球变暖的背景下，由土地利用变化导致的土壤碳库的变化已经受到越来越多的关注。首先采用物种分布模型预测了天山北坡雪岭云杉林的潜在分布，其次估计了与被开垦为农田的雪岭云杉林面积（PSC）以及由林地开垦为农田造成的有机碳损失。PSC分别由雪岭云杉林的现实分布、潜在分布和农田的现实分布确定。云杉林地和农田的土壤有机碳含量由野外采样和实验室分析获得。研究发现，PSC面积为2.68×10^6hm^2，被开垦为农田的雪岭云杉林土壤有机碳的损失为171.7 t/hm^2；研究区总有机碳的损失为459.70Tg。结果表明，研究区的林地恢复和重建项目将会使土壤有机碳储量有所增加，且土壤表层的增加量多于深层。

英文摘要：

The effect of land-use changes on soil carbon stocks is an increasing concern in the context of global climate warming. In this study, we initially delineated the deforestation area of a Picea schrenkiana forest cultivated to cropland （PSC） at the north slope of the Tianshan Mountains. We then estimated the corresponding soil organic carbon （SOC） loss during the land-use change. The PSC was estimated by the potential, actual distributions of forest and cropland. The SOC content of the forest and cropland soils was obtained through field sampling and laboratory analysis. We found that the area of the PSC was 2.68×10^6 hm^2, and the SOC loss （per unit area） caused by the cultivation of forest to cropland was 171.7 t/hm^2, correspondingly. The total SOC loss in the study area was 459.70 Tg. This result implies that continuing the afforestation and reforestation programs currently implemented in the study area would increase the SOC. In addition, we found that the potential SOC sequestration is expected to increase to a greater extent in the upper soil layers than the lower layers.