1990~2000年中国土壤碳氮蓄积量与土地利用变化

基于2473个土壤剖面资料和1980年代末~1990年代末陆地卫星TM影像分析中国1990~2000年林地、草地、耕地之间的土地利用变化对土壤碳氮蓄积量的影响。IPCC建议的国家温室气体清单方法计算表明从1990~2000年中国林地、草地、耕地土壤(30 cm) 有机碳氮库分别损失了77.6±35.2 TgC (1Tg = 106 t) 和5.6±2.6 TgN,年均损失约7.76 TgC/yr和0.56 TgN/yr,其中耕地土壤碳库分别增加了79.0±7.7 TgC 和9.0±0.7 TgN,草地土壤碳氮蓄积量分别损失了100.7±25.9 TgC和9.8±2.2 TgN,林地土壤碳氮蓄积量分别损失了55.9±17.0 TgC和4.9±1.1 TgN。同时根据中国6大行政区林地、耕地和草地之间的相互转换面积、土壤有机碳氮密度的变化率进行估算,表明土壤(30 cm和100 cm) 有机碳氮蓄积量分别损失了53.7 TgC、5.1 TgN和99.5 TgC 、9.4 TgN。由于中国不同地区土地利用变化的空间格局差异显著,从而导致东北地区土壤碳氮蓄积量变化较大,而华东地区变化较小。

Storages of Soil Organic Carbon and Nitrogen and Land Use Changes in China: 1990-2000

The impacts of land use changes on soil organic carbon (SoC) and soil organic nitrogen (SON) storage have been analyzed from 1990 to 2000 in China between forest, grassland and cropland based on 2473 soil profiles and Landsat TM images from the end of 1980s to the end of 1990s. Estimation of the greenhouse gasses inventory approach suggested by IPCC indicated that the losses of SoC and SON pools were 77.6±35.2 TgC (Tg = 10⁶ t) and 5.6±2.6 TgN to a depth of 30 cm in China, in which the mean annul losses of SoC and SON were 7.76 TgC/yr and 0.56 TgN/yr, respectively. SoC and SON pools of cropland increased 79.0±7.7 TgC and 9.0±0.7 TgN, grassland lost 100.7±25.9 TgC and 9.8±2.2 TgN, and forest lost 55.9±17.0 TgC and 4.9±1.1 TgN, respectively. In order to estimate the uncertainty range of calculated results, this paper adopted the land use conversion approach to compare with IPCC's approach. The calculation of the land use conversion approach showed that the losses of SoC and SON pools were 53.7 TgC and 5.1 TgN to a depth of 30 cm, and 99.5 TgC and 9.4 TgN to a depth of 100 cm respectively, which the calculation proCedure was designed according to the conversion area and the changing rate of SoC and SON densities among forest, cropland and grassland during 10 years.