近50a玛纳斯河流域土地利用/覆被变化对碳储量的影响

土地利用变化对碳收支的影响是当前全球变化研究领域的重点内容之一,中国西北干旱区土地利用变化对陆地生态系统碳收支的影响尚不清楚。论文以西北干旱区流域绿洲水土开发的典范--玛纳斯河流域为研究区,基于Bookkeeping模型,利用多期土地覆被类型图、植被和土壤碳密度历史文献及实地调查资料,开展玛纳斯河流域近50 a荒漠转变为绿洲农田和农田弃耕两种主要土地覆被变化对碳收支的影响研究。玛纳斯河流域的垦殖活动有利于碳储量的增加,在1962-2008年的46 a间,土地利用变化导致流域植被碳储量增加6.34×10⁵ t,土壤碳储量增加3.14×10⁶ t,总碳储量增加3.77×10⁶ t。受土地覆被变化面积和转换类型碳密度差异的影响,不同土地覆被类型转换对碳储量的影响存在显著差异:荒漠草地、裸地开垦为耕地均引起植被和土壤碳储量显著增加;林地开垦为耕地引起植被碳储量减少,土壤碳储量增加,总碳储量减少;而耕地弃耕通常会导致流域碳储量减少。

Effects of Land Use/Land Cover Change on Carbon Storage in Manas River Watershed over the Past 50 Years

Research on the impact of land use/land cover change on carbon budget is one of the key issues in the field of global change, as well as a possible way to answer the question of "Missing carbon sink". However, this issue in northwest arid area of China is weak, which limits comprehensive understanding of the mechanism of the interaction between land use change and carbon cycle. In this paper, Manas River Watershed was chosen as the study area due to its representativeness of water and land exploitation in this area. By adopting empirical statistical model—Bookkeeping model, research on effects of two main types of land use/cover change (desert change into farmland and farmland abandonment) on the carbon budget were carried out in Manas River Watershed over the past 50 years. Land cover map, published vegetation/soil carbon density data as well as field survey data are utilized for this research. Results showed that the reclamation activity of Manas River Watershed increases carbon stocks. From 1962 to 2008, vegetation and soil carbon storage of the watershed increased by 6.34×10⁵ and 3.14×10⁶ t, respectively, which result in the total carbon stock increase by 3.77×10⁶ t. The impacts of different land use/land cover change on carbon budget are significantly different because of the variation in area and carbon density between conversion types: Vegetation and soil carbon storage are significantly increased with reclamation of arable land from desert grassland and bare land; the vegetation and total carbon storage reduced while soil carbon storage increased with the conversion of woodland to arable land; carbon storage in Manas River Watershed reduced because of farmland abandonment.