中国东北地区20世纪末土地利用变化的土壤碳源汇效应

Soil carbon source/sink caused by landuse change in the last decades of the last century in Northeast China

土地利用变化是土壤有机碳库变化的重要原因之一。文中选择中国东北地区,利用多目标区域地球化学调查数据,结合20世纪80年代和2000年土地利用数据,分析了不同土地利用方式下土壤有机碳密度分布特征,以及由于土地利用方式变化形成的土壤碳源汇效应。结果发现:(1)不同土地利用下土壤表层有机碳密度(SOCD)差异较大,沼泽地、有林地等是SOCD相对较高的土地利用类型,而沙地、盐碱地、低覆盖草地等土地利用方式下SOCD较低;(2)按照土地利用方式的构成推算,研究区表层(0～20cm)土壤有机碳储量为482.1×1010 kg,其主要储库为有林地和旱地,分别占土壤总有机碳储量的43.8%和21.4%;(3)东北地区由于土地利用方式变化造成的土壤总碳源值为5.73×1010 kg,总碳汇值为3.56×1010 kg,因此研究区总体上表现为2.17×1010 kg(21.7Tg)的碳源;(4)研究区起到土壤碳汇作用的典型土地利用转化方式有旱地到水田的转化、其他林地和疏林地到有林地的转化等;起到土壤碳源作用的典型土地利用转化方式为有林地到旱地的转化、高覆盖草地到旱地的转化、沼泽到水田和旱地等耕地的转化等。

Landuse change is one of the most important factors that influence the variation of the soil organic carbon pool. Soil organic carbon density （SOCD） under different landuses and the effect of soil carbon source/ sink caused by landuse change in Northeast China was investigated using soil data from the regional multi-purpose geochemical survey and landuse data of two temporal points： 1980s and the year of 2000. The following conclusions were drawn： （1） SOCD varied significantly with different landuses; bog and thick forest have the highest SOCD, and sand land, saline land and thin grass land are the landuse types with low SOCD; （2） the reserve of surface soil （0- 20 cm） organic carbon in the study area is 482. 1 ×10^10 kg, and the two most large soil carbon pools are the thick forest and the dry farm and, which account for, respectively, 43. 8% and 21.4% of the total organic carbon pool of the study area; （3） the carbon source caused by landuse change is 5.73× 10^10 kg, and the carbon sink is 3.56 × 10^10 kg, so the aggregate effect of the landuse changes results in an effect of soil carbon source of 2. 17×10^10 kg （21.7 Tg） in the study area; （4） the typical landuse change types that caused soil carbon sinks are the change of dry farm land to paddy field, and the change of thin forest and other forest to thick forest; and the typical landuse change types that caused soil carbon sources are the changes of thick forest and thick grass land to dry farm land, and the change of bog to dry farm land, paddy field, etc.