黄土高原土壤有机碳固存对植被恢复的动态响应及其碳汇价值

Dynamic Responses of Sequestration of Soil Organic Carbon to Vegetation Restoration and the Values of Carbon Sink in the Loess Plateau

量化黄土高原区域尺度土壤有机碳固存对生态修复的动态响应及其碳汇价值转化,为区域生态修复、碳汇交易、生态补偿等提供理论依据。以黄土高原地区有机碳变化相关文献为基础,采用文献整合分析方法量化了有机碳固存对黄土高原不同植被类型、树种、恢复阶段、气候、坡度、坡向的动态响应,并采用经济价值理论货币化碳汇价值。结果表明:与农田相比,黄土高原退耕还林工程增加了61.60%的碳固存,退耕还乔、灌、草分别增加88.20%,55.15%和43.18%。其中,常绿乔木优于落叶乔木,沙棘优于柠条,天然草地优于人工草地。3种植被类型(乔、灌、草)有机碳在不同恢复阶段的变化范围分别为38.87%~154.80%,21.59%~98.07%,32.80%~85.65%,恢复后期固碳最佳。气候条件、坡度、坡向对土壤固碳具有显著影响,在降雨量较高(>550 mm)的地区种植乔、灌,而在降雨量低(<450 mm)的地区以草地恢复为主。且阴坡、陡坡植被恢复能够有效增加有机碳含量。综合当前固碳价值以及未来固碳价值潜力,黄土高原0—20 cm, 0—100 cm土壤总固碳价值分别为3 601.5万元/年,9 089.5万元/年。退耕还林深刻改变了黄土高原的土壤碳固存,在植被管理过程中,应充分重视植被类型、树种、恢复阶段、气候及立地因子的影响,并在碳交易及生态补偿中应将土壤固碳效益考虑在内。

Quantifying the responses of soil organic carbon(SOC) sequestration in Loess Plateau to vegetation restoration and the carbon sink value conversion can provide a theoretical basis for ‘Grain for Green’ project, carbon sink trade, and ecological compensation. Based on the literatures related to the changes of SOC in the Loess Plateau, the synthesis analysis was used to analyze the dynamic response of SOC sequestration to different vegetation types, tree species, restoration stages, slopes, and aspects, and the economic value theory was used to monetize the carbon sink value. Compared with cropland, ‘Grain for Green’ increased SOC sequestration by 61.60%, and SOC sequestration resulting from conversions of croplands to forest, shrub and grassland increased by 88.20%, 55.15% and 43.18%, respectively, among which SOC sequestration of evergreen trees was better than that of the deciduous trees, SOC sequestration of sea buckthorn was better than Caragana, and SOC sequestration of natural grassland was better than artificial grassland. The SOC sequestration of the three vegetation types(forest, shrub, and grassland) varied in different restoration stages from 38.87%~154.80%, 21.59%~98.07%, and 32.80%~85.65%, respectively, and SOC sequestration was the best in the later restoration stage. Climatic condition, slope, and aspect had the significant effects on SOC sequestration. Planting trees and shrubs should be carried out in areas with high rainfall, and grassland restoration should be adopted in areas with low rainfall. Moreover, vegetation restoration on shady slopes and steep slopes can effectively increase SOC. Based on the current values of SOC sequestration and the potential of future SOC sequestration, the total SOC sequestration values of 0—20 cm and 0—100 cm soil layers in the Loess Plateau are 3.6×106 yuan and 9.09×106 yuan per year, respectively. ‘Green for Grain’ had profoundly changed the SOC sequestration in the Loess Plateau. In the process of vegetation management, more attention should be paid to the effects of vegetation types, tree species, restoration stages, climate, and topography factors. In addition, SOC sequestration benefits should be taken into account in carbon trade and ecological compensation.