1980s-2010s中国陆地生态系统土壤碳储量的变化

土壤作为陆地生态系统有机碳库的主体,在全球碳循环中起着重要作用。然而,当前区域土壤有机碳储量的变化情况及其碳源/汇功能仍然不清楚。利用中国1980s （1979-1985年）第二次土壤普查数据,同时收集整理2010s（2004-2014年）已发表的有关中国土壤有机碳储量（0~20 cm和0~100 cm）的文献数据,综合评估了1980s-2010s中国土壤有机碳储量的变化情况,并分析森林、草地、农田和湿地等生态系统土壤碳源/汇功能;同时结合现有的中国植被碳储量变化研究,进一步探讨了1980s-2010s中国陆地生态系统的碳源/汇效应。研究发现：① 1980s-2010s中国土壤（0~100 cm）有机碳储量净增长3.04±1.65 Pg C,增长速率为0.101±0.055 Pg C yr^-1,其中表层土壤（0~20 cm）的碳汇效应明显;② 森林土壤是固碳主体,净增长2.52±0.77 Pg C,而草地和农田土壤增长有限,分别为0.40±0.78和0.07±0.31 Pg C;③ 湿地有机碳储量净减少0.76±0.29 Pg C;④ 中国陆地生态系统的碳汇效应较强,总碳汇量相当于同期（1980-2009年）化石燃料和水泥生产排放CO₂总量的14.85%~27.79%。随着中国森林和草地生态系统植被和土壤的进一步保护、恢复和重建,中国陆地生态系统具有较大的碳汇潜力,在未来全球碳平衡中将发挥更大的作用。

Changes of soil organic carbon storage in Chinese terrestrial ecosystems from the 1980s to the 2010s

Soils store a large amount of the terrestrial ecosystem carbon (C) and play an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in the main types of ecosystems (forest, grassland, cropland, and wetland) across 18 regions of China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated whether trends changed over the 30-year period. The SOC storage (0-100 cm) in China was 83.46±11.89 Pg C in the 1980s and 86.50±8.71 Pg C in the 2010s, and the net increase over 30 years was 3.04±1.65 Pg C, with a rate of 0.101±0.055 Pg C yr^-1. This increase was mainly observed in the topsoil (0-20 cm). Forest, grassland, and cropland SOC storage increased by 2.52±0.77, 0.40±0.78, and 0.07±0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined by 0.76±0.29 Pg C, most likely due to the decrease in wetland area and SOC density. These results, combined with those of vegetation C sink (0.100 Pg C yr^-1), show that the net C sink in Chinese terrestrial ecosystems was about 0.201±0.061 Pg C yr^-1, which offsets 14.85%-27.79% of the C emissions from fossil fuels from the 1980s to the 2010s. These estimates of soil C sink based on field measured data supported the premise that China's terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.