Gao Yang, Tian Jing, Pang Yue, Liu Jiabin
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F UniversityYangling, China.
College of Forestry, Northwest A&F UniversityYangling, China.
Front Plant Sci. 2017 Jul 19;8:1282. doi: 10.3389/fpls.2017.01282. eCollection 2017.
In arid and semiarid areas, the effects of afforestation on soil organic carbon (SOC) have received considerable attention. In these areas, in fact, soil inorganic carbon (SIC), rather than SOC, is the dominant form of carbon, with a reservoir approximately 2-10 times larger than that of SOC. A subtle fluctuation of SIC pool can strongly alter the regional carbon budget. However, few studies have focused on the variations in SIC, or have used stable soil carbon isotopes to analyze the reason for SIC variations following afforestation in degraded semiarid lands. In the Mu Us Desert, northwest China, we selected a shifting sand land (SL) and three nearby forestlands () with ages of 8 (P-8), 20 (P-20) and 30 (P-30) years, and measured SIC, SOC, soil organic and inorganic δC values (δC-SOC and δC-SIC) and other soil properties. The results showed that SIC stock at 0-100 cm in SL was 34.2 Mg ha, and it increased significantly to 42.5, 49.2, and 68.3 Mg ha in P-8, P-20, and P-30 lands, respectively. Both δC-SIC and δC-SOC within the 0-100 cm soil layer in the three forestlands were more negative than those in SL, and gradually decreased with plantation age. Afforestation elevated soil fine particles only at a depth of 0-40 cm. The entire dataset (260 soil samples) exhibited a negative correlation between δC-SIC and SIC content ( = 0.71, < 0.01), whereas it showed positive correlation between SOC content and SIC content ( = 0.52, < 0.01) and between δC-SOC and δC-SIC ( = 0.63, < 0.01). However, no correlation was observed between SIC content and soil fine particles. The results indicated that afforestation on shifting SL has a high potential to sequester SIC in degraded semiarid regions. The contribution of soil fine particle deposition by canopy to SIC sequestration is limited. The SIC sequestration following afforestation is very probably caused by pedogenic carbonate formation, which is closely related to SOC accumulation. Our findings suggest that SIC plays an important role in the carbon cycle in semiarid areas and that overlooking this carbon pool may substantially lead to underestimating carbon sequestration capacity following vegetation rehabilitation.
在干旱和半干旱地区，造林对土壤有机碳（SOC）的影响受到了广泛关注。事实上，在这些地区，土壤无机碳（SIC）而非SOC是碳的主要存在形式，其储量约为SOC的2至10倍。SIC库的微小波动会强烈改变区域碳收支。然而，很少有研究关注SIC的变化，或利用稳定的土壤碳同位素分析退化半干旱土地造林后SIC变化的原因。在中国西北的毛乌素沙漠，我们选取了一块流动沙地（SL）和附近三块林地（分别为树龄8年（P - 8）、20年（P - 20）和30年（P - 30）），测量了SIC、SOC、土壤有机和无机δC值（δC - SOC和δC - SIC）以及其他土壤性质。结果表明，SL中0至100厘米深度的SIC储量为34.2 Mg/ha，在P - 8、P - 20和P - 30林地中分别显著增加到42.5、49.2和68.3 Mg/ha。三块林地0至100厘米土层内的δC - SIC和δC - SOC均比SL中的更负，并随造林年龄逐渐降低。造林仅在0至40厘米深度提高了土壤细颗粒含量。整个数据集（260个土壤样本）显示，δC - SIC与SIC含量呈负相关（r = 0.71，P < 0.01），而SOC含量与SIC含量呈正相关（r = 0.52，P < 0.01），δC - SOC与δC - SIC也呈正相关（r = 0.63，P < 0.01）。然而，未观察到SIC含量与土壤细颗粒之间的相关性。结果表明，在退化半干旱地区，流动沙地造林具有很高的SIC固存潜力。冠层土壤细颗粒沉积对SIC固存的贡献有限。造林后的SIC固存很可能是由成土碳酸盐形成导致的，这与SOC积累密切相关。我们的研究结果表明，SIC在半干旱地区的碳循环中起着重要作用，忽视这一碳库可能会导致大幅低估植被恢复后的碳固存能力。
