半干旱区退化草地开垦为苜蓿地对土壤无机碳的影响

Effects of the reclamation of degraded semi-arid grassland into alfalfa field on soil inorganic carbon

为分析半干旱区退化草地开垦后土壤无机碳储量的变化,探讨开垦对土壤无机碳的影响机制,以半干旱区开垦农田(苜蓿地)为研究对象,以邻近的退化草地(荒漠草原)作为对照,借助碳稳定同位素技术,测定并计算0~300 cm土壤深度土壤无机碳(SIC)、次生碳酸盐(PIC)和原生碳酸盐(LIC)的储量。结果表明,与退化草地相比,苜蓿地0~300 cm处的SIC总储量显著增加了88.42 Mg·hm^(-2),PIC总储量显著增加了105.71 Mg·hm^(-2),LIC总储量显著减少了17.29 Mg·hm^(-2)。退化草地开垦促进了PIC在深层土壤的积累,进而促进了SIC的增加,表明开垦能够增强半干旱地区土壤的固碳能力,且PIC的增加导致了SIC的净累积。

To explore the effects of the reclamation of degraded grassland on soil inorganic carbon(SIC)stocks and identify the mechanisms of SIC accumulation in a semi-arid region of China,we compared the SIC stock in a reclaimed farmland(alfalfa field),with that of an adjacent control site(degraded grassland desert).We used carbon stable isotope measurements to calculate the stock of SIC,pedogenic inorganic carbon(PIC),and lithogenic inorganic carbon(LIC)in 0–300 cm soil profiles at both sites.Our results showed that,in the alfalfa field soil,the total SIC and PIC were enriched by 88.42 and 105.71 Mg·hm^(-2),respectively,while the total LIC stock was depleted by 17.29 Mg·hm^(-2) compared with the degraded grassland.The reclamation of the degraded grassland promoted the accumulation of SIC,which was mainly caused by the accumulation of PIC in deep soil.Our findings indicate that,in semi-arid areas,reclamation can enhance the soil’s carbon sequestration capacity,and that the net accumulation of SIC is mainly driven by the increase in PIC.