大气CO_(2)浓度升高对黑土有机碳稳定性的影响

Effects of elevated atmospheric CO_(2) concentration on stability of black soil organic carbon

【目的】阐明大气CO_(2)浓度升高对黑土有机碳稳定性的影响,为黑土碳中和应对气候变化提供理论依据。【方法】以黑土为研究对象,依托中国科学院海伦农业生态试验站长期定位模拟气候变化开顶箱(OTC)试验平台,设2个处理,分别为对照处理(CK,CO_(2)浓度400μmol/mol)和CO_(2)浓度升高处理(eCO_(2),CO_(2)浓度700μmol/mol),采用13C同位素示踪法,研究大气CO_(2)浓度升高对黑土及不同粒级团聚体有机碳稳定性的影响,并对土壤有机碳含量与更新率和半衰期进行相关分析。【结果】与CK相比,eCO_(2)处理使>0.25 mm粒级团聚体含量显著增加11.09%(P<0.05,下同),0.25~0.053 mm粒级团聚体含量显著减少23.85%,提升团聚体的平均重量直径(MWD)和几何平均直径(GMD);大气CO_(2)浓度升高使>0.25 mm粒级团聚体有机碳显著增加11.61%,0.25~0.053 mm粒级团聚体有机碳含量显著减少8.72%,全土及<0.053 mm粒级团聚体有机碳含量无显著变化(P>0.05,下同)。13C丰度随着粒级减小而依次增大,且CO_(2)浓度升高使全土及各个粒级团聚体的13C丰度均显著降低,全土、>0.25 mm粒级及0.25~0.053 mm粒级团聚体的更新率分别显著增加34.62%、21.60%和57.22%,半衰期依次显著降低34.61%、19.63%和36.84%,<0.053 mm粒级团聚体更新率和半衰期未发生显著变化;更新率与全土和>0.25 mm团聚体有机碳含量呈显著正相关,半衰期与全土和>0.25 mm团聚体有机碳含量呈显著负相关。【结论】大气CO_(2)浓度升高对黑土有机碳含量影响不显著,但使大团聚体结构稳定性和有机碳含量增加,加快全土和大团聚体有机碳更新周转,有利于提升黑土肥力。

【Objective】The purpose of the study was to clarify the effects of elevated atmospheric CO_(2) concentration on the stability of black soil organic carbon,and to provide theoretical basis for black soil carbon neutralization in response to climate change【.Method】With black soil as the research object,on the basis of the open-top chamber(OTCs)experimental platform of long-term positioning simulation of climate change at Hailun Agroecological Experiment Station of the Chinese Academy of Sciences,two treatments were set in this study,which were the control treatment(CK,with a CO_(2) concentration of 400μmol/mol)and elevated CO_(2) concentration treatment(eCO_(2),with a CO_(2) concentration of 700μmol/mol).13C isotope tracing method was used to study the effect of elevated atmospheric CO_(2) concentration on the stability of organic carbon in black soil and aggregates with different particle sizes.And correlation analysis on soil organic carbon with replacement rate and half-life period was conducted.【Result】Compared with CK,eCO_(2) treatment significantly increased the content of>0.25 mm particle size aggregate by 11.09%(P<0.05,the same below),significantly decreased the content of 0.25-0.053 mm particle size aggregate by 23.85%,and improved the mean weight diameter(MWD)and geometric mean diameter(GMD)of aggregates.Elevated atmospheric CO_(2) concentration significantly increased the organic carbon content of>0.25 mm particle size aggregate by 11.61%,and the organic carbon content of 0.25-0.053 mm particle size aggregate significantly decreased by 8.72%.The organic carbon content of bulk soil and the<0.053 mm particle size aggregate did not change significantly(P>0.05,the same below).Abundance of 13C sequentially increased with the decrease of particle size,and the elevated CO_(2) concentration significantly decreased the 13C abundance of bulk soil and all particle sizes.The replacement rates of the bulk soil,>0.25 mm particle size and 0.25-0.053 mm particle size aggregates increased by 34.62%,21.60%,and 57.22%,respectively,and the half-life periods significantly decreased by 34.61%,19.63%,and 36.84%,respectively,but the replacement rate and half-life period of<0.053 mm particle size aggregate did not change significantly.The replacement rate was significantly and positively correlated with the organic carbon content of the bulk soil and>0.25 mm aggregate,and the half-life period was significantly and negatively correlated with the organic carbon content of the bulk soil and>0.25 mm aggregate.【Conclusion】The effects of elevated atmospheric CO_(2) concentration on the organic carbon content of black soil is not significant,but it increases the structural stability and the organic carbon content of macroaggregate,accelerates the turnover of organic carbon renewal in bulk soil and macroaggregate,and is beneficial to the improvement of black soil fertility.