1981—2010年内蒙古草地土壤有机碳时空变化及其气候敏感性

Spatial-Temporal Change of Soil Organic Carbon and Its Susceptibility to Climate Change in Inner Mongolia Grassland during 1981-2010

草地土壤有机碳储量巨大,其较小幅度的波动即可能显著反馈于气候变化.基于1981—2010年内蒙古自治区境内及其周边共计92个气象台站气候要素插值数据,采用空间化的生物地球化学模型——CENTURY 4.5,模拟分析近30年来内蒙古草地表层（0~20 cm）土壤有机碳的空间格局与动态变化特征,并通过构建气候变化情景探讨其对主要气候要素的敏感性.结果表明：近30年内蒙古草地表层土壤有机碳密度平均值约为1.99 kg/m2（以C计）,在空间上呈由东北向西南逐渐减少的分布特征.近30年来内蒙古草地表层土壤有机碳密度略有增加,年均增幅约0.22%,其中草甸草原的增速〔14.25 g/（m2·a）〕最大,荒漠草原的增速〔1.36 g/（m2·a）〕最小.草地表层土壤有机碳密度年际变化差异明显,1980s至1990s的增加较为缓慢,1990s至2000s的增幅约为前者的2倍,其中草甸草原和典型草原土壤有机碳增幅较大.气候敏感性分析结果显示,区域降水量变化可能是近30年内蒙古草地表层土壤有机碳密度变化的主要影响因素,但不同草地类型表层土壤有机碳密度对气候变化的敏感性存在较大差异;典型草原与草甸草原表层土壤有机碳变化主要受控于降水量变化,荒漠草原则主要受控于温度变化.

Grassland soil is a large organic carbon reservoir,and a slight change in soil organic carbon（ SOC） stocks has a considerable effect on atmospheric CO2 concentration,which contributes to climate warming. A comprehensive assessment on SOC dynamics and their susceptibility to climate change in Inner Mongolia grassland is still lacking. Based on the climatic interpolation data from 92 meteorological stations over Inner Mongolia and surrounding areas,the spatial distribution of topsoil（ 0-20 cm） organic carbon storage in Inner Mongolia grassland and its dynamics during 1981-2010 were estimated using the CENTURY-based modeling system（ complying CENTURY model from a site-based model into a spatial model）. The sensitivity to climate change was also examined based on scenario simulation analysis.The results showed that the spatial distribution of SOC density（ SOCD） in Inner Mongolia grassland showed a decreasing trend from the northeast to the southwest,with an average density of1. 99 kg/m2. Inner Mongolia grassland SOCD significantly increased over the past three decades,with an annual increase of0. 22%, while SOCD also showed a marked heterogeneity corresponding to grassland types,with the largest increase rate of14. 25 g/（ m2·a） in meadow steppe and the least rate（ 1. 36g/（ m2·a）） in desert steppe. There was also a large decadal variability in SOCD. From the 1980 s to the 1990 s,it changed very slowly,while it was shown to change greatly from the 1990 s to the 2000 s,about twice as much as the former,primarily attributed to changes in meadow steppe and typical steppe. At the regional scale,change in precipitation played a critical role in the increase of SOCD,but its relative role was not constant across the study area. Increase in SOCD over the typical steppe and meadow steppe was primarily attributed to precipitation changes,while rising temperature was the main cause of SOCD increase in desert steppe.