灌丛化对干旱区草地土壤有机碳化学结构和热稳定性的影响

Effects of Woody Proliferation on Chemical Structure and Thermal Stability of Soil Organic Carbon in Arid Grasslands

在典型的干旱区新疆,选取沿海拔分布的4类草地,使用固态13C核磁共振技术与热分析技术研究了灌丛化对草地土壤有机碳(SOC)化学结构和热稳定性的影响。结果表明:灌丛间的芳香碳比例沿海拔从温性荒漠到山地草甸逐渐降低。在温性荒漠、温性草原化荒漠、温性荒漠草原和山地草甸,灌丛下烷基碳/烷氧碳的比值相对于灌丛间分别增加了0.10、0.09、0.03、0.21。低海拔的温性荒漠和温性草原化荒漠的热易分解SOC质量(较低温度下分解的SOC)与SOC总质量的比值(%Exo1)、SOC分解一半时的温度(TG-T50)和SOC在能量释放一半时对应的温度(DSC-T50)显著低于高海拔的温性荒漠草原和山地草甸。在草原化荒漠、荒漠草原和山地草甸中,灌丛下的%Exo1和DSC-T50均高于灌丛间,而TG-T50低于灌丛间。在温性荒漠,从灌丛间到灌丛下,低温时SOC燃烧释放出的能量占总燃烧能量(Q)的比例减小,而高温时SOC燃烧释放出的能量增加。本研究结果表明灌丛化增加了干旱区SOC化学结构的稳定性和热稳定性。

In this study,four grassland types distributed along the altitude were selected in the typical arid area of Xinjiang,and the effects of shrub on the chemical structure and thermal stability of grassland soil organic carbon (SOC) were revealed by using solid-state13C nuclear magnetic resonance technology and thermal analysis technology.The results show that the proportion of aromatic C among shrubs is decreased gradually from temperate desert to mountain meadow along the altitude.In temperate desert,temperate grassland desertification,temperate desert grassland and mountain meadow,the alkyl C/O-alkyl C values under shrubs are increased by 0.10,0.09,0.03 and 0.21 respectively.The index of low altitude temperate desert and temperate grassland desertification,the ratio of the mass of SOC easily decomposed by heat (SOC decomposed at lower temperature) to the total mass of SOC (%Exo1),the temperature at half of SOC decomposition (TG-T50) and the corresponding temperature at half of SOC energy release (DSC-T50) are significantly lower than those of high-altitude temperate desert grassland and mountain meadow.In grassland desertification,desert grassland and mountain meadow,the%Exo1and DSC-T50under shrub are higher than those between shrubs,while TG-T50is lower than that between shrubs.In temperate desert,from shrub to shrub,the proportion of energy released by SOC combustion in total combustion energy (Q) is decreased at low temperature,while the energy released by SOC combustion is increased at high temperature.The results show that shrub can increase the stability of SOC chemical structure and thermal stability in arid area.