黄土典型坝系流域碳沉积特征及其源解析

Characteristics of the soil carbon content and its carbon sources in deposition area at a watershed with check-dam in Loess Plateau China

沉积物信息能够反映流域侵蚀环境变化,研究沉积物碳赋存规律对流域侵蚀过程和生态恢复具有重要指示意义。本文选取黄土高原典型坝系流域,通过土壤沉积剖面取样和室内测试分析,同时利用稳定同位素技术,分析了坝地及沟道沉积土壤剖面的碳分布特征及其来源解析。结果显示:(1)淤地坝沉积土壤总碳含量和土壤有机碳含量变化范围分别为12.80—14.76 g/kg和1.34—3.53 g/kg;沟道沉积土壤总碳含量和土壤有机碳含量变化范围分别为13.61—17.86 g/kg和1.52—5.04 g/kg。(2)淤地坝土壤总碳含量在土壤深度0—100 cm和350—500 cm区间波动较为平缓,100—350 cm波动较大;沟道0—200 cm土壤层总碳含量沉积变化较大,而200—390 cm土壤层变化平缓。淤地坝和沟道沉积土壤有机碳含量随土壤深度增加呈现降低趋势。(3)淤地坝有机碳同位素变化范围为-23.96‰—-22.09‰,整体上呈现表层土偏正,并随土壤深度增加而呈现偏负的趋势;沟道沉积土壤有机碳同位素变化范围为-27.04‰—-24.58‰,随土壤随深度增加呈现偏正的趋势。(4)羊圈沟坝地表层土壤有机碳多来源于灌木(占96.80%),沟道表层土壤有机碳则多来自于灌木和草地(分别占62.05%、32.4%)。

Sediment information can reflect the changes of the erosion environment in a watershed.In addition,studies regarding the sedimentation process have significant implications for the erosion process and ecological restoration within a watershed.Therefore,this study analyzed the distribution patterns and sources of carbon in both gullies and check dams in the Loess Plateau.Soil samples were obtained from field study and analyzed using stable isotope techniques.The results showed that:(1)the soil total carbon(STC)and the soil organic carbon(SOC)in the check dams ranged from 12.80 to 14.76 g/kg and 1.34 to 3.53 g/kg,respectively,and that of gullies ranged from 13.61 to 17.86 g/kg and 1.52 to 5.04 g/kg,respectively.(2)The fluctuation of STC in check dams was relatively less in the depth of 0—100 cm and 350—500 cm soil profile,while relatively greater in the depth of 100 to 350 cm.The fluctuation range of STC in the gullies was relatively less in the depth of 200 to 390 cm,while relatively greater in the depth of 0 to 200 cm.Besides,the SOC in the check dams and gullies decreased with the increase of soil profile.(3)The SOC isotope in the dams ranged from-23.96‰to-22.09‰with the higher values observed in the surface soil layer and a decline with the increasing soil depth.The SOC isotope of gullies ranged from-27.04‰to-24.58‰,which showed an increasing trend with increasing soil depth.(4)The SOC in the surface soil of the dams mainly originated from the shrubland(96.80%),and that of the gullies was mostly derived from the shrubland(62.05%)and grassland(32.4%).