碳氮同位素结合稳定同位素模型解析沉积土壤碳源

Contribution of Carbon Sources in Sedimentary Soils Combining Carbon and Nitrogen Isotope with Stable Isotope Model

【目的】研究辽西褐土丘陵区典型小流域不同土地利用方式下经侵蚀沉积过程沉积土壤碳来源,为合理调控小流域土壤侵蚀造成的土壤碳流失提供科学参考。【方法】通过对辽西丘陵沟壑区小流域野外取样,研究小流域沉积土壤碳的来源并量化其贡献。通过GIS结合GPS技术对小流域4种不同土地利用类型(耕地、林地、草地、沟渠)表层土壤及小流域拦沙坝3个位点(S1坝前、S2坝中、S3坝后)0-100 cm土壤剖面进行取样,结合碳、氮同位素混合模型对沉积土壤碳源进行解析。【结果】利用^(13)C和^(15)N同位素特征及其元素组成(土壤有机碳和全氮)对辽西丘陵沟壑区侵蚀沉积物土壤有机碳进行了定性和定量鉴定。辽西丘陵沟壑区小流域沉积物中有机碳主要来源为耕地,其次是沟渠、草地和林地。耕地贡献平均为58.75%,沟渠25.49%,草地6.49%,林地9.2%。【结论】碳氮稳定性同位素模型作为一种重要的"指纹"工具可以成功应用于辽西丘陵沟壑区小流域沉积土壤碳来源定性及定量的分析。研究成果可以为受水力侵蚀的小流域的土壤保护和养分流失控制以及维持生态系统的可持续性提供理论参考。

【Objective】To study the sources of deposited soil organic carbon(SOC)under different land use patterns in a typical small watershed in the brown soil hilly area of western Liaoning through eroded sedimentation,and to provide a scientific reference for the reasonable control of soil carbon loss caused by soil erosion in the small watershed.【Method】Through field sampling of small watersheds in the hilly and gully area of western Liaoning,the sources of deposited soil carbon in the small watersheds were studied and their contribution was quantified.Using GIS and GPS technology to analyze the surface soil of 4 different land use types(cropland,forest,grassland,gully)in the small watershed and 3 locations of the check dam in the small watershed(S1 in front of the dam,S2 in the middle of the dam,S3 behind the dam)0-100 cm soil profile was sampled to analyze the carbon source of the sedimentary soil based on a mixed carbon and nitrogen isotope model.【Result】Using ^(13)C and ^(15)N isotopic characteristics and their elemental composition qualitative and quantitative identification of soil organic carbon in eroded sediments in the hilly and gully area of western Liaoning was carried out.The SOC loss was primarily from cropland,accounting for 58.75%,followed by gully(25.49%),forest(9.2%),and grassland(6.49%).【Conclusion】The stable isotope SIAR mixing model,as a reliable"fingerprint"tool,could be successfully employed to estimate the contribution of various C sources within a complex ecosystem,The research results can provide theoretical references for soil protection and nutrient loss control in small watersheds affected by water erosion,and for maintaining the sustainability of the ecosystem.