【摘要】 表层土壤中总有机碳（TOC）与相应上覆植物/植被之间的正/负δ¹³C偏移量已被广泛报道，并被认为可能是由多种因素（如大气、气候和土壤因素）变化引起的。开展更大空间尺度的研究，可以更好地揭示其主导因素。本文对中国内陆空间跨度数千公里的107个样点的表土和食草动物粪便样品进行了采集，对表土TOC、表土中分离出来的植物残体全样（PL）、食草动物粪便全样（HF）、表土植物残体和食草动物粪便中提取的α纤维素（α-cellulose）开展了δ¹³C分析测试。数据分析显示，表土TOC与表土中植物残体全样之间的δ¹³C偏移量(Δ¹³C_TOC-PL)和食草动物粪便全样与表土中植物残体全样之间的δ¹³C偏移量(Δ¹³C_HF-PL)均与δ¹³C_PL呈负相关关系。同样，食草动物粪便α纤维素与表土中植物残体α纤维素之间的δ¹³偏移量(Δ¹³C_HF-PL-cell)也与δ13CPL-cell呈负相关关系。对这些负相关关系最合理的解释是，在表土中的分解过程和食草动物体内的消化过程中，C₄植物的分解/消化速度比C3植物更快。研究结果表明，基于现代表土、沉积物和动物残骸δ¹³C数据估算的C₄植物相对丰度，可能被普遍低估，在以后的相关研究当中应当予以适当考虑和评估。更多还原

【Abstract】 The positive or negative δ¹³C shifts between total organic carbon（TOC） in surface soils and the corresponding overlying plants/vegetation have been widely reported and are thought to result from various factors, such as atmospheric, climatic, and soil changes.Conducting studies on a larger spatial scale can better reveal the dominant factors. In this study,107 surface soil and herbivore fecal samples were collected across several thousand kilometers of inland China. δ¹³C analyses were performed on surface soil TOC, bulk plant litter separated from surface soil（PL）, bulk herbivore feces（HF）, and α-cellulose extracted from both surface soil plant litter and herbivore feces. Data analysis showed that the δ¹³C shift between surface soil TOC and bulk plant litter(Δ¹³C_TOC-PL) and the δ¹³C shift between bulk herbivore feces and bulk plant litter in surface soils(Δ¹³C_HF-PL) both exhibited a negative correlation with δ¹³C_PL.Similarly, the δ¹³C shift between herbivore feces α-cellulose and surface soil plant α-cellulose(Δ¹³C_HF-PL-cell) also showed a negative correlation with δ¹³C_PL-cell. The most reasonable explanation for these negative correlations is that during decomposition in surface soils and digestion within herbivores, C₄ plants decompose/digest faster than C₃ plants. The findings suggest that the relative abundance of C₄ plants, estimated based on modern surface soils, sediments, and animal remains δ¹³C data, may have been commonly underestimated, and this should be appropriately considered and evaluated in future studies.更多还原