Data from: Effects of grazing on soil nitrogen spatial heterogeneity depend on herbivore assemblage and pre-grazing plant diversity

The spatial heterogeneity of limiting soil resources is an essential factor determining ecosystem processes and function. It has been reported that large herbivores can strongly impact the variation and spatial distribution pattern of soil nitrogen (N). However, it remains unclear how large herbivores affect soil spatial heterogeneity and whether this influence is dependent on plant community diversity. Here we examined effects of different herbivore assemblages [no grazing; cattle grazing (CG); sheep grazing (SG); and mixed grazing (MG) of cattle and sheep] on soil N spatial heterogeneity in grasslands with high and low pre-grazing plant diversity in an eastern Eurasian steppe. We found that herbivore grazing generated and maintained spatial patterns of soil nutrients, depending on herbivore assemblage and the level of pre-grazing plant diversity. CG increased the spatial heterogeneity of soil available N in Leymus chinensis-dominated steppe meadows, which were independent of pre-grazing plant diversity. However, the effects of SG and MG strongly depended on grassland plant diversity, with an increased spatial heterogeneity of soil available N in the high-diversity grassland, but not in the low-diversity grassland. Synthesis and applications. We concluded that in a L. chinensis-dominated eastern Eurasian steppe, cattle ranching could be considered as an optimal grazing management protocol to improve soil spatial heterogeneity because cattle grazing (CG) consistently increased soil spatial heterogeneity in the context of both low and high plant diversity. Nevertheless, soil spatial heterogeneity could be improved by any herbivore grazing regime [CG and/or sheep grazing (SG)] when high plant diversity is maintained. These findings highlight the importance of conserving plant diversity to maintain grassland structure and ecosystem function. In grassland systems with high plant diversity, herbivore grazing and plant diversity would jointly improve soil spatial heterogeneity, thus feeding back to maintain higher plant diversity. Therefore, high plant diversity could generate a positive feedback loop of herbivore–plant–soil interactions in grazed grassland systems. Our findings indicate the importance of herbivore assemblages in maintaining spatial heterogeneity in low- and high-diversity grassland systems.限制性土壤资源的空间异质性是决定生态系统过程与功能的核心调控因子。已有研究表明，大型草食动物可显著影响土壤氮（N）的变异特征与空间分布格局，但目前仍尚不明确大型草食动物如何调控土壤空间异质性，且其影响效应是否依赖于植物群落多样性。 本研究以欧亚大陆东部草原为研究对象，设置了4组草食动物采食处理：无放牧、牛放牧（CG）、羊放牧（SG）以及牛羊混合放牧（MG），探究放牧前植物多样性高低对土壤氮空间异质性的调控效应。 研究结果显示，草食动物放牧可塑造并维持土壤养分的空间格局，且该效应取决于草食动物采食组合与放牧前植物多样性水平。在以羊草（Leymus chinensis）为优势种的草原草甸中，牛放牧（CG）可提升土壤有效氮的空间异质性，且该效应不受放牧前植物多样性水平的影响；而羊放牧（SG）与混合放牧（MG）的效应则显著依赖于草原植物多样性：在高植物多样性草原中可提升土壤有效氮的空间异质性，但在低多样性草原中无此效应。 综合与应用分析表明，在以羊草（Leymus chinensis）为优势种的欧亚大陆东部草原中，牛放牧可作为提升土壤空间异质性的最优放牧管理方案，因为无论放牧前植物多样性高低，牛放牧（CG）均能持续提升土壤空间异质性。而在维持高植物多样性的前提下，任意草食动物放牧方案[牛放牧（CG）和/或羊放牧（SG）]均可改善土壤空间异质性。 本研究结果凸显了保护植物多样性对维持草原结构与生态系统功能的重要性。在高植物多样性的草原生态系统中，草食动物放牧与植物多样性可共同提升土壤空间异质性，进而反馈维持更高的植物多样性水平。因此，在放牧草原生态系统中，高植物多样性可形成草食动物-植物-土壤互作的正反馈循环。本研究结果证实，草食动物采食组合在维持低、高多样性草原系统的空间异质性中具有关键作用。