Aims In water-limited areas, shrubs influence biological soil crust (biocrust) composition and diversity via soil microenvironment alterations and through modifying biotic interactions amongst biocrust taxa. However, the relative contributions of shrubs to biocrust succession and assembly via the biotic and abiotic influences are poorly known. Methods The community composition of biocrusts and soil properties in the interspace and beneath the dominant shrub ( Artemisia ordosica ) along a biocrust succession sequence were investigated. Biocrust interspecific interactions at a small scale (within shrub) were evaluated based on the co-occurrence pattern using null models. A hypothetical multigroup structural equation model (SEM) was proposed to evaluate the influence of multiple variables on the biocrust richness and to investigate the path variance between successional stages. Results Along the biocrust succession, shrubs significantly increased the size of bare soil gap by 489%, decreased lichens by 43% and increased soil organic matter by 13%. In years 18, 31and 37, the paths in SEM explained 59% of the variation in richness, only the effect of abiotic amelioration was significant (0.62). In years 54 and 62, the shrubs had direct (0.37) and indirect effect (0.10) via species interaction to biocrust richness. Conclusions Shrubs directly and indirectly affected the community assembly of biocrusts. Biocrust species interactions are an important driver of biocrust diversity and primarily affect late succession. The increasing influences of shrubs suggests a close relationship between shrub and biocrust components in arid or semiarid ecosystems, with shrubs playing an important role in regulating biocrust assembly and maintaining biocrust richness.

中文翻译：

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灌木在生物结皮群落组装中的作用：沿生物结皮演替梯度的生物和非生物影响

目的 在缺水地区，灌木通过改变土壤微环境和改变生物结皮分类群之间的生物相互作用来影响生物土壤结皮（生物结皮）的组成和多样性。然而，灌木通过生物和非生物影响对生物地壳继承和组装的相对贡献知之甚少。方法沿生物地壳演替序列，调查优势灌木（青蒿）间隙和下方的生物地壳群落组成和土壤性质。小规模（灌木内）的生物地壳种间相互作用基于使用无效模型的共现模式进行评估。提出了一个假设的多组结构方程模型（SEM）来评估多个变量对生物地壳丰富度的影响并研究演替阶段之间的路径方差。结果在生物地壳演替过程中，灌木显着增加了489%的裸土间隙，减少了43%的地衣，增加了13%的土壤有机质。在第 18、31 和 37 年，SEM 中的路径解释了 59% 的丰富度变化，只有非生物改良的影响显着（0.62）。在第 54 年和第 62 年，灌木通过物种相互作用对生物地壳丰富度产生直接 (0.37) 和间接影响 (0.10)。结论 灌木直接和间接影响了生物结皮的群落组装。生物地壳物种相互作用是生物地壳多样性的重要驱动因素，主要影响后期演替。