Abstract. Understanding patterns of habitat natural recovery after human-made disturbances is critical for the conservation of ecosystems under high environmental stress, such as drylands. In particular, the unassisted establishment of nonvascular plants such as biological soil crusts or biocrust communities (e.g., soil lichens, mosses and cyanobacteria) in newly formed habitats is not yet fully understood. However, the potential of biocrusts to improve soil structure and function at the early stages of succession and promote ecosystem recovery is enormous. In this study, we evaluated the capacity of lichen biocrusts to spontaneously establish and develop on road slopes in a Mediterranean shrubland. We also compared taxonomic and functional diversity of biocrusts between road slopes and natural habitats in the surroundings. Biocrust richness and cover, species composition, and functional structure were measured in 17 road slopes (nine roadcuts and eight embankments) along a 13 km highway stretch. Topography, soil properties and vascular plant communities of road slopes were also characterized. We used Kruskal–Wallis tests and applied redundancy analysis (RDA) to test the effect of environmental scenario (road slopes vs. natural habitat) and other local factors on biocrust features. We found that biocrusts were common in road slopes after ∼20 years of construction with no human assistance needed. However, species richness and cover were still lower than in natural remnants. Also, functional structure was quite similar between roadcuts (i.e., after soil excavation) and natural remnants, and topography and soil properties influenced species composition while environmental scenario type and vascular plant cover did not. These findings further support the idea of biocrusts as promising restoration tools in drylands and confirm the critical role of edaphic factors in biocrust establishment and development in land-use change scenarios.

中文翻译：

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在旱地道路斜坡上无辅助地建立生物土壤结皮

摘要。了解人为干扰后栖息地自然恢复的模式对于在高环境压力下（例如旱地）保护生态系统至关重要。特别是，在新形成的栖息地中无辅助地建立非维管植物，如生物土壤结皮或生物结皮群落（例如，土壤地衣、苔藓和蓝藻）尚未完全了解。然而，生物结皮在演替早期改善土壤结构和功能以及促进生态系统恢复的潜力是巨大的。在这项研究中，我们评估了地衣生物结皮在地中海灌木丛中的道路斜坡上自发建立和发育的能力。我们还比较了道路斜坡和周围自然栖息地之间生物结皮的分类和功能多样性。在 13 公里高速公路路段沿线的 17 个道路斜坡（9 个路基和 8 个堤防）中测量了生物地壳的丰富度和覆盖度、物种组成和功能结构。还表征了道路斜坡的地形、土壤特性和维管植物群落。我们使用 Kruskal-Wallis 测试和应用冗余分析 (RDA) 来测试环境情景（道路坡度与自然栖息地）和其他局部因素对生物地壳特征的影响。我们发现，经过大约 20 年的建设，在不需要人工帮助的情况下，生物结皮在道路边坡中很常见。然而，物种丰富度和覆盖率仍低于自然遗迹。此外，道路切割（即土壤开挖后）和自然残余物之间的功能结构非常相似，地形和土壤特性影响物种组成，而环境情景类型和维管植物覆盖则没有。这些发现进一步支持了生物结皮作为旱地恢复工具的想法，并证实了土壤因子在土地利用变化情景中生物结皮形成和发展中的关键作用。