What is a biocrust? A refined, contemporary definition for a broadening research community

Bettina Weber, Jayne Belnap, Burkhard Büdel, Anita J. Antoninka, Nichole N. Barger, V. Bala Chaudhary, Anthony Darrouzet-Nardi, David J. Eldridge, Akasha M. Faist, Scott Ferrenberg, Caroline A. Havrilla, Elisabeth Huber-Sannwald, Oumarou Malam Issa, Fernando T. Maestre, Sasha C. Reed, Emilio Rodriguez-Caballero, Colin Tucker, Kristina E. Young, Yuanming Zhang, Yunge ZhaoXiaobing Zhou, Matthew A. Bowker

Research output: Contribution to journalArticlepeer-review

99 Scopus citations


Studies of biological soil crusts (biocrusts) have proliferated over the last few decades. The biocrust literature has broadened, with more studies assessing and describing the function of a variety of biocrust communities in a broad range of biomes and habitats and across a large spectrum of disciplines, and also by the incorporation of biocrusts into global perspectives and biogeochemical models. As the number of biocrust researchers increases, along with the scope of soil communities defined as ‘biocrust’, it is worth asking whether we all share a clear, universal, and fully articulated definition of what constitutes a biocrust. In this review, we synthesize the literature with the views of new and experienced biocrust researchers, to provide a refined and fully elaborated definition of biocrusts. In doing so, we illustrate the ecological relevance and ecosystem services provided by them. We demonstrate that biocrusts are defined by four distinct elements: physical structure, functional characteristics, habitat, and taxonomic composition. We describe outgroups, which have some, but not all, of the characteristics necessary to be fully consistent with our definition and thus would not be considered biocrusts. We also summarize the wide variety of different types of communities that fall under our definition of biocrusts, in the process of highlighting their global distribution. Finally, we suggest the universal use of the Belnap, Büdel & Lange definition, with minor modifications: Biological soil crusts (biocrusts) result from an intimate association between soil particles and differing proportions of photoautotrophic (e.g. cyanobacteria, algae, lichens, bryophytes) and heterotrophic (e.g. bacteria, fungi, archaea) organisms, which live within, or immediately on top of, the uppermost millimetres of soil. Soil particles are aggregated through the presence and activity of these often extremotolerant biota that desiccate regularly, and the resultant living crust covers the surface of the ground as a coherent layer. With this detailed definition of biocrusts, illustrating their ecological functions and widespread distribution, we hope to stimulate interest in biocrust research and inform various stakeholders (e.g. land managers, land users) on their overall importance to ecosystem and Earth system functioning.

Original languageEnglish
Pages (from-to)1768-1785
Number of pages18
JournalBiological Reviews
Issue number5
StatePublished - Oct 2022


  • biocrust
  • biological soil crust
  • climate.
  • definition
  • function
  • habitat
  • physical structure
  • taxonomy


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