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Biological soil crusts (biocrusts) are a complex community of algae, cyanobacteria, lichens, bryophytes, and assorted bacteria, fungi, archaea, and bacteriophages that colonize the soil surface. Biocrusts are particularly common in drylands and are found in arid and semiarid ecosystems worldwide. While diminutive in size, biocrusts often cover large terrestrial areas, provide numerous ecosystem benefits, enhance biodiversity, and are found in multiple configurations and assemblages across different climate and disturbance regimes. Biocrusts have been a focus of many ecologists, especially those working in semiarid and arid lands, as biocrusts are foundational community members, play fundamental roles in ecosystem processes, and offer rare opportunities to study biological interactions at small and large spatial scales. Due to these same characteristics, biocrusts have the potential to serve as an excellent teaching tool. The purpose of this paper is to demonstrate the utility of biocrust communities as a model system in science education. Functioning as portable, dynamic mini ecosystems, biocrusts can be used to teach about organisms, biodiversity, biotic interactions, abiotic controls, ecosystem processes, and even global change, and can be easy to use in nearly every classroom setup. For example, education principles, such as evolution and adaptation to stress, or structure and function (patterns and processes) can be applied by bringing biocrusts into the classroom as a teaching tool. In addition, discussing the utility of biocrusts in the classroom – including theory, hypothesis testing, experimentation, and hands-on learning – this document also provides tips and resources for developing education tools and activities geared toward impactful learning. 

Drylands are a widely degraded biome characterized by low productivity and high abiotic stress. Biological soil crust (biocrust) inoculants hold promise as a rehabilitation material in drylands, useful for boosting ecosystem functions including stabilization of eroding soil surfaces. However, biocrust materials cultivated ex situ by humans inconsistently establish under field conditions. We tested two approaches aimed at improving field establishment of biocrust inoculum: exposing the organisms within the inoculum to abiotic stress in an attempt to harden them, and applying habitat ameliorations intended to reduce the stressfulness of the environment. We hypothesized that both approaches in concert would lead to the most consistent field establishment of biocrusts. Overall, addition of biocrust inoculum did enhance biocrust establishment over the 1.5‐year duration of the study but did not result in full recovery. Generally, hardened biocrust inoculum performed no better than inoculum that was not hardened, although one indicator (chlorophylla) was enhanced by addition of hardened inoculum in some circumstances. Temporary irrigation was initially an effective habitat amelioration but had no effect on biocrust establishment by 1.5 years. In contrast, application of jute net to the soil surface promoted biocrust establishment both in synergy with and in the absence of inoculum addition. We hypothesize that jute net stabilizes the soil surface, reduces abiotic stress, and enhances resource availability, overcoming barriers to establishment of biocrusts. Currently, there is broad support for the efficacy of habitat amelioration approaches in biocrust rehabilitation, but effective hardening techniques remain elusive. 

Abstract Understanding the importance of biotic interactions in driving the distribution and abundance of species is a central goal of plant ecology. Early vascular plants likely colonized land occupied by biocrusts — photoautotrophic, surface‐dwelling soil communities comprised of cyanobacteria, bryophytes, lichens and fungi — suggesting biotic interactions between biocrusts and plants have been at play for some 2,000 million years. Today, biocrusts coexist with plants in dryland ecosystems worldwide, and have been shown to both facilitate or inhibit plant species performance depending on ecological context. Yet, the factors that drive the direction and magnitude of these effects remain largely unknown.We conducted a meta‐analysis of plant responses to biocrusts using a global dataset encompassing 1,004 studies from six continents.Meta‐analysis revealed there is no simple positive or negative effect of biocrusts on plants. Rather, plant responses differ by biocrust composition and plant species traits and vary across plant ontogeny. Moss‐dominated biocrusts facilitated, while lichen‐dominated biocrusts inhibited overall plant performance. Plant responses also varied among plant functional groups: C₄grasses received greater benefits from biocrusts compared to C₃grasses, and plants without N‐fixing symbionts responded more positively to biocrusts than plants with N‐fixing symbionts. Biocrusts decreased germination but facilitated growth of non‐native plant species.Synthesis. Results suggest that interspecific variation in plant responses to biocrusts, contingent on biocrust type, plant traits, and ontogeny can have strong impacts on plant species performance. These findings have important implications for understanding biocrust contributions to plant productivity and community assembly processes in ecosystems worldwide.