title: Microbial Nursery Production of High-Quality Biological Soil Crust Biomass for Restoration of Degraded Dryland Soils.
abstract: Biological soil crusts (biocrusts) are slow-growing, phototroph-based microbial assemblages that develop on the topsoils of drylands. Biocrusts help maintain soil fertility and reduce erosion. Because their loss through human activities has negative ecological and environmental health consequences, biocrust restoration is of interest. Active soil inoculation with biocrust microorganisms can be an important tool in this endeavor. We present a culture-independent, two-step process to grow multispecies biocrusts in open greenhouse nursery facilities, based on the inoculation of local soils with local biocrust remnants and incubation under seminatural conditions that maintain the essence of the habitat but lessen its harshness. In each of four U.S. Southwest sites, we tested and deployed combinations of factors that maximized growth (gauged as chlorophyll a content) while minimizing microbial community shifts (assessed by 16S rRNA sequencing and bioinformatics), particularly for crust-forming cyanobacteria. Generally, doubling the frequency of natural wetting events, a 60% reduction in sunlight, and inoculation by slurry were optimal. Nutrient addition effects were site specific. In 4 months, our approach yielded crusts of high inoculum quality reared on local soil exposed to locally matched climates, acclimated to desiccation, and containing communities minimally shifted in composition from local ones. Our inoculum contained abundant crust-forming cyanobacteria and no significant numbers of allochthonous phototrophs, and it was sufficient to treat ca. 6,000 m2of degraded dryland soils at 1 to 5% of the typical crust biomass concentration, having started from a natural crust remnant as small as 6 to 30 cm2IMPORTANCE: Soil surface crusts can protect dryland soils from erosion, but they are often negatively impacted by human activities. Their degradation causes a loss of fertility, increased production of fugitive dust and intensity of dust storms with associated traffic problems, and provokes general public health hazards. Our results constitute an advance in the quest to actively restore biological soil covers by providing a means to obtain high-quality inoculum within a reasonable time (a few months), thereby allowing land managers to recover essential, but damaged, ecosystem services in a sustainable, self-perpetuating way as provided by biocrust communities.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Velasco Ayuso
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, USA.|Center for Fundamental and Applied Microbiomics, Biodesign Institute, Arizona State University, Tempe, Arizona, USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Giraldo Silva
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, USA.|Center for Fundamental and Applied Microbiomics, Biodesign Institute, Arizona State University, Tempe, Arizona, USA.
authors.forename: Corey
authors.initials: C
authors.lastname: Nelson
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA.
authors.forename: Nichole N
authors.initials: NN
authors.lastname: Barger
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, USA ferran@asu.edu.|Center for Fundamental and Applied Microbiomics, Biodesign Institute, Arizona State University, Tempe, Arizona, USA.
authors.forename: Ferran
authors.initials: F
authors.lastname: Garcia-Pichel
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D018533:Biomass; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D003247:Conservation of Natural Resources / Q000379:methods*; D003889:Desert Climate; D009516:New Mexico; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D017423:Sequence Analysis, RNA; D012988:Soil Microbiology; D013781:Texas; D014589:Utah
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: 16S rRNA; biological soil crusts; cyanobacteria; degraded soils; drylands; erosion control; soil microbiome; soil restoration