Photosynthetic communities in soil: the good, the bad and the ugly

Ferran GARCIA-PICHEL (Arizona): During the last two decades it has become increasingly apparent that biological soils crusts, thin topsoil microbial communities that thrive in plant interspaces and are driven by microbial or cryptogamic photosynthesis, while perhaps inconspicuous to the untrained eye, are an important and dynamic component of rangelands and deserts. A component that influences numerous aspects of the ecosystems that host them, including primary productivity, fertility, soil stability, as well as biogeochemical, thermal and hydrologic cy-cles, helping support plants and decomposers. Logically, most studies on the biology and ecology of biocrust organisms have focused on the photosynthetic primary producers. I will present evidence that the microbial primary producers, judt like plants, have establish relationships with their surrounding soil microbiome members. Some good, some bad, and some downright ugly. Importantly, these interactions are determinant of biocrust growth dynamics, of the ecosystem services that biocrusts deliver to rangelands, and applicable to ongoing efforts to attain self-sustaining arid and rangeland soil restoration and manage-ment through interventional biocrust re-seeding. This is consistent with a developing no-tion of an evolutionarily deeply rooted continuum of interconnections between photo-trophic and heterotrophic systems, from cyanospheres to plant root microbiomes.