El clima determina la estructura y el funcionamiento de la costra biológica del suelo a lo largo de gradientes geográficos grandes en las zonas áridas y semiáridas de Argentina

SERGIO VELASCO AYUSO; JUAN IGNACIO MARTINEZ; CALZADA PABLO; FEDERICO IBARBALZ; ROMINA C. RUSCICA

Congreso; 3er Congreso Latinoamericano de Ecologia Microbiana, ISME-Lat 2023; 2023

Biological soil crusts are topsoil biological communities that develop at the soil-atmosphere ecotone. Cyanobacteria are the main photosynthetic primary producers in biocrusts, along with green algae, lichens and mosses, and their ecological role as atmospheric C and N fixers allow the development of diverse biological assemblages that also include heterotrophic bacteria, archaea and fungi. Biocrusts are found in almost all terrestrial ecosystems, but are especially abundant in sparsely vegetated soils where the sunlight can reach the soil surface, as it happens in drylands. Biocrusts play key ecological roles in soil fertility, stability and biogeochemical cycles, and are central in water, gas and nutrient transfers between the soil and the atmosphere. Because they occupy a large surface, their role in global ecological processes is important although it has remained unnoticed until recently. To understand how ongoing climate change will alter the abundance and the functioning of biocrusts, it is essential to know which factors Determine abundance and functioning patterns under current conditions. Here, we show how climatic variables are underlying forces controlling the distribution and functioning of biocrusts across large geographical gradients in Argentinean drylands. The cover of cyanobacteria-dominated biocrusts, as well as the total cover of biocrusts, positively responds to mean annual soil surface temperature, mean annual evapotranspiration and aridity index, whereas negatively to mean annual precipitation, and decreases with latitude. Biocrusts present higher soil resistance penetrance values regardless of climatic conditions and compared to bare soils, which is related to a higher soil stability and resistance to hydric and aeolian erosion. And there is a spatial pattern in the soil C flux associated with biocrusts that also responds to climatic gradients of Argentinean drylands, which show contrasting soil C flux patterns depending on monthly mean precipitation, temperature and soil humidity conditions. Our project, based on field collected data and satellite products, is pioneer in Argentina and South America and aims to improve our understanding of climate change impacts on drylands and the effects of desertification processes by incorporating structural and functional aspects of biocrusts into global ecological models.