Effects of biological soil crust and water availability on seedlings of three perennial Patagonian species

Abstract

Biological soil crusts are communities composed of mosses, lichens and cyanobacteria. They cover a large portion of the arid and semiarid regions of the world and play key roles in nutrient cycles and soil erosion diminution. Biological soil crust might affect germination, establishment and growth of vascular plants. In this study we examined the differential response to soil cover and water availability of grasses and shrubs. Our hypothesis was that seed germination and seedling survival are greater in soils with biological soil crust cover because crust have positive effects on vascular plant establishment. We evaluated the effect of biological soil crust cover on seed emergence, survival and seedling growth of Nassella tenuis, Senecio subulatus and Larrea divaricata. The experiment had four treatments combining biological soil crust (C) or bare soil (BS) with drought (D) or soil at field capacity (FC). Seeds of L. divaricata did not germinate and S. subulatus only germinated in BS-FC. Emergence and biomass of seedlings of N. tenuis were higher with C and at FC. There were no differences in seedling survival. Soil cover with biological soil crust and water availability influenced germination and seedling growth and their effects are different according to the species or plant functional groups. Germination of seeds varies with the composition and structure of the biological soil crust and the vascular plants, and the response may change with different species or plant functional groups.