Morphological diversity and abundance of biological soil crusts differ in relation to landscape setting and vegetation type

Abstract

Biological soil crusts are common in many arid and semi-arid regions of the world, including Australia. Crusts alter soil factors including water availability, nutrient content and erosion susceptibility and are likely to both directly and indirectly affect vascular plants. Despite emerging recognition as important ecosystem components, these soil communities are understudied. We describe the morphological composition and distribution of lichens and bryophytes in soil crusts from the northern riverine plains, Victoria, in relation to landscape setting and vegetation type. Sampling was conducted across a geomorphological gradient in three different vegetation types (Callitris glaucophylla woodland, Eucalyptus woodland and red-soil native tussock grassland) with an annual rainfall of ~400 mm. Mean cover of biological soil crust for the study area was 18%, with mosses and crustose and foliose lichens the most conspicuous components. Total cover of biological soil crust increased as bare ground and vascular plant cover increased, and litter cover decreased. As a consequence, cover and morphological composition of biological soil crusts differed in the three vegetation types, with mosses responding differently from lichens and liverworts in relation to the cover of litter, bare ground and vascular plants. Hence, biological soil crusts were a conspicuous component in vegetation where they had not previously been described and may play an important role in regulating the structure and function of these plant communities.