Hillslope geodiversity effects on properties and composition of biological soil crusts in drylands

Biological soil crusts (biocrusts) play important roles in ecosystem functioning and are considered ecosystem engineers: stabilizing the soil surface, preventing soil erosion, changing soil surface hydrology, and enriching the soil with carbon and nitrogen. The link between geodiversity and biodiversity incorporates physical aspects from geology, geomorphology and pedology. We aimed to assess the effects of hillslope geodiversity on the cover, composition and biophysiological properties of biological soil crusts (biocrusts) in a dryland ecosystem. The geodiversity of the hillslope is determined by the stone cover on the ground surface, the content, stones in the soil profile, and the soil depth. It is known from the scientific literature that geodiversity affects biodiversity; thus, we hypothesized that the hillslope type may affect biocrust properties that develop on these hillslopes. The results indicate that the mean covers of biocrust types in the homogeneous (low geodiversity) hillslopes were 60.6% cyanobacterial crusts and 39.4% biocrusts composed of cyanobacteria, moss and lichens, whereas those of the heterogeneous (high geodiversity) hillslopes were 81.6% cyanobacterial crusts and 18.4% biocrusts composed of cyanobacteria, moss and lichens. It was concluded that geodiversity enhances the growth of biocrust species that require higher soil moisture. The results imply that wherever restoration activities are planned, and especially in drylands, the geodiversity of the area should be taken into account. Highlights: Geodiversity expressed by the degree of stoniness impacts ecosystem functioning and soil properties Geodiversity impacts the biocrust's cover and composition Geodiversity enhances the growth of biocrusts that require high soil moisture Chlorophyll a, b and a + b in biocrusts are increased in heterogeneous hillslopes.