Organismal composition and photosynthetic traits of biological soil crusts in prairie ecosystems of the Great Plains

Abstract

Biological soil crusts (BSCs) are soil-surface microecosystems composed of a close association of algae, cyanobacteria, fungi, lichens, and non-vascular plants with soil particles. BSCs have several ecological functions including carbon fixation, nitrogen fixation, nutrient relations, soil stabilization, water relations, and floral community development, which make them extremely important in the dryland ecosystems where they occur. While BSCs have been studied throughout the American West, little work has been done in the Great Plains region where they are less prominent among the dominant vascular plant communities. This novel study examined organismal and photosynthetic traits of BSCs in four ecosystems within the Great Plains—sandsage, short grass, mixed grass, and tall grass prairies. To document the BSCs, seasonal photosynthesis measurements were performed in the field and samples were collected for lab analysis. The BSCs primarily consisted of lichens, bryophytes, and cyanobacteria with lichens being dominant in all ecosystems and an increasing bryophyte presence in the wetter and cooler ecosystems. Heterocystic (nitrogen-fixing) and non-heterocystic cyanobacteria were present in lichens at all sites, which contribute to soil nitrogen content. Photosynthesis rates varied between sites and seasons, ranging from 0.26 to 3.31 µmol CO2 m-2 s-1 CO2 m-2 s-1, that were generally correlated with precipitation and temperature. Not only does this research provide more knowledge about BSCs, but its information could also be incorporated into the conservation, restoration, and management of prairie ecosystems.