Articles | Volume 15, issue 7
Research article
03 Apr 2018
Research article |  | 03 Apr 2018

Ecophysiological characterization of early successional biological soil crusts in heavily human-impacted areas

Michelle Szyja, Burkhard Büdel, and Claudia Colesie

Abstract. Ecophysiological characterizations of photoautotrophic communities are not only necessary to identify the response of carbon fixation related to different climatic factors, but also to evaluate risks connected to changing environments. In biological soil crusts (BSCs), the description of ecophysiological features is difficult, due to the high variability in taxonomic composition and variable methodologies applied. Especially for BSCs in early successional stages, the available datasets are rare or focused on individual constituents, although these crusts may represent the only photoautotrophic component in many heavily disturbed ruderal areas, such as parking lots or building areas with increasing surface area worldwide. We analyzed the response of photosynthesis and respiration to changing BSC water contents (WCs), temperature and light in two early successional BSCs. We investigated whether the response of these parameters was different between intact BSC and the isolated dominating components. BSCs dominated by the cyanobacterium Nostoc commune and dominated by the green alga Zygogonium ericetorum were examined. A major divergence between the two BSCs was their absolute carbon fixation rate on a chlorophyll basis, which was significantly higher for the cyanobacterial crust. Nevertheless, independent of species composition, both crust types and their isolated organisms had convergent features such as high light acclimatization and a minor and very late-occurring depression in carbon uptake at water suprasaturation. This particular setup of ecophysiological features may enable these communities to cope with a high variety of climatic stresses and may therefore be a reason for their success in heavily disturbed areas with ongoing human impact. However, the shape of the response was different for intact BSC compared to separated organisms, especially in absolute net photosynthesis (NP) rates. This emphasizes the importance of measuring intact BSCs under natural conditions for collecting reliable data for meaningful analysis of BSC ecosystem services.

Short summary
Ongoing human impact transforms habitats into surfaces lacking higher vegetation. Here, biological soil crusts (BSCs) provide ecosystem services like soil creation and carbon uptake. To understand the functioning of these areas, we examined the physiological capability of early successional BSCs. We found features enabling BSCs to cope with varying climatic stresses. BSCs are important carbon fixers independent of the dominating organism. We provide baseline data for modeling carbon fluxes.
Final-revised paper