Environmental determinants of biocrust carbon fluxes across Europe: possibilities for a functional type approach

Background and aims Due to the well-known importance of biocrusts for several ecosystem properties linked to soil functionality, we aim to go deeper into the physiological performance of biocrusts components. Possible functional convergences in the physiology of biocrust constituents would facilitate the understanding of both species and genus distributional patterns and improve the possibility of modelling their response to climate change. Methods We measured gas exchange in the laboratory under controlled conditions of lichen- and moss-dominated biocrusts from four environmentally different locations in Europe. Field data were used to determine the natural hydration sources that drive metabolic activity of biocrusts. Results Our results show different activity drivers at the four sites. Within site analyses showed similar C fixation for the different crust types in the three sites without hydric stress whilst light use related parameters and respiration at 15 degrees C were similar in the between sites analyses. There were significant differences in water relations between the biocrusts types, with moss-dominated crusts showing higher maximum and optimum water contents. Conclusions The functional type approach for biocrusts can be justified from a physiological perspective when similar values are found in the within and between site analyses, the latter indicating habitat independent adaptation patterns. Our multi-site analyses for biocrusts functional performance provide comparisons of C fluxes and water relations in the plant-soil interface that will help to understand the adaptation ability of these communities to possible environmental changes.