Exopolysaccharides in biological soil crusts are important contributors to carbon and nutrient storage after the restoration of inland sand dunes

Abstract

Background and aims: Inland sand dunes in a temperate climate constitute challenging environments for plant colonization. Organisms forming biological soil crusts (BSCs) secrete exopolysaccharides (EPS), which are key for soil aggregation and water/nutrient accumulation. We aimed to estimate the contribution of EPS excreted by BSCs to total organic carbon (TOC) and cationic nutrient accumulation and the contribution of photoautotrophs to C fixation and production of EPS in the succession process of inland dunes. Methods: We quantified EPS, TOC, exchangeable K, and Ca concentrations, and photosynthetic biomass in BSCs collected from three successional stages after the restoration of inland dunes. Results: Our study showed that C originated from EPS contributed mostly to TOC accumulated in BSC in the initial succession stage, however, this contribution was lower than observed in BSCs from arid climates. EPS content increased with BSC development, which was facilitated by photoautotrophs, yet participation of heterotrophs in EPS secretion cannot be excluded. Glycocalyx EPS fraction dominated and contributed to nutrient enrichment in BSCs. Conclusion: Our results contribute to a deeper understanding of the importance of BSC in the accumulation of organic carbon and nutrients. This may prove useful in the restoration aimed at maintaining the specific vegetation of temperate inland dune ecosystems. Locally dispersed mechanical disturbances of biocrusts should be applied already in the initial stages of succession to maintain the aeolian activity and prevent accumulation of carbon and nutrients caused by the development of BSC.