Effect of water availability on induced cyanobacterial biocrust development

Cyanobacteria inoculation has recently become an innovative biotechnological tool for restoring degraded arid soils. A major challenge for researchers, however, is the search for suitable species able to cope with water stress under field conditions. The aim of this study was to test the effect of water availability on induced biocrust growth in three different degraded soils from semiarid areas of Almeria (Spain). Three native N-fixing cyanobacterial strains, Nostoc commune, Scytonema hyalinum and Tolypothrix distorta, were inoculated on soil samples from the study areas, individually and as a consortium. Two different irrigation treatments simulating the water availability in the selected areas, in a dry year (180 mm/year) and a wet year (380 mm/year), were applied for three months under laboratory conditions. Cyanobacteria cover, chlorophyll a spectral absorption (Chla spectral absorption), soil organic carbon (SOC) and total exopolysaccharide (EPS) gains were measured as indicators of biocrust development. Cyanobacteria crust cover, SOC and EPS gains were higher in inoculated soils than in uninoculated soils. Even though the hydration regime had a generally significant effect on cyanobacteria cover, Chla spectral absorption and EPS, similar biocrust development and improvement in edaphic conditions were observed under both hydration regimes for all treatments. Of the candidate inoculants, N. commune showed remarkably higher performance under dry conditions than the rest, providing evidence of high potential for growing under water-limited conditions and being a good candidate inoculant for restoration of arid degraded areas.

Automated summary

This study investigated the effects of water availability on induced biocrust growth in different degraded soils, showing that cyanobacteria inoculation can improve cover, SOC, and EPS gains. The irrigation regime significantly affected cyanobacteria cover, Chla spectral absorption, and EPS, with N. commune performing particularly well under dry conditions.