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Abstract:
Biological soil crusts (BSC) perform several important environmental functions such as soil erosion prevention, soil nutrient enrichment through photosynthesis and nitrogen fixation, and are receiving growing interest due to their importance in some changing habitats with soils under degradation risk. Primary producers within BSC (cyanobacteria, lichens, algae and bryophytes) are all poikilohydric and active only when wet, meaning that knowledge of the period of metabolic activity is essential to understand growth and adaptation to environment. Finding links with macroclimatic factors would allow not only prediction of activity but also the effects of any climate change over these communities. Metabolic activity and microclimate of BSC at four sites across Europe with different soils from semi-arid (Almeria, SE Spain) to alpine (Austria) was monitored during one year using a chlorophyll fluorometer. Local climatic data were also recorded. Mean monthly activity of crust within each site were strongly linked irrespective of crust type whilst, using the data from all sites, highly significant linear relationships (mean monthly values) were found for activity with incident light, air temperature and air relative humidity, and a nonlinear response to rainfall saturating at about 40 mm per month. Air relative humidity and air temperature were the best predictors of metabolic activity duration. The links observed are all highly significant allowing climate data to be used to model activity and to gain inferences about the effects of climate change over BSC communities, soil structure and fertility. Linear relationships mean that small changes in the environment will not produce massive alterations in activity. BSC also appear to behave as a single functional group, which is helpful when proposing general management policies for soil ecosystems protection.
