Spatial and temporal variations of soil function in a Mediterranean serpentine ecosystem

We investigated the variations in space and time of soil functionality in a Mediterranean serpentine soil for heavy metal and nutrient concentrations, microbial biomass and soil enzymatic activities (urease, dehydrogenase and alkaline phosphatase) in the rhizospheres of different plant species and in bare soil, during the humid and dry seasons of the year. Nutrients and heavy metals were also estimated in leaves of shrubs inhabiting the study area. Four species of serpentine-tolerant shrubs were present: the cvergreen-sclerophyllous Juniperus oxycedrus and Buxus sempervirens and the phryganic Cistus creticus and Thymus sibthorpii. The most significant differentiation of the soil environment was between bare and rhizosphcrc soil, and was mainly driven by the availability of potassium. Spatial variations related to plant identity were clear but less important than temporal variations. There was no relationship between soil and foliar concentrations of nutrients and heavy metals. Higher foliar concentrations were recorded in the phryganic species. Finally, there was no enzyme inhibition due to the heavy metal load of the serpentine soil. Enzymatic activities were lower for bare soil samples, while their temporal variations probably followed the temporal variations of temperature and humidity imposed by the Mediterranean climate. Additional keywords: enzyme activities, heavy metals, microbial biomass, soil nutrients, ultramafic soil. Received 9 October 2015, accepted 3 March 2016, published online 22 August 2016
Introduction Serpentine ecosystems develop on ultramatic soils that exhibit a series of characteristics, which together constitute the so-called 'serpentine syndrome'. The latter refers to the deficiency of serpentine soils in [...]