ACESSO via B-on: http://dx.doi.org/10.1016/j.envpol.2007.12.007 ; Heterogeneity and dynamics of eight soil surface characteristics essential for plantsdammonium and nitrate concentrations, water content, temperature, pH, organic matter, nitrification and ammonification ratesdwere studied in a Mediterranean-type ecosystem on four occasions over a year. Soil properties varied seasonally and were influenced by plant species. Nitrate and ammonium were present in the soil at similar concentrations throughout the year. The positive correlation between them at the time of greatest plant development indicates that ammonium is a readily available nitrogen source in Mediterranean-type ecosystems. The results presented here suggest that plant cover significantly affects soil surface characteristics.