Nutrient, metal contents and microbiological properties of litter and soil along a tree age gradient in Mediterranean forest ecosystems

The link among the age of aboveground tree species, litter, soil quality and status in Mediterranean forests is not entirely comprehended (especially in Mediterranean forest sites). This study evaluates whether and by what extent tree stand composition and forest structure modify nutrient depository or alter physical, chemical and microbiological properties of soil and litter in a 120 years old pine forest chronosequence. In general, the enzymatic activity related to the phosphorous, carbon and nitrogen cycles were more developed in litter than in soil surface, while the sulphur enzymatic activity was not significantly different between the two analyzed systems. The higher dehydrogenase content measured in the litter may be an index of a higher extracellular microbial activity, compared to soil. A noticeable effect of forest age and structure on the majority of analyzed elements was detected, with nutrients and metals tending to accumulate in soil rather in the litter. Moreover, the contents of P and some metals and sulphur enzymatic activity in the litter are influenced by forest age and associated forest structure. Finally, since nutrient, metals and enzyme contents in the litter increase with forest age, forest management strategies targeted to increase the stand structure may be advisable in order to achieve higher soil functionality.