Effects of different fire intensities on chemical and biological soil components and related feedbacks on a Mediterranean shrub (Phillyrea angustifolia L.)

In July 2000, six plots of Mediterranean maquis in the Castel Volturno Nature Reserve were burnt at two intensity levels to examine the effects of fire intensities on chemical and biological soil components and their relationships with ecophysiological processes of Phillyrea angustifolia L. Net photosynthesis and stomatal conductance, as well as P availability, were higher in burnt plots than in control plots, even 2 years after fire; the TM density of total soil microfungi was significantly lower in the first 8 months after fire, while xerotolerant and heat-stimulated soil microfungi were still higher 2 years after fire. Significant correlations between photosynthesis and stomatal conductance in resprouts and mycorrhizal status, as well as changes in the soil fungal components of the communities, suggest that both soil and mycorrhizal fungi play a role in immobilizing and translocating nutrients temporarily released in the below-ground system by fire. Nutrient balance interacts with physiological processes, and a feedback mechanism is well represented by stomatal conductance, which allows both the influx of water and mineral nutrients from the soil; moreover, the post-fire increase in photosynthetic activity promotes vigorous resprouting and may lead to increased availability of carbohydrates for soil biota and, consequently, to enhanced vegetation resilience