Soil Indicators for Evaluating Nutrient Cycling during Natural Regeneration in Postfire Forests Under Mediterranean Climate

Wildfires cause serious effects on the ecosystem with consequences for soil functionality which may require long recovery. The identification of specific soil indicators for nutrient cycles and the application of remote sensing might contribute to better quantify the soil degradation and to assess the post-fire recovery. The aim of the study was to evaluate the effects of fire on soil properties in two Mediterranean forests and to identify suitable soil indicators that, coupled with remote sensing, would allow an efficient monitoring of soil health status and nutrient cycles during the natural regeneration process. two forest stands dominated by Pinus pinaster L. and Castanea sativa L. were monitored over time following a destructive fire event occurred in 2018 on Monte Pisano (Tuscany, Italy). Fire severity and geomorphology produced different effects between the two stands, therefore burned and unburned sites were selected in both pine and chestnut stands and compared in terms of soil properties, mycorrhizal abundance, stable N isotopes, and enzyme activities after two and five years from the fire event. the satellite data indicated a higher fire severity and a slower vegetation recovery in pine sites than chestnut sites. Although a soil recovery in terms of available nutrients occurred, N isotopes and enzyme activities indicated an alteration of nutrient cycling, especially in pine sites, where the mycorrhizal colonization was also lower than in the chestnut soil. Soil enzymes, N isotopes and mycorrhizal colonization were effective for monitoring the progress in natural restoration of ecosystem functionality.