No abstract

Forest wildfires usually occur due to natural processes such as lightning and volcanic eruptions, but at the same time they are also an effect of uncontrolled and illegal anthropogenic activities. Different factors can influence forest wildfires, like the type of vegetation, morphology, climate, and proximity to human activities. A precise evaluation of forest fire issues and of the countermeasures needed to limit their impact could be satisfactory especially when forest fire risk (FFR) mapping is available. Here, we proposed an FFR evaluation methodology based on Geographic Information System (GIS) and the analytic hierarchy process (AHP). The study area is the Campania region (Southern Italy) that, for the last 30 years, has been affected by numerous wildfires. The proposed methodology analyzed 12 factors, and AHP was used for weight assignment, offering a new approach to some parameters. The method divided the study area into five risk classes, from very low to very high. Validation with fire alerts showed a good correlation between observed and predicted fires (0.79 R2). Analyzing the climate projections, a future FFR for 2040 was also assessed. The proposed methodology represents a reliable screening tool to identify areas under forest fire risk, and can help authorities to direct preventive actions.

No abstract

Wildfires are a growing concern in the Mediterranean area. Prescribed burning (PB) is often used to reduce fire risk, through fine fuel reduction. However, the monitoring of PB effects on ecosystem processes is mandatory before its spread. This study aims to assess hydrological effects of PB on the topsoil by controlled laboratory experiments. The evaporation flux successive to interception of a simulated rain in the litter and the fermentation layers was determined using both a water balance approach and an experimental 2 H and 18 O isotopes mass balance approach. PB was performed in spring 2014 in three Southern Italy pine plantations, dominated, respectively, by Pinus pinea L. (in Castel Volturno Nature State Reserve), P. halepensis Mill. (in Cilento, Vallo di Diano e Alburni National Park) and P. pinaster Ait. (in Tirone Alto-Vesuvio Nature State Reserve). In each study site, two cores, both including litter and fermentation layers, were sampled, 18 months after PB, in burned and in near unburned (control) areas, respectively, by means of customized collectors allowing to extract "undisturbed" cores. Afterwards, each core was moved into a lysimeter set-up in the laboratory, under controlled conditions (temperature of 22°C, relative humidity of 50%), to carry out duplicate infiltration and evaporation experiments. To simulate rainfall, 1 L of tap water (=32 mm of rain) was sprinkled uniformly on the litter layer in the lysimeter and intercepted water from the litter and fermentation layer was collected for isotope analysis at two different depths for each layer, two times per day until 2 days after the rain simulation. The results of the water balance and isotope mass balance showed a slightly lower evaporation of intercepted water from the forest floor in burned areas, compared to unburned ones, but in most cases not statistically significant. The isotopic profiles of 2 H and 18 O also confirmed independently this finding, since they showed more enrichment in the unburned areas compared to the areas treated with PB. This could be due to thinner litter layers in burned areas of the three plantations, at least up to 18 months after treatment.

Microbial diversity plays a crucial role in ecosystem processes, including organic matter decomposition and nutrient cycling. This research explores the effect of prescribed burning (PB) on soil microbial diversity, as well as biomass and activity in Mediterranean pine plantations. In burned and adjacent unburned plots of Pinus pinea and P. pinaster plantations of Southern Italy protected areas, the fermentation layer and the 5 cm thick layer of mineral soil underneath were sampled at intervals during the first year after PB. The experimental protocol encompassed measurements of total microbial abundance (Cmic and soil DNA), fungal mycelium, fungal fraction of Cmic, microbial activity, bacterial genetic diversity (16S rDNA PCR-DGGE), microbial metabolic quotient (qCO2), and C mineralization rate (CMR), as well as physical and chemical soil properties. PB caused only temporary (up to 3 h–32 d) reductions in Cmic, DNA amount, fungal mycelium, respiration, and CMR in the P. pinaster plantation, and had no appreciable negative effect on the microbial community in P. pinea plantation, where fire intensity was lower because of less abundant litter fuel. In either plantation, PB did not generally reduce bacterial genetic diversity (evaluated as band richness, Shannon index, and evenness), thus, also accounting for the fast recovery in microbial growth and activity after high-intensity PB in P. pinaster plantation. While confirming PB as a sustainable practice to reduce wildfire risk, also supported by data on plant community obtained in the same plantations, the results suggest that an integrated analysis of microbial diversity, growth, and activity is essential for an accurate description of PB effects on soil microbial communities.