Abstract
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.
Highlights
Soil microbial community plays a key role in terrestrial ecosystems, by being involved in several ecosystem services
With the aim to provide useful information on the sustainability of this practice for forest management in Mediterranean ecosystems, we investigated soil microbial diversity, abundance, and activity, and the relationships among these variables, in two pine plantations of Southern Italy treated with prescribed burning (PB)
In the P. pinaster plantation, an increase in the mass of the fermentation layer (F-layer) was observed (839 ± 373 g m−2 before PB vs. 1231 ± 331 g m−2 after PB), suggesting that partially mineralized litter was transferred to this layer
Summary
Soil microbial community plays a key role in terrestrial ecosystems, by being involved in several ecosystem services. It provides supporting services (soil formation, nutrient cycling, and plant growth), as well as regulating services (i.e., climate and gas regulation, C sequestration, water purification, disease and pest regulation, and bioremediation) and provisioning ones (i.e., the supply of food, fiber, fuel, genetic resources, chemicals, and pharmaceuticals) [1,2,3]. Research on soil microbial community currently concerns the evaluation of changes in quantity or biomass, structure (ranging from community fingerprint to species identification), and activity as indicators of environmental changes [7] by using traditional biochemical and microscopy techniques, as well as the newer molecular procedures [8]. Only a few studies have simultaneously used microbial indicators of quantity or biomass, structure, and activity, notwithstanding the relationship among them is still unclear; studies in this research field should include the assessment of each of these three groups of indicators [7]
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