Fire impacts on soil and post fire emergency stabilization treatments in Mediterranean-climate regions

Abstract

Wildfires are non-controlled large-scale fires of various vegetation types that have long affected the Mediterranean-climate regions, but their increased frequency and severity has led to the degradation of the ecosystems. Particularly in Chile, 147 major wildfires in 2017, were responsible of burning 546 678 ha, which included 28 729 ha of traditional small-scale non irrigated agricultural systems, highlighting the vulnerability of these agricultural soils to wildfires. Soil biological properties are more sensitive to heating than physicochemical properties. Thus, a reduction of microbial communities and associated enzyme activities generally occur in low-intensity fires (< 200 °C). Most significant changes in physicochemical properties of soil occurring in moderately intense fires (250 to 450 °C) are increases of soil pH, nutrient availability, bulk density and soil water repellency, whereas soil aggregate stability and water holding capacity generally decrease. When vegetation cover is completely destroyed by fire, emergency stabilization treatments such as mulching and seeding provide an immediate ground cover to reduce soil erosion and preserve nutrients. Therefore, it is important to define the impacts of wildfire on soil properties of agricultural lands to establish a roadmap to implement an adequate and viable restoration.