Post-fire recovery of temperate and mediterranean ecosystems: An interplay between fire severity, soil nutrients, and vegetation from early-stage to decadal-scale dynamics

Abstract

Wildfires strongly alter soil properties, which in turn affect ecosystem recovery over extended periods, though long-term impacts are less certain. This study investigated a 14-year post-fire chronosequence in Chile’s mediterranean and temperate humid forests, revealing ecosystem-specific soil properties and nutrient recovery mechanisms. By analysing sites at successional stages, the chronosequence approach assessed temporal changes and ecosystem recovery, revealing long-term wildfire effects on soil dynamics and nutrients recovery.

Wildfires raised soil bulk density to 0.9 g cm⁻³ in humid temperate and 1.2 g cm⁻³ in mediterranean ecosystems. Mediterranean soils experienced greater compaction from organic matter loss, soil aggregate destruction, ash-clogged pores, and topsoil erosion. Soil texture shifts were ecosystem-dependent: mediterranean soils increased 10–12 % in clay and silt through ash redistribution and aggregation, while temperate soils saw sand content rise by 0.74 % and 0.32 % yearly at 0–5 and 5–10 cm depths from thermal disaggregation and erosion. Ground vegetation recovers quickly, but physical soil properties like bulk density require over 14 years to return to pre-fire conditions.

In humid temperate forests, ash input initially increased soil pH (4.8 to 5.8), reducing acidity, mitigating aluminium toxicity, while increasing nutrient availability. Base cation stocks increased in mediterranean woodlands (e.g., Ca: up to 0.41 Mg ha⁻¹ y⁻¹) due to ash retention, lower leaching, and ash infiltration into subsoil. Nutrient stocks in humid forests recovered slowly (Ca: 0.087–0.13 Mg ha⁻¹ y⁻¹) due to rainfall-driven leaching and low subsoil reserves. Carbon and N losses were restricted to the litter horizon in temperate forests, recovering via fire-resistant tree inputs, whereas mediterranean soils suffered severe C and N depletion from vegetation loss, erosion, and low N fixation.

Fire effects and recovery are ecosystem-specific, shaped by landscape, geology, hydrology, and vegetation resilience. Understanding how fire regimes affect soil and nutrient recovery is vital for improving projections in fire-prone regions.