Mulching treatments favour the recovery of ecosystem multifunctionality after a large wildfire in Northwest Spain

Abstract

Wildfires are a widespread phenomenon in forests across the Mediterranean Basin but have increased in severity and extent in recent decades. Post-fire treatments are measures that help recover burned vegetation and their functionality but to what extent they also help recover soil functionality is currently unknown. The main objective of this study was to assess the effect of post-fire treatments on ecosystem multifunctionality after a large wildfire in the Cabrera mountain range in 2017 (NW Spain) where close to 10000 Ha of forest were burnt. At the end of 2017 and during 2018, the administration applied different post-fire treatments in high fire severity affected areas: i) straw mulching, ii) woody debris and iii) subsoiling and iv) mechanical hole afforestation. In each treatment, we established ten 2 x 2 m plots and ten adjacent untreated burned plots and collected a composite soil sample from each plot four years after the fire (2021). We calculated regulating services as the standardized mean of total soil organic C (climate regulation), soil water repellence (water regulation) and soil aggregation (soil protection). Supporting services were measured as the standardized mean of mineral N-NH4+ and N-NO3- and available P (soil fertility), β-glucosidase, urease and acid phosphatase (nutrient cycling) and microbial biomass (soil quality). Ecosystem multifunctionality was measured as the standardized mean of all functions measured. Application of straw mulch and woody debris increased regulating ecosystem services in relation to burned control plots. Afforestation with holes had not impact but subsoiling decreased regulating ecosystem services in relation to burned control plots. Post-fire treatments did not have any effect on supporting services. Straw mulch, Woody debris and afforestation with holes improved ecosystem multifunctionality when compared with subsoiling methods. These results show that post-fire stabilisation treatments, in particular straw mulching have a significant positive impact on regulating services and are effective measures in restoring the ecosystem multifunctionality, helping develop effective management based-decisions for the recovery of ecosystem services and functioning after large wildfires.