Repeated prescribed burning lessens subsequent wildfire impacts on soil mesofauna communities and soil multifunctionality in a maritime pine reforestation

Résumé fourni par la source

Wildfires are becoming more frequent and severe globally, particularly in the Mediterranean Basin due to rapid climate and land-use changes. These trends threaten soil biodiversity and ecosystem functioning. In fire-prone forests, prescribed burning is increasingly used to reduce fuel loads, yet the long-term effects of repeated prescribed fires on post-wildfire soil functioning remain unclear, particularly regarding soil fauna, which has rarely been examined in this context. We assessed the effects of a wildfire that took place in 2021 affecting an area treated five times with low-intensity prescribed burns (conducted between 1984 and 2017) on soil mesofauna communities, the QBS-ar index (Soil Biological Quality-arthropods; an index based on the ecological adaptation of soil fauna), soil functions, and soil multifunctionality (SMF) in a maritime pine (Pinus pinaster Ait.) reforestation in northwestern Spain. Three fire history treatments were compared: unburned (U), wildfire only (C + W; plots used as unburned controls during the prescribed fires that were burned in 2021), and prescribed burning followed by wildfire (PF + W). Soils were sampled at three post-wildfire time points to assess mesofauna and physical, chemical, and microbiological properties used to calculate four soil functions (water regulation, fertility, climate regulation, and organic matter decomposition) and SMF. PF + W plots hosted more resilient mesofauna communities than W plots and shared several indicator taxa with unburned soils. Similarly, a principal component analyses (PCA) revealed that overall soil conditions in PF + W plots were intermediate between U and C + W. Wildfire alone had the strongest negative impact on climate regulation and decomposition, whereas water regulation and soil fertility functions were similar among treatments. Soil multifunctionality was lowest in W plots and highest in both U and PF + W plots, with fire treatment and mesofauna jointly explaining 44 % of SMF variation, and soil properties accounting for 25 %. These findings indicate that repeated low-intensity prescribed burns can precondition soils, thereby maintaining biodiversity and soil multifunctionality after a wildfire, and highlight the importance of ecological memory and soil biota in post-fire recovery.