Effects of forest residue mulching on organic matter and nutrient exports after wildfire in North-Central Portugal

S A Prats; D Serpa; L Santos; J J Keizer

doi:10.1016/j.scitotenv.2023.163825

Effects of forest residue mulching on organic matter and nutrient exports after wildfire in North-Central Portugal

Sci Total Environ. 2023 Aug 10:885:163825. doi: 10.1016/j.scitotenv.2023.163825. Epub 2023 Apr 29.

Authors

S A Prats¹, D Serpa², L Santos², J J Keizer²

Affiliations

¹ MED&CHANGE | MED - Mediterranean Institute for Agriculture, Environment and Development & CHANGE - Global Change and Sustainability Institute, University of Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal. Electronic address: sergio.prats@uevora.pt.
² CESAM | Centre for Environmental and Maritime Studies, Department of Environment and Planning, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.

PMID: 37127167
DOI: 10.1016/j.scitotenv.2023.163825

Abstract

The quick implementation of emergency stabilization measures is vital for minimizing post-fire soil erosion and the associated fertility loss. Mulching has proven to be highly effective in minimizing post-fire soil erosion, however few studies have investigated its impacts on organic matter (OM) and nutrient mobilization from burned forest areas. This study evaluates the effectiveness of forest residue mulching at reducing OM, N and P losses within the sediments after a moderate-severity wildfire over a period of 5 years (Ermida, North-central Portugal). Untreated and mulched plots of ca. 100 m² were bounded with geotextile fabric and sediments were collected from silt fences after a total of 29 periods. During the first five years after the fire, the accumulated OM, N and P exportations in the untreated plots were, respectively, 199, 5.2 and 0.38 g m^-2; and mulch significantly reduced these figures in, respectively, 91 %, 94 % and 95 % (p < 0.05). The overall OM content in the sediments of the untreated plots (45 %) was not different from the OM content of the mulched plots (34 %, p = 0.16). However, the N (8.9 g kg^-1) and P_av contents (0.62 g kg^-1) in the untreated plots were significantly higher than the N (5.6 g kg^-1; p < 0.05) and P_av contents (0.36 g kg^-1; p < 0.05) in the mulched plots. This effect was especially noticeable in the first year after fire. OM and TN contents in the sediments were highly variable throughout the study period, whereas P_av contents declined sharply in the first post-fire rainfall events, maintaining low values afterwards. The main factors driving nutrient exports were ash and litter cover, whereas no significant relationship was observed for OM exports. The present work has shown that forest residues application can be a sustainable strategy for the conservation of soil carbon and nutrients in fire-affected areas.

Keywords: Forest fires; Mediterranean; Natural resources; Post-fire stabilization treatments; Soil erosion.