Polyacrylamide application versus forest residue mulching for reducing post-fire runoff and soil erosion

• Published in: The Science of the total environment 2014-01, Vol.468-469, p.464-474
• Main Authors: Prats, Sergio Alegre, Martins, Martinho António dos Santos, Malvar, Maruxa Cortizo, Ben-Hur, Meni, Keizer, Jan Jacob
• Format: Article
• Language: English
• Subjects: Acrylic Resins; Emergency treatments; Eucalyptus; Fires; Mulching; Polyacrylamide; Runoff; Soil; Soil erosion; Water Movements; Wildfire
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2013.08.066

For several years now, forest fires have been known to increase overland flow and soil erosion. However, mitigation of these effects has been little studied, especially outside the USA. This study aimed to quantify the effectiveness of two so-called emergency treatments to reduce post-fire runoff and soil losses at the microplot scale in a eucalyptus plantation in north-central Portugal. The treatments involved the application of chopped eucalyptus bark mulch at a rate of 10–12Mgha−1, and surface application of a dry, granular, anionic polyacrylamide (PAM) at a rate of 50kgha−1. During the first year after a wildfire in 2010, 1419mm of rainfall produced, on average, 785mm of overland flow in the untreated plots and 8.4Mgha−1 of soil losses. Mulching reduced these two figures significantly, by an average 52 and 93%, respectively. In contrast, the PAM-treated plots did not differ from the control plots, despite slightly lower runoff but higher soil erosion figures. When compared to the control plots, mean key factors for runoff and soil erosion were different in the case of the mulched but not the PAM plots. Notably, the plots on the lower half of the slope registered bigger runoff and erosion figures than those on the upper half of the slope. This could be explained by differences in fire intensity and, ultimately, in pre-fire standing biomass. •The effectiveness of two soil erosion control treatments was contrasted after a wildfire.•Chopped bark mulch reduced runoff and soil erosion, whereas dry polyacrylamide did not.•Rainfall amount and soil cover were key factors respectively for runoff and soil erosion.•Fire intensity across the burnt slope also affected soil erosion and organic matter content on the eroded sediments.