Are erosion barriers and straw mulching effective for controlling soil erosion after a high severity wildfire in NW Spain?

Abstract

Erosion barriers have traditionally been used in Europe by land managers to reduce runoff and erosion after high severity wildfires. However, field research investigating the effectiveness of this treatment is scarce in Europe. Previous research in the US and Europe has demonstrated that application of straw mulch at a rate of 2Mgha−1 effectively reduced post-fire sediment yields. For logistic and economic reasons, it would be useful to know whether a small reduction (25%) in the amount of straw mulch applied would significantly reduce the effectiveness of the treatment. In this study, we compared the effectiveness of a low rate of straw mulching (1.5Mgha−1) and of erosion barriers in reducing soil erosion during the first three years after a wildfire in Galicia (NW Spain). Twelve experimental plots (80m2) were established along a hillslope burned at high severity. During the three years of study, the accumulated soil loss in the untreated burned soils was 77.9Mgha−1. Mulching and erosion barriers both reduced soil loss (by respectively 38% and 26%). In all cases, soil erosion losses were high during the first two years after fire, which is an unusual response in the area. Maximum concentrated precipitation (rainfall >20mm accumulated in two consecutive days) and the Wischmeier's rainfall erosivity factor were the variables most strongly associated with soil loss during the study period. Although erosion barriers and mulch cover both reduced soil loss, relative to the untreated control, the effectiveness of these measures was low after the high-severity wildfire in an area affected by high rainfall. The lack of effect of vegetation cover on soil loss highlights the need for emergency measures to be implemented immediately after fire to protect the soil from erosion.