Effects of pre-fire site preparation and post-fire erosion barriers on soil erosion after a wildfire in NW Spain

Abstract

Thousands of hectares of conifer plantations are affected every year by wildfire and subsequent erosion in the Mediterranean region. However, little is known about how post-fire erosion is influenced by the mechanical site preparation (MSP) techniques used at plantation establishment. Such information is needed for planning further reforestation, for reducing the hydrological impact of wildfire and subsequent soil degradation, and for favouring the natural resilience of perturbed ecosystems. Here we present a study conducted in NW Spain to evaluate how two MSP techniques commonly used at plantation establishment- hole planting and contour rip-plowing-, affected post-wildfire soil erosion and some edaphic properties (carbon content, penetration resistance, bulk density and aggregate stability) compared to the absence of intervention. The possible relationships between the soil properties and post-fire soil erosion were also examined. Finally, the effectiveness of erosion barriers, installed in burned sites originally established by hole planting and contour rip-plowing was evaluated. At the end of the two-year long study period, the accumulated soil loss was significantly lower in the contour rip-plowing treatment (0.7 Mg ha−1) than in the hole planting treatment (6.7 Mg ha−1) and the no intervention treatment (4.9 Mg ha−1), but did not differ in the latter two treatments. Erosion barriers did not reduce post-fire soil erosion, which varied from 2.1 Mg ha−1 in the contour rip-plowing + erosion barriers treatment to 8.3 Mg ha−1 in the hole planting + erosion barriers treatment. Soil loss was related to soil burn severity. No significant relationship was observed between sediment production and any of the soil properties considered. The recovery of vegetation cover was not affected by the site preparation technique used. The study findings can be applied to reforestation planning and post-fire emergency stabilization actions.