Mid-Term Effects of Postfire Mulching With Straw or Wood Chips on Soil Erosion in Semi-Arid Forests

Abstract

Soil mulching has been studied as a postfire management action to reduce soil erosion in several forest environments. Less research exists about the effectiveness of mulching with straw and wood chips beyond the first year after a wildfire on sites with different slopes. To fill this gap, this study has measured soil erosion in three burned sites (untreated soils, and soils mulched using wheat straw or pine wood chips) throughout a 2.5-year observation period in a forest of Castilla-La Mancha (Central Eastern Spain). Soil condition and slope (gentle, < 32%, gentle vs. steep, > 38%, slopes) significantly influenced erosion, which, however, was of low entity due to the relatively low rainfall erosivity. Mulching was generally effective after the most intense events (maximum 30-min rainfall intensity over 15 mm/h). On the gentle hillslopes, mulch application did not reduce postfire soil loss compared with the untreated sites. In contrast, on the steep slopes, the effectiveness of soil mulching was significant for the two most intense rainfall events (−30% of soil loss in plots treated with wheat straw compared with the burned and untreated sites). The cumulated soil loss significantly decreased on the treated sites (−40%) only when wheat straw was used. On steep slopes, the anti-erosive effects of mulching were almost durable, since the mulch covered more than one-third of the plot areas until the end of the monitoring period. These results help land managers adopt the most effective measures of postfire management in semi-arid forests affected by severe wildfires.