Persistence of the effects of easy barriers and log erosion barriers with mulching on plant diversity, erosion and soil properties four years after wildfire

The need to mitigate soil erosion and accelerate recovery of soil properties and vegetation cover after a wildfire suggests that forest managers implement post-fire eco-engineering techniques on burned hillslopes. The effectiveness of many techniques has been generally acknowledged in several environments. However, most studies have mainly explored these effects in the short-term (one or two years after their implementation), while longer studies are scarcer. Therefore, there is a knowledge gap about the time and extent required by soil and vegetation to recover the pre-fire conditions under the effects of eco-engineering techniques. To fill this gap, this study has evaluated plant diversity, erosion and key soil properties in the medium term after a severe wildfire in a pine forest of Castilla-La Mancha (Central Eastern Spain). Here, easy and log erosion barriers, the latter combined with straw mulching, were built four years after burning for soil conservation and vegetation regeneration. Log erosion barriers and mulching did not influence post-fire erosion rates, while erosion barriers significantly reduced soil loss (−78%) compared to untreated areas after a rainfall of 22 mm (intensity of 69 in 30 min). This general loss of effectiveness of these techniques against erosion can be explained by the similar ground covers, physico-chemical properties and enzymatic activities of soil as the non-treated area. In contrast, plant diversity was significantly different between burned sites on one side, and burned and treated soils on the other side. Macrochloa tenacissima L. and Rosmarinus officinalis L. were the most abundant species surveyed in the treated sites. Overall, this snapshot assessment, conducted four years after the fire and treatment implementation, indicates that, in general, these eco-engineering techniques have lost their anti-erosive action but still influence plant diversity in the medium term.