Influence of straw mulch application on the properties of a soil affected by a forest wildfire


Mulching treatment is often recommended in order to reduce post-fire erosion and sediment yields, but information concerning their effects on soil properties and hence on soil quality is scarce. In the present investigation, the influence of straw application on soil quality was evaluated on hillslope shrubland in Saviñao (Lugo, NW Spain) that is susceptible to post-fire erosion (38% slope). In this area, which was affected by a medium-high severity wildfire in September 2012, different treatments with wheat straw were applied to the burnt soil in mulch strips (0.8 and 1 Mg ha-1) using quadruplicate 10 m x 40 m plots and compared with the corresponding burnt untreated control. Soil samples were collected from the A horizon (0-2.5 cm depth) at different sampling times for 12 months after the wildfire, and a wide range of physicochemical, chemical and biochemical soil properties (water retention, pH, electric conductivity, total C, 13C, extractable C, water soluble C, soluble carbohydrates, total N, 15N, microbial biomass C, soil respiration, bacterial activity, b-glucosidase, urease and phosphatase activities) were analyzed. The results showed that the application of straw mulch had a minor influence on the post-fire soil quality but, in contrast, the sampling time showed a significant influence attributed to short- and medium term changes in soil properties induced by both fire and climatic conditions.