No abstract

No abstract

No abstract

The effect of wildfire and the subsequent harvesting on soil degradation was evaluated in a burned Pinus pinaster stand in Galicia (NW Spain). During the first year following a fire of moderate intensity, burned trees were not harvested and soil erosion losses, measured by sediment collection at the bottom of bordered plots, were very low. An apparently limited impact of fire on soil and reduced rainfall erosivity for this period could be responsible for that result.Salvage logging took place 13 months after fire. Three post-fire alternatives were compared: no harvesting (standing burned trees), harvesting þ windrowed slash and harvesting þ slash chopping. Soil losses were even lower during the 14 months after these treatments than for the previous pre-harvesting period. Again, low mineral soil exposition and rainfall erosivity seemed to contribute to that result.Changes in soil bulk density and soil shear strength after clearcutting and slash manipulation were small and not enough to trigger sediment yield significantly.Harvesting and logging operations apparently increased soil inhomogeneities. This degree of variability was more adequately assessed by using micro-plot fences instead of plot fences. The percentage of soil disturbed by machinery was the variable most related with the observed minor soil losses after harvesting, at micro-plot level. This study indicated that the combined effect of wildfire and clearcutting caused only an acceleration of soil erosion when significant exposition of mineral soil occurred after these perturbations. However, these results must be taken with caution because rain erosivity during the study was low. To delay post-fire clearcutting until several months after the fire could reduce the impact of this forestry operation on burned soils, taking advantage of the natural mulch created by scorched leaves fall, although other issues must be taken into account.

The effects of two different soil rehabilitation treatments on runoff, infiltration, erosion and species diversity were evaluated in a shrubland area in Galicia (NW Spain) after an experimental fire by means of rainfall simulations. The treatments compared were: seeding, seeding + mulching and control (untreated). Rainfall simulations were conducted 9 months after fire and the application of soil rehabilitation treatments. A rainfall rate of 67 mm h−1 was applied for 30 min to each runoff plot. Seeding significantly increased plant species richness in the treated plots relative to the control plots, although it had no effect on diversity or evenness. Rehabilitation treatments did not significantly increase soil cover or affect runoff and infiltration. Soil losses were low in all cases, varying from 75·6 kg ha−1 in the seeded + mulched plots to 212·1 kg ha−1 in the untreated plots. However, there were no significant differences in sediment yields between treatments. The percentage of bare soil appeared to be a critical variable in controlling runoff and erosion. Copyright © 2010 John Wiley & Sons, Ltd.

This study assessed the effectiveness of different methods of reducing soil erosion after a severe wildfire in Galicia (NW Spain). The treatments compared were: straw mulch (2.5 Mg ha À1 ), wood-chip mulch (4 Mg ha À1 ), cut-shrub barriers and control. Straw mulch provided an initial ground cover of 80% and the wood chips only 45%. Sediment yields were measured by means of sediment fences in 500-m 2 bordered plots. During the first year after wildfire, mean precipitation was 1520 mm. The mean sediment yield in the control plots was 35 Mg ha À1 . During this period, only straw mulch application significantly reduced soil erosion relative to controls (66%). The mean sediment yields in the wood-chip mulch and erosion barrier treatments, 33 and 30 Mg ha À1 respectively, were similar to rates in the untreated plots (35 Mg ha À1 ). Soil erosion decreased sharply during the second year after wildfire when mean precipitation was 1194 mm. Vegetation regrowth was very fast and treatments had no significant effect on the rate of recovery of vegetation cover, which was ,80% at the end of the study. The results obtained showed that ground cover was a key factor in determining post-fire soil loss. Stabilisation treatments such as wood-chip mulch and erosion barriers were not effective in reducing soil loss relative to the untreated control.

No abstract

No abstract