Seeding and mulching treatments as conservation measures of two burned soils in the Central Ebro Valley, NE Spain

The effectiveness of seeding introduced species, with or without straw mulching, was tested as a measure of post-fire erosion control in gypsiferous (Xeric Haplogypsid) and calcareous soils (Xeric Torriorthent) in Central Ebro Valley (NE-Spain). Paired control, seeding, and combined seeding and mulching plots were established in four replicated plots for each soil tested. Seeding rate was 30 g m(-2) and straw mulch was applied at 100 g m(-2) in each plot. Plant projective cover (total and specific), plant biomass, bare soil cover and sediment yield were determined over a 2-year period. During the first year of sampling, species introduced by seeding increased plant cover (about 30%) without significant differences observed between soils. Plant cover was similar in seeding-only and seeding-mulching treatments, although the latter treatment significantly enhanced plant weight. During the second year these differences disappeared because species introduced by seeding practically did not survive. So, the introduced herbs did not interfere with native plants. Bare soil cover remained significantly lower in treated plots than on the control plots for both soils during both years of sampling. In the second year, the reduction of bare soil was attributed to both the straw mulch and litter from the seeding species. Soil protection was significantly higher in calcareous soils than in gypsiferous soils which is related to their physical and chemical properties. Cumulative sediment yield decreased significantly over time with both treatments on both soils. Soil losses from control plots were three times higher than seeding plots and 3.3 times higher than from seeding and mulching plots in gypsiferous soils. Soil losses from control plots were two times higher than from seeding plots and 2.7 times higher than the combined seeding and mulching plots in the calcareous soils. Cumulative soil loss was higher from the gypsiferous soils than from the calcareous soils due to the lower plant cover.