Impacts to soil properties still evident 27 years after abandonment in Amazonian log landings

Logging machinery impacts site soil properties mainly through topsoil removal and compaction. The greatest soil disturbance occurs in the logging infrastructure areas: skid trails, roads and log landings. Although landings generally occupy less of the site than skid trails and roads, they suffer severe compaction usually accompanied with complete topsoil removal to level the soil surface for log decking and loading. Few long-term studies have quantified if landing soil properties recover, with none in the humid tropical forests of Amazonia. The aim of this study was to determine if soil bulk density, penetration resistance and fine root biomass in 27-year-old aban-doned log landings had returned to a similar state of the adjacent old-growth forest soils. The working hypothesis was that impacts on soil remained despite the regenerated stand of trees present on the landings. Results revealed that the soil physical properties in the log landings were still significantly higher than the controls. Furthermore, fine root biomass was still below the levels presented in the controls. Therefore, in log landings located on very clayey soils in Central Amazonia, soil compaction persists for at least 27 years.