Forest harvesting impacts on clay and sandy soils

Several studies investigated the impact caused by forest vehicles on soil. Many mechanized forest operations generate stress on soil due to applications of heavy loads. Often these stresses are associated at soil degradation and soil compaction that are linked at number of passages, silvicultural treatments and at type of soil. Soil structure and its physical properties may affect the type and extent of damage. The aim of this study is to evaluate the impact on soil, with particular attention to soil compaction, caused by different harvesting operations on different type of soil. Two areas with different type of soil were selected. The first area, characterized by a sandy soil, was located inside the Regional Park of Migliarino-San Rossore-Massaciuccoli (Central Italy). In this area the silvicultural treatment was a clear cut on small forest of Umbrella pine (Pinus pinea L.). Soil impacts of cuts carried out in 2006 and 2011 were investigated in order to evaluate the effect of time on the recovery of physical properties of soil. The second area was selected on a clay soil on Apennines (Central Italy) in a conifer mixed stand (Picea abies, Pseudotsuga menziesii, Abies alba and Chamaecyparis). The silvicultural treatment in this area was a thinning carried out in 2013. In both area samples of soil were collected by means a steel cylinder of known volume (after litter removal). The samples were placed in plastic bins and transported to the laboratory where for each soil sample collected were determined bulk density and porosity. Close to each sample point, penetration resistance and shear resistance were measure by means of penetrometer (H-4200) and scissometer (16-T0174). In both areas measurements were done on trafficked and control areas. The results showed the differences in soil degradation in relation to soil characteristic and silvicultural treatment.