Impact of harvesting thinning on the soil environment

The impact on soil of forest harvesting have increased as a consequence of the heavier and heavier used machinery. Soil compaction and rutting are consequences of ground based extraction systems. Many studies were addressed to investigate this topic in the last decades. Nevertheless, some aspects are still unclear or disregarded, in particular the impact caused to soil microbiota and its relation with the physical-chemical degradation of soil.The aim of this work is to evaluate the impact of the machines on soil i) physical properties (bulk density, porosity, shear and penetration resistance, temperature, humidity); ii) chemical properties (pH, C and N concentrations); iii) biological properties (composition of soil microbial communities). The study was carried out in a conifer mixed stand (Picea abies, Pseudotsuga menziesii, Abies alba and Chamaecyparis spp. on Apennines (Central Italy) under thinning. Logs extraction was carried out applying both skidding (3 plots) and winching alone (3 plots). Measurements were done in the same places before and after thinning in order to directly determine how much forest operations affected the various soil properties. Soil samples after thinning were collected on skid trails (in skidding plots) and on pulling trails (in winching plots). The results showed a substantial impact of thinning operations on soil, although different between treatments.