Effect of organic matter on soil properties of forest roads

Knowledge on physical and mechanical properties of soil is necessary for forest road construction and in turn for optimal forest management. Avoiding a mixture of organic matter with soil is considered as being principal in constructing forest roads which is, however, often neglected. Therefore, quantifying the consequences of such mixture can help optimizing the high economic and environmental costs associated with road constructions. The aim of this study was to assess if and how the level of organic matter affects the physical and mechanical properties of soil on forest roads. To this aim, soil samples were collected by profile excavation. Organic matter was collected from residual and litter layer of forest floor. Different mixtures of organic matter with soil were tested (0%, 5%, 10% and 15% of weight), followed by Atterberg limits and CBR tests conducted on the samples. Results showed that increasing organic matter content would increase plastic and liquid limits, which in turn increases the CBR values. Results also showed a significant negative effect of organic matter on soil engineering properties. Therefore, it necessitates a separation between the organic matter and soil during forest road construction.