The evaluation of soil detachment capacity induced by vegetal species based on the comparison between natural and planted forests

Abstract

Planted forests and management operation method can potentially alter the soil properties as a consequence of changes in the characteristics of tree and plant species. However, the effects of planted forest species with different root systems on the soil detachment capacity (Dc) have not well been quantified. This study investigates the effects of plantation practice on the soil detachment capacity of soil with six vegetal species (Quercus castaneifolia, Alnus glutinosa, and Zelkova carpinifolia, as planted forest species) and Carpinus betulus, Parrotia persica, and Pinus taeda (as natural forest species) based on a comparison between natural and planted forests in forestland of the Saqalaksar Park (Northern Iran). To this aim, the soil detachment capacity on samples collected under trees of the studied species was measured in an experimental flume at five slopes (0.26, 0.35, 0.46, 0.57 and 0.69 m m−1) and flow rates (0.037, 0.086, 0.185, 0.285 and 0.376 L m−1 s−1). Moreover, simple prediction equations are suggested to evaluate the soil detachment capacity and rill erodibility (Kr) for studied species. The soils of natural forestland showed the lower soil detachment capacity compared to soils of the planted forestland, due to the different influence of plant root systems. Moreover, the inappropriate management practices in planted forestland could have worsened the soil properties and thus increased the soil detachment rate. The unit stream power was better predictor of Dc compared to other hydraulic parameters in both natural and planted forestlands. The rill erodibility of soils was higher in planted forestland than in natural forestland. According to the results, the natural forestland is able to show higher resistance against soil erosion in comparison with the planted forestland. These findings indicate that for sustainable management of forest ecosystems, the maintenance of natural vegetal species can be an effective practice to reduce the soil erosion.