Effects of forest roads on vegetation biodiversity and soil characteristics in Hyrcanian forests

As one of the main components of forest operations and sustainable management, forest roads affect the vegetation communities around the road. In this study, the effects of the edge of forest roads were investigated to understand the changes caused by the network of forest roads on the Hyrcanian forest ecosystem in northern Iran. In order to investigate the impact of forest roads on the biodiversity of herbaceous species, tree regeneration and lichen. Sampling was used at different distances from the road in two control and harvested areas. The effects of roads on vegetation diversity in relation to soil characteristics were also investigated. The results showed that harvesting caused the destruction and reduction of tree regeneration, herbaceous and lichen, but the physical and chemical properties of the soil were not affected. The distance from the road has affected the diversity and richness of herbaceous and lichen, tree regenaration and all physical and chemical characteristics of the soil (except C). There was a significant correlation between most of the physical and chemical properties of the soil with the regeneration of trees and herbaceous species. Also, most of the physical and chemical properties of soil have increased with increasing distance from the road. Results showed that the buffering effect of the roadside in these forests up to a distance of 45 meters had an effect on biodiversity and richness. Also, the results of this study are consistent with the fact that the road affects the biodiversity and properties of the forest soil. 

Methods
In this study, the effects of the edge of forest roads were investigated to understand the changes caused by the network of forest roads on the Hyrcanian forest ecosystem in northern Iran. Field and laboratory data have been used for statistics and collection of vegetation and soil data. A 120-meter buffer was created on the side of the excavation shoulder for inventory and collection of vegetation and soil data. Then this buffer was divided into distances D0 (side of the road), D15 (15 meters from the roadside), D45 (45 meters from the roadside), D75 (75 meters from the road side), and D105 (105 meters from the roadside). The length of the sampling line to the end of the selected road was determined on the map. Sampling lines were located with a width distance of 50 meters in the 2 harvesting and control forests. Then, perpendicular to the road, square macro-plots with an area of 400 m2 were located on these roads. Inside each macroplot, 4 rectangular microplots with an area of 4 m2 were created to collect and record the type of plant species, abundance of herbaceous cover, and regeneration and collection of soil samples. Identification of plant species was done based on common methods and using identification keys. To collect lichen samples, frames with dimensions of 40 * 60 cm were prepared. Sampling was carried out from a height of 1.30 meters. The Corticolous lichen samples were identified by reliable sources of lichenology and using laboratory studies and existing identification keys. The physiochemical properties of the soil were investigated at the sampling site and in the laboratory based on the instructions. Parameters of soil including of soil moisture percentage (SM), wet weight (WW), dry weight (WD), bulk density (BD), total porosity (TP%), soil penetration resistance (PR), C%, N%, P, K, Ca, Mg were measured. In the next step, Shannon-Wiener biodiversity index, Margalf richness index and Pielou evenness index of herbaceous cover, tree regeneration and lichen were obtained based on calculations. ANOVA analysis was used to compare the value of each biodiversity index at different distances from the road. The same test was used to investigate the effect of distance from the road on soil properties. Pearson correlation analysis was used to investigate the relationship between soil parameters and the abundance of tree regeneration, harbaceous and lichens. PCA analysis was used to investigate the relationship between vegetation and soil physical and chemical properties.