Indicator species are one of the important components in vegetation classification, and studying and determining them on the roadside of old roads is very important for maintaining the habitat for rare and endangered plant species. Awareness of the road age can be effective in preserving and developing the plant communities, as the road effect can be helpful in optimal management of vegetation when constructing or maintaining new roads. The purpose of this study was ecological classification as well as identification of indicator species in roadside of forest roads with different ages in Nav-e-Asalem area, west of Guilan province.
Data were collected by random sampling, as in the seven forest areas of Nav-e-Aslam, Guilan, a number of 28 transects (150 m in length) perpendicular to the road from roadside to the inside of the forest using line transect method, linear transect method was used and 28 transects (150 m in length) perpendicular to the road were taken. The distance between the transects was 100 m, Five sample plots (30 × 5 m) were taken for sampling trees and shrubs with a distance of 30 m from each other. In 4 m2 sample plots herbaceous species were identified using vegetation flora and vegetation percentage was recorded in different strata (tree, shrubs and herbaceous) using Braun-Blanquet scale. Also, indicator species analysis was performed using ecological group sample in PC-ORD for Win. Ver 5 software.
The results of indicator species analysis showed that 146 species were found in the roadside of roads with several years’ age. The presence of tree and regeneration species was higher on old roads compared to new ones. In this research, newly constructed roads (10 years) occurred in two groups of second and fourth ecological species, roads with medium ages (10-20 years) in the third ecological group and older roads (>20 years) in the first ecological species group. By using two-way indicator species analysis (TWINSPAN), vegetation cover was classified into two groups: Viola alba Besser, Carpinus betulus L. and Brachypodium sylvaticum, Carex divulsa Stokes. In this research, the presence of Alnus subcordata CAMey and Acer velutinum Boiss species was higher in the sample plots near the road compared to inside forest. The diversity of these tree species and their relative frequency decreased by increasing the distance from the roadside and moving to inside forest. In this research, Carex divulsa Stokes was identified as a rare species and Fagus orientalis Lipsky as a species with high frequency.
The results of this research emphasize the importance of road age not only in determining the ecological species group, but also in identifying the indicator species in the area as well as in improving the classification results of tree, herbaceous and regeneration species in roadside area. Determination of the indicator species is effective not only in determining the extent of the ecological groups classified on the roadside, but also in improving the classification results of plant groups as well as identifying the factors affecting ecological groups seems to be useful for proper management and sustainable exploitation of forest ecosystems.