تأثیر سن جاده در شناسایی گروه گونه های بوم شناختی و عوامل محیطی مؤثر بر آنها درجنگل های غرب استان گیلان

Forest roads can create small- scale climate change. These changes can vary with the road age and topographic conditions. This study aimed to identify ecological species group as well as study the relationship between vegetation and environmental factors based on the road age. The study was carried out in three-districts of Nav- Asalem in Watershed 7 of forests of North of Iran. Therefore, 140 sample plats (rectangular in shape and150 m2 in area) with different ages and different topographic conditions were taken. Information related to tree and shrub cover, regeneration and weed cover along with slope (%) and slope aspect of sample plots, road age and elevation, as well as the amount of light receiving to forest floor, temperature and humidity at the center of the sample plots were recorded. The ecological group distribution pattern was evaluated using non-limited ordination method and classification of ecological groups was performed using Two Way Indicator Species Analysis (TWINSPAN) and CCA gradient analysis. Data analysis was carried out using Excel and PC-ORD software. The results of the analysis of indicator species showed that of 72 plant species, only 52 species were determined as indicator species that were defined as indicator species of beech communities on roadside. In this research, newly constructed roads (with age below 10 years) occurred in second and fourth ecological species groups, roads with moderate ages (10-20 years in age) in the third ecological group and older roads (with age more than 20 years) in the first ecological species group. The results of MRPP analysis (multi-response permutation procedure) showed that the ecological groups are characterized by higher distance from each other. Among the ecological groups, the abundance and presence or absence of species with environmental variables were not the same in all sample plots. The final results showed that the road age not only affects the ecological species group but it also serves as a useful factor in determining the indicator species and improving the results of the ordination of the ecological species group on the roads with age more than several years.