Ecological species group—Environmental factors relationships in unharvested beech forests in the north of Iran

•The majority of indigenous forests in Guilan Province, Iran are Oriental beech.•Forests dominated by Fagus orientalis cover about 565,000 ha in Guilan Province.•TWINSPAN, ISA, DCA and CCA were used for vegetation analysis.•The results of TWINSPAN are showed that six ecological species groups are distinct.•Topographic and soil variable were separation factors of the six ecological groups.

Beech forests are the richest forest community in Iran because they are both economically and environmentally valuable. The greatest forest volume occurs in Iran's beech forests. Forests dominated by oriental beech (Fagus orientalis Lipskey) cover about 565,000 ha and represent the total area of indigenous forests in Guilan Province. A system for classifying beech forests over such a large area is needed to aid its management. The aim of this study was to investigate the relationship between environmental factors with ecological species groups in unharvested beech forests in Guilan province in northern Iran using multivariate techniques of DCA and CCA. For this purpose, a random systematic 150 m × 200 m gird sampling plan was used to establish 60 1000 m2 circular plots. In each plot, environmental factors (topographic and soil variables) and percent cover of each herbaceous species were recorded. The result of TWINSPAN analysis showed that six groups were distinct. Multivariate analysis was performed through CANOCO 4.5 to explore the relationship between the environmental factors and the plant community. The most important environmental factors associated with plant composition in beech communities were elevation, slope, slope aspect, N, P, K, pH, C, C/N ratio, organic matter, leaf litter, soil texture (clay, sand, silt) and EC. The use of natural vegetation as an indicator for site quality provides good results, due to the close relationship it has with abiotic site characteristics.