Ecotones and forest communities along an elevation gradient in Hyrcanian forests, north of Iran

A comprehensive understanding of plant associations, especially in transition areas can be achieved by identification of vegetation and study of relationships between plant species and environment. Borders of ecotones and forest communities (Tiremrud basin in the southern part of Tonekabon, Iran) were found based on environmental factors such as elevation, slope and changes in floristic patterns. Totally, 44 plots (20 × 20 m) were collected by the transect method with at least one sample plot per contour line and 50 m interval. A total number of tree species was recorded separately in each sample plot. Herbaceous species were sampled based on the Brown-Blanket cover percentage and frequency of vegetative elements by 5 × 2 m2 micro plots in four corners and centre of each main plot. Four ecological groups were identified on altitudes 2070, 1236, 924, and 375 m above sea level with mean slopes of 43, 50, 40, and 59%, respectively. The first and fourth ecological groups were at the highest and the lowest elevations, respectively, while the second and third ones in the middle of the two groups. A comparison of ecological groups in terms of plant biodiversity indicated significant differences altogether. In terms of species diversity indices, Shannon-Wiener and Simpson-Pilo ​​revealed that the first, fourth, and second ecological groups had maximum, minimum, and average values, respectively. According to findings of this study, ecological groups had significant differences in terms of altitude factor.