Effect of Fragmentation on plant diversity and soil properties in open canopy oak forests in Iran

Edge effects in temperate and tropical forests have been extensively researched, but there has been relatively less focus on open canopy forests. Our study delved into the impact of forest edges on the diversity of plant species and soil properties in sparse oak forest fragments. Data were gathered from three transects spanning from the edge to the interior of oak forest fragments in Kermanshah province, Iran, comprising of three small (less than ۱۰ ha) and three large (over ۱۰ ha) fragments. Herbaceous plants (< ۰.۵ m in height) and soil characteristics were measured at ۰ (forest edge), ۲۵, ۵۰, ۱۰۰, and ۱۵۰ m. Species diversity was assessed using the Shannon index, while rarefaction was employed to compare species richness between different fragment sizes. Non-metric multidimensional scaling ordination was used to explore the variation in species composition. The distance of edge influence was estimated using randomization tests. Post-hoc Tukey's HSD test was utilized to evaluate the impact of distance from the edge and fragment size on diversity and soil properties. We observed a higher variety of species, as well as greater diversity at the edge of both small and large fragments. Compared to the interior of large fragments, there was a lower presence of nitrogen and organic carbon at the edge, with most changes occurring within ۵۰ meters of the edge. There were noticeable differences in species composition, organic carbon, and total nitrogen between small and large fragments. We recommend establishing a ۵۰-meter buffer zone along edges in the oak forests in Iran to minimize negative edge influence on herbaceous plant diversity.