OOS 16-1 - Edge influence in forested ecosystems in an underrepresented region: Iran

Background/Question/Methods
Studies on vegetation at edges are still lacking in many ecosystems, particularly in Africa and the Middle-East. Iran is one such region with few, if any, published studies on vegetation at edges. Zagros forests (largest forested land in Iran), dominated by Quercus spp., have been fragmented by human activities and have an open canopy and may show different patterns of edge influence compared to dense forests. In northern Iran, edge effects in the fragments of deciduous temperate forests surrounded by agricultural lands compared to the conserved fragments may show different variations. Our main research question in both ecosystems was to assess how vegetation changed with distance from the edge by collecting vegetation data along transects perpendicular to the edge. In Zagros forest we sampled herbaceous data in ten quadrats at 1 m intervals from the base of trees toward open space at different sampling distances within small and large fragments. In northern Iran, we sampled herbaceous data in ten quadrats at different sampling distances within agriculture-created and conserved fragments. We calculated the magnitude and distance of edge influence on species diversity and used GLMM to assess effects of fragment size, distance from forest edge and distance from base of trees.

Results/Conclusions
We found a significant interaction between fragment size, distance to forest edge and distance from base of trees for diversity. Distance from the forest edge and from the base of the tree significantly affected diversity in the open canopy oak forests. The majority of changes in herbaceous species diversity occurred within 50 m of the forest edge. In small and large fragments, diversity significantly decreased from base of the tree toward open space at the forest edge but significantly increased in the forest interior. Overall, the effects of fragmentation were greater in smaller oak forest fragments compared to larger ones in sparse oak forest. In northern Iran, preliminary results indicated that a significant interaction observed between fragment types and distance to forest edge for diversity in the close-canopy deciduous temperate forests. Herbaceous species diversity and richness decreased by distance from the edge and the majority of changes occurred within 10 m. We need urgent forest management strategies to prevent continuous disturbance or connecting small fragments to minimize edge influence.