Effects of Reforestation by Exotic Fast Growing Species on Understory Plants Diversity; Case Study: Gahar Forest Park, Doroud, Lorestan Province

Plantations can effect on understory plants by changing in soil components or by shade effects of canopy cover positively or negatively. This study aimed to investigate effects of reforestation by exotic fast growing trees on understory plants diversity. Three plantation stands, Turkish red pine stand, black locust stand, and mixed stand of Turkish red pine and black locust, and a natural Iranian Oak stand were sampled. In order to measure plants diversity, sampling was performed in the same physiographic landform, using 400 m2 main plots composed of 5, 4 m2 subplots in center and corners of main plot. Soils were sampled in three 0-10, 10-20, and 20-30 cm horizons. Results showed that species richness in Turkish red pine, black locust stand, and mixed stand of Turkish red pine and black locust, and Iranian Oak stand were 16 – 30 – 31- and 34 respectively. Sorenson and Jaccard similarity indices showed the most similarity between black locust stand, and mixed stand of Turkish red pine and black locust, and least similarity between Iranian Oak stand and Turkish red pine stand. Maximum and minimum value of Simpson dominance index was seen in Turkish red pine stand and Iranian Oak stand respectively. Iranian Oak stand with six species had the most endemic ground flora species and Turkish red pine with one species had the least. Respect to trivial changes in soil properties, in addition to soil changes effects, changes in species diversity may relate to heavy canopy cover and shade effects of it.