Effect of man-made disturbances on understory plant richness of oak forests in Iran

The purpose of this study was to investigate the impacts of disturbance degree on the species richness and species diversity of oak forests in the Kurdistan Province (Iran). The study ran on three treatments: undisturbed, moderately disturbed, and highly disturbed. For each treatment, there were selected three forest patches with similar physiographic conditions and on each patch there were specified three 400 m² plots for recording floristic data. The species’ name and the abundance of herbaceous species were recorded on 5 micro plots sized 1.5 × 1.5 m for each sample. Menhinick, Margalef, the number of species indices and also rarefaction, jackknife methods and species abundance distribution models were used to estimate the herbaceous species richness for the three treatments. The results showed that all the richness indices had the highest values for the undisturbed forests and the lowest values for the highly disturbed ones. Based on all models, undisturbed forests were showed more diverse than highly disturbed area. Generally the negative impact of human activities (wood cutting and grazing) on the herbaceous species richness was found much stronger in the highly disturbed forests and in moderately disturbed forests compared the undisturbed ones. With increasing destruction intensity, the herbaceous species richness in the oak forests decreased dramatically.