Influence of Traditional Forest Harvesting on Woody Species Diversity at Different Vertical Layers of Oak Forest: A Case Study

Abstract

The aim of this study was to assess the influence of traditional harvesting on woody species richness and diversity at different vertical layers in the northwest of Zagros forests, Iran.Two forest stands including disturbed and less disturbed with similar physiographic condition were selected. 30 circularly shaped plots with 1000 m surface area were selected based on random-systematic sampling with 50×50 m network dimensions. The means of different diversity indices in total and at different vertical strata were calculated and student’s t-test was used to compare the mean of all indices difference in the treatments. Importance Value Index (IVI) of different species at different layers was calculated.The results showed that the mean of all indices in the disturbed stand were significantly lower than in the less disturbed one, however, the mean of evenness index did not statistically show any significant differences between two stands. In total, the Shannon diversity, Simpson diversity and Margalef richness indices of the disturbed stand were 47.59 %, 36.62% and 63.72%, respectively lower than in the less disturbed stand. In the disturbed stand, the most important species were Quercusinfectoria (with 70.48% IVI), Quercuslibanii (with 50.79% IVI) and Crataegus spp. (with 33.59% IVI). These species were also important species in the less disturbed stand with 61.38%, 54.89% and 43.11%, respectively importance value.As a whole, the results revealed thatthe traditional harvesting threats the forest species diversity and also simplifies the structure of these precious forests. Our results showed that the current traditional harvesting and grazing reduced the woody species diversity and simplified the forest structure to only one story.