Evaluation of Periodical Changes in Plant Biodiversity Indices: A Case Study of Zanjanroud Watershed, Iran

Investigation of relationships between plant communities and environmental factors is among the most important, complex issues associated with management of natural resources and environment. Land use changes, soil degradation and erosion, loss of soil-water balance and over exploitation of plant resources have led to drastic changes in plant biodiversity. In the present study, one of the important components of biodiversity (alpha diversity index) was investigated at local scale. For this purpose, the most important environmental factors affecting the natural growth and distribution of plant communities in Zanjanroud Watershed were initially investigated. Accordingly, satellite images, statistics and GIS maps of the study area were applied to analyze the impact of the environmental factors on biodiversity indices. Accordingly, SPSS software was used to investigate correlations among the studied variables. The obtained results indicated that there is a statistically significant regression between the data on species diversity indices as well as uniformity in the study area during the research periods. As the findings suggest, based on Shannon Index, the species diversity has been declined from 3.12 to 2.73 with a statistically significant difference of 5% during the investigated period of 23 years. Likewise, Pielou's uniformity index has been decreased from 0.92 to 0.82 with a statistically significant difference of 5% and based on Menhinick Index; the species richness has been declined from 0.21 to 0.16. Among the reasons affecting the deterioration can be pointed to land use changes from pristine areas to farmlands, overexploitation of rangeland areas and some environmental characteristics including climate change especially precipitation changes in the research period.