Changes in indices of species diversity and richness of good, degraded rangelands and abandoned dry lands in Fereydan, Isfahan

Changing land use and overexploiting rangelands beyond the ecosystems potential are effective factors reducing species diversity that could threaten these ecosystems’ health and stability. In the present study effects of grazing on species diversity of rangelands and abandoned drylands in Fereydan, Isfahan was evaluated. In each rangeland site the percentage of crown cover and species diversity were obtained and the effects of distance from village were also studied. Along three transects of 100-meters according to sample size one square meter plots were randomly selected. Calculated sample size was 20 for each range site. Non-parametric indices such as Margalof species richness index, Hill (N1) and Shannon-winner species diversity were calculated. Parametric algorithms (frequency-order models) also were used for species diversity evaluation. In order to investigate the relationship between species diversity and environmental factors, multivariate data analysis was (ordination method) applied. Results indicated that Margalof species richness index was significantly higher in good rangelands than others (P>0.01). Non-parametric diversity indices such as, Hill (N1) and Shanonn-winner showed significant differences (P>0.05) between good rangeland and both, degraded rangeland and abandoned dryland sites. Frequency-order model in parametric method indicated that data followed log normal model. Distance from rural area was recognized as the most important variable effective on species diversity and species richness. Ordination analysis (PCA) showed that there is a positive correlation between species diversity and soil organic matter, moisture saturation, lime and clay percentages and a negative correlation with sand percentage and soil electrical conductivity.