Relative contribution of vegetation types to regional biodiversity in Central Zagross forests of Iran

Abstract

Managers in conservation biology are continually faced with the dilemma of needing to demonstrate which areas should receive conservation priority based on the diversity of species contained. Darenasab (Hashtadpahloo) forest catchment with domi- nated oak species in Mediterranean forests of Zagross in Iran was chosen as a case study. In order to estimate plant species richness in different vegetation types at landscape level, field method that sample both trees and herbs strata simultaneously (modified multi-scale Whittaker plots) was used to make species-area curves. Twenty-one modified multi-scale Whittaker plots (250 m 2 area) were located randomly in four vegetation types. Three species-area, species-log (area) and log (species)-log (area) curves models were con- structed. The log (species)-log (area) model had the highest adjusted r 2 among others. Based on Jaccard's coefficient, the pure oak vegetation type was the most heterogeneous (22% overlap), and the cushion plants vegetation type is the most homogeneous (29% overlap). The slope of species-area curves had the least range (0.05) and the slope of species-log (area) curves had the largest range (4.38). When the slopes of species-log (area) curves divided by mean Jaccard's coefficient, the species-log (area) curves esti- mated values closest to those observed. The index of vegetation types contribution to regional diversity for determining conservation priority in off-reserve area, based on ranking of the observed mean species per plots, slopes of the species-log (area) curves, mean of Jaccard's coefficient, mean unique species per plot, and the number of threatened species in each vegetation types were calculated. This composite index may provide a scientific method to rank vegetation types with high conservation value.