Endangered vegetation ecosystems are rich in unique woody species and hold significant conservation potential before reaching a critical ecological tipping point

Abstract

In most cases, the patterns of species assemblies in vegetation ecosystems are shaped by socio-ecological processes. However, the relationship between unique species and threat statuses of vegetation ecosystems remains unexplored. This study assessed how both overall and unique woody species in adjoining vegetation ecosystems are associated with their threat statuses. For this, woody species assessment was undertaken by laying out a line transect (620 m in length) on the adjoining four vegetation ecosystem types to the interior direction at nine sites. Six sample plots (size: 20 ´ 20 m each) were arranged on transects with a 100 m interval. In total, 18 transects and 108 plots were used for data collection. The list of species and number of stems of mature trees and shrubs, saplings and seedlings were recorded. The dataset was organized into three sub-datasets: mature trees and shrubs, saplings, and seedlings. These ecosystems were sorted into four threat categories based on the IUCN threat categories of vegetation ecosystems. The variations in compositions of the overall and the unique woody species between adjoining vegetation ecosystem types having threat categories were tested using Adonis2 function within vegan package. Similarly, the differences in species richness and number of stems were analyzed using one-way ANOVA. The multivariate analysis of variance indicated that the species compositions of all growth stages significantly vary between the ecosystem threat categories (P<0.003). Similarly, both the overall and unique woody species richness is significantly higher in a critically endangered vegetation ecosystems than the adjoining ecosystems with either least concern, near threatened or vulnerable threat categories (P<0.004). These results suggest that the vegetation ecosystems, which were previously floristically diverse but are currently critically endangered, are comprised of higher unique woody species. Hence, this potential needs to be restored before the tipping point triggered by the continuing socio-ecological disturbances.