Analysing highly biodiverse tropical dry forests for improved conservation

Tropical dry forests (TDF) support the livelihoods of millions of people worldwide, but in contrast with the humid tropical forests, knowledge of their structure and biology is limited. This study aims to fill that gap using observations from the South Indian Deccan Plateau. Based on large, tree-mapped field plots, within or near a densely populated metropolitan area, we present details of 130 woody plant species, including a large number of climbers. The modelling approach includes a new function for developing species–area relations (SAR’s). In addition to the greater flexibility of the function, when compared with traditional power and asymptotic functions, the Monod function not only provides greater flexibility, but also allows reasonable estimates of SAR's if the overall regional species richness is known. This is an important advantage when compared to the standard methods. Another new finding concerns the species abundance distribution (SAD) which explains processes of community assembly and species turnover. The SAD follows the Weibull model which is a significant improvement compared with the traditional use of the Lognormal model because the Weibull parameters seem to be related to species richness. We also present a new cell-based (in addition to the individual neighbourhood-based) approach for analysing structure. The cell-based analysis combines small-grain measures of density and crowding, richness and size variation and can be used to assess the degree of similarity or dissimilarity among forest stands, or between a current and some ideal target structure. The methods of analysis and the proposed framework for pro-active conservation presented in this study may be helpful in regions of the world where complex multi-species forests require advanced methods for sustaining their resilience and functions.