Habitat associations, density-dependence, and tree species diversity in a tropical dry deciduous forest in Mudumalai Southern India

Abstract

Understanding Tree Species Coexistence in Tropical Dry Deciduous Forests: Habitat Specialization and Density-Dependence in Mudumalai, Southern India

Abstract and Synopsis Introduction The coexistence of tree species in species-rich tropical forests remains a central challenge in ecology. While moist tropical forests have been extensively studied, dry tropical forests are less explored. This thesis investigates habitat specialization and density-dependence in a 50-ha tropical dry deciduous forest plot in Mudumalai, southern India.

Habitat Specialization (Chapter 4)

Habitat associations of tree and shrub species were tested using torus randomization, an improvement over traditional chi-square analyses.

Results showed significant positive and negative associations, but most species behaved as habitat generalists with respect to topography.

Demographic performance (growth, mortality, recruitment) did not align with habitat affinities, suggesting that factors beyond topography influence tree demography.

Density-Dependence (Chapters 5 & 6)

Using eight years of data (1988-1996), distance- and density-dependence in mortality and recruitment were tested.

Recruitment was inhibited near conspecific adults in Lagerstroemia microcarpa and Tectona grandis. Juvenile mortality showed non-random patterns but averaged out over time.

Quadrat-based analyses revealed strong negative correlations between recruitment and conspecific density in L. microcarpa, T. grandis, and Cassia fistula.

Mortality was also negatively correlated with conspecific density, possibly due to reduced fire intensity under dense patches.

Conclusions

Both habitat specialization and density-dependent forces play roles in regulating tree populations in tropical dry deciduous forests.

However, recurrent grass fires alter these dynamics, promoting dominance of a few species and reducing diversity.

These findings highlight the complex interplay of ecological processes and disturbances in shaping forest community structure.