Thesis Defense at CES on 20 March 2018 at 10:00 am titled "The structure and dynamics of a tropical dry forest plant community" by Sandeep pulla from CES
This thesis is spurred by the overarching question “why is a plant where it is in space and time?”, asked in the context of a tropical dry forest plant community in southern India, based on long-term research conducted in a large (0.5 km2) permanent sampling plot. We attempted to deconstruct the structure and dynamics of the plant community by first establishing the spatial structure of soils, topography and lithology in the plot. We then assessed how this spatial structure, together with temporal variation in precipitation, affected abundances of the eight most dominant species in the plot. Finally, we broke up abundance variation into the components of recruitment, mortality and stem radial growth and assessed how these respond to variation in environmental factors (precipitation, temperature, soils, topography and fire) and biotic neighborhoods.
Local-scale lithological variation was an important first-order control over soil variability at the hillslope scale in this tropical dry forest, by both direct influence on nutrient stocks and indirect influence via control of local relief. Species separated into two broad groups in niche space – one consisting of three canopy species and the other of a canopy species and four understory species – along axes that corresponded mainly to variation in soil P, Al and a topographic index of wetness. Our results suggest that this tropical dry forest community consists of several tree species with broadly overlapping niches, and where significant niche differences do exist, they are parsimoniously viewed as autecological differences between species that exist independently of interspecific interactions. Temporal environmental factors (time since last fire, precipitation, and minimum and maximum temperatures) appear to be the strongest drivers of dynamics in this community, followed by conspecific and heterospecific neighborhoods, followed by spatial environmental factors (soils and topography). It is hoped these results will provide information relevant to understanding, managing, and predicting the future of this ecosystem and contribute towards the development of general theories of plant community ecology