Thesis Defense at CES on 25 August 2020 at 3:00 pm titled "Impact of the invasive shrub Lantana camara L. (Verbenaceae) on carbon and nitrogen stocks in a seasonally dry tropical forest" by Debarshi Dasgupta from CES, IISc
The effects of invasive plant species on ecosystems are manifested in various ways which might often be counter-intuitive and confusing. Existing literature has largely stressed upon the negative impacts of invasive species on certain ecosystem properties, like suppression of growth of native seedlings. However, the holistic view of the effects of such species on ecosystems is still not clear. There is a need to understand that invasive species are a structural and functional part of invaded ecosystems. Studying ecosystem functions like nutrient cycling and regulation, in relation to invasion, is necessary because it directly linked to all organisms in an ecosystem and it is modified by the characteristics and abundance of the invasive species.
In this study, we aimed to understand the effects of plant invasion on nutrient stocks in biomass, litter and soil. First, we aimed to estimate for resident carbon and nitrogen pools, in a tropical dry deciduous forest (considered to be one of the most at-risk ecosystems in the world) in Mudumalai Tiger Reserve, India, over a period of one year. Then, we tried to understand how pools of these elements are modified under the influence of increasing abundance of the invasive shrub species Lantana camara.
This study reinforces the fact that it is difficult to predict the impacts of invasive plants on soil nutrient cycling processes. Through time, we see areas of higher density of Lantana camara showing more pronounced effects on parameters like soil microbial biomass carbon and nitrogen as compared to lower densities. In other parameters like litter carbon and nitrogen, soil carbon and nitrogen and biomass carbon and nitrogen, the results vary among the density categories through time. For most of the study, the carbon and nitrogen stock changes under different density of infestations did not vary significantly from the mean values of the forest. Expected patterns do emerge in certain cases, but do not remain consistent both throughout the course of study as well as the density categories. In many cases, places with low or intermediate levels of the shrub show more significant effects. These results validate the need of more consolidated research on such issues to gain in-depth understanding of ecosystem functions for better forest management and policy formulations.