Research Projects

Invasive species pose major threats to biodiversity and human livelihoods worldwide. They impact the structure and composition of native communities, cause losses of ecosystem services and function, and can have profound effects on human health and wellbeing, with the monetary costs associated with invasions running into billions of dollars annually. The eradication of invasive species and the restoration of native communities is thus a global priority. Managing invasive species and restoring native ecosystems is a major priority in India’s national and international commitments including the Govt. of India’s pledge to restore 26 Million hectares of land by 2030 (Bonn Challenge). However, lack of detailed information on the ecosystem level impacts of different invasive species, particularly with regards to how they alter belowground processes and soil biodiversity, and how this in turn, hinders the growth of native vegetation, limits our ability to effectively restore ecosystems. Here, we propose to investigate the legacy effects of woody plant invasions in montane forest-grassland mosaics of the Western Ghats, as mediated by their effects on soils and belowground processes, and evaluate the implications of these for the restoration of native vegetation communities in these grasslands. Our study system, the montane shola-grasslands of the Nilgiri Biosphere Reserve, has witnessed large scale introductions of over 40+ exotic species for timber and ornamental purposes over the last century, three of which – Acacia mearnsii (black wattle), Ulex europaeus (gorse) and Cytisus scoparius (scotch broom) – have since become invasive in grasslands. Wattle and gorse are ranked amongst the 100 worst invasive species globally, and over the last few decades ~66% of montane grasslands in the Western Ghats have been lost to invasive species and exotic plantations. Restoring invaded grasslands is a priority for conserving native biodiversity and is also a mandate of the Tamil Nadu Government, directed by the Madras High Court. However, little is currently known about how these species alter plant-soil feedbacks and influence belowground processes, and how these in turn, facilitate or hinder the regeneration of both native and invasive species. Specifically, our objectives are to: i) characterize the impacts of three different woody invasive species – Acacia mearnsii, Ulex europaeus and Cytisus scoparius – on soil biodiversity, ii) quantify their impacts on soil seedbanks of both native and invasive species, and iii) experimentally evaluate how past invasions impact the growth and performance of both native and invasive species via their legacy effects of soils. Results of this study will provide us with a more nuanced understanding of the ecosystem-level impacts of woody plant invasions in these threatened grasslands, and will be invaluable for designing effective management and restoration strategies for these grasslands.