Executive Summary : | Climate change-related changes in global surface temperature are mediating variation in precipitation patterns resulting in the uneven distribution of rainfall under different regions of the world. Water limitation stress entangled with the anthropogenic disturbances is resulting in vegetation degradation and shift in plant community and composition, globally. However, responses of different vegetation types may vary with their resilience and adaptability to the changing climatic conditions. For example, savannas, which are distributed on 10-25% of the global land surface, have been considered as the most sensitive ecosystems of the world. The plants growing in savannas show distinct eco-physiological adaptations and growth behaviour under different climatic conditions, particularly precipitation and temperature regimes. Like other vegetation types, the savannas are facing major threats by the alien plant invasion which is replacing the naturally existing tree-grass interactions with woody vegetation. For example, fine-leafed open tree-grass savannas existing in the arid and semi-arid regions of South Asia and Southeast Asia have been severely invaded by Prosopis juliflora with less or no ground vegetation. Similarly, deciduous broad-leafed savannas of the mesic environments have been invaded by Lantana camara. Such changes in vegetation structure and composition are not only affecting the plant biodiversity but also different soil biogeochemical cycling. Thus, the invasion of alien species in different ecosystems, particularly savannas, is gaining wider research attention in the climate change scenario. In recent years, although a number of precipitation manipulation experiments have been performed in various ecosystems, the understanding of how the invasive plant–soil–climate interaction will control ecosystem processes like nutrient cycling is lacking. This project has been planned to fill this research gap by considering two invasive species viz., Prosopis juliflora and Leucaena leucocephala growing under three rainfall conditions viz., low (mimicking drought), average and high (mimicking future rainfall changes) precipitation levels, and competition by native grasses (mimicking savannas) under ambient conditions. Moreover, the impact of different species interaction on soil pools and processes has also been emphasized. Specifically, we proposed to test the following four hypotheses: (i) rainfall variability may lead to eco-physiological adaptations in invasive plant species, (ii) invasive species co-occurrence may have neutral, facilitative or competitive impacts on each other under different rainfall conditions, (iii) seedling-native grass interaction would be of the facilitative or competitive type under ambient conditions, and (iv) inter-and intra-specific interaction of invasive species will be regulated by plant-soil feedback mechanism under different rainfall regimes and grass competition. |