Impact of alien invasive species (cassia spectabilis) on floristic diversity and natural regeneration in southern tropical dry deciduous forest of Nagarahole Tiger Reserve

The aggressive behavior of Invasive Alien Plants has been reported to alter plant species composition and even replace native species. Hence the current study was carried out to assess the forest structure and diversity in relation to C. spectabilis infestation and also evaluate the impact of C. spectabilis on natural regeneration in D B Kuppe and Anechowkur Rangeof Nagarahole Tiger Reserve, located in Karnataka, India. The intensity of infestation was categorized into three levels: highly infested, moderately infested, and non-infested areas. In each category, 20 quadrates of 20 × 20 m were laid randomly in ranges to study the floristic diversity, growing stock and regeneration pattern. It has been observed that the species richness, Shannon-Wiener index and Simpson’s index of dominance was highest in non-infested areas, followed by moderately and highly infested areas. Similar pattern was also observed in regeneration pattern where regeneration diversity was found to be highest in the non-infested areas followed by moderately infested areas. Both basal area and density varied significantly among the different levels of C. spectabilis infestation. The values of density of regenerates were highest in the non-infested areas followed by moderately infested areas in both range of forests. From the study it was evident that the non-infested areas helping in improving the regeneration status of tree species.