Invasion of Alien Senna Spectabilis Causes Loss of Natural Vegetation in the Wayanad Wildlife Sanctuary of India and Edaphic Factors of the Invaded Areas Assist its Profuse Sprouting

Abstract

The Indian region because of its diverse climatic and environmental conditions is highly vulnerable to biotic invasion. In the Wayanad Wildlife Sanctuary of India we studied the effect of the invasion of one of the alien species, Senna spectabilis , on natural vegetation and analyzed whether the edaphic factors of invaded regions induce its profuse sprouting. We observed that the invasion of S. spectabilis leads to a drastic loss in the natural vegetation there. No ground cover was found in the invaded region whereas heavy sprouting of S. spectabilis seeds was detected. The reappearance of lost flora with high diversity and species richness were noticed in the regions where S. spectabilis were manually eradicated. A study on the seed germination under laboratory conditions showed that the seeds of S. spectabilis are highly dormant and scarification using concentrated H 2 SO 4 or water incubation induces its germination. Further analysis of soil samples of the invaded area revealed that soils are acidic and have high water holding capacity. The results imply that the invasion of S. spectabilis is a major threat to the indigenous plant diversity and edaphic factors of the invaded areas assist the profuse sprouting.