Plant communities and invasive species in forest fragments
When continuous forests are carved into smaller fragments, plant communities in the remnants are affected by the ensuing environmental changes. It also influences the ecology of native and alien species differently. Understanding which species persist and which ones decline and disappear is crucial for conservation.
Plants in fragments and continuous rainforest
How does fragmentation affect plants? To answer this, we studied plant communities in forest fragments and continuous forests in the Anamalai Tiger Reserve. By systematic study of trees, lianas (woody climbers), shrubs, and herbs, in sample plots, we found interesting trends. Rainforest trees tended to decrease in diversity and density in smaller and more disturbed fragments, while lianas increased in moderately disturbed sites. Shrubs and herbs in the forest understorey showed a tendency to increase in density and diversity in smaller fragments overall, but this was partly because decline in native evergreen species was masked by an increase in weedy, alien species, that appeared to thrive in disturbed sites. Still, even in the relatively small sample area (4 ha for trees and lianas, 0.16 ha for understorey plants), the rainforests retained an astonishing plant diversity. There were 144 tree species, 60 liana species, and 108 understorey plant species; of these 70 species are endemic to the Western Ghats.
Invasion by coffee and other alien species
Where forest fragments abut farms and plantations, there is a possibility that crop plants may run wild into forests. While this does not happen with many cultivated species, plants such as coffee which has its origins in African forests and which can grow under the shade of trees, may manage to invade forests. In the Anamalai hills, we studied invasion by coffee and other alien species from the edge of forest fragments abutting coffee plantations into the interior. Robusta coffee was found to be highly invasive in both relatively undisturbed and disturbed forests. Arabica coffee, in comparison, was less invasive, and occurred more in disturbed fragments. Other invasive alien species such as Lantana camara, Chromolaena odorata, and Maesopsis eminii, showed divergent patterns related to disturbance history and present status.