Effect of Canopy Cover on Understory Invasive Alien Species in the Wayanad Wildlife Sanctuary, Kerala, India
We assessed the diversity of invasive alien plant species in the Wayanad Wildlife Sanctuary (one of the main protected areas located in the Nilgiri Biosphere Reserve) to see whether the density and diversity were associated with forest canopy cover. This study was carried out in the pre-monsoon season from January to March 2015, when deciduous trees had shed their leaves and the canopy was relatively open.
A total of 45 (20 m by 20 m) quadrats in different areas of the sanctuary were sampled. The total area sampled was 1.8 ha. All the plant species with a height of 10 cm and above were recorded and after proper identification only invasive alien species were considered. The GPS coordinates, the type of canopy cover (evergreen or deciduous) and the percentage of canopy cover were also recorded.
A total of 22 invasive alien plant species belonging to nine families was recorded. Out of this, 14 species (64%) belong to the Neotropics, 5 species (23%) to Africa, 2 species (9%) to West Indies and 1 species (4%) to South East Asia. Eupatorium odoratum (42.8±6.3) had the highest density followed by Lantana camara (13.6±3.2). Eupatorium odoratum was significantly and negatively correlated with canopy cover (Pearson’s correlation coefficient = -0.38, p=0.03), whereas L. camara was not associated with canopy cover (Pearson’s correlation coefficient = - 0.09, ns). This suggests that E. odoratum is more sensitive to the light levels than L. camara.
This study provides little insights into the status of invasive alien species in an area known for its high levels of endemism.