The Nodal Centre for Biological Invasions (NCBI) at the Kerala Forest Research Institute (KFRI) has come out with a management plan to eradicate Senna spectabilis, the exotic invasive plant that is posing a severe threat to the State’s wildlife habitat.
Based on the results of the experimental study done at the Periyar Tiger Reserve, the plan envisages landscape-level management of the tree. The two key factors considered in developing the management protocol were the fast nature of the spread of the tree in natural forests, and restoration of natural forests based on landscape.
The process
The results of the field trials were presented at a recent national conference on bio-invasions organised by the Kerala State Biodiversity Board. The management plan stipulates that there should not be an attempt to kill the trees before a detailed reforestation programme and the resources for implementing it are in place, T.V. Sajeev, Chief Scientist, KFRI told The Hindu.
This involves developing an adequate number of large-sized saplings of native trees, identification of nucleus sites where the planting is to be made, and the provision for manpower, Dr. Sajeev said. Once the resources and material for landscape restoration are ready, the invasive species has to be removed using a threefold approach for large trees, large saplings, and small saplings, he said.
Debarking large trees
The large trees need to be debarked from breast height downwards (1.3 m above ground level), including the collar part of the tree. Once done, the trees should be visited once a month to remove the new growth across the debarked area.
Once the trees start to dry up, their soil seed bank will become active and a large number of plantlets will sprout. Manpower should be made available to remove the sprouting plantlets. The next is the larger saplings which can be uprooted using specially designed weed pullers which were successfully tested at the Periyar Tiger Reserve, he said.
The third is the removal of small plantlets which need to be removed mechanically. It is important to make sure that the pulled-out saplings are dried without any contact with soil. Planting of large saplings of native tree species should start along with or before the start of Senna removal. Adequate training should be given to the labourers and measures should be in place to ensure their safety while within active wildlife areas.
18 months to dry up
The large trees would take a minimum of 18 months to completely dry up after debarking. While the invasion of Senna spectabilis is most severe in Wayanad Wildlife Sanctuary and nearby forests, the sporadic presence of the tree is found in the fringes of many other forest areas of the State. These trees need to be destroyed before they reach the reproductive age, Dr. Sajeev added.
