Tropical rainforests are unique ecosystems that support essential ecological functions. They not only include trees and animals, but also an inclusive ecosystem of various taxonomic groups. One of the lesser-known components of this diverse ecosystem in India is the forest canopy. The emerging field of canopy ecology is largely associated with the study of the flora and fauna found high in the treetops of tropical forests.
Forest canopies are home to species ranging from insects to plants. Changes or damage to any species can cause imbalance and impact the ecosystem as a whole, which can have long-term ecological implications. Epiphytes are a group of plants that grow profusely in forest canopies. They grow on other plants or trees and have no connection with the soil. Rather, they absorb nutrition using specialized roots.
Epiphytes play an essential role in the canopy ecosystem, and their moisture and nutrient retention properties are required by many terrestrial invertebrates and lower vertebrates.
They also support biodiversity, being a refuge for insects, in addition to providing nectar, pollen, fruits and seeds for other organisms to collect. Certain epiphytes have co-evolved with certain faunas exhibiting mutualism, in particular with certain species of ants.
A team of researchers from the Ashoka Trust for Ecology and the Environment (ATREE) and the Center for Ecological Sciences, Indian Institute of Science (IISc) recently documented the impact of selective logging on the Ghats epiphytic community westerners. The study finds that even though it has been over 3 to 4 decades since logging stopped, their effects continue to persist and are impacting the epiphytic community. The study was published in the journal Frontiers for forests and global change.
For a long time, canopy research was not undertaken due to lack of access, and forest canopies were therefore dubbed the last biological frontier. Dr Nalini Nadkarni, an American environmentalist of Indian descent, pioneered the field of canopy ecology with her work in the tropical forests of Costa Rica during the 1980s. With improved techniques for reaching canopies, researchers show renewed interest in the field.
“The forest canopy is the first layer to interact with the atmosphere and form the roof of our forest ecosystems and yet our knowledge of this important ecosystem is incredibly scarce,” said Dr Soubadra Devy, senior researcher at the ATREE and lead author of the study. Dr Devy pioneered canopy ecology in India in the 1990s when she conducted pollination biology experiments in the high forest canopy with only rickety scales.
âWe had to climb trees to study epiphytes because they wouldn’t be visible from the ground. However, swinging 100 feet above the ground is not for the faint of heart. The single-rope technique is incredibly safe but requires a high level of fitness and agility, âsaid Dr. Seshadri KS, the lead author of this study, who is currently a DST-INSPIRE faculty member at the Center for Ecological Sciences, Indian Institute of Science.
Researchers conducted a study on the ecology of epiphytes in the remote forests of the Kalakad Mundanthurai Tiger Reserve in Tamil Nadu. The researchers identified 100 trees each in an area comprising an area logged until the 1980s and an area not logged. They found 2,129 varieties of epiphytes, belonging to 20 species growing on 22 species of host trees. A large proportion of the epiphytes were orchids (85%) in the selectively harvested and non-harvested areas.
The study notes that the epiphytic community is markedly altered, as evidenced by the increased diversity and abundance of epiphytes in the selectively logged forest. They further found that the association of epiphytes to its host was also altered, as more epiphytes overlapped more in the selectively logged forest. A host tree species, Cullenia exarillata, was home to the greatest diversity and abundance of epiphytes in logged and non-logged forests. Overall, taller trees with abundant moss growth harbored a greater number of epiphytes.
The availability of moisture at the top of the canopy plays a crucial role for epiphytes to assimilate nutrition from dead and decaying material collected on branches.
âDue to the selective cutting of trees, the unbroken canopy of the forest is broken. The deviations created would modify the temperature and humidity profiles. There is an increase in light irradiance in the selectively logged forest and a combination of these factors may be the reason why we are seeing greater diversity and abundance of epiphytes in the selectively logged forest, âexplains Dr Seshadri.
âCanopy epiphytes reproduce by producing seeds or microscopic spores, which are dispersed by the wind. If the seeds or spores fall on branches that are brighter or have abundant growth of moss, then the chances of colonization by the epiphyte are greater, as the moss acts like a sponge and retains moisture, âhe notes. -he.
Clearly, the researchers caution against using the results of increased epiphyte abundance in logged areas as an excuse to continue logging. Previously, the research team studied the impacts of logging on various taxonomic groups such as amphibians, butterflies and vegetation in the same study area. They also attempted to archive forest regeneration in the Kalakkad Mundanthurai Tiger Reserve.
In any case, selectively logged forest communities are radically different from untapped forest, even after 3-4 decades, since selective logging in the Kalakad region ceased and forests were incorporated into the forest. tiger reserve.
Another study by the National Center for Biological Sciences (NCBS), Bengaluru, and the Nature Conservation Foundation (NCF), Mysuru, showed how even a few cases of selective tree cutting impact biodiversity and the storage of carbon from Andaman forests.
The present epiphytic study provides insight into how epiphytic plants would cope with disturbance and raises more intriguing questions about the growth rate, physiology, and biology of epiphytic populations in the Western Ghats. Hopefully in the days to come there will be many more researchers going into canopy research and looking for answers to some of these questions.
(The author is with Gubbi Labs, a private research collective)