The Sholas are a mosaic of forests and grasslands associated with the South Western Ghats Montane Rain Forests of Karnataka, Kerala and Tamil Nadu. They are characterized by the presence of vegetation that is dependent on cloud-borne moisture, so common in the wet and cold mountains of the region. Located at altitudes of 1700 m asl or more, they are a patchwork of forest (nestled in the valleys) and grassland (on the mountain slopes) carpeting the rolling hills of the Western Ghats, harbouring a wealth of plants and animals, many of which are to be found nowhere else.
The word ‘Shola’ derives from the Tamil ‘Sholai’ (cōlai) which means forest, grove or thicket. There is a debate over the status of the Shola ecosystem. Some botanists consider them to be a climax community (a community of microbes, plants and animals, that after a process of ecological succession, have reached a stage of long-term stability). Others think that they are the result of human interference, the aftermath of pastoralists clearing forest using fire and livestock.
On the other hand, analysis of peat samples from the region have revealed that Sholas have undergone cyclical shifts in vegetation. Periods of low rainfall gave rise to drought-tolerant flora (between 20,000 to 16,000 years ago) while humid conditions allowed forests to expand and flourish (from 16,000 to 6,000 years ago). Around 6,000 years ago, the monsoon weakened again, leading to fragmentation of forest cover. This cycle of ecological transformation, and the relative isolation of the Western Ghats might have made the Sholas a centre of biological diversity.
Shola forests have profusely branched and stunted trees (rarely exceeding 15 m) with an abundance of epiphytes. Species of the genera Rubus, Daphiphyllum, Eurya, Rhododendron, Berberis and Mahonia are found on the fringes of the forests or as lone individuals amidst the grasslands. Members of the families Lauraceae, Rubiaceae, Symplocaceae, Myrtaceae, Myrsinaceae and Oleaceae form the over-storey while Asteraceae, Fabaceae, Acanthaceae, Poaceae, Orchidaceae and Cyperaceae make up the under-storey.
Epiphytes can account for as much as 25% of the Shola forest biomass and play a crucial role – recycling nutrients, storing water and providing microhabitats for small arthropod and vertebrate species. Apart from rare insects, fish, amphibians, reptiles and birds, the Shola mosaic supports a number of large mammals – Asian Elephant (Elephas maximus), Sambar (Rusa unicolor), Gaur (Bos gaurus), Nilgiri Tahr (Nilgiritragus hylocrius), Tiger (Panthera tigris), Leopard (Panthera pardus), Dhole (Cuon alpinus), Nilgiri Marten (Martes gwatkinsii), and Sloth Bear (Melursus ursinus).
Some of the important plant species associated with the Shola forests are Magnolia nilagarica, Bischofia javanica, Calophyllum tomentosum, Toona ciliata, Ficus racemosa, Maesa indica, Microtropis ramiflora, Rhododendron arboreum, Prunus ceylanica, Schefflera racemosa, Chionanthus ramiflorus, Elaeocarpus recurvatus, Ilex denticulata, Actinodaphne bourdillonii, Litsea wightiana, Archidendron clypearia, Ixora notoniana, and Syzygium densiflorum. Ligustrum perrottetii, Turpinia cochinchinensis, Mahonia leschenaultii, Rhodomyrtus tomentosa, Berberis tinctoria and Vaccinium neilgherrense grow around the forest margins.
The under-storey has plants like Impatiens phoenicea, Impatiens coelotropis, Gaultheria fragrantissima, Moonia heterophylla, and Smithia blanda. Climbers include Piper schmidtii, Rubia cordifolia and Connarus wightii. Vaccinium leschenaultii, Impatiens tangachee, Sonerila grandiflora, Osmunda regalis and Eurya japonica grow along the streams. The forests also harbour epiphytic orchids – Aerides ringens, Coelogyne nervosa, Coelogyne mossiae, Conchidium filiforme and Eria pauciflora.
Andropogon polyptychos, Chrysopogon zeylanicus and Eulalia phaeothrix dominate the Shola grasslands. Also found in the open are several species of Strobilanthes – Strobilanthes cuspidatus, Strobilanthes foliosus, Strobilanthes gracilis, Strobilanthes luridus, Strobilanthes micranthus, Strobilanthes pulneyensis, Strobilanthes violaceus and Strobilanthes wightianus. Most of them are endemic to the region.
The Shola forest-grassland mosaic acts as a natural sponge. The moisture present in the cold mountain air is trapped by the dense foliage – formed by the trees, epiphytes, climbers, ferns, lichens, mosses and ferns. The water soaked up by the vegetation seeps into the soil and feeds the water courses. Such is the efficiency of the Shola ecosystem at capturing and retaining this precious resource that both human beings and animals can rely on it during the harshest of summers. Unfortunately, large-scale clearance of the forest-grassland complex for cultivation of plantation crops is putting them at grave risk.
Illustration: The image above, sourced from Wikimedia Commons, is a photograph of a Shola forest-grassland mosaic from the Kudhremukha National Park, Karnataka. It was uploaded by Mr. Sudeep.
- The Shola-Grassland Ecosystem Mosaic of Peninsular India by Milind Bunyan, Sougata Bardhan and Shibu Jose (in the American Journal of Plant Sciences, 2012)
- Nilgiri Tahr Info
- Saving the Sholas (by S Gopikrishna Warrier, dated May 28, 2017), The News Minute