Deccan Plateau dry deciduous forests

• Category: Forest Biomes.
• Geographic Location: India.
• Summary: The dry forests of the southern Deccan Plateau provide a habitat stronghold for many species, but the area faces pressures from slash-and-burn agriculture as well as looming climate change.

The Deccan Plateau is a vast geographic feature encompassing most of central and southern India. The term Deccan comes from the Sanskrit word dakshina, meaning “the south.” It comprises the whole of southern peninsular India, encompassing parts of eight states—most of Andhra Pradesh, Karnataka, Kerala, and Tamil Nadu, as well as portions of Maharashtra, Madhya Pradesh, Gujarat, and Orissa. The Deccan Plateau is bounded on all sides by mountains: Western Ghats to the west and Eastern Ghats to the east, Nilgiris to the south, and the Satpura and Vindhya ranges to the north.

Undulating terrains are common here; the elevation ranges from 1,500 to 2,500 feet (457 to 762 meters). Several major rivers—including the Cauvery, Godavari, Krishna, and Penner—flow across the plateau before reaching the Bay of Bengal. The Deccan Plateau has a dry season that lasts six to nine months. The maximum temperature in the region varies from 77 to 90 degrees F (25 to 32 degrees C), while the minimum varies from 55 to 70 degrees F (13 to 21 degrees C). Annual rainfall can vary from 47 to 197 inches (1,200 to 5,000 millimeters).

Vegetation

The forest types of the Deccan Plateau fall into six categories: tropical wet evergreen, south montane wet temperate, tropical semi-evergreen, tropical moist deciduous, tropical dry deciduous, and tropical thorn. Three ecoregions dominate the plateau: the southwestern hill ranges, with rich, dense montane rainforests; southwestern hill ranges, with moist deciduous forests; and the southern Deccan Plateau, with dry deciduous forests.

Dry deciduous forests form the largest tract of the Deccan Plateau. The tall mountain range toward the western part of the Deccan Plateau intercepts the moisture from the southwestern monsoons assuring that the eastern slopes receive very little rainfall, resulting in totally different vegetation formations here, the dominant being dry deciduous forests. The interior districts of Andhra Pradesh, for example, contain pure tropical dry deciduous forest stands with pockets of semi-evergreen and moist deciduous forests.

The dry deciduous forests of the Deccan Plateau have a three-storied structure: an upper canopy reaching from about 50 to 100 feet (15 to 30 meters), an understory of 33 to 50 feet (10 to 15 meters), and an undergrowth of 10 to 16 feet (three to five meters). The top canopy is mostly open. Stand density varies from 200 to 350 stems per 2.4 acres (one hectare). The Tectona grandis-Pterocarpus santalinus forests may be considered a climax forest community in the region, while the Anogeissus latifolia-Terminalia alata community is most common. Some of the most characteristic tree species in the dry forests include Albizia amara, Anogeissus latifolia, Tectona grandis, Chyloroxylon swietenia, Lannea coromandelica, Lagerstroemia parvifolia, Diospyros spp., Hardwickia binata, Holarrhena pubescens, Pterocarpus santalinus, P. marsupium, Terminalia chebula, Terminalia tomentosa, and Dalbergia latifolia. The undergrowth contains a variety of these species.

The important grass types include Cymbopogon and Themeda spp. The deciduous forests of the Deccan Plateau also host a significant number of climbers and diverse liana. The most common kinds include Acacia sinuata, Combretum albidum, Cissus quadrangularis, Coccinia grandis, Tinospora cordifolia, Carissa spinarum, Ziziphus oenoplia, Capparis brevispina, Hugonia mystax, and Ipomoea staphylina.

Several of these forest species have both timber and medicinal value. The deciduous nature of vegetation helps to reduce evapotranspiration and rehydration of stems, which is useful for subsequent flushing or flowering. Leaf flushing occurs after the first rains and the onset of flowering following the cessation of rains.

Wildlife

In addition to flora, the dry deciduous forests of the Deccan Plateau support significant faunal wealth and are of some significance from a zoogeographic point of view. Among the mammals the dry forests of the region support are: the blackbuck (Antilope cervicapra), blacknaped hare (Lepus nigricollis), blue bull (Boselaphus tragocamelus), common langur (Presbytes entellus), common leopard (Panthera pardus), Indian gazelle (Gazella gazella), sambar (Cervus unicolor), sloth bear (Melursus ursinus), spotted deer (Cervus axis), tiger (Panthera tigris), and wild pig (Sus scrofa).

About 350 bird species have been recorded in the region, including endangered or rare birds like Jerdon's courser (Rhinoptilus bitorquatus) and Blewitt's owl (Athene blewitti). The tree sparrow (Passer montana) is recorded in the Vizag region of Andhra Pradesh and is unique to the area.

Threats and Protection

Deciduous forests in the region are undergoing rapid rates of degradation. The main reasons include fire, cattle grazing, and wood extraction for fuel. Indigenous peoples in several regions on the Eastern Ghats side practice slash-and-burn agriculture, locally called podu. This practice significantly affects the vegetation and, most importantly, plant succession. The immediate colonizers after podu agriculture include Acacia spp., Cleistanthes collinus, Kydia calycina, Dichrostachys cinerea, and Tarenna asiatica. Invasive species such as Eupatorium odoratum, Lantana camara, Ageratum conyzoides, and Cassia occidentalis also dominate at some of these farmed sites.

For the conservation of wildlife, as many as 27 areas in the Deccan Plateau have been demarcated as protected zones. Some of the popular national parks in the region are Nagerhole, Bandipur, Periyar, Kanha, Biligiri Rangan, and Nagarjunasagar National Parks. Although the core areas in these preserves are well protected, the buffer zones are characterized by high anthropogenic influence and resource use. Land-use conflicts are common around park areas, and more stringent policy measures are needed to conserve floral and faunal diversity in the dry deciduous forests here.

Climate change can potentially affect both the wet and dry areas of the Deccan Plateau in ways that could adversely impact each forest stand. More rain in the wet areas and longer droughts in the more arid areas each have been projected. Either scenario would impact the habitats and species distribution, leading to forced migration and new openings for invasive species.

Bibliography

Champion, H. G. and S. K. Seth. A Revised Survey of the Forest Types of India. New Delhi: Government of India Press, 1968.

Chatterjee, Nilanjan, et.al. "Population Estimate Habitat-Use and Activity Patterns of the Honey Badger in a Dry-Deciduous Forest of Central India." Frontiers in Ecology and Evolution, 23 Dec. 2020, doi.org/10.3389/fevo.2020.585256. Accessed 23 Dec. 2024.

Meher-Homji, V. M. “Tropical Dry Deciduous Forests of Peninsular India.” Feddes Repertorium 88, no. 1–2 (1977).

Singh, K. P. and C. P. Kushwaha. “Emerging Paradigms of Tree Phenology in Dry Tropics.” Current Science 89, no. 6 (2005).