(Last Updated on : 21/10/2013)
The Deccan Thorn scrub forests in India are located in the arid parts of the Deccan Plateau. The region is spread across the Indian states of Tamil Nadu, Andhra Pradesh, Karnataka and Maharashtra and part of northern Sri Lanka is also included in this region. These forests harbour the last populations of the globally threatened Jerdon's Courser, which was rediscovered recently, almost after eighty-six years, since it was last recorded in 1900. However, apart from this, the region is neither exceptionally species-rich nor high in endemism and many ecologists believe that, the thorn scrub vegetation actually represents a degraded stage of the tropical dry forests.
The annual rainfall in the Deccan Thorn scrub forests in India does not cross 750 millimetres. The region receives all the rainfall during the brief wet season and it receives no rainfall during the months of November to April. The ambient temperatures in these forests can exceed a sweltering 40oC during the hotter months of the year. Though, the forests are mostly of southern tropical thorn scrub type, they also include patches of tropical dry deciduous forests, which are believed to be the original vegetation. The southern tropical thorn scrub type forests consist of open, low vegetation that is characterised by thorny trees with short trunks and low, branching crowns that rarely meet to form a closed canopy. In this vegetation, the trees attain maximum heights of 6-9 meters.
The second story of the Deccan Thorn scrub forests in India is poorly developed and mainly consists spiny and xerophytic species, mostly shrubs. An ill-defined lower story can also be discerned, during the brief wet season. The plant species that dominate the vegetation in these forests is the Acacia species, including Balanites roxburghii, Cordia myxa, Capparis spp., Prosopis spp., Azadirachta indica, Cassia fistula, Diospyros chloroxylon, Carrisa carandas, and Phoenix sylvestris, etc. There are also several other habitat types found in these forests. In some areas that receive particularly low rainfall and have rocky soils, the thorn scrub transitions into a Euphorbia-dominated scrub. The soil is usually bare in these areas; however, some grassy growth may also appear during the short monsoon season.
The parts of the Deccan Thorn scrub forests in India that are located in Tamil Nadu receive less rainfall and the vegetation in these parts is mainly made up of open thorny forests with scattered Acacia planifrons, which are characterised by umbrella-shaped crowns. The patches of dry grasslands providing habitat for the native fauna also remain scattered amid the thorn scrub. The grasslands of southern Andhra Pradesh support a good population of the Indian Bustard and Blackbuck. The typical grasses in this habitat include the species like Chrysopogon fulvus, Heteropogon contortus, Eremopogon foveolatus, Aristida setacea, and Dactyloctenium spp., etc. The forests are also home to a large number of medicinal plants and various other species of botanical interest. Some of the important among these include the rare endemic cycad and Psilotum nudum. A small patch of the tree, Shorea talura also exists within the Chittoor forest division, part of which is being maintained as a preservation plot by the Forest Department of Andhra Pradesh.
The Srilankamalleswara Sanctuary is situated within the Deccan Thorn scrub forests in India, between the Nallamalais and Sechachalam hill ranges. This sanctuary is well known for a rare, endemic tree species, named the Red Sanders. This area is also the southern distributional limit of the Nilgai in the Indian Peninsula. The forests used to provide habitat to the important mammal species like Tiger and Asian Elephant, until recent past. However, their populations have dwindled and even become locally extinct, over the years. The forests are home to a total of ninety-six mammal fauna species, out of which, three are considered as endemics. These species are Hipposideros schistaceus, Millardia kondana, and Cremnomys elvira, etc. Some of the other threatened mammal species found in these forests include the Tiger, Gaur, Wild Dog, Sloth Bear, Chousingha, and Blackbuck.
The Deccan Thorn scrub forests in India are home to a richer variety of bird species, consisting almost 350 species. Among these species, three are considered as near-endemic. These species are the Jerdon's Courser, Ceylon Jungle Fowl, and Yellow-fronted barbet, etc. Among these, the Jerdon's Courser is also considered as globally threatened species that was rediscovered in this ecoregion in 1986, after being recorded for the last time, in 1900. Apart from the near-endemic species, the globally threatened bird species like Lesser Florican and Indian Bustard can also be found in the Deccan Thorn scrub forests in India.