Vegetation types of peninsular India

 

Peninsular India has numerous vegetation types largely resulting from the considerable climatic, edaphic and topographic heterogeneity in the region. For instance, there exist the Western and Eastern Ghats mountain ranges abutting the coastline and encircling the Deccan Plateau, thus the elevation ranges from sea level to over 2500 m above sea level. The Western Ghats significantly alter the climatic regime within India by serving as an orographic barrier to the southwest monsoon winds, resulting in a sharp precipitation gradient in the western side of the peninsula and bringing drier conditions to the rest of the peninsula. Soils vary considerably, particularly under to the influence of topography, climate and diverse parent material types. Finally, the remarkable biogeographic history of the Indian subcontinent has resulted in plants of numerous biogeographic affinities being present in most assemblages.

A number of neo-classic vegetation type classifications (e.g. Champion and Seth 1968, Puri et al. 1983, Pascal 1986) have been attempted in the past for regions within peninsular India. Here, we follow the most recent, comprehensive classifications (Roy et al. 2015, Reddy et al. 2015) that are based on satellite data vetted by experts.

Tropical evergreen forests, characterized by tall (> 30 m), often buttressed evergreen trees, and multiple strata, are largely confined to the windward, high-rainfall zones of the Western Ghats. As the rainfall decreases, so does the ratio of evergreen-to-deciduous plants. Tropical semi-evergreen forests, characterized by a predominance (> 75%) of evergreen trees as well as climbers and epiphytes in proximity to tropical evergreen and tropical moist deciduous forests. Tropical moist deciduous forests, characterized by the dominance of deciduous species, an irregular top storey and a lower storey dominated by evergreen trees and shrubs found in large parts of peninsular India where the annual rainfall typically exceeds 1000 mm but is less than 2000 mm. Thus, they grade into tropical semi-evergreen and dry deciduous forests. Tropical dry deciduous forests, characterized by intermediate (< 20 m) open canopies consisting almost entirely of deciduous species that become leafless for 1-4 months. Grasses and so frequent fires are common in large parts of peninsular India in these drier zones. They are often dominated by teak (Tectona grandis) and sal (Shorea robusta). These drier vegetation types consisting of a tree-grass mixtures that have historically been classified as forests are now been reclassified as savannas (Ratnam et al. 2016). Tropical thorn forests, characterized by short (< 10 m) open canopies, consisting largely of thorny, leguminous (e.g. Acacia), hardwood species, sun-loving shrubs and grasses are found in the semi-arid parts of peninsular India. Tropical dry evergreen forests, characterized by the dominance (> 75%) of hard-leaved evergreen woody plants, are largely restricted to the Eastern Ghats of Andhra Pradesh and Tamil Nadu. Subtropical broad-leaved hill forests, characterized by a mixture of wet evergreen and temperate forest species, and dominated by species in the family Lauraceae are found in the lower slopes of the Western Ghats. Montane wet temperate forests (“shola”), a closed-canopied evergreen forests characterized by relatively short (< 15 m) trees, mosses, ferns, epiphytes and woody climbers are restricted to the higher (> 1500 m) elevations of the Nilgiris, Palnis, Anamalais and Tirunelveli hills in the Western Ghats. These stunted forests are found in valleys amidst rolling grasslands. Littoral and swamp forests (mangroves) consisting of halophytic evergreen plants with stilt roots and seeds that germinate while still on the parent tree, are found in river deltas along the coastal regions of peninsular India. A number of moist and dry open-canopied (< 10%) scrub vegetation types consisting largely of evergreen or deciduous shrubs are distributed throughout in the drier parts of peninsular India. Grasslands, characterized by the presence of grasses and herbs, and the near absence of trees, are found on both hilltops and plains, often close to scrub or savanna vegetation types.

REFERENCES:

  • CHAMPION, H. G. and SETH, S. K. 1968. A revised survey of the forest types of India. Govt. of India Press, New Delhi, India.
  • PASCAL, J.-P. 1986. Explanatory booklet on the forest map of South India. Sheets: Belgaum-Dharwar-Panaji, Shimoga, Mercara-Mysore. Institut Français de Pondichéry. 88 pp.
  • PURI, G. S., MEHER-HOMJI, V. M., GUPTA, R. K. and PURI, S. 1983. Forest Ecology. I - Phytogeography and forest conservation (Second). Oxford & IBH Publishing Co. Ltd., New Delhi, India.
  • RATNAM, J., TOMLINSON, K. W., RASQUINHA, D. N. and SANKARAN, M. 2016. Savannahs of Asia: antiquity, biogeography, and an uncertain future. Phil. Trans. R. Soc. B 371:20150305.
  • REDDY, C. S., JHA, C. S., DIWAKAR, P. G. and DADHWAL, V. K. 2015. Nationwide classification of forest types of India using remote sensing and GIS. Environmental Monitoring and Assessment 187:777.
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