Karnataka State has a rich and varied vegetation resulting from several lines of plant migration conditioned by climate, soil and topography. Biotic factors have in many areas modified the original climaxes evolved through the centuries. Considering topography, bio-climate and soil, the vegetation of Karnataka could be grouped under the following four categories viz, 1) Littoral vegetation, 2) West coast tropical vegetation. 3) Upland deciduous vegetation and 4) Southern tropical montane vegetation. Littoral vegetation : There are two types of littoral vegetation in Karnataka. The first is terrestrial on the sand dunes and the second, halophytic along estuaries. The limitations imposed by the scorching sun, shifting sands and salt-laden winds are overcome by special plants called psammophytes. The dunes above the tide mark are held down by a number of sand binders. Sundews and bladder worts often form a seasonal carpet on the wet sands of the rear beach.
Limited mangrove formations occur in the riverine estuaries where the salinity gradient rises rapidly towards the sea. The best examples of halophytic vegetation are near Kundapur and Gokarna. It is mostly of the Rhizophora – Avicenia – Bruguiera type. The trees and shrubs have to overcome the restrictions of a marshy saline habitat with strong tidal currents and fluctuations in water level as well as the asphyxiating conditions of a slushy soil. These littoral plant formations have ecological role in the balance of nature. The psammophytes help in preventing the sand of the beaches from being blown landwards on to agricultural lands and human habitations. They also protect the beaches for their recreational value. Mangroves stabilise the river embankments against erosion. They afford breeding ground to several fishes and other marine animals.
Moist Deciduous Coastal Vegetation: The natural vegetation in this region immediately to the east of the coastline is of the secondary moist deciduous type. It is sometimes considered a degraded stage of an evergreen climax. In the broader coastal low land of Dakshina Kannada, the Hopea – Syzygium- Holigama series is usually found with dense understorey of shrubs like Grewia, Ixora and Psychotria. Lianas especially Hugonia mystax and Uvaria riorum are frequent. The secondary moist deciduous forests are better preserved towards the foothill of the Ghats. The biotic factor which is high in the vicinity of the Coastal urban centres is less towards the Ghats.
West Coast Tropical Evergreens: The lower slopes and valleys of the Ghats present fine examples of the West Coast tropical evergreen forests. These close canopy forests are nurtured by the heavy seasonal precipitation to form a climax vegetation. Erect buttressed trunks, unbranched for 20 or more metres fan out to meet the contiguous tree tops. There are several variations in the dominant canopy trees. The commonest association is of EUpterocarpus ~ Kingiodendron-Vataria between 70 to 600 metres above mean sea level. There are several other plant forms in these forests. The biological diversity and its
spatial distribution within the forest apportions solar energy as effectively in the conversion of water and carbon-di-oxide into life sustaining organic compounds.Upland moist Deciduous Vegetation: The decreasing rainfall on the leeward side of the mountain gives rise to another climax type – the upland moist deciduous vegetation. While in leaf, the canopy of these forests is dense, during the dry months there is a short period of leaf fall to avoid loss of water due to transpiration. Flowering of the trees occurs during the leafless period. This moist deciduous belt running from Belgaum to Kodagu is the habitat of the Tectona – Dillenia – Lagerstroemia – Terrrtinalia series which include teak, matti, kanagalu, nondi, which are local names. Extensive areas on the eastern fringe of the Ghats were once covered with clumps of bamboos. Upland dry deciduous vegetation : The bio climate of the eastern part of the Maidan permits a climax dry deciduous vegetation in several protected areas. The canopy is open and the trees leafless during the driest months.
Flowering and fruiting are generally far advanced before the first flush of new leaves appears with the conventional showers in April-May.
Upland thorn and scrub : There are several parts of Chitradurga, Davanagere, Bellary, Raichur, Koppal, Gulbarga and Bidar districts where broad leaved deciduous forests give place to armed trees with tiny leaflets. Some remaining patches of these forests are made-up of Acacia, Albizia and Hardwickia. (Jali, Bilwara, ennemara being local names). The Maidan is dotted with numerous irrigation tanks usually supporting an interesting aquatic Jlora, Southern Tropical Montane Vegetation: An altitudinal variation of the tropical evergreens, is found above 1,500 metres especially at Kudremukh, and in the Bababudan and Biligirirangan Hills. This vegetation of grassy meadows and low wooded patches forms the Southern Tropical Montane Vegetation. The grassy mountain meadows present a quick succession of herbs that appear in short lived profusion. A good part of the wet forests has been greatly altered by biotic factors. The vegetation dynamics in Karnataka indicate several changes in the natural vegetation due to biotic factors especially human intervention. Inhabited coastal areas present a thick canopy of coconut trees. The climax formations of dry types of vegetation with a distinct canopy, an understorey of shrubs and a ground cover of herbs are confined to a few inaccessible pockets or to areas of reserved forests. Felling for fuel and grazing especially by goats threatened even these remnants of the original plant cover. The forest unless covered is slowly converted into grasslands with scattered trees. In some areas forests have been cleared and low lying areas are converted into paddy fields while the hilly terrain is often planted with plantation crops.