Vegetation-climate parallelism along Pondicherry - Mysore - Murkal transect, South India
Meher-Homji, V. M.
The transect extending from the east coast towards the Western Ghats presents gradual variations in rainfall amount, length of dry period, season of occurrence of rains and peak rainfall month. The tropical regime in the extreme west of the transect corresponds to a deciduous forest. The dry evergreen scrub-woodland typical of the dissymetric regime of the eastern Coromandel coast with bulk of rains in October-November and May-June dry, persists under the bixeric climate of Tiruvannamalai-Hosur with two dry periods, from December to April, and June. Further westwards the regime shows progressive transitions towards tropical type and the plant-formations also exhibit intermingling of the species of the dry evergreen and deciduous forest affinities, the proportion of the two affinities depending upon the degree of transition of the climatic regime. Soils are mainly ferruginous and the minor types being under cultivation, they do not play a decisive role in determining the vegetation patterns. Man has interfered with the original forests but the view that the dry evergreen thickets of Coromandel are derived from the degradation of the deciduous forests is not supported; these thickets seem to owe their origin to the dissymetric regime and the intermediate tract between Bangalore-Hunsur is an ecotone between the dry evergreen formation and the deciduous forest.