The Bioclimates of India in Relation to the Vegetational Criteria

The purpose of a climatic classification is to characterise the climatic regions in terms of meteorological elements like temperature and precipitation which are the most decisive factors in determining the landscape of the earth. The plant-climate relation is so close that it is possible to differentiate the types of climates such as equatorial, tropical, mediterranean, with their different shades such as humid, sub-humid, arid using the characters of the plant-cover. In a physical classification of the climate, an arid or a humid region is defined on the basis of annual precipitation, the number of dry days or dry months in the year or by means of several climatic formulae.In the present work emphasis is laid on the term "bioclimate". It is defined as the climate in relation to the life and is expressed by an index of aridity-humidity. This index is proposed on the basis of combining three essential ecological factors viz. temperature, precipitation and dry period. Correlations are obtained between the above index of aridity-humidity and four distinct criteria of the plant-kingdom : (1) Floristic criteria, (2) Vegetational criteria, (3) Morpho-ecological criteria and (4) Agronomic criteria.