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CHAPTER IV

ON THE CHARACTER AND DISTRIBUTION OF THE FORESTS

T

HE distribution of the tree growth and of the chief types of forest in India, as also the size of the individual trees, varies in direct proportion to the amount of rainfall experienced in the different parts of the country. Rainfall is not, however, the sole factor regulating this distribution and change in type. Elevation also produces marked changes. In a country where every variety of climate exists, from the sub-Arctic or Alpine to the Tropic, sharp changes will of necessity make their appearance in different regions. Aspect also has a considerable influence on the character of the forests, accompanied, as it may be, by either sharp frosts or scorching winds. The overflow of the large rivers and percolation are responsible for a considerable variety in the type of the forest present in large tracts of the country. In areas where the rainfall is scanty, or almost wanting, as in the deserts of Rajputana, for instance, tree growth is absent, whilst in other regions the character of the forests is decided by their position on the seaboard or in the deltas of the great rivers, where the mangrove forests reign supreme.

Before proceeding to a consideration of the history of the forests it becomes necessary to give some brief description of the great differences in the main types of forest growth in the country. The following brief exposition is based on Ribbentrop's treatment of the subject in his Forestry in British India (1900). This treatment follows the lines adopted by Brandis in a paper read before the Geographical Section of the British Association at Brighton in 1872. The meteorological maps were, however, more accurate in 1900 than in 1872. Therefore Ribbentrop's subdivisions of the "zones" of forest growth are more detailed.

Gamble's Manual of Indian Timbers and Brandis' Indian Trees have also been consulted and made use of.1

1 This chapter was written before the publication of Professor R. S. Troup's Sylviculture of Indian Trees (1921). Professor Troup divides the

India may be divided into four climatic zones which exert a marked influence in the distribution of the forest types.

(1) The Dry Zone. An average rainfall of from 15 to 30 inches. This zone comprises the large oval plateau-like tract in which the Godaveri, Kistna and Cauvery have their sources. It extends from Nasik in the Bombay Presidency southeastwards to below Bangalore, with an average breadth of 200 to 250 miles.

(2) The Intermediate Zone. An average rainfall of between 30 to 50 inches. This consists of a narrow strip situated to the west of the dry zone, but includes the whole of the tracts to the north, north-east and east of the latter as far as the Bay of Bengal.

(3) The Moist Zone. An average rainfall of 50 to 75 inches. This forms a narrow belt to the west of the intermediate zone along the eastern slopes of the Western Ghats, and embracing also the seaboard of the southern portion of the Gulf of Cambay and the northern part of Travancore.

(4) The Wet Zone. An average rainfall of over 75 inches. This zone includes the remaining portion of the Gháts lying to the westward, consisting of the western slopes with which the moisture-laden south-west monsoon currents first come into contact on their passage north-eastwards.

Curiously enough differences in latitude-the Indian Empire extends from the eighth to the thirty-fifth degree northern latitude-exert comparatively small changes in the forest flora. There are no such abrupt changes as exist in Europe, where the Alps sharply divide the northern and southern forest floras. A study of the India flora discloses the fact that certain species are characteristic of the southern part of the country, as, for example, the teak and Xylia dolabriformis, whereas others are representative of the north; but there are many others which occur throughout the length and breadth of the Empire. That no sharp changes or marked contrasts exist in the flora is attributable to the fact, which is equally true of the fauna, that the great Indian continent is completely isolated on the north by the great wall of the Himalaya and surrounded on the other sides by the sea.

types of forest in India and Burma, including the Andamans, into twelve regions, viz.: the W. Himalayan, the E. Himalayan, the Trans-Indus, the N.-W. dry region, the Gangetic Plain, the West Coast region, the Central Indian, the Deccan and Carnatic, Assam, Chittagong and Arakan, Burma, the Andamans.

From the forester's point of view India may be divided into seven zones, containing fairly distinct forest types of growth.

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Exceptions occur within these zones in which, owing to soil characteristics, forests of a different nature to the zone type exist or in which the areas may be treeless.

A. THE EVERGREEN FOREST ZONE

The Evergreen Zone may be subdivided into four distinct geographical regions: (1) The West Coast Region. (2) The Burma and Chittagong Region (including the Andamans). (3) The Carnatic Region, and (4) The Sub or Outer Himalayan Region. The growth in the Carnatic Region is influenced by the north-east monsoon, that of the other three by the southwest monsoon.

(1) The West Coast Region. This region covers the coast districts of the Konkan, Canara, Malabar, and Travancore, and extends over the western scarps of the mountainous ranges behind them in the Mahratta country, Coorg, the Nilgiris, Anaimalais, Cochin, and the Travancore Hills. The trees occupying the forests of this region mainly belong to the families Anonacea, Guttiferæ, Dipterocarpeæ, Anacardiacea, Myrtacea, Rubiacea, Lauracea and Euphorbiacea.

In parts of this region dry areas exist with a growth not unlike that of the deciduous forests of Central India and with a good deal of teak. The greater part, however, consists of hill forests, the lower hill slopes being covered with evergreen forest growth of large trees such as Dalbergia latifolia, Xylia, Artocarpus, Pterocarpus, Lagerstroemia, Terminalia, Vateria, Canarium, Cullenia, Polyalthia, Mesua.

Higher up, and especially in the hill ranges of the Nilgiris, Anaimalais, Pulneys and Travancore mountains, these ever

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green forests merge into what are known as the sholas," the principal vegetation consisting of Eugenia, Michelia, Ilex, Hydnocarpus, Elæocarpus, Ternstroemia, Gordonia, Symplocos, rhododendrons and laurels, with an undergrowth of Strobilanthes and tree ferns, etc. In this region teak is the chief tree of export, followed by blackwood (Dalbergia latifolia). In the hill ranges plantations of exotic trees have been formed, chiefly of Australian Eucalyptus and Acacia, but also of various pines, cypress, etc., all of local importance for the provision of fuel. In the coast tract the Talipat palm is conspicuous, and in the Ghát Region are found Bentinckia and Arenga Wightii, with many canes and bamboos, such as Teinostachyum Wightii, Oxytenanthera Thwaitesii, and species of Ochlandra and Arundinaria Wightiana on the higher hills.

(2) The Burmese Region. This region covers the coast and the western mountain slopes of the Mergui, Tavoy, Amherst, Kyaukpyu and Arakan districts, broadening and contracting according to the formation of the mountain chains, and spreading into favourably situated moist side-valleys of the Tenasserim, Salween, Sittang, Irrawady and Attaran rivers. The region extends into Bengal, and occupies considerable areas in the coast districts of Chittagong.

The variety of trees in these forests is very great, and the constituents of the forests vary considerably even in contiguous tracts. The height of the trees forming the upper canopy ranges from 150 to 200 feet, the tallest being such species as Dipterocarpus turbinatus and alatus; Sterculia spicigera, fætida and campanulata; Tetrameles nudiflora, Parkia leiophylla, Acrocarpus fraxinifolius, Albizzia Lebbek and stipulata ; Xylia dolabriformis, and a few other species.

The above are leaf-shedding trees, which tower above the mass of evergreens. Of less lofty trees the variety is considerable, and include such species as Mesua ferrea, Mitrephora vandaflora, Bursera serrata, Kurrimia robusta, Stereospermum fimbriatum, Vitex peduncularis, Adenanthera pavonina, Cedrela Toona, Lagerstroemia calyculata, villosa and tomentosa; Mangifera indica, Trewia nudiflora; these species being associated with a large number of others. Of those which form a lower story under the shade of the loftier trees, a few may be mentioned, such as Pterospermum, Garcinia, Xanthochymus, Cinnamomum, Tetranthera, etc.

As a rule, tropical evergreen forests which grow on metamorphic rocks are richest in species, while those occurring on

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MELOCANNA BAMBUSIOIDES, 6 YEARS OLD. KASSALONG RIVER, CHITTAGONG

HILL. TRACTS

R. S. Pearson, "Indian Forester," Vol. XLVI

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