A History of Agriculture in India v1.c10.s2: 2. The Tropical Thorn Forests
A History of Agriculture in India v1.c10.s2
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2. The Tropical Thorn Forests
v1.c10.s2.1
These forests are characterized by a xerophytic flora of low and open formations, with many species adapted to xerophytic conditions. Thorny trees and plants are very common. Forests of this type are distributed over the Indus Plain region in southern Punjab, Haryana, Gujarat, Rajasthan, the Upper Gangetic Plains and in the Deccan Plateau.
v1.c10.s2.2
The Indus Plain Region. This region includes the Punjab, Haryana, Gujarat and Rajasthan to the west of the Aravalli Hills. With a few exceptions, all trees in this region are deciduous, and most of the herbs are desiccated and burnt in the hot season. The vegetation of this region is typically xerophytic. The principal indigenous trees are: *Tamarix aphylla* (*T. articulata*), *Sterculia urens*, *Grewia damine* (*G. salicifolia*), *Aegle marmelos*, *Moringa oleifera*, *Dalbergia sissoo*, *Butea monosperma*, *Prosopis cineraria* (*P. spicigera*), *Acacia nilotica* (*A. arabica*), *Salvadora persica*, *S. oleoides*, *Anogeissus pendula*, *Cordia dichotoma* (*C. myxa*), *Terminalia alata* (*T. tomentosa*), *Tecomella undulata*, *Ficus lacor* (*F. infectoria*) and *Morus indica*.
v1.c10.s2.3
Among the shrubs, the most conspicuous are the isolated clumps of the columnar, almost leafless *Euphorbia royleana* and *E. neriifolia*. Of special interest in this region are two species of cotton, *Gossypium stocksii* and *G. herbaceum* (*G. wightianum*). The other more or less prevalent shrubs and undershrubs in certain districts are: *Capparis decidua* (*C. aphylla*), *C. zeylanica* (*C. horrida*), *C. spinosa*, *Flacourtia ramontchi*, *Tamarix dioica*, *T. troupii* (*T. gallica*), *Grewia* sp., *Fagonia cretica* (*F. arabica*), *Rhamnus pentapomica* (*R. persica*), *R. virgata*, *Ziziphus nummularia*, *Z. jujuba* (*Z. vulgaris*), *Z. oenoplia*, *Dodonaea viscosa*, *Alhagi pseudalhagi* (*A. maurorum*), *Edwardsia mollis* (*Sophora mollis*), *Cassia auriculata*, *C. tora*, *C. obtusa* (*C. obovata*), *Mimosa rubicaulis*, *Pluchea lanceolata*, *Reptonia buxifolia*, *Carissa spinarum* (*C. diffusa*), *Rhazya stricta*, *Nerium indicum* (*N. odorum*), *Orthanthera viminea*, *Periploca aphylla*, *Calotropis procera*, *C. gigantea*, *Withania coagulans*, *Adhatoda vasica*, *Calligonum polygonoides*, *Pteropyrum oliveri*, *Salsola baryosma* (*S. foetida*) and species of *Kochia*. The fleshy *Suaeda* and *Salsola* grow on saline soils and *Calligonum polygonoides* on sandy soils.
v1.c10.s2.4
In the Thar Desert, the fleshy *Euphorbia neriifolia* is the most characteristic species. It is poisonous and is not eaten by cattle. This explains its widespread occurrence. Trees are also indicators of soil types to a large extent. *Salvadora persica* and *Prosopis cineraria* (*P. spicigera*) grow on loam.
v1.c10.s2.5
*Tamarix aphylla* (*T. articulata*) grows on saline soil, and, in areas where it grows, wells too have saline and bitter water. *Butea monosperma* grows on *usar* and *reh* lands impregnated with calcium bicarbonates on which no other trees can thrive.
v1.c10.s2.6
The trees found in the xerophytic forests of Rajasthan are those with reduced leaf surface or with fleshy leaves. Various species of *Acacia* and *Prosopis*, the commonest being *Acacia nilotica* (*A. arabica*) and *A. leucophloea*, are associated with *Prosopis cineraria* (*P. spicigera*) and the exotic *P. chilensis* (*P. juliflora*). *Acacia catechu* is found in considerable numbers in Kutch. In the southern Aravallis, *Anogeissus pendula* occurs in fairly homogeneous patches. Other typical species are *Salvadora oleoides*, *Tamarix aphylla* (*T. articulata*), *Ziziphus mauritiana* (*Z. jujuba*), *Grewia tenax* (*G. populifolia*) and *Ehretia laevis*. The undergrowth consists of *Capparis decidua* (*C. aphylla*), *C. spinosa*, *Asclepias* and *Calotropis*, with the fleshy *Suaeda* and *Salsola* growing on saline soils, and *Calligonum polygonoides* on sandy soils. *Euphorbia nivulia*, with a thorny stem, is also very characteristic at the foot of dry mountains.