HOLE : SOME INDIAN GRASSES AND THEIR (ECOLOGY. 15 



localities and for certain species, methods of treatment which result in the more or less 

 complete removal of the vegetative covering are unsuitable, while a method of treatment 

 like the Selection System under which the exposure of the soil is reduced to a minimum is 

 the most successful. 



A point, also, which is frequently not appreciated is that, by making clearings in the 

 middle of woodland, conditions are often created which are quite unsuitable for the healthy 

 development of the species composing the surrounding woodland and which are caused by 

 the absence of free air-circulation. 



The grassy plains, so common in the Sal forests of India, frequently illustrate this 

 point. These areas are usually clearings which were originally made in the forest for 

 cultivation and then abandoned. Owing to the absence of air-circulation caused by the 

 surrounding forest belt, such areas are intensely heated by the sun in the day and hot season 

 and cooled by radiation at night and in the cold season. In dry localities this action is 

 intensified and in such places the stool shoots, springing from any stumps of the felled 

 trees which happen to have been left in the ground and to have survived, are annually cut 

 back by frost, while the absence of humus and dryness of the soil prevent the establish- 

 ment of new seedlings. The natural re-establishment of the mesophilous Sal forest is 

 therefore rendered impossible, except very slowly in the narrow belt immediately adjoining 

 the forest. The Forest Officer who wishes to quickly afforest such areas, therefore, will be 

 most successful if he recognises the fact that a regressive change has taken place, that a 

 habitat which recently supported mesophilous vegetation has now become strongly xerophy- 

 tic and that xerophilous and frost-hardy species like Acacia Catechu should accordingly 

 be introduced. 



Coppice fellings in the middle of forest growth may similarly cause a regressive 

 succession. 



Finally there is a type of succession which we may distinguish as parallel succession, parallel 



Succession. 



Types of both grassland and woodland are found in all kinds of habitats, ranging from 

 the most xerophytic to the most hygrophytic, and it is of great importance for the Forest. 

 Officer to realise that, for each type of grassland, there is, as a rule, a corresponding type 

 of woodland capable of thriving under similar conditions of the environment, seeing that 

 this has a direct bearing on the question of afforesting grasslands. When a type of grass- 

 land, such as Munj savannah, is replaced by a parallel type of woodland, e.g. dry miscel- 

 laneous forest of A cacia Catechu, Dalbergia Sissoo and others, we may therefore regard it 

 as a case of parallel succession to distinguish it from the progressive and regressive changes 

 considered above. 



Parallel changes can be frequently effected more easily and rapidly than progressive 

 changes and with reference to such questions as the afforestation of grasslands and the 

 extension of woodlands parallel changes are probably as a rule of more practical import- 

 ance. 



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