30 INDIAN FOREST MEMOIRS. 



of ' readymade ' experiments can be comparatively quickly done, and by comparing a 

 number of such cecological records it is frequently possible to find several cases in which all 

 important factors, with one exception, have varied very slightly or remained practically 

 constant and thus to directly obtain information regarding the effect of the factor which 

 varied considerably. Even when such comparisons do not at once enable a satisfactory 

 conclusion to be reached they indicate the lines on which an experiment should be organised 

 in order to give the necessary result. An idea frequently prevails that no really valuable 

 information can be obtained regarding such a factor as the quality of the soil, except by 

 detailed and skilled work such as by the chemical analysis of the soil. In the present 

 state of our knowledge of the nutrition of our principal species, however, a chemical analy- 

 sis alone can teach us practically nothing regarding its suitability for a particular species, 

 whereas careful comparative observations regarding the depth of soil, admixture of gravel, 

 sand, clay and humus, moisture content, and depth of water table can be made by anyone 

 and are as a rule, except in rare cases such as where an excess of salts is present, of primary 

 importance in deciding the suitability or otherwise of a soil for a particular species, inas- 

 much as these factors regulate the quantity of water and soluble salts and also of the 

 oxygen available for the roots. 



More or less complete data of rainfall and temperature are usually available and the 

 other most important factors constituting the environment of our forest plants are probably 

 winds, light, associated plants, grazing and fire damage regarding all of which comparative 

 observations of value are possible. 



It should also be noted that it is by no means always necessary to extend observations 

 over a wide area before satisfactory conclusions can be obtained. Experience has shown 

 that if observations are made in different carefully selected habitats good results can be 

 obtained in a limited area, e.g. of a single district or division, where the total range of 

 intensity of the various environmental factors, within which the existence of a particular 

 plant is possible, can often be found to be operative, and it must be remembered that local 

 differences in soil and situation are capable of exerting an effect on the water content of 

 the soil equivalent to that caused by the most arid or humid climate. 



While Forest Officers in India have few facilities or opportunities for carrying out and 

 recording the results of prolonged experiments, the work of carefully observing and record- 

 ing descriptions of the types of vegetation and of the environmental factors which exist in 

 the forests constantly traversed by them on tour is comparatively easy. 



Forest Officers in India have a unique opportunity of adding to cecological knowledge 

 which besides being of great scientific value will enormously increase the efficiency of forest 

 management; they have in their charge every type of both grassland and woodland, ranging 

 from the lowest type of alpine or desert grassland to the luxuriance of the evergreen tropi- 

 cal forest. 



It is hoped that Forest Officers, realising the possibilities of such work, will do their 

 utmost to systematically publish accurate descriptions and photographs of the chief types 



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