Page:The Journal of Indian Botany.djvu/367

THE ECOLOGY OF THE UPPER GANGETIC PLAIN. 321 Such a climax forest as has been sketched above is purely hypothetical for the area, but all natural conditions seem to warrant the assumption that it would develop. It would be a typical deciduous monsoon forest, decidedly tropophytic, leaf- less during some portion of the hot season. It would contain few bulbous herbs, few epiphytes, abundants lianas, and would have a great abundance and variety of grasses in the more open places. The fine forests at the north side of the Upper Gangetic Plain adjacent to the Himalayas, and in the more inaccessible parts of the Vindhias to the south (Fig. 16) may be taken as a picture of this hypothetical forest.

1. The area under discussion lies in a 10 mile radius about Allahabad, and is representative of a large part of the Upper Gangetic Plain.

2. The vegetation is influenced and determined as much by biotic as by climatic factors.

3. The climatic factors, rainfall, insolation, temperature, humi- dity, and air movements, are periodic in distribution, and produce three distinct seasons :

(a) Rainy season, from the middle of June to the end of September, with high rainfull, low insolation, high tempe- rature, and high humidity. .

{b) Cold season, from the first of October to the end of Febru- ary, with low rainlall, high insolation, low temperature, and high humidity.

(c) Hot season, from the first of March to the middle of June, with low rainfall, high insolation, high temperature, low humidity, and large air movement.

4. The biotic factors are an agricultural population of about 530 er square mile, and associated domestic grazing animals of about

4?0 per square mile. Cultivation, grazing, and cutting for food and fuel have profoundly modified the original vegetation ; constantly interfere with the normal development of the vegetation ; and cause retrogression from the original climatic climax. White ants also prob- ably exert marked influence on the vegetation.