SUCCESSIONS OF THE SAT TAL VALLEY. 245 



It is the task of dynamic ecology to point out the order of 

 succession by virtue of which existing formations come into being. 

 Cowles (6) and Clements (4) have done much toward the elucidation 

 of this problem on the western continent. But little has been done 

 in India. Dudgeon (7) has pointed out the probable succession in the 

 Upper Gangetic plain, beginning with pond vegetation. He feels 

 that the intense human competition prevents vegetation from reach- 

 ing the climax stage which would otherwise occur. The inquiry 

 arises what would be the order of succession of these formations at 

 Sat Tal if they were left to themselves. Here, as in the plains, the 

 human disturbance is great and increases the difficulties in the solu- 

 tion of the problem. Sat Tal valley has been protected, but not for a 

 long enough period to enable us to read the whole story. 



In the narrow altitudinal zone, 4,000 to 5,000 feet, where all 

 three formations are found, the pine and the Bauhinia seem to be 

 xerarch pioneers and the oak the climax toward which the former 

 two tend. Evidences were found in my study that the oak invades 

 the pine regions. Oak seedlings could be seen frequently along the 

 borders of the pine. On the other hand pine seedlings do not 

 thrive in the oak forest because of the continual shade. In such 

 situations could be found pines thirty years of age which do not 

 exceed 10 feet in height. In this particular altitude the oak forest 

 seems to be encroaching on the Bauhinia. When oaks become 

 established it is probable that their shade is too dense for the 

 establishment of Bauhinia seedlings, which germinate in the sunny 

 Bauhinia forest at the very beginning of the rains. In other words, 

 the oak appears to be the climatic climax in the Sat Tal valley. It 

 must be remembered, however, that the Bauhinia formation is the 

 climax one for the altitudinal zone just adjoining and below that in 

 which the oak is climax. In the zone of the Bauhinia, the oak 

 occurs as an edaphic hydrach pioneer in stream valleys, lake depres- 

 sions and shaded slopes and tends, as the contour becomes more 

 level to give way to the Bauhinia. As between the pines and 

 the Bauhinias it is probable that the latter invades the former in 

 edaphic situations favorable to Bauhinias. The pine forest is, as 

 has been stated, singularly free from other plants, not excluding 

 epiphytes and lianas. But at times one can see a pine tree overgrown 

 and weighted down by Bauhinia Vahlii. The pine, then, seems to 

 be mainly restricted to well-drained and exposed situations above the 

 altitudinal range of the Bauhinia and to situations which, although 

 within the altitudinal range of the latter, are on north exposures and 

 hence probably subject to low temperatures for periods too long to 

 permit Bauhinia to get a foothold. 



