462 



Succession and Fluctuation 



1850 1860 1870 1880 1890 1900 1910 



Fig. 12.15. Fluctuating series of animal populations and tree growth compared 

 with series of random numbers. In the 2-point moving sum curve the height of 

 each point depends upon the values of two successive random numbers, much as 

 population size might be affected not only by conditions this year but also by the 

 size of last year's population. (Cole, 1951.) 



i 



