350 



INTRODUCTION TO PLANT GEOGRAPHY 



[chap. 



saprophytes, and under-shrubs. Fig. 99 shows an example of this 

 type in summer, and Fig. 100 shows the selfsame area in winter. 



5. Besides the above we should mention some other Conifer- 

 dominated types such as the montane and subalpine forests of 

 western North America which, as their names imply, are due in 

 part to local physiographic factors ; also the various ' Pine-barrens ' 



Fig. 100. — The same area of ' lake-forest ' as that shown in Fig. 99, but under 

 winter conditions, with snow covering the ground. 



and other characteristic communities of eastern North America, 

 which are due in part at least to fire or other disturbance, and 

 consequently are of serai or subclimax nature. Somewhat com- 

 parable but apparently still more often edaphically engendered types 

 exist in various parts of Eurasia south of the boreal forest belt, or 

 as outliers for example in the Mediterranean region. 



Warm-Temperate Rain Forests 



In warm-temperate as in subtropical regions where rainfall is 

 plentiful and well-distributed through the year, evergreen forests 

 are developed. The total precipitation is usually between 150 and 

 300 cm. per annum and frosts are no more than occasional and slight. 

 Towards the tropics these hygrophilous {i.e. moisture-loving) forests 

 merge into the subtropical and finally the tropical types described 



