28 FORESTS AND MANKIND 



with very light seeds well adapted to travelling great distances 

 in the wind poplar, birch, and sycamore. So within a few 

 years our burned and cut area probably has become completely 

 covered with a thick growth of trees quite different from the 

 ones that the fires and axe had destroyed. Poplar seeds and 

 birch seeds, have blown in, perhaps from many miles away, 

 and the young seedlings of these species are springing up thick 

 as bristles on a brush. They are not very valuable for lumber, 

 these trees, but they serve a very useful purpose in that they 

 protect the soil against hot sun and driving rain, and each year 

 dropping their leaves they help to build up the soil and make 

 it more fertile. At this stage in the regeneration of our tract 

 we have in place of the original pine, maple and oak, a thick 

 young forest of birch and poplar and around the edges of the 

 old forest a fringe of young oak, maple and pine that have 

 sprung up from seeds cast by the neighboring trees. 



Gradually during the next twenty or fifty years, scattered by 

 one agency or another, seeds of pine and maple and beech find 

 their way throughout the area. Birds bring some. Squirrels 

 others. Streams and wind may carry still others and so the 

 seeds of the original forest trees make their way, not with any 

 regularity, but scattered here and there back into the waste 

 places. These newly-born trees are protected from drying out 

 and from being withered by the hot sun because of the protect- 

 ing shade cast by the poplar and birch. These act from now 

 on as nurse trees to the young pines and hardwoods. 



Beneath the light shade of these nurse trees the new seedlings 

 have ample light for growth and in a few years they spring 

 up about their former nurses and overshadow them. At this 

 stage we find a scattered stand of pine and maple and oak 



