HABIT. 



13 



irregular grain. The rate of growth often quickens as the tree pushes 

 up toward the light, ?nd the grain becomes coarser and the wood 

 lighter. Red Fir, on the other hand, or Hemlock which has enjoyed 

 light in 3^outh, shows a rapid growth near the heart and a slow growth 

 near the bark, when age has diminished the rate. 



A peculiar silvicultural problem is presented by the constant!}^ 

 diminishing density of the Red Fir overwood. Nearly all Red Fir 

 forests start on burns or open land and are very dense for the first lif ty 

 or one hundred 3'ears. The young Hemlock which starts beneath the 

 Fir during this period gets little light and grows slowly. Later, as 



fm 



•i^-^^lttinn-j|H;iHH^^tfHtl !lljUl ili l!^|^^ 



n 



ai^/ 



1 .'^'^- 



v.^-. 



Fig. 2.— Diagraiu showing diumt-ler growth of mature Red Fir and ol' Htmlock, calculated ou a basis 



of age. 



the Firs begin to crowd each other out, more light is admitted and the 

 lower storj^ of Hemlock grows more rapidly. Hence, the older the 

 overwood the faster grow the Hemlock seedlings which come in beneath 

 it. The culmination of height growth as the Hemlock approaches 

 maturity therefore differs greatl}^ from that under the usual forest 

 conditions where the supply of light remains constant. Instead of 

 falling off normally, as the trees approach maturity' the growth of 

 the Hemlock forming the lower story is constantly stimulated by the 

 diminishing density of the upper stor}- of Red Fir. (Figs. 1, 2.) 



