HABITS OF GROWTH. 



39 



this is not the least of the advantages promised by growing 

 conifer crops suitable for any given soil and situation. 



The following may serve as rough averages as to the rotation in which 

 timber-crops can usually be most profitably worked in Britain : 



But a wood that has been heavily thinned will mature (financially) 

 sooner than one kept in close cover ; and if not then cleared, both the 

 crop and the soil will deteriorate. 



General Characteristics or Habits of Growth as Woodlands 

 Crops arise from the combined influence of the above special 

 characteristics when large masses of trees are collected together, 

 for each kind of tree then assumes a definite relation towards 

 itself and towards other trees, and becomes either gregarious 

 or sporadic in habit. Gregarious trees tend to predominate 

 throughout the whole woodlands, and to form pure woods un- 

 mixed with other trees ; while sporadic trees are more or less 

 scattered and subordinate in number, and thrive best when 

 scattered throughout mixed woods, either as single stems or 

 in small patches (e.g., the Larch, in the Alps), and are de- 

 pendent on the gregarious trees for maintaining the productivity 

 of the soil. Other things being equal, shade-enduring trees 

 would gradually, in course of time, oust light-demanding trees, 

 and become ruling species over large areas, as where the Silver 

 Fir, the Beech, and the Spruce form large and more or less 



