476 REARING OF THE ESTABLISHED CROP. 



tiuctly lower level than all the other trees, the selection of the 

 stems to remove offers little or no difficulty. Such is abo the case 

 even when all the crowns form one compact mass together, pro- 

 vided the component species are shade-enduring, for then any 

 slight mistakes that may be made would not be of much conse- 

 quence, since they would correct themselves before any evil results 

 could follow. In any case the experienced forester will never find 

 any difficulty in recognizing the vigorous and growing elements 

 of a crop, which are after all the main thing to keep in sight in 

 making a thinning. 



(h) Composition of the crop. From what has been said in res- 

 pect of Advantages II, VII, VIII and X resulting from a mixture 

 of species (pp. 108-113), it is evident that, cceteris paribus, thin- 

 nings should be heavier in mixed than in pure forest. 



(') Exposure of locality to dangerous winds. In places exposed 

 to winds that are dangerous only on account of their violence, the 

 crop should be formed of strong, well-rooted trees capable of offer- 

 ing the necessary resistance. To obtain such trees quickly, mode- 

 rate thinnings should be made and these should be begun early 

 and repeated at short intervals. In the case of very hot winds, 

 which dry up the soil and blow away the covering of dead leaves, 

 the undergrowth in the protective fringe maintained along the ex- 

 posed edge of the forest can never be too thick, and hence thin- 

 nings should there be carefully -avoided. To obtain further pro- 

 tection unthiuned bands of forest, running at right angles to the 

 wind, should be left at regular intervals throughout the entire 

 area. Against very cold winds also the undergrowth should be 

 preserved along the wind-struck edge of the forest. 



(j) The length and fulness of bole desired. Thinnings, up to 

 the close of the stage of rapid elongation, will be light in propor- 

 tion to the length of bole required and its approximation to a 

 cylindrical shape. 



Stated briefly, the seventy of a thinning in any given case will 

 vary with (a) the rapidity with which the leaf-canopy can close up 

 again, which rapidity depends on the age and origin of the crop, 

 on the nature of the component species and their proportionate 

 distribution if mixed together, and on the suitability of the soil, 

 locality and climate ; (//) the ability of the soil to take care of 

 itself ; (c) the stability of the trees ; (d) the length, fulness and clean- 

 ness of bole demanded ; and (<?) the age fixed for the exploitation of 

 the crop. A safe rule to follow in making any thinning is to remove 

 every stem that may be taken out consistently with keeping the 



