SYLVICULTUEE. 



of the air remains above 50%. Exception— immediate neighborliood 

 of lakes and rivers witli their sub-soil percolation. 



R. A fairly moist soil is the best for all species in tlieir 

 optimum climate. In hotter places the locality must be more 

 damp, while in colder ones it may be dry without hindering 

 grovth (White Pine in the Pink Beds in swamps, in Canada on 

 dry soil; Sitka Spruce in Washington in swamps; in Alaska on 

 dry land). 



S. Snow protects those parts of a plant which it covers; it 

 increases the danger, however, for the parts just above the snow 

 level. Snowy winters are, therefore, useful to low plants, but 

 harmful to trees (except broad-leaved trees). 



T. As regards the winds, the most dangerous are those which 

 follow the direcrtion of the barometric minima, which in Eastern 

 America travel from east- to west; in Europe from west to east; 

 in East Asia from south to north. Next dangerous are the winds 

 traveling in the opposite direction, whilst those from other points 

 of the compass are more harmless. Every mountain, however, cre- 

 ates a deflection of the current and possibly a return in the oppo- 

 site direction. 



U. In their youth trees are almost indifferent to the quality 

 of the soil; with increasing age their exigencies increase. Thus 

 plantations on poor soil may thrive well for a number of years, 

 only to-be suddenly arrested at the beginning of the pole stage. 



V. In their most suitable situation (natural optimum) a species 

 succeeds on soil of any mineral description. In a less favorable 

 climate the soil requirements .of the species increase. 



W. The light most favorable to activity of the chlorophyll is 

 not the light of the blazing sun, nor is it the diffused light coming 

 through rain or fog, but that light which is reflected by brilliant 

 white clouds. Leaf cover overhead is favorable when it filters 

 the rays of a burning sun and unfavorable when it excessively 

 reduces the intensity of insolation. Under a continental climate, 

 cloudless days are more numerous than near the coast. The influ- 

 ence of thinnings and removal cuttings on the remaining growth 

 consequently depends on the continental position of a forest — not 

 solely on species and soil. 



X. The regeneration of forests approaching exploitable age is 

 easiest in their optimum climate. If the climate is too warm, seed 

 will be more abundant, and the young plants will endure cover 

 better. The moisture of the air, however, is wanting, and the 



39 



