CHAP, in.] Characteristics of Trees 53 



Silver Fir, and Willow are more exacting than Larch, Hornbeam, 

 Alder, Spruce, and Aspen ; whilst Poplars, Pines, and Birch can thrive 

 fairly well on indifferent classes of soil. 



Here again it may be noted that, on the whole, the broad- 

 leaved species of trees are more exacting than the conifers. 

 As a broad generalization it may be asserted that the power of 

 any species to accommodate itself to soils and situations not 

 naturally suited to its normal requirements varies in the in- 

 verse ratio of the demands it makes as to mineral strength ; for 

 it is greatest in Scots Pine and Birch, and least in Elms, 

 Maple, Sycamore, and Ash. 



It would be wrong to state broadly that a clayey, limy, 

 sandy, or loamy soil is, or is not, suited for any given species 

 of tree; because so very much depends on other considerations, 

 and particularly on the amount of humus present in it, owing 

 to the very favourable influence which this exerts on the 

 physical properties of the soil. Gustav Heyer even went so far 

 as to maintain ' that almost any soil was capable of producing 

 any given kind of timber, provided that it contained the 

 requisite amount of moisture. 



Ney 2 thus summarizes the best practical opinions that have 

 yet been expressed on this subject : 



' As regards the chemical composition of the soil, even slightly sour 

 marshy soils are unfavourable to all species of trees except Alder, Birch, 

 and Spruce ; whilst sour soils, liable to dry up at certain seasons, are 

 unsuited to all except Birch, Spruce, Scots and Weymouth Pines. 

 Only these last-named species thrive on pure peat, and not even the 

 Spruce when it is dry. Ash, Maple, Sycamore, and Elm require 

 a moderate quantity of lime in the soil, and Beech, Hornbeam, Oak, as 

 also Larch and Austrian Pine, thrive best on soils that have at least 

 some lime in their composition. The hardwoods Oak, Ash, Maple, 

 Sycamore, Elm, Chestnut, Beech, and Hornbeam also appear to de- 

 mand the presence of a considerable quantity of potash ; whilst, on the 

 other hand, Spruce, Silver Fir, and especially Scots Pine and Birch, 

 thrive on soils rich neither in lime nor potash.' 



1 Forstliche Bodenkunde und Klimalologie, 1856, p. 488. 



2 Lehre vom Waldbau, 1885, p. 64. 



