CLIMATE. 33 



(4) Soil- temperature depends greatly on the quantity of moisture and 

 the colour of the soil. Clay soil is cold and inactive ; but once heated, it 

 cools gradually. Sand or gravel is easily warmed, but cools rapidly, and 

 in damp localities this increases the danger from frost. 



Climate or the Influence of Situation affects tree -growth 

 in a very marked degree, though the several factors (1) 

 temperature and humidity in atmosphere and in soil, (2) amount 

 and intensity of sunlight, (3) aspect or exposure towards N., E., 

 S., or W., (4) slope or gradient of hillsides, and (5) shelter from 

 strong winds, due to the local configuration of the land and the 

 surrounding country all act and react on each other, and also 

 in conjunction with the physical properties of the soil, in such 

 a way as often to obscure the causes why any particular kind of 

 tree may perhaps not thrive in any given situation. 



The Sylvicultural Characteristics of Trees are (I.) their 

 special peculiarities regarding climate, soil, and situation ; light 

 and shade ; shape of root- system, stem, and crown ; rate of 

 growth ; reproductive and regenerative power ; and maturity 

 and longevity ; and (II.) their general characteristics as wood- 

 land crops, in consequence of these special peculiarities. 



(1) As regards climate or temperature and rainfall, each kind 

 of tree has a northern and a southern limit determined by 

 winter cold and summer heat or drought, and also a limit of 

 altitude in mountain-tracts determined by cold. But owing to 

 geographical conditions and local configuration, there are no 

 hard-and-fast lines of demarcation throughout Western Europe 

 in either of these respects. Our mild equable climate is well 

 suited for all the Central European trees, and many North 

 American trees also thrive well here. Nor are there any well- 

 marked zones of elevation, as shelter from strong winds is a 

 very important factor in this respect. But of our common 

 woodland trees, experience shows that Birch, Scots Elm, and 

 Scots Pine grow better in Scotland than in the South of 

 England ; that Beech, English Elm. Pedunculate Oak, Chestnut, 



c 



