68 



THE NEW FORESTRY. 



must always exert a sensible effect on vegetation in the aggre- 

 gate, even though the difference may not exceed one or two 

 degrees. But high or low, north or south, exposure to cold 

 winds, or even persistent winds not necessarily keen, always 

 • exert an injurious effect upon forest trees, inasmuch as they 

 check or repress growth to a greater extent than all other 

 causes put together. This is seen in any wood on the side 

 exposed to prevailing winds, where, by repressed growth alone, 

 the trees are often not half as large as the trees in the middle 

 of the wood or on the sheltered side. It is seen in a marked 

 manner in young plantations before the trees meet and cover 

 the ground and shelter each other, when a sensible increase 

 in the rate of height-growth is always observable ; and also in 

 over-thinned plantations where the wind reaches every tree indi- 

 vidually. German foresters are well aware of the ill effects of 

 cold winds and take every precaution against them. These 

 precautions consist in selecting the most sheltered situations 

 for the tenderest species, and on exposed situations in planting 

 the margins thickly — in planting thickly generally and 

 thinning sparingly. 



The following table, contributed by the writer to the 

 " Transactions of the Royal Horticultural Society," in 1895, 

 bears on this point, and shows to what an extent the weight 

 and value of a crop of timber may be affected by exposure to 

 winds alone. All the trees grow under the same conditions, 

 except that on one side the plantation is exposed to. severe 

 west and north-west gales about seven hundred feet above 

 sea-level. 



TABLE showing the effects of Exposure and Shelter on the 



growth of Forest Trees in Mill-Moor Plantation Belt 



on the Wortley Estate. 



