THE EFFECT OF MAN 543 



come. Roads and lanes are cut to facilitate the care of the forest and 

 the marketing of its products. Reproduction is regulated, and in so 

 doing the species of trees are selected according to the requirements 

 of man. A natural forest is thus transformed into an artificial one. 

 For economic reasons these cultivated forests are frequently restricted 

 to a single species of tree, and uniform stands replace the original 

 mixed forest. Numerous factors have been in operation for some cen- 

 turies to favor the propagation of conifers over that of hardwoods in 

 areas subject to such control. The planting of pine, in particular, has 

 made notable advances since the middle of the past century. The cut- 

 ting of timber is simplified by cutting off specific areas completely and 

 planting them anew. The result of such plot culture is a stand uniform 

 not only as to species, but as to age as well, and areas differing widely 

 in the age of their timber may thus be juxtaposed. 



The fauna of such artificial woodland differs in important respects 

 from that of the natural forest, in consequence of the altered habitat 

 conditions. Old and injured trees, which might contain hollows, are 

 removed. Hornets and wild bees which place their nests in such hol- 

 lows are driven away; numerous birds which use hollows for shelter 

 or nesting sites are discouraged, such as the stock dove (Columba 

 oenas), the wood owlet {Strix aluco), the woodland eared owl (Asio 

 otus) , the common roller (Coracias garrulus) , and many others. The 

 marten, too, and the dormouse (Glis glis) , are robbed of their living 

 quarters. Roads and lanes create numerous interruptions and openings 

 in which grow wild berry bushes such as elderberry, dogwood, and 

 bird cherry. These openings attract a numerous population, just as 

 the natural openings, the stream courses, and the borders of a natural 

 forest harbor the greatest abundance of animal life. 



The selection of the species of trees is a primary factor in the de- 

 termination of the animal population. In Europe, virgin stands of 

 trees of a single species are practically restricted to high mountains 

 and the subpolar regions. This is not true of North America, where 

 nearly pure stands of conifers are found locally or on an extensive 

 scale in many parts of the continent and even in Central America. In 

 cultivated forests, single species of trees, especially fir and pine, are 

 frequently planted alone, because they bring the highest return, al- 

 though these stands of timber are exposed to special dangers in the 

 temperate zone. Extensive damage, such as is caused in coniferous 

 forests by the bark beetle (Bostrychus stenographies), the tussock moth 

 (Lymantria monacha) , the pine lappet moth {Dendrolimiis pini), or 

 the bordered white moth (Bupalus piniarius) , is quite unknown in 

 European hardwood forests. In cold regions, poor in insect life, and in 



