THE PACIFIC NORTHWEST 109 



locust, is more frost-hardy but less desirable in other respects, 

 though an excellent tree nevertheless. Other fairly hardy 

 and drought-resistant trees are osage orange and Eussian mul- 

 berry. Their value for fuel and fence posts is high, but they 

 will not succeed in the most severe situations. Box elder is 

 hardy and has been widely planted, but it is of low fuel value 

 and short lived. 



In favorable localities at low altitudes, where moisture is 

 abundant either through natural precipitation or from irriga- 

 tion, the number of species which are adapted to woodlot 

 planting is largely increased. Black walnut, black cherry 

 and hardy catalpa are probably the most valuable of these 

 The latter, however, is sensitive to early and late frosts. 



Windbreaks 



The planting of windbreaks and shelter belts around dwell- 

 ings and fields is of prime importance to the settler in an 

 open country. Nothing adds more to the comfort of the 

 dweller than a belt of timber about the home to protect it 

 from the wind. Orchards need windbreaks to save them from 

 injury in a wind-swept country, and gardens are more suc- 

 cessful when surrounded by trees. One of the most important 

 functions of the windbreak, however, is the saving of soil 

 moisture within the protected area, for it is a well established 

 fact that evaporation takes place more rapidly when there is 

 a movement of the atmosphere than when it is calm. It is 

 safe to say that a windbreak is effective in preventing evapora- 

 tion for a distance equal to ten to fifteen times its height. 



Some species, because of the form of their crowns and their 

 rapid growth, are more effective for windbreaks than others. 

 Since more coniferous trees retain their foliage throughout 

 the entire year, they afford protection in winter as well as in 

 summer. Such species as western yellow, Scotch and Austrian 

 pine grow rapidly, are hardy, and serve the purpose well. In 

 regions of abundant moisture Douglas fir or Norway and 

 Sitka spruce are unequaled. European larch has also been 



