102 THE STUDY OF PLANT COMMUNITIES • Chapter V 



Asymmetric growth, matted vegetation, and sheared tops as 

 seen along the coast are likewise produced by wind to some extent, 

 but here an added factor plays a part. The wind picks up spray as 



FlG. 47. Prostrate and matted, wind-sheared trees {Firms albicaulis, Tsuga 

 mertensiana) on a leeward slope near timber line, Mt. Hood, Ore. The 

 twisted form is commonly termed Krummholz.—U . S. Forest Service. 



it comes in over the breaking waves. The spray may be carried 

 several miles inland, especially in severe storms, but its major 

 effects are most noticeable near the coast. The spray that strikes 

 any obstacle is dropped there and, of course, the salt from the 

 spray accumulates on that object. Few dune and coastal plants are 

 completely tolerant to salt spray, but, fortunately, most strong 

 winds are accompanied by rain, which minimizes the effects by 

 dilution and washing. If a severe windstorm is not accompanied 

 by or soon followed by rain, much vegetation will be injured or 

 killed by salt spray even for some distance inland. 



Those plants growing near the beach are sprayed lightly almost 

 daily and, as might be expected, show different degrees of toler- 

 ance. This results in zonation of vegetation associated with expos- 

 ure to the wind. 188 Undoubtedly salt spray is one of the strong 

 factors in determining the make-up and distribution of all plant 

 communities on coastal dunes. 270 



When trees grow on one side only, they may become so heavy 

 as to uproot themselves, but usually the eccentric growth is slow 

 enough to permit compensating anatomical changes, particularly 

 in the trunk. Secondary growth may cease completely on the 



