THE ENVIRONMENT 



325 



TABLE 17.3 WIND EFFECTS ON THE ENVIRONMENT 



Soil 



Climate 



Plants 



Animals 



Deflation (rocky) 



Desiccation 



Moistening 



Desiccation 

 Moistening 

 Zonation 



Transportation 



Desiccation 



Moistening 



Zonation 



Dwarfing 



Deformation 



Breakage 



Abrasion 



Uprooting 



Burying 



Transportation 

 Desiccation 



Moistening 

 Zonation 

 Mechanical damage 



Behavioral changes 



strong prevailing winds have the maximum veloci- 

 ties. These limited sites are related to geomorphic 

 features that channel winds, causing considerable air 

 to be forced through a narrow defile. Such natural, 

 high-altitude wind tunnels may always have winds 

 above 100 m.p.h. 



Temperature and wind together contribute to a 

 factor called wind chill. This is due to the well known 

 fact that an actually higher air temperature as- 

 sociated with a strong wind can remove heat from an 

 object much faster than a lower air temperature re- 

 lated to little or no wind. Therefore, because of 

 high wind velocity in the area, the body temperature 

 of alpine organisms can be sharply reduced, with 

 lethal effects in many organisms. 



Alpine water fluctuations are largely a consequence 

 of topography. Precipitation can be extensive, but so 

 is runoff. In addition to reflecting angle of slope, 

 runoff is related to the soil, another factor of con- 

 siderable alpine importance. The soil is generally 

 thin, not having the characteristics that would tend 

 to hold water. Also, the soil is such that it is sub- 

 ject to geological mass movements. Gravity, es- 

 pecially when supplemented by the lubricating ac- 

 tion of water, causes all kinds of landslides and their 

 side effects to prevail at high altitudes. 



ALPINE PLANTS 



Although high mountain plants vary in their 

 adaptations, there is enough similarity among the 

 species for generalizations to be made about the typi- 

 cal alpine plant (Figure 17.17). Most alpine plants 

 are perennials. An examination of the structures and 



functions of well-adapted plants will show why 

 annuals are unlikely to prove successful. 



The typical alpine plant has many adaptations. 

 The aerial parts are closely set in an over-all 

 clumped cushion or tufted growth. This arrangement 

 traps daytime heat and retards interior heat loss; at 

 night interior temperatures may be 20 or more de- 

 grees higher than the outside air. The clump is 

 broad but low owing to dwarfing, which locates the 

 plant in an area of lesser wind velocity created by 

 ground friction. However, the growth form is not due 

 to inherent causes. The exposed uppermost plant 

 parts are pruned by winter wind and subfreezing 

 temperatures, and the untrimmed lower parts are 

 protected by a blanket of snow that shields against 

 the wind and prevents temperatures much below 

 freezing. In addition, the aerial parts tend not to be 

 woody, but rather to be extremely flexible, thus re- 

 ducing the possibility of wind breakage. 



Figure 17.17 An alpine adopted plant. 



