236 



F. H. WHITEHEAD 



6 



5 



E 

 " U 



^ 3 



X 2 



2^0 



CM 



>|,200 

 en 

 _ 160 



tl20 



>, 80 



AO 



• Inflorescence height 

 X Plant height 



(a) 





30 

 25 



^20 



"' 15 

 o 



o" 10 



A E 0-2 G OA 



HO-6 



(b) 



• No, of growth forms . . 

 xNo. of species 



A EO-2 G O'-i 



H 0-6. 



(d) 



• K as % dry weight 

 xP 



10 

 6-2 



■ o 



A E 0-2 G O-A H 0'6 A E 0-2 G 0-U 



Values of Zo in relation to areas A-H 



HO-6 



Fig. I. Relationship of average wind speed (Zo) on mountain top to 

 (a) heights of inflorescences and plants (b) annual yield of dry matter 

 (c) number of growth forms and species and (d) uptake of potassium 

 and phosphorus. 



growth form is found in area A and these progressively increase until in 

 the most sheltered area H the largest number of species and the greatest 

 diversity of growth form is found. 



These data show a relationship between the degree of shelter and the 

 characteristics of the communities. If this relationship were causal then 

 alteration to the degree of shelter in a given area should result in changes 

 in the community characteristics. This simple experiment was carried out 

 in the field by erecting low stone walls around mapped and recorded 

 quadrats in the most exposed areas. After a period of time changes did 

 occur in the vegetation of the kind which had been predicted and are 



