60 THE STUDY OF PLANT COMMUNITIES • Chapter IV 



Raunkiaer 202 used these five classes and, on the basis of more than 

 eight thousand frequency percentages, found that Class A included 

 53 percent of the species; B, 14 percent; C, 9 percent; D, 8 percent; 

 and E, 16 percent. From these data he drew his "Law of Fre- 

 quency" which states that Class A>B>C|D<E. This led 

 to numerous investigations to check on the validity and univer- 



TABLE 3. The effect on frequency of increasing size of quadrat as illus- 

 trated by data on Alpine fell-field vegetation in the Rockies. Quadrat sizes 

 in sq. m. From( 4y ). 



Arenaria sajanensis . . . 



Selaginella densa 



Trifolium dasyphyllum 

 Eritrichium argenteum . 

 Sieversia turbinata .... 

 Polemonium conjertum . 



Phlox caespitosa 



Sedum stenopetalum . . . 

 Paronychia pulvinata . . 



Silene acaulis 



Potentilla nelsoniana . . 

 Potentilla quinquefolia. 



Potentilla sp 



Polygonum bistortoides . 

 Artemisia scopulorum . 



Sieversia ciliata 



Arenaria macrantha. . . 

 Erigeron compositus . . . 



Total species 



Average frequencies . . 



1 1 10 



100 

 100 

 80 

 80 

 50 

 40 

 30 

 30 

 30 

 20 

 20 

 20 

 10 

 10 

 10 



15 



42 



i/4 



100 

 100 

 100 

 80 

 50 

 40 

 50 

 50 

 30 

 30 

 20 

 20 

 20 

 20 

 10 

 10 



16 

 45.6 



■12 



100 

 100 

 100 

 90 

 60 

 40 

 50 

 50 

 50 

 30 

 30 

 20 

 30 

 20 

 20 

 20 



16 



48.7 



i/i 



100 

 100 

 100 

 90 

 80 

 50 

 60 

 60 

 50 

 70 

 30 

 30 

 30 

 20 

 20 

 30 

 10 

 10 

 18 

 52.2 



sality of the principle of frequency distributions in plant com- 

 munities. 137 The results have been in essential agreement regardless 

 of the vegetation type. Class A will normally be very high because 

 of the numerous sporadic species to be found with low frequency 

 in most stands. Class E, and to a lesser extent D, must always bi 

 relatively high because of the species that dominate the commu- 



