48 THE STUDY OF PLANT COMMUNITIES ■ Chapter III 



of data if each quadrat is subdivided into successively smaller plots 

 (e.g. : 1, /z, 54, Vs sq. m.) for which the records are kept sep- 

 arately. The data obtained from the smallest area then become a 

 part of those for the next larger area, and so on. When the number 

 of species is plotted against increase in area sampled, the usual 

 curve is formed. The information regarding numbers and sizes of 

 10m 4m 



4 



2 



a b e 



FIG. 18. Nested quadrats. (A) shows a plan used successfully for sampling 

 the several strata in forest stands. (B) and (C) show systems of dividing plots 

 of any size for accumulating data to be used in determining the desirable size 

 of plot by means of species : area curves. 



plots is then applied to sampling of similar or closely related com- 

 munities. The procedure for determination of numbers and sizes 

 of plots is well illustrated by Cain's study of sample-plot tech- 

 niques applied to alpine vegetation in Wyoming. 49 



When vegetation is stratified, a series of sample plots large 

 enough to include the trees will certainly be large enough for all 

 plants and strata. The work involved in measuring or counting the 

 lesser vegetation in such plots, however, would be unnecessarily 

 great. It, therefore, becomes advisable to sample each stratum sep- 

 arately with an appropriate size of plot for each. These plots can 

 be "nested" one within the other and the work thus materially 

 reduced. Sampling forest vegetation in the Piedmont area of North 

 Carolina has been done satisfactorily by using 10 x 10 m. plots for 

 trees, 4 x 4 m. plots for all other woody vegetation up to ten feet 

 tall, and 1 x 1 m. plots for herbs. 183 By separating the data for 

 trees into overstory and understory individuals and by recording 

 separately those woody plants less than one foot tall and those 

 from one to ten feet tall, five strata were distinguished. More 

 might be necessary or advisable under other conditions. 



