340 RESEARCH METHODS 



stock and tending toward a replacement of the undesirable 

 (nonpalatable and poisonous) plants by palatable, nutritious, 

 and heavy-yielding species, preferably perennials. 



Only reliable information can be helpful in the develop- 

 ment of a rational grazing plan that is to bring about a maximum 

 forage yield, with a minimum of disturbance and loss in the 

 forage use during the revegetational period. This presupposes 

 a detailed knowledge of the successional stages in the develop- 

 ment of the vegetation. To obtain such reliable data requires 

 the use of various forms of sample plots so located over the 

 pasture area studied and in such relation to forage types, soils, 

 and topographic features as to show the developmental trend 

 of the vegetation as a whole. 



The author feels that a brief summary of his fifteen years of 

 intensive study of the use of sample plots and their establish- 

 ment, of the various ways of mapping the cover, and of methods 

 of summarizing the data with a view to interpreting the results 

 correctly, may be of value to the junior investigator. 



Permanent Sample Plots. — To be of real value sample plots 

 must be so established that future mappings will show clearly 

 what changes have taken place in the plant cover, and hence 

 how much the pasture has increased or decreased in grazing 

 capacity. For such a study the sample plots must be reason- 

 ably permanent. Permanency of plots presupposes two con- 

 ditions: (i) The locating and marking of the plots in such a 

 manner that fires, grazing, and other ordinary destructive 

 factors will not hamper the re-location of the area; and (2) the 

 mapping of the vegetation and the summarizing of the map 

 data in such a way that comparisons may readily be made, 

 and in such detail that satisfactory future relationships may be 

 insured. Permanent sample plots should be available for study 

 by trained investigators at any time during a period of years, 

 possibly a century or more. 



Kinds of Plots and Their Establishment. — Sample plots 

 may be of various sizes and shapes; for intensive studies a few 

 square feet (or, indeed, a meter) may suffice, whereas for the 

 more general work many acres may be used. In shape they may 



