LIST PLOT 347 



It is pointed out by the designer that the instrument needs 

 some refinement, and that its further use will doubtless suggest 

 certain minor improvements. 



List Plot. — This form of plot is used by most ecologists merely 

 to procure a systematic record of the species which occur within 

 a given plant unit. Such a record in itself, however, affords 

 little data of value upon which to base a rational and judicious 

 plan of pasture study, and its use in successional and distribu- 

 tional studies is often overestimated. 



In the more recent natural reseeding studies the writer has 

 made a new apphcation of the method of charting which has 

 greatly popularized the use of the hst plot. The method em- 

 ployed is simply a combination of charting and listing. 



The former record showing the exact number of individual 

 specimens of a species is substituted for the percentage of the 

 cover which each species produces, and this is recorded per one 

 one-hundredth unit of the plot, as indicated in Figure 126. 

 Each division area of the map shows the species occurring within 

 the unit, regardless of the exact location of the plants, and in 

 addition the percentage of cover formed by each species and the 

 density of cover within each unit. For example: If Polygonum 

 Douglasii composed 15 per cent of the cover within a given one- 

 hundredth unit of the plot, Stipa minor 10 per cent, and Bromus 

 marginatus 5 per cent, the vegetation would be listed as P-15, 

 S-io, and B-5, respectively, one under the other. In the upper 

 right-hand corner of the unit is recorded the density of that 

 unit. Such a record is noted for each unit division of the plot 

 so that its average density may be determined. From these 

 facts the cover may be expressed in terms of forage-acre factor — 

 density X palatahility of the cover. 



Some of the advantages in the use of the list plot are that 

 the mapping can be done in about one-fifth of the time required 

 for complete " location " charting; that the plan lessens ma- 

 terially the work required in summarizing the data; and that 

 the record furnishes the additional valuable information of the 

 actual density of individual species and of the plot as a whole, 

 factors which are not available where the cover is charted merely 

 in situ 



