more feasible as well as more precise to measure the area occu- 

 pied by each species than to attempt to count the stalks. Because 

 of difficulties in distinguishing separate, individual plants, par- 

 ticularly those that propagate by rhizomes or runners, or because 

 of limitations in time, estimation scales are often used. In a 5-fold 

 scale, 1 denotes that the individuals are very sparse; 2, sparse; 3, 

 infrequent; 4, frequent to numerous; and 5, very numerous. Such 

 a scale has greater value if the grades are based upon approxi- 

 mate numbers, for example, S denoting 1 to 4 stalks per square 

 meter; /, 5 to 14; F, 15 to 29; A^, 30 to 99; and VN, 100 stalks or 

 more. Or a logarithmic scale may be used. 



Data on population density are often indispensable in measur- 

 ing the effects of reseeding, burning, spraying, and successional 

 changes. An interesting example is a recent study^^i on the nat- 

 ural replacement of the chestnut {Castanea dentata) (Figure 1-24C) 

 which has been destroyed by blight in the southern Appalachian 

 region. In 2569 openings created by the death of the chestnuts, 

 5046 individual replacement trees were found. The most numer- 

 ous were Quercus prinus which made up 17 per cent of the total; 

 Q. rubra, 16 per cent; and Acer rubrum, 13 per cent. Species of 

 Quercus made up a total of 41 per cent of all the replacements. 

 In another example in southern Idaho it was shown that if 

 Bromus tectorum can be reduced from about 570 to 50 plants per 

 square foot for one season, competition will be sufficiently re- 

 duced so that perennial grasses such as bluebunch wheatgrass 

 {Agropyron spicatum), crested wheatgrass {A. cnstatum), and others 

 will grow after seeding.^ ^^ 



The number of stalks that have been grazed compared to those 

 not grazed have been used to determine the proper degree of 

 utilization of the range. The effects of drought and subsequent 

 recovery were measured by the number of stalks of common 

 grasses in western North Dakota. In 1935 when the precipitation 

 was about average, Andropogon scoparius had 874 stalks per square 

 meter; in 1936, a drought year, 509 stalks; in 1937, 235 stalks; 

 and in 1938, 303. Both 1937 and 1938 were nearly normal years. 

 The number of stalks of Agropyron smithii for the same years were 

 140, 51, 69, and 98, respectively.202A 



Analytic Chaz-acteristics of tHe Community • lOl 



