August, 1955 



EvERs: Hill Prmries of Iii.inois 



381 



For the three bunch grasses, .-Jnilnjfxj- 

 goii scoparius, A. gcrardi, and BouUloua 

 curtipendula, the shoots that grew as in- 

 dividuals or in small bunches were counted 

 and recorded. In the Phegley prairie, the 

 shoots were small and mostly distinct and 

 separate. In the Sampson prairie, the shoots 

 were mostly aggregated into "tufts," and 

 these into bunches of varying sizes. In 

 this prairie, A. scoparius occurred also in 

 several large patches within the plots. 

 The number of shoots in such patches was 

 estimated as follows: the average number 

 of shoots per square inch in the smaller 

 bunches was determined by counts ; this 

 number was multiplied by the number of 

 square inches in each of the larger patches. 



During later stages of preparation of 

 this report, it was evident that an esti- 

 mate of numbers of grass-plant individuals 

 per unit of area could be of great value 

 in finding average plant densities in hill 

 prairies. Other workers have made such 

 estimates. Steiger (1930), in his study of 

 high and low prairies of Nebraska, ap- 

 parently counted each occurrence, whether 

 a single shoot or a bunch, as a grass-plant 

 individual. From the quadrat maps in his 

 report, the bunches of grass appear not 

 so large as those in hill prairies in Illi- 

 nois. Korstian & Coile (1938), in a 

 study of plant competition in forest stands, 

 found the most densely covered forest- 

 floor milacre had about 10 grass plants 

 per 0.01 milacre. "Thus each 0.01 mil- 

 acre occupied by a colony was regarded as 

 fully stocked, even though it contained 

 few or no individual plants." Neither 

 Steiger's procedure nor the one followed 

 by Korstian iSc Coile seemed adequate for 

 Illinois hill prairies. The estimate of 

 numbers of grass-plant individuals for 

 these prairies was therefore made by a 

 different method. 



Two bunches of Andropogon scuparius 

 were obtained, one from the Northeast 

 Meredosia prairie, one from the basal 

 slope at Reavis Spring prairie. Each 

 bunch was taken from an unpastured 

 prairie strip that was separated from the 

 adjacent pastured prairie slopes by a fence. 

 These- bunches were carefully dissected 

 to find how many shoots were connected 

 by living stems in what might be consid- 

 ered as individual plants. For convenience, 



each aggregate of shoots considered to be 

 an individual plant was called a tuft. Be- 

 fore separation, each bunch was mapped 

 with a pantograph to show foliage area or 

 crown cover, area at ground surface, lo- 

 cation of solitary live shoots, and what 

 appeared to be aggregates of shoots or 

 "apparent tufts." (It was recognized 

 that separation of a bunch into tufts might 

 give very different results from tliose of 

 the preliminary surface examination.) It 

 was found that the average number of 

 shoots per tuft of A. scoparius was 3.375 

 for the Northeast Meredosia sample and 

 3.793 for the one from Reavis Spring. 

 The characteristic tuft (grass-plant indi- 

 \idual) of A. scoparius was found to be 

 an aggregate of 3 or 4 shoots, average 3.5. 



The same method was used by H. A. 

 Moore and A. G. Vestal to determine the 

 number of shoots per plant individual for 

 Andropogon gerardi. In a clump of big 

 bluestem, collected b>- Moore from a rail- 

 road trackway east of Urbana, Moore and 

 \'estal found b\ separation that the aver- 

 age number of shoots per tuft or grass 

 plant was 1.739. The characteristic tuft 

 (grass-plant individual) of big bluestem 

 consisted of 1 or 2 shoots, average 1.75. 



As a preliminary step in estimating the 

 number of plants of Bouteloua curtipen- 

 dula, the writer obtained a small sample 

 from Mud Creek prairie and carefully 

 dissected the bunches to determine the 

 number of shoots per plant or tuft. It 

 was found that the average number of 

 shoots per tuft was 3.437 ; the individual 

 plant of B. curtipendula was an aggre- 

 gation of 3 or 4 shoots, average 3.5. 



For each of the bunch-grass species, the 

 estimated number of tufts in bunches was 

 found b\- dividing the number of shoots 

 in bunches by the a\erage number of 

 shoots per tuft, or by a factor based upon 

 this average. 



Density of Vegetation. — The meas- 

 ure of vegetation density in this study is 

 the number of plants per milacre. The 

 mapped central milacre of the Sampson 

 and that of the Phegley prairie were used 

 in determining density for this report. 



Grasses. — In the central milacre of the 

 Sampson prairie, 4,051 shoots of Andro- 

 pogon scoparius grew in bunches and 

 patches. The 4,05] shoots formed an es- 



