i92 



Illinois Natural History Survey Bulletin 



Vol. 26, Art. 5 



and a moderate number of minor species, 

 is an area 5 times as large as the smallest 

 represt'ntative area and usually contains 

 1.44 to 1.5 times as many species. It is 

 the smallest size to be used if a single one- 

 piece sample is to be examined. The fair- 

 sized stand (Af) is an area 50 times as 

 large as the smallest representative area 

 and contains twice as main species. 



For Sampson prairie, the curve indi- 

 cates the smallest representative area to 

 be ().7b milacre, with 10.8 species; the 

 computed minimum area 3.80 niilacres, 

 with 15.6 species, or 1.444 times as many 

 species as in the smallest representative 

 area; the fair-sized stand 38.0 milacres, 

 with 21.6 species. 



For Phegley prairie, the curve indi- 

 cates the smallest representative area in 

 be 1.26 milacres, with 14.3 species; the 

 computed minimum area 6.30 milacres, 

 with 21.4 species, or 1.497 times the num- 

 ber in the smallest representative area; the 

 fair-sized stand ()3.0 milacres, with 2S.6 

 species. 



The *)-milacre square was larger than 

 the smallest representative area and mini- 

 mum area for both prairies. Both prairies 

 were of more than sufficient size to qual- 

 ify as fair-sized stands. The number of 

 species in 1 acre was estimated to be 2S.0 

 in Sampson and 35.2 in Phegley. 



Summary of Pastured and I'npas- 

 tured Prairies. — Some of the differences 

 in vegetation of the pastured and the un- 

 pastured hill prairies are here summarized. 



1. The number of species in a quadrat 

 was larger in the pastured than in the un- 

 pastured hill prairie. 



2. Plant density, based on the number 

 of plants in a quadrat, was smaller in the 

 pastured than in the unpastured prairie; 

 the grass bunches were smaller, less vig- 

 orous, and not so tall. 



3. Grasses constituted a smaller per- 

 centage of the total number of individual 

 plants in the pastured prairie than in the 

 unpastured. 



4. The ground space occupied by 

 grasses was smaller in the pastured prairie 

 than in the unpastured. 



5. Foliage area, or crown cover, was 

 understandably much smaller in the pas- 

 tured than in the unpastured prairie. Also, 

 the ratio of crown cover to ground space 



was smaller in the pastured prairie than 

 in the unpastured prairie. 



Vegetation Characters From Other 

 Stands 



In the preceding section, some analytic 

 characters of vegetation were described for 

 two hill prairie stands, Sampson and Pheg- 

 ley prairies. Anal) tic characters of vege- 

 tation, according to some phytosociologists, 

 are those traits which are studied in each 

 stand. Synthetic characters of vegetation 

 are those which are studied from compari- 

 sons of large numbers of stands. Presence, 

 a synthetic character of vegetation, and 

 seasonal aspect, also synthetic in that it 

 was described from observations made on 

 must of the stands of llliiKii-- hill prairies, 

 are here brief!)' presented. 



Presence. — Presence, as used here, is 

 defined as the more or less persistent oc- 

 currence of a species in the stands of a 

 plant community. Used for this study 

 were 36 stands of hill prairies that the 

 writer visited at least twice during the 

 Held work. From species lists of the 36 

 stands, a table was devised which lists the 

 species and the stands in which they oc- 

 curred, table 14. Species of forests or 

 thickets and those of foreign origin were 

 not included in the table unless they oc- 

 curred in 18 or more of the stands. 



Ihree species were present in 90 per 

 cent or more of the stands. They were 

 .hidropoi/on scop/iriiis, F.rigeron strigosus, 

 and Bnuteloua curtipendula. Six species 

 were present in 80 to 89 per cent of the 

 stands. The)' were Pelalnsteriium pur- 

 pureum. Euphorbia cnniUata, Penslrmnn 

 pallidus, A. gerardi, lerbena stricia, and 

 Kuhnia eupatorioides. These nine species 

 were the "constants" of the association ; 

 they can be classed as "constantly pres- 

 ent." The "commonly present" species, 

 that is, those present in 60 to 79 per cent 

 of the stands, were Kupatorium nltisai- 

 miiiii, Rhus glabra, Oxalis viulacea, Snli- 

 dago nemnralis, Panicum scrihnerlauum. 

 Aster ohlongifolius, and Riiellia humilis. 

 Species in 50 to 59 per cent of the stands 

 were Liniim sulcatum, Llthospermum in- 

 cisum, Melil'itus alba. Lespedeza rapi- 

 tata, Pycnanthemum pllosu/n, Poa pra- 

 t en sis, Psoralea tenuiflora. Cassia jascicu- 



