An associational study of Illinois sand prairie . ation and the blowout formation. The Prairie Formation. ? The important ecological feature of the prairie formation is thecontrol of the physical environment by the vegetation. Though theformation is open, it is usually quite stable, and the processes atwork tend toward the binding of the sand, the gradual enrictinient ofthe soil through the accumulation of humus and the ultimate of a closed formation. The dominant plants are grasses; thedominant are grass-eaters, such as locusts and other phytoph-agous insects, rodents
An associational study of Illinois sand prairie . ation and the blowout formation. The Prairie Formation. ? The important ecological feature of the prairie formation is thecontrol of the physical environment by the vegetation. Though theformation is open, it is usually quite stable, and the processes atwork tend toward the binding of the sand, the gradual enrictinient ofthe soil through the accumulation of humus and the ultimate of a closed formation. The dominant plants are grasses; thedominant are grass-eaters, such as locusts and other phytoph-agous insects, rodents, and other The associations in theprairie formation are throe: the bunch-grass association, the Panicurn,pseudopubescens association, and a closed association v/hich repre-sents the culmination of the sand-prairie, which may tentatively becalled the climax sand-prairie association. The Bunch-grass Association. The soil of the bunch-grass association is sand, mixed vfith alittle humus. The association is open, usually about twenty or. 39 thirty per cent, of the surface being exposed. The patches of baresand are dry at the surface, but are not greatly subject to windaction. The topography is usually undulating, the elevations havingthe aspect of stabilized dunes, v;hich, in fact, they almost invari-ably are ( , ; ,). The dominant plants of this association are the bunch-grasses,Y/hich form dense tufts or bunches, in which the dead leaves of theyear before remain. The bunches are separated by patches of baresand. The general appearance of the association depends upon thatof the species of bunch-grass which happen to be abundant. The im-portant bunch-grass species are Koeleria cristata (Linn.) forminglarge regular tufts, higher in the center; Leptoloma cognatum (Schultesi)Chase, with large, compact, flat-topped tufts; Stipa spartea Trin.,tall, loose, few-leaved; Panicum pseudopubescens Nash, with short,broad leaves, forming very flat bunches, often eig
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Keywords: ., bookcentury1900, bookdecade1910, bookidassocia, booksubjecttheses
