The abundant and conspicuous animals of the blowsand are the 

 surface forms — a few Acridiidac and a large number of roving pre- 

 daceous animals. 



The blowsand association, though consisting often of an abundant 

 growth of plants and animals, is nevertheless dependent upon the 

 physical environment, and may be exterminated in a winter of severe 

 wind action. Several times lee slopes of blowouts were found with 

 the horizontal roots of the last year's annuals exposed at the sur- 

 face, which indicates that a depth of about three inches of sand had 

 been blown away during the winter. 



THE BLOWSAND COMPLEX 



The large waste areas of bare sand (PI. IV, Figs, i, 2, 3) are 

 also referred by Gleason to the blowsand association. The bare areas 

 are not always, however, of the same origin as the lee slope area of 

 the blowout, nor is the vegetation homogeneous. The large areas 

 originate in three ways ; by the continued growth of a large blowout, 

 by the confluence of a number of blowouts, or through plowing, or 

 trampling of cattle. The second cause is perhaps most influential. 

 The tendency in bare sand, when obstructions are absent, is towards 

 a slow drifting of the sand across the level surface, with very little 

 deposition or excavation. The only plants to be found are annuals, 

 particularly Cenchrus and Aristida. In general, physical conditions 

 and vegetation approximate those of the blowsand association of lee 

 slopes. Practically, however, in any considerable area one finds com- 

 plications in the form of dunes, blowouts, and relic colonies of bunch- 

 grass vegetation. It would therefore, seem preferable to distinguish 

 between the large bare areas and the lee slope areas by giving the 

 former the name blowsand complex. 



The vegetation of the blowsand complex is quite varied in nature. 

 In abandoned fields, where plowing has started wind action, the dy- 

 namic tendency is in either of two directions, according to the degree 

 of humus in the soil, and, perhaps, the degree of exposure to wind. 

 When the sand is almost pure, wind action dominates, and the result 

 is an unvegetated area of shifting sand. If, however, there is enough 

 humus in the soil, the vegetation dominates, and there is a gradual 

 development from plant growth of very sparse type to bunch-grass. 

 Such areas are frequently covered with OcnofJicra rhoiiibipctala, 

 which is one of the successful invaders. Lcspcdcza capitata is an- 

 other frequent pioneer species. Cenchrus and Aristida are found 

 in abandoned fields also, and are succeeded by Bragrostis trichodes 



