GRASS CULTURE AND RANGE IMPROVEMENT 5 



doned land. The latter species was less important at lower altitudes 

 and in the Southern Plains than elsewhere in the region. Frederic 

 E. Clements, of the Carnegie Institution of Washington, reports 

 informally that this species rarely if ever enters early in abandoned 

 fields unless plant-lets or rootstalks had persisted through the period 

 of cultivation. With few exceptions, sand dropseed was more active 

 and abundant than either of the others in reclaiming sandy soils. 

 On soils of heavy texture these species usually were followed by a 

 slow but ultimately complete invasion of buffalo grass, and much 

 later by scattering traces of blue grama. On the lighter but not 

 active dune soils sand dropseed was often followed soon by sand 

 paspalum, and later by side-oats grama, hairy grama, switchgrass, 

 prairie beardgrass (little bluestem), and turkeyfoot (sand blue- 

 stem). Often blowout grass, prairie sandgrass (sand reedgrass), 

 and giant reedgrass, particularly blowout grass, were the first grass 

 species to invade active sand dunes and, after stabilizing such areas, 

 were gradually replaced by many of the other species listed above. 

 Blue grama was ordinarily the last species to become established and 

 in no place, except on fields grazed only in the winter near Colorado 

 Springs, was it an important agent in natural recovery. 



On the heavier soils abandoned fields finally became covered with 

 a nearly pure stand of buffalo grass, accompanied by very little blue 

 grama. Under similar conditions adjacent virgin pastures usually 

 contained a disclimax mixture of these species in nearly equal 

 amounts. Abandoned fields fully covered with buffalo grass sur- 

 vived the recent drought with much thicker stands and appeared 

 to be more productive than adjacent virgin pastures similarly grazed. 

 The residual effect of earlier cultivation in making the soil more 

 receptive to moisture may have been partly responsible for these 

 advantages. It is possible that the earlier cultivation had removed 

 the competition of the deeper-rooted forbs. 



These results indicate that it is important that only light or de- 

 ferred grazing be permitted during the early stages of recovery 

 after abandonment for all species except buffalo grass which will 

 endure heavier grazing (58, 59). The slowness with which blue 

 grama reclaims abandoned fields unassisted indicates that a thin 

 stand of this species may not be expected to thicken very fast with- 

 out considerable protection from grazing and may require special 

 care in establishment to increase seed production and facilitate seed- 

 ling survival. Buffalo grass, on the other hand, reseeds itself more 

 readily, and, being stoloniferous, usually spreads a foot or more each 

 season. 



Natural revegetation of cultivated land may be expected to proceed 

 at much slower rates in the future than in the past, because fewer 

 seeds and seed-producing plants are available on adjacent areas. 

 Less land is in grass than formerly and most pastures are severely 

 damaged or practically denuded of vegetation. A reserve of grass 

 seed was present on the surface of many pastures at the beginning 

 of the recent drought and many seeds germinated following the first 

 rains, but practically all of the seedlings died during recurrent pe- 

 riods of dry weather. Each interval of relief from drought wit- 

 nessed the appearance of successively fewer seedlings, most of which 

 met the same fate as the first, resulting in exhaustion of seed 

 reserves. 



