64 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



although they meander back and forth through distances of 4 to 8 inches. 

 They were examined to a depth of 10 feet, a very few penetrating beyond this 

 depth. In the first foot of soil they are practically unbranched; indeed, the 

 branching is poor throughout. Sometimes the roots extended 1 to 3 feet, 

 giving off scarcely a single branch. Near the ends of the roots the branching 

 is fairly well developed, while rather infrequently along their course groups of 

 well-branched rootlets arise. This plant, like Artemisia canadensis, which 

 was excavated from the same trench (p. 59), has an extensive, deep-seated 

 root system. 



Several other species were studied in this sandhills area. Since they 

 have been described heretofore (Weaver, 1919) they will be mentioned 

 in the chapter on ecads. 



The sandhills near Central City, in east-central Nebraska, are of 

 especial ecological interest. Between the Platte River on the south 

 and the Loup River on the north there lies, well back from their respec- 

 tive flood-plains, an area of long, low ridges of hills, approximately 8 

 miles wide and consisting of very sandy soil. These are extra-regional 

 sandhills and probably represent their furthest eastward extension in 

 Nebraska. They are surrounded by rather typical true prairies, but, 

 under the edaphic conditions afforded by the sand and often as a result 

 of overgrazing, the tall-grasses show an undergrowth of short-grasses 

 resulting in mixed prairie. 



In the area studied the hills had been greatly overgrazed. Much 

 destruction had been wrought in the grassland both by wind erosion 

 and deposit. In several places large active blowouts were in evidence, 

 while perhaps a mile away drifting sand had covered the more stable 

 valley vegetation to depths of a few inches to more than a foot (cf. p. 23). 

 This condition had prevailed for several years, when all stock was 

 removed and an attempt was made to reclaim the land by planting 

 rye, sorghum, millet, and sweet clover (plates 10 and 20, a). Most of 

 the typical sand-binding pioneers are to be found in the blowouts, and 

 whole hillsides are being reclaimed by a rank growth of Calamovilfa 

 longifolia, Andropogon hallii, Redfieldia flexuosa, and Sporobolus 

 cryptandrus. On the other hand, the valleys are sodded over with Poa 

 pratensis, Andropogon nutans, Panicum virgatum, and mats of Bouteloua 

 hirsuta and Carex stenophylla, while all intermediate conditions between 

 these extremes prevail. Much of the area is passing through a ruderal 

 stage, with Salsola tragus, Cycloloma atriplicifolium, and Cenchrus 

 tribuloides dominating. The successional record shows all stages in the 

 reclamation of blowouts, distinct lines of demarcation existing between 

 stable and disturbed populations. The thoroughness of the destruction 

 even in the valleys, is evidenced by the occurrence of Juncus balticus, 

 partially unearthed, its rhizomes and roots dangling from hummocks of 

 sand 2 feet above the eroded valle}^ floor. Naturally, in these sandhill 

 outposts, the soil is often mixed with clay. The presence of these clay 



