IV. ROOT SYSTEMS OF MIXED-PRAIRIE SPECIES. 



A study of the root systems of mixed-prairie species has been made 

 both in hard, black -loam soils and in the sandhills. Since root devel- 

 opment is usually quite different under varying edaphic conditions, 

 even where the same species is concerned (Weaver, 1919: 110), it will be 

 more convenient to consider the root systems in the two kinds of soil 

 separately. 



SPECIES EXCAVATED IN SANDY SOIL. 



Extensive investigations were made in the sandhills near Haigler, 

 Seneca, and Central City, Nebraska, and Yuma, Colorado (plates 7, 

 8, 9, and 10). Because of the wide territory investigated during the 

 field season, no regular stations for the securing of habitat factors were 

 maintained in the sandhills. Complete records of environmental 

 factors, however, were taken in the mixed prairie at Colorado Springs. 

 These have already been contrasted with those of true prairie (p. 27). 

 Since run-off is slight and evaporation of soil moisture low in sandy 

 soil, some notion of water-content may be gained from the precipita- 

 tion records. The average annual precipitation at Haigler is 16.5 

 inches; at Yuma, 17.5; at Seneca, approximately 20; and at Central 

 City, 26. This last station is in the extra-regional sandhills which lie 

 at the extreme eastern border of the mixed prairie, if indeed not in the 

 true-prairie region. 



The vegetation at Haigler, in extreme southwestern Nebraska, is 

 characterized by numerous species of bunch-grasses, a fairly well- 

 developed layer of short-grasses and sedges, and by the large, bushy 

 sandhill sage. Where overgrazing has occurred and the grasses have 

 been reduced both in size and number, Artemisia filifolia, greatly in- 

 creased in abundance, stands out alone as dominant (plate 7, a). The 

 taller dominant grasses are represented by Andropogon scoparius, 

 Stipa comata, Andropogon hallii and Calamovilfa longifolia. Kceleria 

 cristata and Aristida purpurea are of lesser importance. The short- 

 grasses are well represented by Bouteloua hirsuta and B. gracilis. 

 These, with the less abundant Carex pennsylvanica, Festuca octoflora, 

 and Carex stenophylla, which are common throughout, form mats over 

 extensive areas, especially in the more compact soil. In the loose 

 sands of blowouts, Redfieldia flexuosa and Sporobolus cryptaiidrus, with 

 the shorter Muhlenbergia pungens, are abundant. Subdominant spe- 

 cies are numerous; the following are the most important: 



Acerates spp. Eriogonum annuum. Lygodesmia juncea. 



Allionia linearis. Frceliehia floridana. Meriolix serrulata. 



Artemisia filifolia. Haplopappus spinulosus. Paspalum setaceum. 



Asclepias arenaria. Helianthus subrhomboideus. Pentstemon angustifolius. 



Carduus plattensis. Ipomcea leptophylla. Petalostemon villosus. 



Chrysopsis villosa. Liatris punctata. Thelesperma gracile. 



Cyperus schweinitzii. Liatris squarrosa. Yucca glauca. 

 Erigeron bellidiastrum. 

 44 



