74 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



arise mostly in clusters of 3 to 10. They also originate from other points 

 along the rhizomes and from the nodes of the stolons, but usually in smaller 

 numbers. The roots are less than a millimeter in diameter, but very tough 

 and wiry. Many of the surface roots spread laterally to distances of 0.8 to 

 1.7 feet from their origin. The tiny laterals are usually not over 0.5 inch in 

 length and rebranch rather poorly. The working depth was determined at 

 about 5 feet, but some roots were traced to a depth of 7 feet (fig. 27). 



At Burlington, Colorado, are also found typical short-grass areas. In the 

 area examined the sod of buffalo grass was well developed and bare areas 

 were not much in evidence (plate 2, b). Other species were relative^ few 

 and of much less importance. They consisted of Bouteloua gracilis, Festuca 

 octoflora, small patches of dwarfed, unbranched Grindelia squarrosa, Opuntia 

 polyacantha, and 0. fragilis. Psoralea tenuiflora and Ratibida columnaris 

 occurred rarely, and Aristida purpurea only occasionally and then in small 

 amounts, while Plantago purshii was scattered sparingly throughout. 



A trench was dug in the pure buffalo-grass sod. The soil consisted of a silt- 

 loam. At a depth of about 2.3 feet, lighter colored but only slightly firmer 

 textured "hardpan" was encountered. It was 0.5 to 0.8 foot thick. The soil 

 was fairly moist to a depth of 3.5 feet, below which it was powdery. The 

 roots literally filled the soil to a depth of 2.5 feet. They were fairly abundant 

 to 4.3 feet. *The maximum penetration was not determined, but buffalo- 

 grass roots were found to penetrate deeply in adjoining fields which made up 

 a part of this level area and where roots of crop plants were traced to a depth 

 of 5 to 6 feet (p. 112). In all cases they reached depths as great as the crop 

 plants and in some of the trenches penetrated even farther. 



At Sterling, Colorado, in a rather open mat type of vegetation of buffalo 

 and grama grass (c/. p. 42), where the silt-loam was underlaid at about 2 feet 

 with "hardpan," further examinations were made. The soil was dry through- 

 out. At a depth of 4.7 feet occurred a layer of gravel and small pebbles mixed 

 with some sand. This was very dry, as was also the sandy loam below. 

 Man}^ roots reached a depth of 5.5 feet, and probably penetrated somewhat 

 farther, while the working depth was determined to be 3.6 feet. 



At Limon, Colorado, the roots of buffalo grass were again examined, both 

 on short-grass land and in mixed prairie. The variation of the type of 

 vegetation is due to eclaphic conditions, the compacted silt-loam being covered 

 with short-grasses, while the sandier soil is rather clearly marked by mixed- 

 prairie species. The vegetation of the latter community at this station has 

 already been briefly described on page 66. While buffalo grass and grama 

 formed a more or less interrupted layer throughout, in the area where it was 

 excavated it was more nearly pure, wire-grass, mountain sage, etc., being 

 rather rare. Such patches, although on high ground, and not to be confused 

 with areas to be described where run-off water collects and stands, indicate a 

 firmer soil texture. The surface foot of soil in this area of buffalo grass con- 

 sisted of a dark-colored loam of hard texture in striking contrast to the easily 

 spaded sandy loam found only a few meters distant, where Astragalus micro- 

 lobus and other species were excavated. The subsoil was also less sandy and 

 more compact in the buffalo-grass trench. Moreover, while in the other 

 trench the soil was moist to a depth of 4 feet, in the latter it was powdeiy at a 

 depth of 2.5 feet. Undoubtedly the difference is largely due to run-off, coupled 

 with greater evaporation from the less sandy soil surface. The roots literally 

 filled the soil to a depth of 2.2 feet, while they were still quite abundant to 

 3.7 feet, a few reaching a depth of 4.5 feet. 



Low areas in swales where water collects and stands are clothed with a dense 

 sod of nearly pure buffalo grass. A long trench was dug near the edge of one 



