SOIL SURVEY OF BANNER COUNTY, NEBRASKA. 19 



structure and compaction being developed usually in inverse ratio 

 to the thickness. Although it is usually rather compact in the virgin 

 condition, it breoks up readily into fine particles. The compaction 

 is most pronounced in its upper part, and decreases gradually down- 

 ward, but the transition from horizon 1 to horizon 2 is usually 

 abrupt. Beneath horizon 2 there may occur a thin brown horizon 

 free from compaction, with low organic matter, and differing from 

 the fourth horizon mainly in the absence of lime carbonate. The 

 fourth honzon is light gray or yellowish in color, deflocculated and 

 therefore poAvdery in structure, except in the sandy members, and 

 carries a high percentage of lime carbonate, the content ranging from 

 1 per cent to almost any amount, though in most samples it does not 

 exceed 2 per cent. This horizon is usually a foot or more in thick- 

 ness and changes gradually downward into the parent rock. This 

 may vary greatly in its characteristics. 



The profile just described is universally present on the smooth 

 parts of the coimty, where the soil has lain in its present position for 

 a considerable period of time without being subjected to any serious 

 effect from erosion, burial by wash from higher areas, or creep and 

 slide down slopes. It does not characterize the soils that are made 

 of material recently accumulated and is less well developed on the 

 slopes than on the smooth upland or terrace areas. This occurrence 

 points to the conclusion that the profile here described is the mature 

 one for the region or at least the most advanced in siage of develop- 

 ment of any in the area, and since soil-survey studies in the northern 

 Great Plains as a whole have found this profile of universal occur- 

 rence in situations such as those in which it is found in this region, 

 the inference seems to be justified that it is the mature j^rofile of the 

 northern Great Plains region. If it be allowable to apply to the soil 

 profile a term used in recent investigations in Ecology ^ it may be 

 designated as the climax 'profle of the northern Great Plains, or, 

 more accurately, the central-northern Great Plains. 



The mature profile as described above is not developed over the 

 whole area. The soils characterized by it are included in the various 

 members of the Posebud, Tripp, and Cheyenne series. The Rosebud 

 soils are the prevailing upland soils and cover somewhat more than 

 55 per cent of the total area of the county. The Tripp soils occur on 

 river terraces and for all practical purposes are the equivalents of 

 corresponding types of the Posebud series. Their profiles are exactly 

 alike and they occur on smooth surfaces. The Cheyenne soils occur 

 on terraces also, but on account of their open gravel or sand subsoils 

 are differentiated from the soils of the Tripp series. 



'F. E. Clements, Plant Indicators. 



