70 Journal of Agricultural Research voi. xix, no. 2 



Since the carrying capacity of the range is largely dependent upon 

 the density of the vegetation, it is obvious that this factor should be 

 carefully determined. If density is determined on the basis of the foliage 

 cover, even when this is possible, the carrying capacity is likely to be 

 placed too high, because of favorable growth conditions or an accumula- 

 tion of previous growth, and overgrazing will result. In normal seasons 

 the amount of forage a given area of ground surface can produce is largely 

 determined by its basal cover. Therefore, the basis for an estimate of 

 the amount of ground surface covered by vegetation should be founded 

 upon the basal cover. The foliage cover is the important consideration 

 for immediate grazing, but the basal cover more nearly determines the 

 future possibilities of a given area of land for grazing purposes. 



AMOUNT OF BASAL COVER AT MANDAN 



From quadrat maps drawn to show bare and covered ground surface 

 the total basal cover has been determined. The maps show about 60 per 

 cent vegetated and 40 per cent bare ground. From quadrat maps, such 

 as that in figure 2, made in the various pastures, the percentages of basal 

 cover of Bouteloua and Stipa were determined. These are approxi- 

 mately 20 and 10 per cent, respectively. These determinations were all 

 made from the maps by means of a planimeter. 



Shantz (7) has made a number of estimates on the amount of cover in 

 a series of quadrats in the mesa region near Pikes Peak. He has ex- 

 pressed the amounts in percentages in each case. The same method is 

 followed in the present studies. This is a most convenient system, 

 especially when it is desired to express a given species in terms of 

 amount of total cover. Sampson (5) expresses the "density of vegeta- 

 tion" in terms of tenths, using 10 as complete ground cover. In order 

 to avoid confusion, the amounts of cover as used in coimection with 

 the Mandan grazing experiment are expressed in percentages. 



From the amounts of basal cover of Bouteloua gracilis and Stipa 

 comata it is readily seen how important they are from the standpoint of 

 grazing in this sec on. Griffiths, Bidwell, and Goodrich (2) have dis- 

 cussed the value ci these grasses for forage. From clipping experiments at 

 Mandan in 191 7, in connection with the grazing studies, the Bouteloua was 

 found to have produced from 40 to 50 per cent and Stipa from 15 to 20 

 per cent of the total forage for the season. When the quadrats were 

 clipped, the vegetation was separated into six parts, as follows : Bouteloua 

 gracilis, Stipa comata, Aristida longiseta, other grasses, Carex fUifolia and 

 C. heliophila, and other plants. Columns are also reserved for the sum 

 of B. gracilis and 5. comata and for the total weight of all grasses and of 

 all species. From these data it is possible to determine the relation of 

 one species or group to another or to the total weight of all species. The 

 various amounts were recorded in grams, weighed both green and air- 

 dried. From these data it appears evident that the ground layer is the 

 important one from the standpoint of grazing in this section. 



