PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



209 



Table 1. — Standing crop, standing dead material, 

 litter, and total plant material above ground 

 on grazed and ungrased sites at the end of the 

 major growth period in the 1970 season (Aug. 

 18) 



Dry weight yield (g./m. 2 ) 



Standing Standing Total plant 



Treatment crop T dead " Litter material 



Grazed 

 Ungrazed 



196 



252 



36 



272 



209 

 662 



441 

 1,185 



1 Current season's production. 



2 Material produced prior to the 1970 season. 



not subjected to grazing until after the end of 

 the growing season. Consequently, all measures 

 of plant materials and microclimatic observations 

 were made on an area which was not disturbed 

 by grazing at the time the measurements were 

 being made. 



The standing crop of vegetation (current pro- 

 duction) on the grazed treatment was about 78 

 percent as much as on the ungrazed treatment, 

 while standing dead material and litter were 13 

 and 31 percent as much on the grazed as on the 

 ungrazed site (table 1). Total aboveground plant 



material at the end of the major growing period 

 in the 1970 season was 441 g./m. 2 on the grazed 

 treatment, 37 percent of the 1,185 on the un- 

 grazed treatment. The reduced mass of plant ma- 

 terial on the grazed site could be expected to 

 have substantial microenvironment influences. 



Evidence of such effects is shown in the species 

 composition of the standing crop (table 2). The 

 taller grasses, such as needle-and-thread, western 

 wheatgrass, and prairie sandreed, decreased un- 

 der grazing, while the shorter blue grama grass 

 increased. Selaginella, which has an average 

 height of about 1 cm., produced 12 percent of the 

 dry matter on the grazed site, but almost nothing 

 on the ungrazed site. Apparently it was the vic- 

 tim of litter accumulation, which frequently av- 

 eraged over 3 cm. in depth. Point analyses have 

 shown the actual basal cover of the grazed vege- 

 tation to average about 38 percent without Sela- 

 ginella hits included and up to 70 percent with 

 these hits included. Basal cover on the ungrazed 

 site determined on the same basis averages less 

 than 25 percent. 



Not only does the grazed vegetation have a 

 higher proportion of shorter species in it than 

 does the ungrazed, but grazed leaf heights and 

 approximate canopy heights are less throughout 

 the season (table 3). Measurements were made of 

 each species on each plot at the time of clipping. 



Table 2. — Species yields and percentage composition of yields 

 of vegetation mi grazed and ungrazed sites at the end of the 

 major growth period in the 1970 season 



Species 





Grazed 



Ungrazed 





Yield 



Composition 



Yield 



Composition 





G./m. 2 



Percent 



G./m. 2 



Percent 



Stipa comata 



45.0 



22.9 



105.1 



41.7 



Agropyron smithii 



19.8 



10.1 



33.8 



13.4 



Calamagrostis mont. 



15.3 



7.8 



— 



— 



Calamovilfa longifolia 



— 



— 



16.6 



6.6 



Koelcria cristata 



16.8 



8.6 



— 



— 



Boutelona gracilis 



59.9 



30.5 



28.9 



11.5 



Carex cJcncharis 



11.5 



5.9 



10.3 



4.1 



Miscellaneous grasses 



0.4 



0.1 



3.3 



1.3 



Perennial forbs 



22.5 



11.5 



48.9 



19.4 



Other forbs 



5.2 



2.6 



5.0 



2.0 



Totals 



196.4 



100.0 



251.9 



11(0.0 



Selaginella densa 



25.9 



— 



0.2 



— 



