PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



215 



Table 13. — Total cm. of water in the 0-50 and 50-120 cm. soil 

 layers on the grazed and ungrazed sites at sampling dates 

 from May to October, 1970 







Grazed 







Ungrazed 





Date 















0-50 



50-120 



Total 



0-50 



50-120 



Total 



5/27 



9.43 



10.78 



20.21 



10.88 



13.97 



24.85 



6/15 



9.30 



12.52 



21.82 



10.59 



13.51 



24.10 



6/22 



6.63 



8.65 



15.28 



7.84 



15.77 



23.61 



6/29 



11.51 



20.19 



31.70 



6.94 



14.10 



21.04 



7/6 



3.95 



8.07 



12.02 



4.03 



13.81 



17.84 



7/13 



3.16 



7.47 



10.63 



3.56 



8.77 



12.33 



7/20 



3.04 



5.95 



8.99 



3.52 



7.58 



11.10 



7/28 



5.11 



5.40 



10.51 



5.09 



7.21 



12.30 



8/4 



6.94 



5.49 



12.43 



8.21 



7.48 



15.69 



8/11 



5.13 



6.52 



11.65 



6.50 



8.60 



15.10 



8/18 



3.63 



6.21 



9.84 



3.45 



5.95 



9.40 



8/24 



6.10 



6.10 



12.20 



3.19 



7.69 



10.88 



8/31 



2.46 



4.76 



7.22 



2.55 



5.29 



7.84 



9/8 



2.93 



4.87 



7.80 



2.71 



5.79 



8.50 



9/14 



3.24 



5.00 



8.24 



3.19 



4.98 



8.17 



9/21 



3.56 



4.86 



8.42 



3.52 



4.95 



8.47 



9/28 



4.75 



5.17 



9.92 



4.65 



5.61 



10.26 



10/5 



3.61 



5.12 



8.73 



3.57 



5.19 



8.76 



was alternately available to a limited extent and 

 then unavailable for most of the rest of the sea- 

 son. Except for late forbs. plant growth was 

 practically complete by the end of July. 



It might bo thought that the large mass of 

 plant material, including litter, on the ungrazed 

 site would protect the upper soil layer on this 

 site from drying as rapidly as the upper soil layer 

 on the grazed site. The data in table 14 show the 

 status of total and available soil moisture in the 

 upper 10 cm. of soil under the grazed and un- 

 grazed treatments. There seems to be little evi- 

 dence that soil moisture from the upper 10 cm. of 

 soil was lost more rapidly on the grazed site than 

 on the ungrazed site. 



Atmospheric Moisture 



Relative humidity values were recorded hourly 

 at 15 cm. above the soil and 1 m. above the 

 canopy on both the grazed and ungrazed areas, 

 using psychrometric elements operating on the 

 Dunmore principle. These readings and air tem- 

 peratures, recorded at the same time, were used to 

 calculate vapor pressure deficits. 



On both sites, weekly average maximum (5:00 

 a.m.) and minimum (4:00 p.m.) relative humidity 

 values were generally higher 15 cm. above the 

 ground than at 1 m. above the canopy (table 15). 

 At the 15 cm. height during the week of June 14- 

 20 average maximum, average minimum, and 

 average weekly relative humidity values were 

 higher on the grazed site than on the ungrazed 

 site. During the week of July 5-11, relative hu- 

 midity values at this height on both sites were 

 practically the same. For the week of Aug. 23-29, 

 average maximum values at this height on both 

 sites were practically the same, and average min- 

 imum and weekly average values were some- 

 what higher on the ungrazed site than on the 

 grazed site. As conditions became more severe 

 with the advance of the season, the influence of 

 the larger vegetation mass on the ungrazed site 

 seemed to become increasingly important in modi- 

 fying the atmospheric moisture regime near the 

 ground. At 1 in. above the canopy (130 cm. — 

 grazed. 145 cm. — ungrazed). relative humidity 

 was appreciable higher over the grazed treatment 



