PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



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Table 4. — Below ground biomass to a depth of 1 meter on 

 grazed and ungrazed, sites at different sampling dates during 

 the 1970 season (ash- free, oven-dry weights — g./m. 2 ) 









Sampling dates 







Treatment 



May 



26 



June 

 15 



June 

 25 



July 

 9 



July 

 30 



Aug. 

 10 



Aug. 

 19 



Grazed 

 Ungrazed 



2,772 

 1,454 



2,301 

 1,489 



2,908 

 2,168 



2,581 

 1,688 



2,370 



1,474 



2,362 

 1,532 



2,342 

 1,693 



on the grazed and ungrazed sites in this study 

 are shown in table 7. Weekly average tempera- 

 tures for the week of July 12-18, 1970, are given 

 for the hours of 4:00 a.m. (daily minimum), 

 2:00 p.m. (daily maximum), and 10:00 p.m. (ap- 

 proximate greatest increase with height). 



During the night the trend of the temperature 

 profile is generally warmer upward, while dur- 

 ing the day the trend is warmer downward. 

 Gradients are similar over grazed and ungrazed 

 vegetation, with the temperature at 2:00 p.m. 

 increasing 5-6° C. from the top of the profile to 

 the maximum temperature, usualty at 2.5 or 7.5 

 cm. Since these temperatures are weekly aver- 

 ages, they do not show the full range that might 

 be expected on any one day. Such ranges might 

 be twice as great as the averages. 



The average temperature for the whole profile 

 at any specific hour was generally greater above 

 the grazed vegetation than above the ungrazed 

 vegetation. However, all temperatures in the pro- 

 file above grazed vegetation would not be expected 

 to be higher than all temperatures in the gradient 

 profile above ungrazed vegetation. 



Table 5. — Soil bulk density values on grazed and 

 ungrazed sites for the 1970 season 





Bulk density 



values 



Depth 



Grazed 



Ungrazed 



Cm. 



O./cc. 



G./cc. 



0-10 



1.16 



1.03 



10-20 



1.35 



1.27 



20-30 



1.40 



1.40 



30-40 



1.40 



1.40 



40-120 



1.50 



1.45 



At 2.5 and 7.5 cm., air temperatures exceeding 

 32° occurred on more days above ungrazed vege- 

 tation than above grazed vegetation (table 8). 

 Above a height of 15 cm., maxima over 32° C. oc- 

 curred more often over grazed vegetation. Higher 

 maximum temperatures close to the ground in the 

 ungrazed vegetation probably were caused by the 

 reduced air movement through the large accumu- 

 lation of vegetation, in contrast to the much 

 smaller accumulation on the grazed area. 



Soil Temperatures 



Soil temperatures were measured with thermo- 

 couples 1.2, 2.5, 7.5, 15, 25, 55, 75, and 120 cm. 

 below the soil surface, with the values recorded 

 hourly, as for air temperatures. Soil under the 

 grazed vegetation averaged 2-4° C. warmer than 

 under the ungrazed vegetation (table 9). 



Substantial gradients in soil temperatures ex- 

 isted under both grazed and ungrazed conditions, 

 with the general tendency for the gradients to be 

 cooler downward in the months of June, July, 

 and August and cooler upwards in September 

 (table 10). Except for some variation in the 

 upper 2.5 cm., temperatures at all measured 

 depths under the grazed vegetation were ap- 

 preciably higher than under the ungrazed vegeta- 

 tion. Differences of 4° to 6° 0. between grazed 

 and ungrazed treatments were not uncommon for 

 the same soil depths. By midSeptember, the soils 

 on both sites had cooled significantly throughout 

 the measured profile. 



Diurnal temperature fluctuations were not 

 marked below a depth of 15 cm. under either of 

 the treatments. The range of diurnal variations 

 in the upper 15 cm. of the soil was considerable 

 greater on the grazed site than on the ungrazed 



