Table 5 — Herbage and shrub production by slope position on the 1955 Eight-Mile treatment area 







1980 







1981 







1985 







Swale 



Side 



Ridge 



Swale 



Side 



Ridge 



Swale 



Side 



Ridge 



Vegetation 



Bottom 



Slope 



Crest 



Bottom 



Slope 



Crest 



Bottom 



Slope 



Crest 



Grasses 





















Perennial 





















Seeded 



'836 ± 77 



592 ± 57 



285 ± 52 



662 ± 47 



444 ± 24 



340 ± 65 



813 ± 149 



620 ± 115 



457 ± 89 







fi1 + 91 



53 + 19 



50 + 50 





94 + 



T9 + 99 



13 + -JO 



31+30 



Annual 



11 ± 4 



33 + 26 



31 ± 22 



15 ± 15 



1 ± 1 



2 ± 2 



2 ± 1 



3 ± 2 



3 ± 1 



Forbs 



13 ± 9 



3 ± 1 



13 ± 5 



9 ± 5 



1 ± 1 



34 ± 26 



± 



± 



13 ± 12 



Shrubs 



7 ± 3 



12 ± 7 



77 ± 24 



7 ± 4 



21 ± 11 



94 ± 20 



5 ± 4 



7 ± 3 



52 ± 27 



Total 



902 ± 74 



701 ± 43 



459 ± 32 



743 ± 25 



523 ± 24 



494 ± 48 



852 + 168 



643 ± 113 



556 ± 31 



Median^ year 





















estimate 



580 



435 



285 



559 



393 



371 



592 



446 



385 



'Pounds per acre As.e. 



'Estimated herbage and shrub production under conditions of median September to June precipitation (Sneva and Britton 1983). 



Table 6 — Herbage and shrub production by slope position on the 1977 Eight-Mile treatment area 



1980 1982 1985 



Swale Side Ridge Swale Side Ridge Swale Side Ridge 



Vegetation Bottom Slope Crest Bottom Slope Crest Bottom Slope Crest 



Grasses 







































Perennial 







































Seeded 



'747 ± 



106 



376 ± 



83 



307 ± 



79 



636 ± 



68 



379 ± 



86 



321 ± 



58 



847 ± 



118 



595 ± 



83 



480 ± 



135 



Native 



66 ± 



20 



157 ± 



36 



144 + 



47 



48 ± 



14 



119 ± 



34 



164 ± 



65 



22 ± 



6 



76 ± 



53 



107 ± 



66 



Annual 



62 ± 



8 



33 ± 



8 



54 ± 



12 



129 ± 



23 



114 ± 



39 



203 ± 



26 



40 ± 



40 



8 ± 



8 



7 ± 



4 



Forbs 



16 ± 



7 



15 ± 



3 



14 ± 



4 



41 ± 



20 



42 ± 



27 



17 ± 



4 



51 ± 



28 



77 ± 



38 



20 ± 



15 



Shrubs 



54 ± 



18 



40 ± 



16 



37 ± 



12 



160 ± 



47 



103 ± 



40 



108 ± 



34 



150 ± 



61 



136 ± 



72 



72 ± 



38 



Total 



945 ± 



89 



621 ± 



48 



556 ± 



33 



1,014 ± 



42 



757 ± 



65 



813 ± 



66 



1,110 ± 



109 



892 ± 



71 



686 ± 



105 



Median^ year 







































estimate 



588 





386 





346 





699 



523 





560 





770 





620 





476 





'Pounds per acre xts.e. 



'Estimated herbage and shrub production under conditions of median September to June precipitation (Sneva and Britton 1983). 



confidence limit of 680 to 800 lb per acre. The more re- 

 cent seedings, for purposes of this evaluation, were con- 

 sidered in "fair" condition within the RPA matrix because 

 of less dominance of seeded species. These sites produced 

 approximately 530 lb per acre (tables 7 and 8) with a con- 

 fidence limit of 490 to 570 lb per acre. The herbage and 

 shrub production appeared, therefore, to average about 

 110 to 220 lb per acre less than expected for a site of aver- 

 age productivity, about 260 to 370 lb per acre less than 

 expected for a site of moderately high productivity, and 

 460 to 570 lb per acre less than expected for a site of high 

 productivity (table 9). 



Precipitation in the Oak Creek area was above average 

 fi-om the late 1970's to the last year of production meas- 

 urements, 1985. At Oak City, precipitation averaged 140 

 percent of normal during the years the older seedings 

 were sampled (used as a basis for long-term productivity 

 estimates). Because average precipitation for the study 

 area was estimated to be 13 to 15 inches per year (U.S. 

 Department of Agriculture-U.S. Department of the 



Interior 1981), a 40 percent increase during measurement 

 years would have resulted in precipitation averaging 

 approximately 20 inches. This is near the upper end of 

 the range of average precipitation — 8 to 22 inches — for 

 the pinyon-juniper ecosystem (Clary 1987). Soil depths of 

 11 to 20 inches (Stoneman and others 1979; and RPA 

 scenario) also suggest the Oak Creek area should be 

 above average in plant production potential for the 

 pinyon-juniper ecosystem. If we assume that during 

 these years the study areas should have exhibited "moder- 

 ately high" productivity (1,000 lb per acre under good 

 condition), the general production levels are approxi- 

 mately one productivity class lower than suggested by the 

 RPA assessment. Only the "swale bottom" topographic 

 position (measured in the older seedings) had sufficient 

 production (average of 928 lb per acre fi-om tables 5 and 6) 

 to approach expectations from the RPA matrix. In addi- 

 tion, the swale bottoms are actually more representative 

 of big sagebrush site inclusions than pinyon-juniper sites, 

 as such. 



7 



