Table 1 — Precipitation at Oak City for those years when tree removal and seeding or vegetation sampling occurred 



Year 



Montn 







■1 Q'7~7 







19o0 



19o1 



1982 



1983 



1984 



1985 



January 



1.55 



2.47 



0.86 



2.60 



1.43 



2.23 



0.72 



1.27 



0.82 



0.78 



0.90 



February 



2.16 



.92 



.12 



2.00 



1.42 



2.62 



.22 



.29 



1.64 



1.05 



1.03 



March 



0.15 



.06 



1.09 



2.74 



2.03 



3.39 



1.60 



1.62 



2.82 



2.54 



1.47 



April 



.30 



.86 



.24 



2.51 



.93 



.65 



2.20 



.74 



2.45 



1.82 



.78 



May 



.99 



.82 



1.54 



1.62 



1.51 



3.20 



2.85 



1.44 



1.47 



.54 



1.88 



June 



1.48 



.28 



.35 



.08 



.91 



.00 



.30 



.36 



.58 



2.54 



1.71 



July 



.74 



.61 



1.16 



.09 



.10 



.47 



.20 



.78 



.33 



2.44 



.84 



August 



.77 



.51 



.84 



.91 



.76 



.32 



.49 



1.33 



2.08 



1.58 



.00 



September 



.75 



.04 



.59 



2.43 



.00 



1.83 



1.96 



5.01 



1.48 



1.17 



1.27 



October 



.28 



1.00 



.73 



.27 



1.44 



1.63 



4.07 



2.31 



1.02 



2.56 



1.31 



November 



.82 



.05 



.30 



2.90 



1.31 



1.33 



1.23 



.93 



3.10 



1.09 



1.84 



December 



.56 



.13 



.76 



1.01 



.43 



.32 



.95 



2.18 



2.44 



1.26 



1.35 



Calendar year 



10.55 



7.75 



8.58 



19.16 



12.27 



17.99 



16.79 



18.26 



20.23 



19.37 



14.38 



Crop year ' 





7.82 



5.42 



13.93 



14.84 



15.27 



13.00 



13.93 



20.21 



17.31 



13.85 



Yield index^ 





72 



42 



145 



156 



161 



133 



145 



221 



186 



144 



' Crop year = September to June (Sneva and Britton 1983). 



' Yield index = expected plant production level compared to a crop year with median precipitation (Sneva and Britton 1983). 



Table 2 — Years of sampling on the four Oak Creek study sites 



Year 



Site 1978 1980 1981 1982 1985 



Church Hills 



Treated X X 



Untreated (or control) X XX 



Clay Springs 



Treated X X 



Untreated (or control) X 



Eight-Mile 1977 



Treated X XX 



Untreated (or control) 



Eight-Mile 1955 



Treated XX X 



Untreated (or control) 



with an intact overstory. The Eight-Mile study sites were 

 estabHshed in two areas previously cleared of trees and 

 seeded to herbaceous species — one in 1955 and one in 

 1977. Twenty sample locations were equally distributed 

 among swale bottom, side slope, and ridge crest topogra- 

 phy on a generally south aspect to study forage production 

 potential of the three slope positions. Each sample loca- 

 tion consisted of two transects of 10 plots each. 



Although measurement of plant production was con- 

 ducted in 3 years on each of the study areas, the sampling 



was spread over an 8-year period due to timing of seeding, 

 grazing rotations, and so forth (table 2). Sampling was 

 conducted only when individual areas were in a rested or 

 deferred grazing situation. The areas were treated in 

 different years (were of different ages), and data were 

 collected in different sets of years. Although differences 

 in planting technique, weather, and site contribute to 

 variation in the field data, the results provide a basis for 

 interpretation of trends. 



2 



