their restoration of rangeland vegetation on millions of acres of abandoned 

 croplands, are, I believe, a little recognized but major contribution to 

 proper land use and sustainable food production in the USA. 



Leaving the problems of rangeland versus cropland, I have two slides 

 that should tell much about rangeland versus timberland . The two slides 

 show forest site index at 5 inch increases in Average Annual Precipitation, 

 from 25 to 60 inches, at the same latitude, on similar soils, with little 

 difference in elevation. The slides show the approximate point at which ra- 

 ngeland grades into timberland as reflected in height of mature native dom- 

 inant trees. Tree maturity is reflected by rounded tops. Foresters call 

 this forest site index, but may use height at a certain age instead of ma- 

 ture height. Foresters commonly regard 45 feet at maturity as the lower 

 limit of commercial forestry. It is also at about this point that low val- 

 ue forest land grades into high value savanna rangeland. The savanna land 

 shown, with precipitation under 45 inches once had tall grasses with scat- 

 tered short trees. It is now thicketized because of cessation of prairie 

 fires and decades of close grazing of the tall grasses. At the latitude of 

 the Oklahoma - Texas border, timberland begins at about the 45 inch isohyet. 

 In Minnesota it is near the 28 or 3O inch isohyet. Savanna borders forest 

 wherever precipitation gradients are gradual but in steep mountainous areas 

 rainfall varies over short distances and rangeland can grade abruptly into 

 timberland, without abrupt change in soil. 



With that we shall leave problems in allocating land, in and near 

 rangeland, to one of the three primary agricultural uses. 



The next slide relates potential productivity of rangeland — when used 

 as native range — to precipitation zones in the plains and prairies. The 

 data shown are from the range experiment stations, indicated by name of a 

 town nearby. Shown on the side scale are acres of range required for 6 

 months of summer grazing on ordinary upland soils with native vegetation 

 near potential condition under moderate and sustainable degrees of range 

 use. At the bottom are inches of Average Annual Precipitation. The data 

 are from averages of decades of grazing trials and weather records. Note 

 the almost straight-line relation between carrying capacity and average pre- 

 cipitation, alone. Evidently, through these 2000 miles of latitude precipi- 



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