Juniper Age and Distribution on an Isolated Butte in Garza County, Texas

Abstract

The density and age distribution of redberry juniper on an isolated butte were determined to learn the possible origin and direction of spread of the juniper. The northern half of butte supported the denser stands. The densest stand was in the northwest corner of the top but the oldest trees were found on north- west mid-slopes indicating the northwestern part of butte as center of distribution and possible source of younger junipers found downslope. The density and age of the redberry juniper, Juniperus pinchotii Sudw., on an isolated butte were studied to learn the center of distri- bution of the juniper and its direction of spread on the butte. The butte is adjacent to the escarpment of the Llano Estacado in Garza County, Texas. Elevations of the Llano Estacado escarpment in this area range from 2800 to 2850 feet. The butte, however, is at a slightly lower elevation indicating erosion of the upper layer of the Llano Estacado. The soils are of the Veal and Potter series, having been formed from wind-blown materials deposited on top of the cretaceous aluvium deposits. The butte is nine acres on top. Elevation is approximately 2450 feet at the north edge with a gentle slope to the south and southeast edge where the elevation is approximately 2360 feet. The relatively smooth surface supports a redberry juniper savannah with a dense grass cover. The most abundant grasses are blue grama, Bouteloua gracilis (Willd. ex H.B.K.) Lag., sideoats grama, Bouteloua curtipendula, (Michx.) Torr., and slim tridens, Tridens muticus, (Torr.) Nash. Soils on the rocky slopes are poorly developed and support little grass cover. Scattered plants of redberry juniper, lotebush, Condalia otbusi- folia (Hook.) Weberb., and shadscale, Atriplex confertifolia (Torr. and Frem.) Wats., predominate on the south slopes. Dense stands of juniper are found along the north slopes just below the steep escarp- ment and in and along drainages. The top of the butte is accessible to livestock only in two places where erosion has made passageways in the caprock. Due to inaccessi-