EFFECT OF GRAZING AND ABANDONED CULTIVATION ON A STIPA-BOUTELOUA COMMUNITY

A Stipa-Bouteloua community, cultivated in the autumn of 1928 and aban doned in the spring of 1932, reverted to a community dominated by need le-and-thread (Stipa comata Trin. and Rupr.). An exclosure to prevent grazing was constructed in 1978 to include equal portions of previousl y cultivated and adjacent native range, while the remainder of the are a continued to be subjected to moderate to heavy grazing pressure. Thi s permitted a study to determine the effects of the brief period of cu ltivation on forage production, species recovery, and soil physical an d chemical characteristics compared to those of native prairie. After 14 years of protection from grazing, needle-and-thread accounted for 7 9% of foliar cover of the abandoned cultivation and 18% of the untreat ed range while blue grama [Bouteloua gracilis (HBK.) Lag. ex Steud] oc cupied 1 and 51% on the same treatments, respectively. After 60 years, the soil on the abandoned cultivated area showed reduced carbon, tota l nitrogen, available phosphorus, and hydraulic conductivity but incre ased N0(3)-N. Grazing reduced hydraulic conductivity, NH4-N, available mineralizable nitrogen (chemical index), available phosphorus, and to tal carbohydrates but increased carbon, total nitrogen, and N0(3)-N. C ultivation and grazing resulted in reduced root mass. To facilitate a rapid transition from blue grama to needle-and-thread stable communiti es, input of energy, such as cultivation, may well be required.