Effect of grazing and abandoned cultivation on a Stipa-Bouteloua community.

Abstract

A Stipa-bouteloua community, cultivated in the autumn of 1928 and abandoned in the spring of 1932, reverted to a community dominated by needle-and-thread (Stipa comata Trin. and Rupr.). An exclosure to prevent grazing was constructed in 1978 to include equal portions of previously cultivated and adjacent native range, while the remainder of the area continued to be subjected to moderate to heavy grazing pressure. This permitted a study to determine the effects of the brief period of cultivation on forage production, species recovery, and soil physical and chemical characteristics compared to those of native prairie. After 14 years of protection from grazing, needle-and-thread accounted for 79% of foliar cover of the abandoned cultivation and 18% of the untreated range while blue grama [Bouteloua gracilis (HBK.) Lag. ex Steud] occupied 1 and 51% on the same treatments, respectively. After 60 years, the soil on the abandoned cultivated area showed reduced carbon, total nitrogen, available phosphorus, and hydraulic conductivity but increased N03-N. Grazing reduced hydraulic conductivity, NH4-N, available mineralizable nitrogen (chemical index), available phosphorus, and total carbohydrates but increased carbon, total nitrogen, and N03-N. Cultivation and grazing resulted in reduced root mass. To facilitate a rapid transition from blue gramb to needle-and-thread stable communities, input of energy, such as cultivation, may well be required.