Grazing intensities, vegetation, and heifer gains: 55 years on shortgrass.

摘要: Shortgrass rangeland, dominated by blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Steud), was grazed at 3 intensities, equivalent to mean stocking rates of 16.7, 23.0, and 36.5 heifer-days ha-1, from 1939 through 1994. Few changes in plant communities had been documented the early 1970's. In 1992-1994, frequency occurrence, basal foliar cover, biomass peak standing crop (PSC) were determined on remaining pasture each grazing intensity, ungrazed exclosures. Blue buffalograss (Buchloe dactyloides [Nutt.] Engelm.) increased, western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) needle-and-thread (Stipa comata Trin. R 4 6 times as high exclosures under any intensity. Heifer gains declined linearly with increasing pressure index. Optimum (most profitable) rate about 20% higher than that moderate which production maintained shrub pricklypear remained low levels. Returns land, labor, management only slightly optimum The intensity appears be both profitable sustainable.