Reduced future forage production, diminished range condition, and reduced animal performance have been major factors considered when setting rangeland stocking rates. The relative economic importance of diminished current period animal performance versus intertemporal forage production impacts was investigated using a dynamic optimal control model. The model is applied to yearling stocker production in eastern Colorado. Results indicate that intertemporal grazing impacts to forage production are not that important; reduced weight gain during the current period drives the economic stocking rate decision. Further, ranchers have no economic incentive as profit maximizers to continually overgraze the range.

A long standing question in range management concerns the relative importance of the stocking rate versus the length of time during which animals graze a particular rangeland. We address this question by analyzing the problem faced by a private rancher who wishes to minimize the long run expected net cost (LRENC) from range operations by choosing either the stocking rate or the length of time during which his animals graze his rangeland. We construct a renewal-theoretic model and show that, in general, this rancher's with an optimally chosen stocking rate is lower than his with an optimally chosen grazing LRENC LRENC cycle length.

A conceptual approach is commonly needed to provide guidance for developing new strategies concerning the use and management of renewable resources such as rangelands. The theoretical model constructed in this paper captures the essential aspects of dynamic and stochastic issues associated with the management of rangelands. We discuss the connections between the model and range policy. Specifically, we point out scenarios in which there is a limited role for policy. This is compared to scenarios when policy has a significant role to play in ensuring the sustainable use of rangelands. Finally, we suggest 2 ways in which our approach might be extended and used in a practical application. Resumen Comunmente se necesita una propuesta conceptual como guia

Conifers (Picea and Abies spp.) have replaced aspen (Populus tremuloides Michx.) over much of aspen's historic range in the western United States. We measured the impact of this change upon the production of understory vegetation potentially useful as forage for livestock and wildlife on two southern Utah national forests. A negative exponential relationship between conifer cover and understory biomass was demonstrated as log(biomass) 5 6.25 2 0.03787(% conifer), adjusted R 2 5 0.57. Understory production in aspen stands begins to decline under very low levels (10% to 20%) of conifer encroachment. Management implications include loss of forage production capability and wildlife habitat and potential overstocking of livestock grazing allotments if the associated loss of forage is not considered. Resumen Las confieras (Picea y Abies spp.) han remplazado al álamo (Populus tremuloides Michx.) en gran parte del rango histórico de distribución de esta especie en el oeste de los Estados Unidos de Ame´rica. Medimos el impacto de este cambio sobre la producción del estrato herbáceo potencialmente útil como forraje para el ganado y fauna silvestre en dos bosques nacionales del sur de Utah. Se demostró una relación exponencial negativa entre la cobertura de coníferas y la biomasa del estrato herbáceo, tal como lo demostró la siguiente ecuación: log(biomasa) 5 6.25 2 0.0378(% conífera), R 2 ajustada 5 0.57. La producción herbácea en las poblaciones de álamo inicia a disminuir a muy bajos niveles (10% a 20%) de expansión de las coníferas. Las implicaciones de manejo incluyen pérdida de capacidad de producción de forraje y del hábitat para la fauna silvestre y una sobrecarga potencial de ganado, si la pérdida de forraje asociadas no se considera.

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