Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Wildland Resources

Department name when degree awarded

Rangeland Resources

Committee Chair(s)

D. Layne Coppock


D. Layne Coppock


Ben Norton


Neil West


Robert Ford


Jon Moris


Pam Riley


Current models of rangeland system dynamics were evaluated in Cosapa, a pastoral community on the Bolivian altiplano. Two specific models were tested: the "equilibrium" model, which assumes biotic interactions dominate rangeland dynamics and lead to system stability, and the "nonequilibrium" model, in which stochastic, abiotic factors control systems such that equilibrium is never attained. A livestock development project (called "Project Alpaca") working in the community was then assessed in terms of how its assumptions of system dynamics compared with empirical findings. The goal of Project Alpaca was to increase incomes for camelid (i.e., llama and alpaca) herders on the Bolivian altiplano by improving the processing, production, and marketing of alpaca wool. Project implementation was carried out by an indigenous herders' association, with funds provided for construction of a modern alpaca wool processing plant and technical interventions at the farm level.

Specific research objectives were to determine which conceptual model of system dynamics (equilibrium or nonequilibrium) best approximated the vegetation and livestock dynamics in Cosapa, and determine the impacts of technical innovations introduced by Project Alpaca. Vegetation dynamics were assessed by comparing plant species composition and production between grazed and ungrazed sites. Pastoral management strategies, livestock population dynamics between 1982 to 1995, and project impacts were assessed using a household survey.

Results from the vegetation analyses showed that grazing protection had little impact on plant productivity, but reduced species diversity in wetland areas. The vegetation thus exhibited nonequilibrial characteristics. Regarding livestock dynamics, populations were relatively stable (over 13 years), although mortality was affected by severe drought, suggesting a combination of equilibrial and nonequilibrial interactions. Project Alpaca assumed an equilibrium model by emphasizing system stability and production maximization. The technical interventions showed positive, negative, and neutral associations with animal productivity. Construction of fenced exclosures on communal land has increased conflicts over land tenure rights, and may marginalize poorer households and increase social stratification. Development recommendations include shifting efforts away from intensification interventions that limit movement and flexibility, and strengthening social and economic networks that buffer the impacts of system variability.