Wayne T. Hamilton

A simple ecological sustainability simulator (SESS) for stocking rate management on semi-arid grazinglands

Abstract We constructed a simple simulation model (SESS) of the dynamics of forage growth and standing crop and cattle production to evaluate the ecological sustainability of management alternatives for extensive cow-calf production systems in northeastern Mexico and south Texas. Equations were written to estimate annual net primary production based on range condition, annual precipitation, and soil characteristics typical of the region. Simulations were conducted for annual precipitation levels of 300, 500, and 700 mm to estimate total and green standing crop dynamics, cattle grazing efficiency, and range condition trend for different stocking rates. The model-estimated stocking rates to achieve stable or slight improvement of range condition for the three precipitation levels were close to 58, 15, and 6 ha per animal-unit-year (AUY), respectively. With the model parameterized for precipitation and soil characteristics combined with the stocking rates recommended by COTECOCA (1979. Coahuila. Tipos de vegetacion, sitos de productividad forrajera y coeficientes de agostadero. Secretaria de Recursos Hidraulicos. Comision Tecnico Consultiva para la Determinacion Regional de los Coeficientes de Agostadero. Mexico), we conducted 20-year simulations for three groups of range sites of Coahuila, Mexico (annual precipitation: 1: 270 mm, 2: 351 mm and 3: 467 mm). The trends of body condition score and range condition for years 5, 10, 15, and 20 were similar within each of the three groups. The stocking rates recommended by COTECOCA were too high for sustainability on range site groups with 270 and 351 mm annual precipitation. The simulated probabilities for pregnancy rates at different stocking rates for the three groups indicated that the stocking rates recommended by COTECOCA were too high to achieve pregnancy rates ⩾80% in 8 out of 10 years with no supplement in the form of hay or concentrated feeds. Model simulations suggested that, in the absence of supplemental feed, ecological sustainability and acceptable livestock production could be achieved simultaneously at light stocking rates.

Insights in development and deployment of the GLA and NUTBAL decision support systems for grazinglands

Abstract The evolution of two decision support systems are traced from their roots in academia to deployment to technical advisors in USDA Natural Resource Conservation Service. The Grazing Lands Application (GLA) decision support system (DSS) was designed to provide forage inventories for grazing management of ranches. The other tool, NUTBAL, evolved as a stand alone DSS, emerging as a component of GLA when a supporting monitoring technology for nutritional profiling of free-ranging animals provided the user rapid estimates of diet quality from fecal scans with near infrared reflectance spectroscopy (NIRS). The adoption pattern of GLA and NUTBAL were quite different, with GLA experiencing less widespread adoption in USDA NRCS. The primary causes were (1) limited adoption rate of GLA within NRCS associated with changing culture in the information technology development group, (2) time overloading and staff reassignments for new programs, (3) changing software/hardware development environments imposed by the client disrupting development and system design and (4) large up front conversion of a largely paper-based system to a digital form. GLA was transformed to web-based delivery and streamlined to gain greater acceptance by users and ease time constraints on use of spatial tools. The NUTBAL system experienced more of a user driven evolution since it emerged from the GLA suite of tools and was supported by on-ranch monitoring systems capability of directly linking the livestock producers animals with the software. NUTBALs linkage to animal monitoring systems seems to have accelerated adoption rates. Ease of access to supporting input data coupled with early involvement of the target user and extensive analysis of the decision environment were critical to future success of these systems. Targeting technical advisors instead of livestock producers appears to be a more viable development track unless new innovations in DSS delivery systems can emerge using the internet.

Management systems analysis as guidance for effective interdisciplinary grazingland research

Abstract Management systems analysis offers scientists a way to link field research with the unique decision environment of private ranch firms. This systematic approach helps clearly identify research needs and offers a high degree of professional security when basic research is brought under scrutiny by commodity groups. A decision support system reflecting management systems analysis is outlined based on our experiences in developing integrated brush management systems. Understanding human needs, priorities and perceptions influencing decisions unique to each rancher is critical to designing applicable decision support systems. The decision support process causes the orderly organization of current knowledge, an assessment of level of precision required to make a decision, and the determination of knowledge limiting the process in an interdisciplinary environment. A series of feedback mechanisms from systems analysis, decision analysis and field research is a continuous iterative process which must be recognized by research organizations to facilitate incorporation of research results into decision support systems and to identify and focus future research needs. Organization, management and pitfalls of interdisciplinary research for development of management systems analysis is presented.

Sustainability of agroecosystems in semi-arid grasslands: simulated management of woody vegetation in the Rio Grande Plains of southern Texas and northeastern Mexico

Abstract We describe a model that simulates use of chemical treatments, mechanical treatments (roller chopping and root plowing), and fire to manage woody vegetation in the Rio Grande Plains of southern Texas and northeastern Mexico. The model consists of two submodels representing dynamics of woody and herbaceous vegetation, respectively. Percent canopy cover of woody vegetation changes as the result of application of management schemes. Aboveground biomass of herbaceous vegetation changes as the result of differences in rates of net primary production, senescence, decomposition, and losses due to grazing and fire. The model is represented as a compartment model based on difference equations with a time step of 1 month. Model predictions of changes in canopy cover of woody vegetation, number of acres required to support a cow, and net production of herbaceous vegetation following application of each of the four treatments are similar to typical 25-year post-treatment response curves for the Rio Grande Plains. Simulation results suggest that the period of opportunity for effective use of fire to manage woody vegetation and sustain production of herbaceous vegetation is longest following root plowing, intermediate following use of chemicals, and shortest following roller chopping. In each case, the efficacy of fire in reducing canopy cover of woody vegetation diminishes rapidly as percent canopy cover increases from roughly 30–50%.

Decision support software for estimating the economic efficiency of grazingland production.

Decision support software has evolved in a number of disciplines to facilitate efficient allocation of resources. Such tools are especially useful where the response of complex systems to human activity are diicult to predict. Decision support systems empower managers to rapidly analyze the ecological and economic implications of alternative management strategies. The Grazingland Alternative Analysis Tool (GAAT), has been developed to estimate the economic efficiency of a wide range of grazingland production systems. Systems that can be analyzed, either individually or in combination, include livestock, wildlife, leased grazing, gram and forage crops, wood products and other nonforage crops. The planning horizon, discount rate, available forage, consumption by class of animal, herd management practices, product yields, product and input prices, and improvement investments must be specified by the user. The GAAT program calculates the resulting annual forage balance for all enterprises being analyzed and the net present value and internal rate of return for the specified management interventions during the planning period. Two examples are presented to demonstrate the flexibility of GAAT for analyzing the economic efficiency of grazingland production systems. The fmt example analyzes the use of prescribed burning to control Ashe juniper (Juniper ashei Buckholz) and the second determines the economic effect of changing a dairy from a concentrate-dependent to a grazingdependent system.

Economic implications of brush treatments to improve water yield

Abstract One possible method of increasing water yield in some water-poor areas is through brush management. Economic modeling of brush control programs designed to improve water yield has been performed for numerous Texas watersheds. These studies assumed a single criteria brush control program. This single criteria program may have negative impacts on certain wildlife habitats, is likely unacceptable to landowners, and does not incorporate additional restoration practices. Our study analyzed the economic consequences of 3 brush management/restoration scenarios for the Edwards Aquifer recharge zone and Twin Buttes watersheds and the drainage basins contained within. Economic measures included total public cost (

Brush Management: Past, Present, Future

) and public cost of producing additional water (

Chemical Weed and Brush Control: Suggestions for Rangeland

/1000 m3 of added water). Because of its larger size, estimated total public cost was higher for the Twin Buttes watershed than for the Edwards Aquifer recharge zone watershed, despite the fact that the Twin Buttes had lower cost per ha of treated brush. Public cost of additional water is lower for basins within the Edwards Aquifer recharge zone watershed (ranging from

THE USE OF BIOPHYSICAL AND EXPECTED PAYOFF PROBABILITY SIMULATION MODELING IN THE ECONOMIC ASSESSMENT OF BRUSH MANAGEMENT ALTERNATIVES

26 to

Integrated Brush Management Systems for Texas

44 per 1000 m3 of added water) than in the Twin Buttes watershed (ranging from