SHORT-AND LONG-RUN FARM PLANNING UNDER UNCERTAINTY; INTEGRATION OF LINEAR PROGRAMMING AND DECISION TREE ANALYSIS

The paper presents an approach to an integrated long-run and short-run farm planning under uncertainty, based on a decomposition of the problem into (i) a series of short-run plans, and (ii) a master long-run plan. The series of the short-run plans are parametrically solved by linear programming "variable right hand" techniques and are later integrated into a long-run program using a (computerized) decision tree analysis. The attitude towards risk of the farm operator is expressed in the willingness to maximize the expected value of the income stream over the planning horizon subject to the restriction that alternatives which may lead to lack of liquidity must be eliminated.
Ce travail présenle une approche tentative ďintégrer, sous conditions incertaines, une planification de ferme à court et long terme. La planification est basée sur la partition du problème en (i) série de courte durée et (ii) de tongue durée. Les séries de courte durée sont résolues àľaide dun programme linéaire, et intégreés ensuite dans un programme à long terme àľaide de ľanalyse de "décision arbre."ľattitude envers les risques de ľentrepreneur est exprimée par la volonté-de maxiliser la valeur de revenu prévu au delá de la planification sous resérve de la restriction que des alternatives qui peuvent conduire à un manque de moyens liquides, doivent être éliminees.     

Effects of Phosphorus Enrichment and Wave Simulation on Populations of Ulothrix Zonata from Northern Lake Superior

The effects of phosphorus enrichment and wave simulation on new (denuded rocks) and established populations of Ulothrix zonata were examined in specially designed stationary and rocking tanks on a bedrock ledge overlooking the western arm of Lake Superior at Castle Danger, Minnesota. Tanks received constant flow of lake water and were exposed to the same insolation and climatic conditions as the lake for a 10-week period during July, August, and September 1972. A rocking tank and a stationary tank were enriched to maintain an average concentration of 0.16 mg/L PO₄–P. Two remaining tanks, receiving only lake water, served as controls. Each week, algal material was harvested from the tanks and analyzed for chlorophyll a, ash-free dry weight, and abundance of U. zonata and associated non-filamentous periphytic algae. Diatoms comprised, on the average, 95% of the total non-filamentous periphytic algae.The results show that phosphorus enrichment has marked effects on established populations of U. zonata in addition to favoring recolonization of U. zonata on bare rock substrates. Statistical analysis of the data revealed that phosphorus enrichment caused a significant increase in Ulothrix biomass and chlorophyll a in the enriched tanks. Wave simulation caused a significant reduction in total numbers of non-filamentous algae associated with Ulothrix in the rocking tanks.