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Internal and external entropy are indicators of evaluation of the success of the firm management. The evaluation of the file of the chosen agricultural firms shows, that the level of internal and external entropy is not too high for the future dynamics and development. Competitiveness of the evaluated firms can be influenced especially by problematic level of their interior social situation (it means social subsystem measured with the help of the internal entropy) that is connected with a not very efficient management of the human resources.

Depuis une dizaine d’années en France, de nouvelles formes d’installations collectives émergent et semblent motivées par la réalisation d’un projet de vie associé à l’exercice du métier d’agriculteur. Encore peu documentées, ces formes d’exploitations collectives pourraient cependant favoriser la conduite de systèmes plus diversifiés, dont la gestion plus complexe serait permise par la diversité des acteurs impliqués dans le processus de production. Pour appréhender les interactions entre l’organisation collective et la combinaison d’activités caractérisant l’exploitation agricole, nous proposons un cadre générique permettant d’analyser et de comparer différentes stratégies organisationnelles. Considérant une combinaison de données récoltées sur treize fermes collectives, nous proposons un cadre conceptuel générique basé sur le formalisme AGR (Agent-Groupe-Rôle) issu du domaine de la recherche en informatique. Sa déclinaison en un cadre d’analyse appliqué à trois cas d’étude contrastés illustre la diversité des formes d’organisation de collectifs et des différents enjeux qu’ils portent, ainsi que les façons dont le partage des ressources structure les groupes. Over the last ten years in France, new forms of collective farming have emerged and seem to promote a life project associated with being a farmer. These forms of collective farming, which are still poorly documented, could promote more diversified systems, more complex, related to the diversity of actors involved in the farm. To understand the interactions between the collective organization and the combination of activities at farm scale, we developed a generic framework to analyze different organizational strategies and their comparison. Using a combination of data collected on 13 collective farms, we propose a generic conceptual framework based on the AGR (Agent-Group-Role) formalism. Its development into an analytical framework is applied to three contrasting case studies to illustrate the diversity of group organization forms and of the different issues they deal with, as well as the role of resource sharing in group structuring.

Historical data (1950-1984) on the duration of outbreaks of the forest tent caterpillar (Malacosoma disstria) in northern Ontario, Canada were examined. Outbreak duration was compared to host tree species dominance and forest structure over large areas of boreal forest partially cleared for agriculture. Abundance of the principal host tree species Populus tremuloides had no consistent effect on duration of outbreak within forest districts, and was negatively correlated with duration of outbreaks among the eight forest districts examined. The amount of forest edge per square km was the best, and most consistent, predictor of the duration of tent caterpillar outbreaks both within individual forest districts and among forest districts. Because forest tent caterpillar populations are driven largely by the impact of parasitoids and pathogens, results here suggest that large-scale increase in forest fragmentation affects the interaction between these natural enemies and forest tent caterpillar. Increased clearing and fragmentation of boreal forests, by agriculture and forestry, may be exacerbating outbreaks of this forest defoliator.

The changing structure of agriculture will have an effect on soil and water resource conservation. A conceptual framework for adoption of resourse conservation measures, in light of the changes, is discussed.

Although the creation of edges during forest fragmentation can have important abiotic and biotic impacts, especially under conditions of future climate change, mechanistic models of edge effects have not been forthcoming. A simple numerical model of two-dimensional heat flow is developed and applied to a vertical forest/clearcut edge profile and to simulated fragmented landscapes. Height-specific thermal diffusivity and conductivity in the forest were assumed to vary in proportion to foliage densities measured in the central Amazon. In the edge profile, the clearcut that abutted the edge served as a heat source and its temperature was maintained at a constant value higher than in the initially cooler forest. In the fragmented landscapes, simulated treefall gaps were heat sources whose temperature varied with sun movements during the day. Gap frequency was varied so as to approximate the gap coverage observed in selectively logged forests. In one set of simulations, temperature in the openings was systematically varied; in another, thermal diffusivity of the forest was varied. Along the edge profile, high temperatures in the clearcut were rapidly transmitted into the upper canopy due to additive edge effects. Temperatures in the forest understory were also very sensitive to clearcut temperatures due to relatively sparse understory foliage. An overall increase in forest diffusivity led to markedly higher temperatures close to the edge and a more even temperature distribution among height strata. In fragmented landscapes, total gap coverage and additivity from neighboring gaps strongly influenced forest temperatures. At low conductivities, heat flowed only into the forest close to the gaps and hence forest temperature increased almost linearly with gap area. However, at high conductivities, heat flowed far into the forest and forest temperature varied as a function of gap density in the surrounding neighborhood. Because of these additive effects, slight increases in total gap area led to disproportionate changes in the thermal profile of the landscape. These results have important implications for the conservation of forest ecosystems.

A typology of models that explain patterns of variation in farm endowments and farm practices and yields shows that insecurity in renting land, financing constraints, and the absence of insurance generate patterns of factor use quite different from the famous \"inverse relationship\" caused by labor supervision problems. One might expect to observe positive relationships between wealth and yields. Village-level data from western Sudan confirm that such positive relationships are not a theoretical curiosity. Wealthy farmers have higher levels of output per hectare because they use more labor per hectare. Insurance and financing constraints appear to be the crucial market failures.

Opportunities for savings in both human labour and technical equipment were tested on the case of large farms situated in less favoured areas (LFA) in the Czech Republic. Large LFA farms were found to be undoubtedly more efficient than the small ones. The diversification of activities (to non-agricultural) was much wider at large than at small farms. The targeting of the objectives of the LFA measure was analysed on the cases of the selected types of small and large farms. The amounts of support devoted to reach these objectives were also evaluated. The paper further analyses economic results of small and large farms in LFA within the Czech Republic, and evaluates the impacts of the current LFA measures, where the payment distribution is based only on the grassland area, regardless of the farm size. Based on these analyses, it was suggested to distribute the LFA payments in the CR per 1 ha of utilised agricultural area of farm. It would be suitable to introduce a graded decrease of the LFA payments rates according to the farm size. The analysis proves that the economic survival of large farms, measured as the farm net value added per one annual work unit, will not be endangered.