Social effects on crowding preferences of urban forest visitors

An image-based stated choice approach was used to investigate the conditions determining why visitors to an urban forest in Vienna feel crowded or not. Respondents (N=213) evaluated several sets of images depicting trail use scenarios with different levels of social crowding conditions and several types of social interferences. Forest users were segmented into three groups based on their global evaluations of use levels during weekends and work days, resulting in a crowding-averse, a crowding-tolerant, and a crowding-indifferent segment. Crowding-averse respondents reacted much more negatively to scenarios with high-use levels, heterogeneous trail use conditions, and violations of personal minimum spatial requirements caused by the presence of others. This user group felt overcrowded because social conditions experienced in the area interfered with their main visiting goals, especially to walk with their dog unleashed and to recreate. By contrast, crowding-tolerant respondents disliked very low-use and high-use situations, and preferred a certain amount of social stimulation in the form of some encounters, and more heterogeneous trail use conditions.     

Introducing spatial grazing impacts into the prediction of moorland vegetation dynamics

Grazing by large herbivores is a major determinant of vegetation dynamics in many semi-natural ecosystems, including the replacement of heather moorland by rough grassland in the British uplands. Herbivore foraging is influenced by vegetation patterns and, in turn, their grazing drives vegetation dynamics. Although vegetation impacts are local, spatially heterogeneous local impacts can have different consequences as would the same impacts distributed uniformly. We constructed a simulation model of the spatial effects of grazing by sheep on the vegetation dynamics of heather moorland, a vegetation community of international conservation importance in the UK. The model comprised three sub-models to predict (1) annual average heather utilisation, (2) spatial variation in heather utilisation (higher near the edge of grass patches) and (3) competition between heather and grass. Here we compare the predicted heather utilisation and vegetation dynamics of the spatial model, relative to those of a non-spatial model. The spatial model resulted in a reduced loss of heather cover for a given sheep stocking rate. The model demonstrates how spatial interactions between large herbivores and their forage drive vegetation dynamics, leading to changes in community structure and composition. Indeed, omitting spatial effects in grazing models may lead to inaccurate predictions. We have shown that ecosystem modelling, based around an iterative dialogue between developers and experienced researchers, has the potential to make a substantial contribution towards the conservation and management of vulnerable landscapes. Combining modelling with experimental studies will facilitate progress towards understanding long-term vegetation/herbivore dynamics.     

The analysis of agricultural distribution systems

The application of systems analysis to the study of agricultural distribution has far-reaching implications for marketing investigations and for managerial decision-making. Concepts developed in the emerging discipline of Physical Distribution Management are applicable to agricultural distribution, an area which has not hitherto been the subject of a systems approach which incorporates such concepts as ‘total distribution analysis’, ‘socio-technical systems’ and ‘synergy’. This paper demonstrates the scope for taking a systems analysis view of agricultural distribution and illustrates three of its aspects—namely, the marketing of farm inputs, the distribution of farm produce and machinery management on the farm.     

The basophil response in blood and bone marrow of tick-infested guinea pigs.

The concentrations of basophils in blood and bone marrow were monitored in guinea pigs subjected to primary and secondary infestations with larvae of Dermacentor andersoni. In these guinea pigs a significant increase of basophils was evident in peripheral blood. The response following the secondary infestation was more rapid and more intense than that following the primary infestation. Similar changes were also shown to occur in bone marrow. The possible significance of these responses in relation to acquired tick resistance in guinea pigs is discussed.