Changes In Resource Use Research Articles

A production system model of hunter-gatherer resource scheduling adaptations

Flannery has suggested that the shift from a hunter-gatherer economy to one based upon incipient agriculture requires a gradual rescheduling of the groups' resource acquisition activities. Here, concepts from Artificial Intelligence and Adaptive Systems are used to develop a model of prehistoric hunter-gatherer decision-making in the valley of Oaxaca, Mexico. This decision-making system was then used to answer the following questions: 1. 1. Given randomly specified strategies and no initial knowledge of what available rescheduling decisions will improve performance, can the system produce changes that lead to a mix of strategies that correspond to those used by hunter-gatherers in the valley prior to the introduction of incipient agriculture? 2. 2. How would the system adjust its' resource acquisition strategies in response to the introduction of techniques for incipient agriculture? It is suggested that this basic model is able to explain a significant percentage of the changes in resource use seen in the archaeological record for the site.

Niche compression: Two tests of an hypothesis using narrowly sympatric predator species

AbstractThe compression hypothesis predicts that when two species occur together in narrow sympatry, individuals in the overlap zone will use a smaller range of habitats and a larger or unchanged range of prey than individuals in allopatry. This report attempts to validate the assumptions underlying this hypothesis, and describes two tests of the predicted resource shifts using narrowly sympatric species of predatory marsupials (Antechinus spp.). In the first test, using A. stuartii and A. flavipes, there was little correspondence between observed and predicted changes in diet and habitat use (as measured by indices of niche breadth) for populations of either species. One index of niche breadth (Levins' B) revealed no trends in resource use, but a proportional similarity index relating resource use to resource abundance consistently indicated that the niche breadths of each species were greater in allopatry than in narrow sympatry. In the second test, using A. stuartii where it occurred alone and in narrow sympatry with A. swainsonii, there was again little correspondence between observed and predicted changes in resource use for seasonal or overall data. Differences in magnitudes of niche breadths between allopatric and narrowly sympatric A. stuartii were smaller in this test than in the first.While these findings provided no support for the compression hypothesis, they suggested three situations in which the predictions of the hypothesis may generally not apply. These are: when the predators are active, dietary generalists (diet cannot expand in sympatry); when one species is a markedly superior competitor to the other (the dominant species suffers little or no niche compression in sympatry); and when the species compete by interference rather than exploitation (one species is evicted from sympatry or both show compression in habitat use and diet).

Trophic relationships among concentrated populations of small fishes in seagrass meadows

Changes in available food and utilized foods for a densely populated guild of animals can uncover periods of niche displacement among particular consumer species or their separate size classes. Dense populations of small fishes and their foods were çensussed for 13 months and studied experimentally in shoalgrass and turtlegrass meadows of Redfish Bay, Texas. Feeding habits were determined with respect to prey availability, and illustrated the extent to which seasonal partitioning of food corresponded to food depletion among these abundant consumers in seagrass meadow food webs. The darter goby, code goby, pinfish, and Gulf pipefish were the most common species throughout the year. Although the darter goby did not show distinct ontogenetic changes in food habits, the code goby, Gulf pipefish, and pinfish demonstrated major ontogenetic progressions of foods selected. Food availability in the seagrass meadows changed seasonally. When major prey such as amphipods were abundant, during spring, many fish species showed high overlap in food use. Regardless of food availability, the code goby and Gulf pipefish fed mainly on amphipods or copepods. The more common darter goby and pinfish seasonally changed their diets with changes in food availability; the darter goby and pinfish were more carnivorous during spring, but they largely consumed epiphytic algae during summer. Cage experiments were used to monitor foods confined with elevated densities of pinfish and darter gobies, relative to control cages at natural overall densities. Prey items in the former cages decreased sharply, with corresponding dietary shifts by these common fishes. During resource depletion, these changes in resource use by these naturally concentrated consumers appeared as temporary partitioning of available resources. This shift occurred during both natural (seasonal) and experimental depletions of food, and appears to result from increased interspecific and intraspecific competition during periods of depleted preferred foods.

Energy analysis of Japanese industries: A time series analysis

Characteristics of Japanese industries in the past 15 years have been investigated in terms of energy intensities, or energy directly and indirectly spent for production of a unit output in industries. The methodology of the analysis is similar to that by Herendern, that is an extension of input-output approach, but with various modifications. Data are seven input-output tables, of about 400 x 400 items published by the Japanese government. Changes in energy intensities with time are disaggregated into two factors, 1) changes in direct energy intensities and 2) changes in nonenergy resource use or in the ratios of value added taxes. Observation of these factors in the last 15 years reveals that the latter factor has been highly significant in energy conservation, especially in machine industries, the raw materials of which are mainly iron and steel. It is also observed that conventional energy conservation efforts have scarcely been dependent on nonenergy resource conservation.

Territoriality and changes in resource use by sunbirds at Leonotis leonurus (Labiatae).

Leonotis leonurus was studied with the aim of characterising nectar quality and quantity, and of monitoring the sunbirds' response to the resource. The flowers produced high quality nectar in low quantities. Nectar quality remained constant during the day and averaged 23.4% sucrose equivalents (an energy content of 3.8j/μl). Nectar production was highest during the morning when flow rates reached a peak of 3.3 μl/h. L. leonurus was visited by four species of sunbirds. In 1977 there were 7.8 visits/h to the flowers. The clump was defended by a single Olive Sunbird (Nectarinia olivacea) who defended the flowers intra- and interspecifically. On one day the territorial bird obtained approximately 57.1 kJ from the Leonotis flowers and expended 5.4 kJ on defence and 13.6 kJ overall while on the territory. Territorial behaviour and intruder pressure was a function of resource availability. When Leonotis nectar levels were high intruder pressure was intense and the territorial bird employed long chases as a defence behaviour. When nectar levels desreased intruder pressure was lower, the territorial bird chased less and employed vocalisations as a relatively inexpensive form of territorial behaviour.In 1978 there was an abundance of nectar sources in the study area due to the late onset of the dry season. Sunbirds were not territorial at Leonotis and visiting rates were lower than in 1977, averaging only 1.7 visits per hour. Instead the sunbirds concentrated on contemporaneously flowering plant species, particularly Halleria lucida.

A Decision Simulation Model for Health Services Management

This model has been designed to assist decision making in the Health Services by predicting the effects on a local population of proposed policy decisions. Policy decisions are considered to:Change the amount of certain resources available, e.g. manpower, hospital beds; or Alter the methods of using resources, e.g. changing the emphasis of health care to the community rather than the hospital; or Change the characteristics of illnesses, e.g. by vaccination or screening. The model predicts the incidence of morbidity and mortality in a specified population and the changes in resource use over a period of years. Thus it is possible to see the long term effects of changes in population size and structure alongside the effects of management decisions on the use of health resources.The model has been designed principally for research purposes but has been used in the context of a health services management game. The validity of the model's predictions have yet to be tested. It is hoped to run the model in parallel with management decision making in a single health district in order to test the model's validity and improve its predictive ability.

Hydraulic development as a process of response

The relationship between political organization and hydraulic development is discussed, using illustrations from the Valley of Oaxaca, Mexico. It is suggested that change in political organization toward greater or lesser centralization of control over local water resource use may be part of a social response to environmental degradation (in this case, a receding water table) resulting from the effects of change in resource use (in this case, intensified water extraction). Economic stress due to environmental degradation varies in duration and intensity; such variations must be taken into account in understanding shifts in response patterns. Small-scale hydraulic development which places pressure on the availability of water for irrigation may elicit an initial response of centralization of control over its use to correct for the disturbance, water shortage. However, this response itself tends to exacerbate the disturbance through reducing previously existing homeostatic controls on the extraction of water and hence leads to greater economic stress, up to the point at which new responses must take place. Other kinds of environmental disturbance resulting from initial development attempts appear to have similar feedback effects which contribute to potential systemic instability.

CHANGES IN FARM PRODUCTION UNDER INTENSIVE FARM MANAGEMENT ADVICE*

This investigation examines the impact of intensive farm management advice on levels and productivities of resource use on samples of farms. A total of 60 members of 13 farm management advisory services and 60 non‐members, matched by locality, were studied in two farming regions of Western Australia. A production model has been formulated and analysed which discriminates between effects of differences and changes in resource use and productivity over time and between members and non‐members. Major differences between members and non‐members over time have been rates of growth of inputs and outputs rather than systematic changes of production relationships.