Increasing Resources (increasing + resource)

Distribution by Scientific Domains

Selected Abstracts

Stability of pitcher-plant microfaunal populations depends on food web structure

OIKOS, Issue 1 2005
M. Kurtis Trzcinski
Enrichment (increasing K) destabilizes simple consumer,resource interactions, but increasing food web complexity in various ways can remove this paradox of enrichment. We varied resources and number of omnivorous predators (mosquitoes) and tested for effects on the stability (persistence and temporal variability) of microfaunal populations living in pitcher plants. Top-down (omnivorous) effects were destabilizing, decreasing the persistence time of a rotifer, Habrotrocha rosa, and perhaps a microflagellate, Bodo sp. Enrichment effects were more complex, in part due to effects of shredding midges on resource availability, and in part due to interactions with predation. The persistence of Bodo increased with resource availability (more bacteria due to shredding by midges; no paradox of enrichment). Increasing resources by adding ants decreased persistence of H. rosa when mosquitoes were rare (paradox of enrichment), but the effect was reversed in leaves with significant colonization by mosquitoes. Thus, in the microfaunal community of pitcher plants, omnivorous predation tends to be destabilizing, and also tends to remove the paradox of enrichment. [source]

Asian carp farming systems: towards a typology and increased resource use efficiency

C G J Michielsens
Abstract Resource use efficiency in Asian carp farming systems is analysed based on a survey of 2493 farms of nine countries. Multivariate classification of farms by intensity and diversity identified six farm types: four types of specialized aquaculture farms at different levels of intensity, and two types of integrated agriculture,aquaculture systems. Pond-based, specialized semi-extensive systems (using mainly inorganic fertilizers and feeds of off-farm origin), and integrated semi-intensive systems (using feeds and fertilizer of both on and off-farm origin) are by far the most common types, accounting for 59% and 27% of all farms respectively. Specialized semi-extensive systems also show the highest protein and nutrient (N and P) use efficiencies, and among the highest labour use efficiency. Super-intensive cage farms are less efficient in nutrient and labour use, but provide very high returns to land and capital investment. On average, the aquaculture components of integrated agriculture, aquaculture systems are less nutrient, land, and labour efficient than specialized semi-extensive systems. Integrated semi-extensive systems (using organic fertilizers of on-farm origin) are particularly inefficient across all indicators. Hence in practice, gains in overall resource use efficiency through on-farm integration with agricultural production are constrained by the relative inefficiency of the aquaculture subsystems on integrated farms. Although such systems can likely be improved, integration as such is not a panacea to increasing resource use efficiency. Wide variation in resource use efficiency within all systems indicates potential for substantial efficiency gains through improved management regardless of the fundamental choice of system. [source]

Dynamic models allowing for flexibility in complex life histories accurately predict timing of metamorphosis and antipredator strategies of prey

Andrew D. Higginson
Summary 1.,The development of antipredator defences in the larval stage of animals with complex life cycles is likely to be affected by costs associated with creating and maintaining such defences because of their impact on the timing of maturation or metamorphosis. 2.,Various theoretical treatments have suggested that investment in defence should both increase or decrease with increasing resource availability, but a recent model predicts investment in defences should be highest at intermediate resource level and predator density. 3.,Previous models of investment in defence and timing of metamorphosis provide a poor match to empirical data. Here we develop a dynamic state-dependent model of investment in behavioural and morphological defences that enables us to allow flexibility in investment in defences over development, the timing of metamorphosis and the size of the organism at metamorphosis that were absent from previous theory. 4.,We show that the inclusion of this flexibility results in different predictions to those of the fixed investment approach used previously, especially when we allow metamorphosis to occur at the optimal time and state for the organism. 5.,Under these more flexible conditions, we predict that morphological defences should be insensitive to resource level whilst behavioural defences should either increase or decrease with increasing resources depending on the predation risk and the magnitude of the fitness benefits of large size at metamorphosis. 6.,Our work provides a formal framework in which we might progress in the study of how the use of antipredator defences is affected by their costs. Most of the predictions of our model in are in good accord with empirical results, and can be understood in terms of the underlying biological assumptions. The reasons why simpler models failed to match empirical observations can be explained, and our predictions that are a poor match help to target the circumstances which warrant future study. [source]

Retrenching or renovating the Australian welfare state: the paradox of the Howard government's neo-liberalism

Philip Mendes
Most conventional studies of the former Australian Liberal,National Coalition government refer to its neo-liberal ideological agenda: its concern to reduce government interference with free market outcomes by restricting access to social security payments. That analysis suggests a substantial retrenchment of the Australian welfare state based on redirecting responsibility for the disadvantaged from government to corporations, private individuals and families. Yet there is increasing evidence from reliable sources that the government has not reduced social expenditure, and that increasing resources have been directed, particularly via the family payments system, towards some disadvantaged groups such as low-income families and the aged. Utilising the theory of the US political scientist Paul Pierson, this article explores the joint paradox of Australian neo-liberalism: the punitive treatment of some disadvantaged groups such as the disabled and lone parents versus the generosity towards other groups and, more generally, the growth rather than decline in social expenditure. The author asks what this paradox tells us about the likely future of the welfare state in Australia and elsewhere. [source]