Intermediate coupling between aboveground and belowground biomass maximises the persistence of grasslands

Aboveground and belowground biomass compartments of vegetation fulfil different functions and they are coupled by complex interactions. These compartments exchange water, carbon and nutrients and the belowground biomass compartment has the capacity to buffer vegetation dynamics when aboveground biomass is removed by disturbances such as herbivory or fire. However, despite their importance, root-shoot interactions are often ignored in more heuristic vegetation models. Here, we present a simple two-compartment grassland model that couples aboveground and belowground biomass. In this model, the growth of belowground biomass is influenced by aboveground biomass and the growth of aboveground biomass is influenced by belowground biomass. We used the model to explore how the dynamics of a grassland ecosystem are influenced by fire and grazing. We show that the grassland system is most persistent at intermediate levels of aboveground-belowground coupling. In this situation, the system can sustain more extreme fire or grazing regimes than in the case of strong coupling. In contrast, the productivity of the system is maximised at high levels of coupling. Our analysis suggests that the yield of a grassland ecosystem is maximised when coupling is strong, however, the intensity of disturbance that can be sustained increases dramatically when coupling is intermediate. Hence, the model predicts that intermediate coupling should be selected for as it maximises the chances of persistence in disturbance driven ecosystems

CATCHMENT SCALE INFLUENCES ON BROWN TROUT FRY POPULATIONS IN THE UPPER URE CATCHMENT, NORTH YORKSHIRE.

A multi-scale approach for restoration site selection is presented and applied to an upland catchment, the River Ure, North Yorkshire. Traditional survey methods, advances in remote sensing, Geographical Information Systems (GIS) and risk-based fine sediment modelling using the SCIMAP module are combined to gather data at the catchment-scale through to the in-stream habitat-scale. The data gathered have been assessed against spatially distributed brown trout fry populations using Pearson’s correlation and multiple stepwise regressions. Fine sediment was shown to have a positive correlation with fry populations when upland drainage channels (grips) were added to the SCIMAP model. This suggests risk from peatland drainage is realised further down the catchment where eroded sediments are deposited. Farm-scale SCIMAP modelling was tested against farmers’ knowledge with variable results. It appears there is a cultural response to risk developed over generations. Management of meadows and pasture land through sub-surface drainage and stock rotation resulted in the risk being negated or re-routed across the holding. At other locations apparently low-risk zones become risky through less sensitive farming methods. This multi-scale approach reveals that the largest impacts on brown trout recruitment operate at the habitat-adjacent scale in tributaries with small upstream areas. The results show a hierarchy of impact, and risk-filters, arising from different intensity land management. This offers potential for targeted restoration site selection. In low-order streams it seems that restoration measures which exclude livestock, and provide bankside shading, can be effective. At such sites the catchment-scale shows a reduced signal on in-stream biota. Thus, brown trout stocks could be significantly enhanced by targeting restoration at riffle-habitat zones and adjacent land in order to disconnect the stream from farm-derived impacts and through adding structure to the stream channel

The sentiments of a Church-of-England man : a study of Swift's politics

This contextualist study re-examines the contested critical question of Jonathan Swift's political character. It is concerned with the historical meaning of Swift's texts and attempts to recover their original political impact. Politically-literate contemporaries claimed to read Jacobite Tory politics in Swift's texts. Rather than dismiss the judgement of Swift's contemporaries, this study asks whether there is anything about Swift's political writing in polemical context that could have led contemporaries to construe the politics of his texts as Jacobite Tory. The conclusion this study reaches is that aspects of Swift's political rhetoric are consonant with Tory and Jacobite polemic. While contesting current conceptions of Swift as a Whig, this study offers a partial revision of that scholarship which describes Swift as a non-Jacobite Tory. The thesis is based on an analysis of Swift's prose, poetry and correspondence and contemporary (mainly printed) sources books, pamphlets, poems on affairs of state and newspapers. Some new or neglected polemical contexts and analogues for Swift's works are suggested. Chapter 1 considers some of the problems and contested issues in interpretation of Swift's political biography and writing. Chapter 2 witnesses Swift's combination of High Church attitudes with a radical political critique of Whig establishment. Swift is read in juxtaposition with Jacobite Tory authors such as George Granville, Lord Lansdowne. Chapter 3 relocates A Tale of a Tub in historical context to reveal the satire's relation to High Church Tory polemical languages. Chapter 4 discusses the disaffected Tory aspect of Gulliver's Travels. Chapter 5 attempts to register the complexity of the textual evidence of Swift's attitude to Jacobitism. Detailed attention is given to his politically-revealing attitudes to the Dutch. A coda briefly describes Swift's discontent with the Revolution settlement, examines this Church-of-England Man's sentiments on the crucial ideological issue of resistance, and suggests the importance of Hugo Grotius in Swift's political thought

Integrated control of invasive alien plants in terrestrial ecosystems

Effective management of invading alien plants in natural and semi-natural systems is imperative if we are to prevent enormous impacts. An integrated approach involving the combined use of a range of methods is usually necessary to control invasive alien plants effectively. The various methods that are available are usually classified as: mechanical methods (felling, removing of invading alien plants, often in conjunction with burning); chemical methods (using environmentally safe herbicides); and biological control (using species-specific insects and diseases from the alien plant's country of origin). Approaches available for integrated control depend on the species under consideration (features of individual species and the number and identity of species that occur together), features of the invaded systems, the availability of resources and other factors. Mechanical and chemical control are short-term activities, whereas rigorous and disciplined follow-up and rehabilitation are necessary in the medium term. Biological control can provide effective control in the short and medium term in some cases, and it is often the only really sustainable solution in the longer term. We suggest that the biological attributes of plants represent a stable set of attributes, which enable managers to devise control approaches, but that such approaches are likely to be upset by stochastic events such as fires, floods or budget cuts. While an approach of adaptive management, based on trial, error and continual improvement is a logical way in which to progress, the advent of powerful computer simulation modelling technologies will allow managers to do hundreds of 'trial and error' runs in order to explore the consequences of certain courses of action. This should represent an improvement on the current state of affairs, and should allow for better decision-making. We present a series of simulations to illustrate this point.Resource /Energy Economics and Policy,

Rainfall or Price Variability: What Determines Rangeland Management Decisions? A Simulation-Optimization Approach to South African Savannas

Savannas cover the greater part of Africa and Australia and almost half of South America and contribute to the livelihoods of more than 350 million people. With the intensification of land use during the second half of the 20th century, savannas have become increasingly degraded through bush encroachment as a consequence of increased grazing pressure. Research on rangeland dynamics, however, provides contradicting answers with regard to the causes and possible remedies of bush encroachment. In this paper we present results from an application of a simulation-optimization model to the case of extensive rangeland management in South Africa. Our model differs from previous approaches in that it explicitly accounts for the influence of stochastic prices and rainfall on economically optimal management decisions. By showing the implications of neglecting price variation and stochasticity in rangeland models we provide new insights with regard to the determinants of bush encroachment and rangeland managers' economic utility. We demonstrate that, in the case of South Africa, optimal rangeland management is likely to lead to bush encroachment that eventually makes livestock holding unprofitable. Yet, we identify the costs of fire management to be a limiting factor for managers to counteract bush encroachment and explore the impact of policy measures to reduce fire control costs on the ecological and economic sustainability of livestock holding.Equilibrium, bio-economic modeling, grassland management, sustainable strategies, stochastic conditions, Livestock Production/Industries, Q57,

CHRONIC RESPIRATORY DISEASE IN MINING COMMUNITIES *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73871/1/j.1749-6632.1972.tb40188.x.pd

Hidden in plain sight? The human resource management practitioner's role in dealing with workplace conflict as a source of organisational–professional power

This article examines the perceived importance of human resource (HR) practitioners' role as ‘organisational professionals’ at national and organisational levels. Informed by institutionalist theory and drawing upon interviews at national and organisational levels, a dissonance is identified in the degree to where HR's non-substitutable expertise lies. It is concluded that HR's role in dealing with workplace conflict is under-recognised at national level as it does not fit with the proactive ‘strategic’ narrative seen to be what HR needs to achieve to be influential. At organisational level, however, conflict management is a source of power because, unlike many other HR roles—valued as they may be—conflict management is the role that can least be substituted by non-specialist HR practitioners because of its unpredictability

Rapid leaf deployment strategies in a deciduous savanna

Deciduous plants avoid the costs of maintaining leaves in the unfavourable season, but carry the costs of constructing new leaves every year. Deciduousness is therefore expected in ecological situations with pronounced seasonality and low costs of leaf construction. In our study system, a seasonally dry tropical savanna, many trees are deciduous, suggesting that leaf construction costs must be low. Previous studies have, however, shown that nitrogen is limiting in this system, suggesting that leaf construction costs are high. Here we examine this conundrum using a time series of soil moisture availability, leaf phenology and nitrogen distribution in the tree canopy to illustrate how trees resorb nitrogen before leaf abscission and use stored reserves of nitrogen and carbon to construct new leaves at the onset of the growing season. Our results show that trees deployed leaves shortly before and in anticipation of the first rains with its associated pulse of nitrogen mineralisation. Our results also show that trees rapidly constructed a full canopy of leaves within two weeks of the first rains. We detected an increase in leaf nitrogen content that corresponded with the first rains and with the movement of nitrogen to more distal branches, suggesting that stored nitrogen reserves are used to construct leaves. Furthermore the stable carbon isotope ratios (δ 13 C) of these leaves suggest the use of stored carbon for leaf construction. Our findings suggest that the early deployment of leaves using stored nitrogen and carbon reserves is a strategy that is integrally linked with the onset of the first rains. This strategy may confer a competitive advantage over species that deploy leaves at or after the onset of the rains