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The long-term water balance (1972–2004) of upland forestry and grassland at Plynlimon, mid-Wales
V. Marc ,M. Robinson
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2007,
Abstract: This paper reviews research into the hydrological impacts of UK upland forestry and updates the water balance of the Plynlimon research catchments for the period 1972–2004. Comparison of this network of densely instrumented coniferous forest and grassland catchments builds upon previously reported differences in annual evaporation of the two land uses and, most crucially, provides evidence of systematic, age-related, variations in forest evaporation losses over a managed plantation forest cycle. In comparison with the grassland catchment, the additional water use of the 70% forested catchment fell from 250 to 150 mm yr 1 because of increasing forest age; this is equivalent to a decline from 370 mm to 210 mm extra evaporation from a complete forest cover. At present, with up to half of the forest area felled or only recently replanted, the difference in evaporation between the forest and grass catchments is negligible. Knowledge of the period of maximum tree water use may be critically important for the future management of multi-use forests. This is also being investigated by micro-meteorological measurements at the scale of the forest stand using eddy covariance, in conjunction with the long-term catchment monitoring.
The effects of riparian forestry on invertebrate drift and brown trout in upland streams of contrasting acidity
S. J. Ormerod,M. E. Jones,M. C. Jones,D. R. Phillips
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2004,
Abstract: Variations in macroinvertebrate drift and benthic invertebrate abundance were assessed in 30 upland Welsh streams of varying acidity (pH < 5.7 or pH.> 6.0) and riparian land-use (conifer, moorland or native broadleaf). The consequences for the diet and condition of wild brown trout Salmo trutta were also assessed. As expected from previous studies, there were significant reductions in benthic invertebrate abundance, aquatic drift density (by >60%), aquatic drift biomass (by >35%), total drift density (by >35%) and total drift biomass (by >20%) at acid sites by comparison with circumneutral sites due largely to the scarcity of mayflies. Absolute drift from terrestrial sources was unrelated to stream pH but formed a significantly greater proportion of total drift at acid sites (30-65% of density) than at circumneutral sites (20-40%) as aquatic contributions declined. Most of this apparent land use effect reflected significantly increased terrestrial drift under broadleaves. There was no significant reduction in terrestrial or aquatic drift at conifer forest sites per se after accounting for low pH. Trout diet varied substantially between locations partly reflecting variations in drift: significantly fewer mayflies and stoneflies were eaten at acid sites, and significantly more terrestrial prey were eaten under broadleaves. However, acidity did not reduce trout condition or gut-fullness. Unexpectedly, trout condition was significantly enhanced at conifer sites, irrespective of their pH. Hence, acidity has greater effects on the benthic abundance and drift density of invertebrates in upland streams than does riparian land use. However, trout forage flexibly enough to offset any possible food deficit, for example by switching to chironomids and terrestrial invertebrates. Enhanced terrestrial contributions to invertebrate drift from riparian broadleaf trees may be important in supplementing foraging opportunities for trout where aquatic prey are scarce. These data illustrate the value of native tree species in riparian locations in upland Britain and the energy subsidy they provide might well be disproportionately important for otherwise impoverished acid streams Keywords: brown trout, land-use, acidification, drift, forestry, streams
Cell Stores  [PDF]
Ghislain Fourny
Computer Science , 2014,
Abstract: Cell stores provide a relational-like, tabular level of abstraction to business users while leveraging recent database technologies, such as key-value stores and document stores. This allows to scale up and out the efficient storage and retrieval of highly dimensional data. Cells are the primary citizens and exist in different forms, which can be explained with an analogy to the state of matter: as a gas for efficient storage, as a solid for efficient retrieval, and as a liquid for efficient interaction with the business users. Cell stores were abstracted from, and are compatible with the XBRL standard for importing and exporting data. The first cell store repository contains roughly 200GB of SEC filings data, and proves that retrieving data cubes can be performed in real time (the threshold acceptable by a human user being at most a few seconds).
Impacts of forestry on nitrogen in upland and lowland catchments: a comparison of the River Severn at Plynlimon in mid-Wales and the Bedford Ouse in south-east England using the INCA Model  [PDF]
P. G. Whitehead,T. J. Hill,C. Neal
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2004,
Abstract: The impacts of afforestation at Plynlimon in the Severn catchment, mid-Wales, and in the Bedford Ouse catchment in south-east England are evaluated using the INCA model to simulate Nitrogen (N) fluxes and concentrations. The INCA model represents the key hydrological and N processes operating in catchments and simulates the daily dynamic behaviour as well as the annual fluxes. INCA has been applied to five years of data from the Hafren and Hore headwater sub-catchments (6.8 km2 area in total) of the River Severn at Plynlimon and the model was calibrated and validated against field data. Simulation of afforestation is achieved by altering the uptake rate parameters in the model. INCA simulates the daily N behaviour in the catchments with good accuracy as well as reconstructing the annual budgets for N release following clearfelling; a four-fold increase in N fluxes was followed by a slow recovery after re-afforestation. For comparison, INCA has been applied to the large (8380 km2) Bedford Ouse catchment to investigate the impact of replacing 20% arable land with forestry. The reduction in fertiliser inputs from arable farming and the N uptake by the forest are predicted to reduce the N flux reaching the main river system, leading to a 33% reduction in N-Nitrate concentrations in the river water. Keywords: afforestation, water quality, nitrogen, modelling, land-use change, Wales, Plynlimon, Hore, Hafren, Bedford Ouse, Severn
Sustainability of UK forestry: contemporary issues for the protection of freshwaters, a conclusion
C. Neal,S. J. Ormerod,S. J. Langan,T. R. Nisbet
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2004,
Abstract: This paper closes the Special Issue of Hydrology and Earth System Sciences entitled 'Sustainability of UK forestry: contemporary issues for the protection of freshwaters' by presenting conclusions from the contributions together with associated research findings. The volume deals largely with issues of upland water quality and biology in the context of environmental research and management. The studies are linked to an array of issues which affect the sustainability of UK forestry in the context of the protection of freshwaters, freshwater ecosystems and freshwater organisms. These issues include atmospheric and climate driven factors (acidification from atmospheric pollutants, critical loads, climate-change and climate variability), forestry practice and hydrobiogeochemical processing both within-catchments and within-rivers. The findings lie within the context of the science and relate to environmental management. Keywords: water quality, forestry, stream ecology, acidification, critical loads, nutrients
Fluvial sediment inputs to upland gravel bed rivers draining forested catchments: potential ecological impacts  [PDF]
S. D. Marks,G. P. Rutt
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 1997,
Abstract: As identified by the detailed long-term monitoring networks at Plynlimon, increased sediment supply to upland fluvial systems is often associated with forestry land-use and practice. Literature is reviewed, in the light of recent results from Plynlimon sediment studies, to enable identification of the potential ecological impacts of fluvial particulate inputs to upland gravel bed rivers draining forested catchments similar to the headwaters of the River Severn. Both sediment transport and deposition can have significant impacts upon aquatic vertebrates, invertebrates and plants.
Effects of Livestock Grazing on Vegetation Composition and Soil Moisture Properties in Grazed and Non-Grazed Range Site
F. Amiri,Ali Ariapour,S. Fadai
Journal of Biological Sciences , 2008,
Abstract: Studies of vegetation and soil dynamics on grazed and non-grazed rangelands are important prerequisites for improving range management. For this reason, the effects of excluding grazing animals for 26 years were studied on vegetation and soil dynamics at two rangeland condition sites (enclosure and exclosure) in Isfahan province, Iran. The vegetation cover and edaphic characteristics were studied simultaneously in both grazed and non-grazed range sites. In this study vegetation characteristics, as well as vegetation floristic, canopy cover, plant density, botanical composition, plant biodiversity and soil moisture infiltration were recorded during the grazing seasons of 2006 to 2007. Vegetation characteristics, in particular vegetation cover and plant density, differed significantly between the non-grazed (enclosed) and grazed sites and increased significantly in the non-grazed range site. The vegetation cover in the non-grazed site consisted mainly of class I and II plants while class III plants predominated in the grazed site. There was no significant difference in the botanical composition of the two areas. There was a significant increase in Gramineae in the enclosure site compared to the surrounding grazed site, but there was a considerable decrease in forb species. We also observed a significant decrease in soil infiltration rates in the grazed range site compared to the enclosed range site. Litter content was higher inside and exposed bare soil greater outside the enclosure. Infiltration rates were higher in the enclosed area than in the grazed exclosure area throughout the grazing season. A comparison of vegetation and soil infiltration within the enclosure showed that vegetation condition and soil infiltration were good and that removal of grazing animals, as in the enclosure, causes an improvement in rangeland condition in this region.
Riparian forestry management and adult stream insects  [PDF]
R. A. Briers,J. H. R. Gee
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2004,
Abstract: The impacts of coniferous plantation forestry on the biology of upland streams in the UK are firmly established. Whilst benthic communities have been well studied, very little research has considered the impacts of riparian forestry management on adult stream insects, yet the essentially terrestrial adult (reproductive) phase may be important in determining the abundance and distribution of larval stages. Riparian vegetation has a potentially strong impact on survival and success of adult stages through alteration of microclimate, habitat structure and potential food sources, in addition to effects carried over from larval stages. Here, current riparian management strategies are analysed in the light of available information on the ecology of adult stream insects. On the whole, management practices appear to favour adult stream insects, although an increase in tree cover in riparian areas could be beneficial, by providing more favourable microclimatic conditions for adults. This conclusion is drawn based on rather limited information, and the need for further research into the effects of riparian forestry management on adult stream insects is highlighted. Keywords: microclimate, plantation, life history, riparian vegetation
Understanding Retailers’ Acceptance of Virtual Stores  [cached]
Irene Y.L. Chen
Knowledge Management & E-Learning : an International Journal , 2010,
Abstract: The acceptance of e-commerce among consumers has stimulated the rise of virtual stores. Increasing traditional retailers or people who do not have sufficient capital for maintaining a brick-and-mortar store have considered using virtual stores to reach global market. In the e-commerce literature, there has been rich research evidence concerning consumers’ acceptance of virtual stores. However, rigorous academic research on retailers’ acceptance of virtual stores is relatively scarce today. This study draws upon the theory of planned behavior and information richness theory to propose an integrated theoretical model. A field survey is used to collect data from e-tailers. The data are analyzed to examine the six relationships posited in the research model. Findings of this study provide a further research avenue for e-commerce, and implications for those who are managing or considering using virtual stores.
Consumer Search with Chain Stores  [PDF]
Sergey Kuniavsky
Computer Science , 2012,
Abstract: The paper explores a consumer search setting where the sellers have asymmetries. The model is an extension of the popular Stahl Model, which is widely used in the literature. The extension introduces sellers with heterogeneous stores number, reflecting the typical market structure. The market consists of several sellers heterogeneous in size consumers, some of which face a cost when sequentially searching. The paper shows that no symmetric model exist in the extension and asymmetric NE of the Stahl model are found for comparison. Additional results suggest that smallest sellers will be the ones offering lowest prices, in line with several real world examples provided in the paper. However, profits remain in most cases fixed per store, making a larger firm more profitable, yet with lower sold quantity. The findings suggest that on some level price dispersion will still exist, together with some level of price stickiness, both observed in reality.
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