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Smith JT, Clarke RT, Bowes MJ. Are groundwater nitrate concentrations reaching a turning point in some chalk aquifers? Sci Total Environ 2010; 408:4722-4732. [PMID: 20673960 DOI: 10.1016/j.scitotenv.2010.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 05/12/2010] [Accepted: 07/01/2010] [Indexed: 05/29/2023]
Abstract
In past decades, there has been much scientific effort dedicated to the development of models for simulation and prediction of nitrate concentrations in groundwaters, but producing truly predictive models remains a major challenge. A time-series model, based on long-term variations in nitrate fertiliser applications and average rainfall, was calibrated against measured concentrations from five boreholes in the River Frome catchment of Southern England for the period spanning from the mid-1970s to 2003. The model was then used to "blind" predict nitrate concentrations for the period 2003-2008. To our knowledge, this represents the first "blind" test of a model for predicting nitrate concentrations in aquifers. It was found that relatively simple time-series models could explain and predict a significant proportion of the variation in nitrate concentrations in these groundwater abstraction points (R(2)=0.6-0.9 and mean absolute prediction errors 4.2-8.0%). The study highlighted some important limitations and uncertainties in this, and other modelling approaches, in particular regarding long-term nitrate fertiliser application data. In three of the five groundwater abstraction points (Hooke, Empool and Eagle Lodge), once seasonal variations were accounted for, there was a recent change in the generally upward historical trend in nitrate concentrations. This may be an early indication of a response to levelling-off (and declining) fertiliser application rates since the 1980s. There was no clear indication of trend change at the Forston and Winterbourne Abbas sites nor in the trend of nitrate concentration in the River Frome itself from 1965 to 2008.
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Affiliation(s)
- J T Smith
- School of Earth and Environmental Sciences, Burnaby Building, University of Portsmouth, Portsmouth, PO1 3QL, UK.
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Clarke RT, Furse MT, Wright JF, Moss D. Derivation of a biological quality index for river sites: Comparison of the observed with the expected fauna. J Appl Stat 2010. [DOI: 10.1080/02664769624279] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Abstract
The little-studied large bacteria Oscillospira, Lampropedia, and ovals attach rapidly in large numbers to the cuticular surface of clover and grass leaves in the rumen. The cuticle of green leaves may constitute a specific niche for these bacteria.
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Affiliation(s)
- R T Clarke
- Applied Biochemistry Division, Department of Scientific and Industrial Research, Palmerston North, New Zealand
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Affiliation(s)
- J. A. Thomas
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK
| | - D. J. Simcox
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK
| | - R. T. Clarke
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK
- Centre for Conservation Ecology and Environmental Change, School of Conservation Sciences, Bournemouth University, Fern Barrow, Talbot Campus, Poole, Dorset BH12 5BB, UK
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Thomas JA, Telfer MG, Roy DB, Preston CD, Greenwood JJD, Asher J, Fox R, Clarke RT, Lawton JH. Comparative losses of British butterflies, birds, and plants and the global extinction crisis. Science 2004; 303:1879-81. [PMID: 15031508 DOI: 10.1126/science.1095046] [Citation(s) in RCA: 299] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
There is growing concern about increased population, regional, and global extinctions of species. A key question is whether extinction rates for one group of organisms are representative of other taxa. We present a comparison at the national scale of population and regional extinctions of birds, butterflies, and vascular plants from Britain in recent decades. Butterflies experienced the greatest net losses, disappearing on average from 13% of their previously occupied 10-kilometer squares. If insects elsewhere in the world are similarly sensitive, the known global extinction rates of vertebrate and plant species have an unrecorded parallel among the invertebrates, strengthening the hypothesis that the natural world is experiencing the sixth major extinction event in its history.
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Affiliation(s)
- J A Thomas
- Natural Environment Research Council (NERC) Centre for Ecology and Hydrology, Dorset Laboratory, Winfrith Technology Centre, Dorchester DT2 8ZD, UK.
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Abstract
A stratified random sample of kilometre squares in Great Britain was visited and completely mapped using four areal themes (agriculture and semi-natural vegetation, forestry, physiography and buildings and communications). The maps were digitised and the attribute information recorded to produce an electronic database. Information was summarised by square and then bootstrap re-sampling techniques were used to produce national estimates with statistical confidence intervals. The results for 1998 showed the terrestrial Broad Habitats had a range in extent covering two orders of magnitude from Montane (49000ha) to Improved Grassland (5482000ha). Just under half of Britain is covered by agricultural Broad Habitats, about 12% by woodland and just under 10% by Urban Habitats. The remaining quarter of the land area is covered by semi-natural Broad Habitats. By revisiting the same sample of squares previously visited in 1990, changes in the quantity and quality of the Broad Habitats have been determined. Significant increases in area have occurred in the Broadleaved, Mixed and Yew Woodland and Built Up and Gardens. The largest areal reduction was in Acid Grassland although that was in part balanced by a gain in Fen, Marsh and Swamp. The most significant ecological loss was in the area of Calcareous Grassland. The consequences of having different sample sizes for the different years are discussed.
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Affiliation(s)
- D C Howard
- Centre for Ecology and Hydrology, Merlewood Research Station, Grange-over-Sands, LA11 6JU, Cumbria, UK.
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Smart SM, Clarke RT, van de Poll HM, Robertson EJ, Shield ER, Bunce RGH, Maskell LC. National-scale vegetation change across Britain; an analysis of sample-based surveillance data from the Countryside Surveys of 1990 and 1998. J Environ Manage 2003; 67:239-54. [PMID: 12667474 DOI: 10.1016/s0301-4797(02)00177-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Patterns of vegetation across Great Britain (GB) between 1990 and 1998 were quantified based on an analysis of plant species data from a total of 9596 fixed plots. Plots were established on a stratified random basis within 501 1 km sample squares located as part of the Countryside Survey of GB. Results are primarily conveyed in terms of a classification of national land-cover into 22 mutually exclusive Broad Habitat types. Each of the fixed vegetation plots could be assigned to the Broad Habitat in which they were located in either year. Two types of analysis are reported, both based on changes in plant species composition within monitoring plots. The first examined turnover and net change between Broad Habitat types. The second quantified more subtle changes that had occurred within each Broad Habitat using a series of condition measures that summarized multivariate plant species data as a single scalar value for each plot at each time. There are major difficulties in using uncontrolled, large-scale surveillance data to unravel causal linkages and no attempt was made to quantitatively partition variation among competing causes. However, it was clear that results were broadly consistent with environmental drivers known to have operated prior to and during the survey interval. Large-scale vegetation changes could be summarized in terms of shifts along gradients of substrate fertility and disturbance. Changes implied increased nutrient availability across upland and lowland ecosystems while, in lowland landscapes, linear features and small biotope fragments saw a marked shift to species compositions associated with greater shade and less disturbance.
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Affiliation(s)
- S M Smart
- Centre for Ecology and Hydrology, Merlewood Research Station, Grange-over-Sands, Cumbria LA11 6JU, UK.
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Thomas JA, Rose RJ, Clarke RT, Thomas CD, Webb NR. Intraspecific variation in habitat availability among ectothermic animals near their climatic limits and their centres of range. Funct Ecol 2002. [DOI: 10.1046/j.1365-2435.1999.00008.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Wright JF, Gunn RJM, Winder JM, Wiggers R, Vowles K, Clarke RT, Harris I. A comparison of the macrophyte cover and macroinvertebrate fauna at three sites on the River Kennet in the mid 1970s and late 1990s. Sci Total Environ 2002; 282-283:121-142. [PMID: 11852906 DOI: 10.1016/s0048-9697(01)00948-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In 1974-1976, baseline studies were carried out on the flora and macroinvertebrate fauna of the R. Kennet at two sites downstream of Marlborough (Savernake Upper and Lower) and at one site upstream of Hungerford (Littlecote). Simplified maps of each site, showing the cover of macrophytes, were obtained monthly between April 1974 and April/June 1976, and replicated quantitative samples of the macroinvertebrates were collected on the dominant macrophyte and on gravel in June 1974, and also in June and December 1975. As a consequence of two major droughts and increasing concern over water quality in the Upper Kennet in the 1990s, the studies recommenced in the summer of 1997 using the same sites and methodologies. Maps and macroinvertebrate samples were obtained in early July and December 1997 and in June of both 1998 and 1999. At the Savernake sites, mapping in summer 1997 confirmed what had been apparent for some years. That is, macrophyte cover (both Ranunculus and Schoenoplectus) was much lower than in the 1970s. In contrast, the site downstream at Littlecote retained a relatively high cover of Ranunculus, despite the drought. In late autumn 1997, phosphate stripping commenced at Marlborough Sewage Treatment Works, the drought ended and in addition, the spring of 1998 was unusually wet. Ranunculus recolonised both Savernake sites with remarkable speed by summer 1998 and retained this dominant position in 1999. Quantitative samples of macroinvertebrates collected on gravel and the dominant macrophyte at each of the three study sites indicated that there was no evidence of major loss of family richness between the 1970s and 1990s as a result of the low flows or enrichment. However, at Savernake (but not Littlecote) in summer 1997, the macroinvertebrate assemblage was affected by low flows and/or enrichment. This took the form of changes in the abundance of some families, with lentic forms being favoured in relation to some lotic families. Following the end of the drought, many macroinvertebrate families at Savernake showed a rapid response to the new conditions and the assemblages reverted to those expected in a fast-flowing cretaceous chalk stream. Continued monitoring through the next drought is advisable to provide a greater understanding of the interplay between water quality, the discharge regime, habitat quality (including macrophyte growth) and the response of the macroinvertebrate fauna.
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Affiliation(s)
- J F Wright
- Centre for Ecology and Hydrology Dorset, Winfrith Technology Centre, Winfrith Newburgh, Dorchester, UK
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Durell SEALVD, Goss-Custard JD, Clarke RT. Modelling the population consequences of age- and sex-related differences in winter mortality in the oystercatcher, Haematopus ostralegus. OIKOS 2001. [DOI: 10.1034/j.1600-0706.2001.950108.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Thomas JA, Bourn NA, Clarke RT, Stewart KE, Simcox DJ, Pearman GS, Curtis R, Goodger B. The quality and isolation of habitat patches both determine where butterflies persist in fragmented landscapes. Proc Biol Sci 2001; 268:1791-6. [PMID: 11522197 PMCID: PMC1088810 DOI: 10.1098/rspb.2001.1693] [Citation(s) in RCA: 371] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Habitat quality and metapopulation effects are the main hypotheses that currently explain the disproportionate decline of insects in cultivated Holarctic landscapes. The former assumes a degradation in habitat quality for insects within surviving ecosystems, the latter that too few, small or isolated islands of ecosystem remain in landscapes for populations to persist. These hypotheses are often treated as alternatives, and this can lead to serious conflict in the interpretations of conservationists. We present the first empirical demonstration that habitat quality and site isolation are both important determinants of where populations persist in modern landscapes. We described the precise habitat requirements of Melitaea cinxia, Polyommatus bellargus and Thymelicus acteon, and quantified the variation in carrying capacity within each butterfly's niche. We then made detailed surveys to compare the distribution and density of every population of each species with the size, distance apart and quality of their specific habitats in all their potential habitat patches in three UK landscapes. In each case, within-site variation in habitat quality explained which patches supported a species' population two to three times better than site isolation. Site area and occupancy were not correlated in any species. Instead of representing alternative paradigms, habitat quality and spatial effects operate at different hierarchical levels within the same process: habitat quality is the missing third parameter in metapopulation dynamics, contributing more to species persistence, on the basis of these results, than site area or isolation. A reorientation in conservation priorities is recommended.
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Affiliation(s)
- J A Thomas
- Natural Environment Research Council Centre for Ecology and Hydrology, CEH Dorset, Winfrith Technology Centre, Dorset DT2 8ZD, UK.
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Abstract
The size and shape of the tail of the seed dispersal curve is important in determining the spatial dynamics of plants, but is difficult to quantify. We devised an experimental protocol to measure long-distance dispersal which involved measuring dispersal by wind from isolated individuals at a range of distances from the source, but maintaining a large and constant sampling intensity at each distance. Seeds were trapped up to 80 m from the plants, the furthest a dispersal curve for an individual plant has been measured for a non-tree species. Standard empirical negative exponential and inverse power models were fitted using likelihood methods. The latter always had a better fit than the former, but in most cases neither described the data well, and strongly under-estimated the tail of the dispersal curve. An alternative model formulation with two kernel components had a much better fit in most cases and described the tail data more accurately. Mechanistic models provide an alternative to direct measurement of dispersal. However, while a previous mechanistic model accurately predicted the modal dispersal distance, it always under-predicted the measured tail. Long-distance dispersal may be caused by rare extremes in horizontal wind speed or turbulence. Therefore, under-estimation of the tail by standard empirical models and mechanistic models may indicate a lack of flexibility to take account of such extremes. Future studies should examine carefully whether the widely used exponential and power models are, in fact, valid, and investigate alternative models.
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Affiliation(s)
- J M Bullock
- NERC Centre for Ecology and Hydrology, CEH Dorset, Winfrith Technology Centre, Dorchester, Dorset, DT2 8ZD, UK, e-mail: Tel.: +44-1305-213591, Fax: +44-1305-213600, , , , , , GB
| | - R T Clarke
- NERC Centre for Ecology and Hydrology, CEH Dorset, Winfrith Technology Centre, Dorchester, Dorset, DT2 8ZD, UK, e-mail: Tel.: +44-1305-213591, Fax: +44-1305-213600, , , , , , GB
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Stillman RA, Goss-Custard JD, West AD, Durell SEALVD, Caldow RWG, Mcgrorty S, Clarke RT. Predicting mortality in novel environments: tests and sensitivity of a behaviour-based model. J Appl Ecol 2000. [DOI: 10.1046/j.1365-2664.2000.00506.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Burchard JD, Clarke RT. The role of individualized care in a service delivery system for children and adolescents with severely maladjusted behavior. J Ment Health Adm 1999; 17:48-60. [PMID: 10104412 DOI: 10.1007/bf02518579] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Individualized care is a total system of care that is tailored to a child with severely maladjusted behavior. The services are unconditional, flexible, child and family focused, and interagency coordinated. The services follow the child until the child is adjusting in a normalized, mainstream environment. Individualized care is illustrated through two different projects. One is the Alaska Youth Initiative where individualized care was used to return children from out-of-state, residential programs. The other is Project Wraparound where it was used to prevent children from being removed from their families. This paper begins with the principles of individualized care and then describes the ecological, multilevel assessment process that coincides with the delivery of services. A case example from Project Wraparound is provided for clarification. Following the case example is a discussion of the need for evaluation data with some suggested strategies for documenting effectiveness. The final section focuses on two barriers to the implementation of individualized care. One is the tendency to think in terms of component programs rather than individualized services. The other barrier is the competition for scarce resources. Strategies are presented for overcoming both barriers.
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Raybould AF, Mogg RJ, Aldam C, Gliddon CJ, Thorpe RS, Clarke RT. The genetic structure of sea beet (Beta vulgaris ssp. maritima) populations. III. Detection of isolation by distance at microsatellite loci. Heredity (Edinb) 1998. [DOI: 10.1046/j.1365-2540.1998.00265.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Raybould AF, Mogg RJ, Clarke RT. The genetic structure of Beta vulgaris ssp. maritima (sea beet) populations: RFLPs and isozymes show different patterns of gene flow. Heredity (Edinb) 1996. [DOI: 10.1038/hdy.1996.138] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Goss-Custard JD, Clarke RT, Durell SEALVD, Caldow RWG, Ens BJ. Population Consequences of Winter Habitat Loss in a Migratory Shorebird. II. Model Predictions. J Appl Ecol 1995. [DOI: 10.2307/2405100] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Clarke RT, Briggs KB, Ens BJ, Exo KM, Smit C, Beintema AJ, Caldow RWG, Catt DC, Clark NA, Durell SEALVD, Harris MP, Hulscher JB, Meininger PL, Picozzi N, Prys-Jones R, Safriel UN, West AD. Population Consequences of Winter Habitat Loss in a Migratory Shorebird. I. Estimating Model Parameters. J Appl Ecol 1995. [DOI: 10.2307/2405099] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Caldow RWG, Clarke RT, West AD. Deriving Population parameters from Individual Variations in Foraging Behaviour. II. Model Tests and Population Parameters. J Anim Ecol 1995. [DOI: 10.2307/5762] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Caldow RWG, Clarke RT, le V. dit Durell SEA, Sutherland WJ. Deriving Population Parameters from Individual Variations in Foraging Behaviour. I. Empirical Game Theory Distribution Model of Oystercatchers Haematopus ostralegus Feeding on Mussels Mytilus edulis. J Anim Ecol 1995. [DOI: 10.2307/5761] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mcgrorty S, Goss-Custard JD, Clarke RT. MusselMytilus edulis (Mytilacea) dynamics in relation to environmental gradients and intraspecific interactions. ACTA ACUST UNITED AC 1993. [DOI: 10.1007/bf02334779] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Yates MG, Goss-Custard JD, McGrorty S, Lakhani KH, Durell SEALVD, Clarke RT, Rispin WE, Moy I, Yates T, Plant RA, Frost AJ. Sediment Characteristics, Invertebrate Densities and Shorebird Densities on the Inner Banks of the Wash. J Appl Ecol 1993. [DOI: 10.2307/2404240] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Caldow RWG, Clarke RT. Correlates of the Density of Foraging Oystercatchers Haematopus ostralegus at Different Population Sizes. J Anim Ecol 1992. [DOI: 10.2307/5519] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Warwick RM, Kirby R, McGrorty S, Clarke RT, Pearson B, Rispin WE, Durell SEALVD, Rose RJ. Towards Predicting Wading Bird Densities from Predicted Prey Densities in a Post-Barrage Severn Estuary. J Appl Ecol 1991. [DOI: 10.2307/2404222] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Chapman SB, Rose RJ, Clarke RT. The Behaviour of Populations of the Marsh Gentian (Gentiana pneumonanthe): A Modelling Approach. J Appl Ecol 1989. [DOI: 10.2307/2403712] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Miller CT, Malcarne VL, Clarke RT, Lobato D, Fitzgerald MD, Brand P. What mentally retarded and nonretarded children expect of one another. Am J Ment Retard 1989; 93:396-405. [PMID: 2930657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Twenty mentally retarded students and nonretarded students matched for chronological age (n = 20) or mental age (n = 16) made judgments about children described as having or not having learning problems. Results showed that students had both positive and negative stereotyped expectations about these children and that there were few differences between the expectations of retarded and nonretarded students. Students' responses to stereotype questions 11 to 18 months later revealed few changes in their stereotypes and no significant differences between stability of retarded and nonretarded students' stereotypes. Results suggest that understanding social relations between retarded and nonretarded children requires consideration of the expectations of both groups.
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Affiliation(s)
- C T Miller
- Psychology Department, University of Vermont, Burlington 05401
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Thomas JA, Thomas CD, Simcox DJ, Clarke RT. Ecology and Declining Status of the Silver-Spotted Skipper Butterfly (Hesperia comma) in Britain. J Appl Ecol 1986. [DOI: 10.2307/2404023] [Citation(s) in RCA: 105] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goss-Custard JD, Clarke RT, le V. dit Durell SEA. Rates of Food Intake and Aggression of Oystercatchers Haematopus ostralegus on the Most and Least Preferred Mussel Mytilus edulis Beds of the Exe Estuary. J Anim Ecol 1984. [DOI: 10.2307/4354] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Clarke RT, Ulyatt MJ, John A. Variation in Numbers and Mass of Ciliate Protozoa in the Rumens of Sheep Fed Chaffed Alfalfa (
Medicago sativa
). Appl Environ Microbiol 1982; 43:1201-4. [PMID: 16346017 PMCID: PMC244206 DOI: 10.1128/aem.43.5.1201-1204.1982] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Masses and numbers of rumen ciliate protozoa were markedly different in individual sheep fed chaffed alfalfa hay under different feeding regimens. Studies on the ciliate contribution to specific aspects of rumen fermentation should take into account the size of members of each genus in individual animals as well as the numbers present.
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Affiliation(s)
- R T Clarke
- Applied Biochemistry Division, Department of Scientific and Industrial Research, Palmerston North, New Zealand
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Kennedy PM, Clarke RT, Milligan LP. Influences of dietary sucrose and urea on transfer of endogenous urea to the rumen of sheep and numbers of epithelial bacteria. Br J Nutr 1981; 46:533-41. [PMID: 7317347 DOI: 10.1079/bjn19810062] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
1. The rates of transfer of plasma urea to the rumen of six sheep given brome grass (Bromus inermis) pellets alone or with supplements of sucrose or urea were determined using [14C] urea and 14C-labelled sodium bicarbonate infusions during three periods. 2. The sheep were slaughtered after the third period and samples of rumen epithelium were taken for assessment of numbers of adherent bacteria. 3. Maximum transfer (0.31 g nitrogen/h) of urea ot the rumen was observed for sheep given supplements of 150 g sucrose/d plus 20 g urea/d. Maximum clearance of plasma urea to the rumen (rate of urea transfer to the rumen per unit plasma urea concentration, 5.8 1/h) was observed for sheep given 300 g sucrose/d. 4. Urea clearance to the rumen was negatively related to rumen ammonia concentration; the slope of the relationship was increased with each addition of sucrose to the diet. 5. Numbers of facultative bacteria adherent to the rumen epithelium were increased by urea and sucrose supplements. 6. The results are discussed in relation to a hypothesis which relates the ureolytic capability of the bacteria adherent to the rumen epithelium to the control of the rate of transfer of urea into the rumen.
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Clarke RT. Captive insurance--still a viable alternative. Hosp Financ Manage 1979; 33:36-7. [PMID: 10242666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
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Clarke RT. Physician contracts: new issues hit the bargaining table. Hosp Med Staff 1979; 8:11-7. [PMID: 10240139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The number of contract physicians in hospitals has been growing, reflecting a dependence on hospitals for new and costly technology. When a physician negotiates his contract, it is important for him to understand the hospital's bargaining strengths and to be aware of his own. This article discusses the basic considerations involved in contractual agreements and the impact of public demands for accountability, health planning agencies, cost containment, and multihospital systems.
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Abstract
High concentrations of the ciliate Epidinium Crawley are associated with damaged regions of fresh plant material undergoing digestion in the sheep rumen. This finding supports that postulate that sequestration in the rumen explains the low rate of passage of protozoa despite the high flow rate of liquid from the rumen. The maintenance of Epidinium in the rumen, despite their slow growth rate, is also explained.
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Abstract
Examination of the rumen epithelium of sheep by scanning electron microscopy revealed bacteria associated with the epithelial surface. Comparison of epithelial surfaces from 10 sheep revealed areas that were consistently densely covered with bacteria and other areas where the cover was consistently light. The bacterial populations were frequently of mixed morphological types, but areas populated with a single type were also observed. This finding, together with the discovery of bacterial forms not previously described in rumen contents, suggests that a specific flora may exist on the rumen epithelial surface. The functional significance of such a population is discussed.
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Clarke RT, Bailey RW, Gaillard BD. Growth of rumen bacteria on plant cell wall polysaccharides. J Gen Microbiol 1969; 56:9-86. [PMID: 5787005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Clarke RT. 252. Note: The Statistical Analysis of a Radio-Active Tracer Experiment to Determine Root Activity in Potato Plants. Biometrics 1968. [DOI: 10.2307/2528332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
The successful cultivation of the anaerobic ciliate Dasytricha ruminantium is described. The cultures were established in a salts medium containing 30% clarified rumen fluid. Sucrose and extract of rumen holotrich protozoa were fed once daily for 2 to 4 hr, and Dasytricha was then transferred to medium free from these nutrients. Rumen fluid was essential. Omission of protozoal extract resulted in gradual death of the ciliates. Bovine serum satisfactorily substituted for the protozoal extract, but various rumen bacteria, extract of rumen bacteria, and extracts of plant materials could not. There was a positive correlation between formation of methane in the cultures and growth of the ciliates. It is possible that methane bacteria were ingested, but it is not excluded that survival of both dasytrichs and the methanogenic bacteria depended on a low redox potential of the medium.
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