bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting the long‐term acidification trends in small subarctic lakes using diatoms
Authors: Korhola Atte , Weckström Jan , Nyman Marjut
Published: March 2003

1. A considerable proportion of the total deposition of sulphur in northernmost Europe originates from the large non‐ferrous smelters of the Kola Peninsula, Russia. Potential long‐term effects of this point source pollution on sensitive subarctic lakes were evaluated using palaeolimnological techniques.

2. Multivariate analysis of a diatom and water chemistry data set from 45 small headwater lakes located in north‐eastern Finnish Lapland demonstrated that pH, calcium and silica were the three most powerful chemical variables in explaining the variance in the diatom data. From these, lake water pH was shown to be the strongest determinator by variance partitioning.

3. Weighted averaging partial least squares regression (WA‐PLS) was used to develop a diatom‐based prediction model for inferring lake water pH from sediment core diatom assemblages. The performance of the model was assessed by leave‐one‐out cross‐validation.

4. The prediction model was applied to radiometrically dated sediment cores taken from three headwater lakes receiving different amounts of acid fallout from the Kola Peninsula smelter industry.

5. Stable diatom assemblages and results of pH reconstructions suggested that no substantial changes in the acidification status of the lakes have occurred within the last century despite the very high local acid deposition.

6. The pollution levels in the study area have not increased to the point where the biology of the lakes has been influenced significantly.
Response of a herbivore community to increased food quality and quantity: an experiment with nitrogen fertilizer in a boreal forest
Authors: Ball John P. , Danell Kjell , Sunesson Peter
Published: March 2003

1.  Herbivores make decisions at different spatial levels in response to food plant quality and quantity. Although experiments have examined the responses of herbivores at lower levels, few have examined how herbivores respond to such variation at the stand level. We assessed the response of a herbivore community in a boreal forest to manipulations of food resources at the stand level by performing a large replicated experiment where we fertilized young forest stands and then followed their use by herbivores during the subsequent year.

2.  We used stands at 25 sites in an area 35 × 45 km. At each site we had one fertilized plot, a close control (100 m away) and a distant control (300 m away), all 50 × 50 m.

3.
 Before the growing season we fertilized treatment plots with calcium–ammonium–nitrate at 600 kg ha−1 (200 kg N ha−1). Fertilization significantly improved browse quality (nitrogen concentration) in both downy birch Betula pubescens and Scots pine Pinus sylvestris. Furthermore, the amount of browse significantly increased for birch, and Scots pine showed a similar trend.

4.  Considering the animal community as a whole, we found that 10 of 13 animal species/groups made more tracks during winter in fertilized than in control plots. The total number of tracks was greater in fertilized plots, followed by close and then distant controls.

5.
 In the summer following fertilization, moose Alces alces strongly selected fertilized plots over controls. Furthermore, during the following winter moose again selected fertilized plots over controls. Hares Lepus timidus similarly left more pellets in the fertilized plots. Other mammals used the fertilized and the close controls similarly, and both were used more than distant controls. The number of grouse pellets did not differ among the treatments, although they followed a similar trend.

6.  Several lines of evidence suggest that moose browsed fertilized plots more. Although not statistically significant, both heavy and light browsing were more common in fertilized than in control plots. Trees with the top shoot removed, or with bark stripped from the stem, did not differ significantly, but once again fertilized plots were browsed more than controls.

7.  Our results are discussed in light of understanding both how herbivores in general respond to changes in food quality and quantity, and if fertilization may be a useful tool in modern forestry to manage herbivores.

8.  Fertilization might be useful as a tool to alter the location of herbivore feeding, but buffer strips around any fertilized areas appear necessary, and other potential environmental effects should be evaluated.
Influence of herbivory, competition and soil fertility on the abundance of Cirsium arvense in acid grassland
Authors: Edwards G.R. , Bourdôt G.W. , Crawley M.J.
Published: March 2003

1.
 The extent to which the weed Cirsium arvense (creeping thistle) may be controlled by manipulating interspecific competition and herbivory was examined in two factorial experiments in order to identify non‐chemical herbicide‐based control methods for the weed.

2.
 In the first experiment, a single spring cultivation of grassland intensively grazed by rabbits led to a 25‐fold increase in C. arvense cover within 3 months, the effects of which were still present the following summer. As well as destroying the competing perennial vegetation, cultivation created and dispersed small root fragments (3–5 cm in length) from which almost all shoot recruitment occurred.

3.
 Fencing the cultivated plots against rabbits decreased the cover of C. arvense because ungrazed regrowth from palatable/grazing intolerant species reduced recruitment of C. arvense seedlings and shoots. Seedling competition, in the form of a wildflower seed mix sown soon after cultivation, reduced C. arvense cover on fenced plots to pre‐cultivation levels.

4.
 In the second experiment, conducted in a permanent grassland, C. arvense shoot densities on plots fenced against rabbits and treated as a hay meadow were about one‐eighth of those found on rabbit‐grazed plots where competing vegetation was kept short. Adventitious shoot recruitment was greater on soil disturbances such as molehills and rabbit scrapes than in intact vegetation. Seedling recruitment occurred only on soil disturbances such as molehills.

5.
 Lime and nitrogen fertilizer application to the fenced grassland increased the standing biomass of competing species, which reduced C. arvense shoot density. Outside the fences, rabbit grazing was so concentrated on the competing species of the nitrogen‐fertilized and limed areas that C. arvense benefited from competitive release, exhibiting increased shoot density. Cirsium arvense showed pronounced competitive release from grasses, with greater shoot densities where grasses were removed with selective herbicides than where no plant species were removed.

6.  Exclusion of insects and molluscs with chemical pesticides had no effect on shoot or seedling recruitment or overall shoot density on cultivated soil or in permanent grassland.

7.
 It is concluded that combinations of management procedures that encourage interspecific competition, such as sowing crops soon after cultivation and delaying grazing of them, and nitrogen fertilizer application and non‐ or reduced grazing of intact grasslands, will help reduce C. arvense abundance.
Long‐term effects of defoliation: incomplete recovery of a New Zealand alpine tussock grass, Chionochloa pallens, after 20 years
Authors: Lee W.G. , Fenner M. , Loughnan A. , Lloyd K.M.
Published: March 2003

1.
 
Chionochloa pallens, a New Zealand low alpine tussock grass, is an important food plant of the takahéPorphyrio hochstetteri, a rare endemic flightless rail. Introduced red deer Cervus elaphus compete with the takahé for this resource.

2.  The experiment reported here measured the long‐term rate of recovery of the grass after simulated severe deer grazing by means of a single clipping in 1977. Biomass, tillering and levels of six mineral nutrients (N, P, K, Ca, Mg, Na) were measured in tussocks 20 years after the clipping was carried out. Growth was compared between treatments (control vs. defoliated) and with a previous sampling in 1986.

3.  Even after two decades, recovery was incomplete. Tiller dry weights and size (length and basal diameter) and tussock dry weight per unit area remained significantly depressed in the clipped plots (by about 30%) compared with the control plots.

4.  Other features, such as biomass allocation to plant parts and mineral concentrations in tissues, no longer showed many significant differences between the treated and control plots, indicating continued convergence towards the controls.

5.  However, at the present rate of recovery it is estimated that the effects of a single severe defoliation on biomass (per tiller and per unit area) will persist for nearly three decades.

6.
 As C. pallens is known to be a relatively fast‐growing species of Chionochloa, recovery of other native snow tussock grasses in these alpine habitats damaged by deer grazing is likely to take even longer.
Artificial selection for aphid tolerance in the polyphagous predatorLepthyphantes tenuis
Authors: Beck Jørgen B. , Toft Søren
Published: March 2003

1. Insight into the capacity of natural enemies to control pests may lead to wiser pest management, including a reduction in the use of pesticides. The presence of polyphagous predators may contribute to the control of aphid populations and thereby prevent outbreaks. Many arthropod generalist predators have a limited tolerance to the consumption of aphids. However, differences exist between and within species in the ability to cope with an aphid diet; some within‐species variation could be due to genetic differences between individuals.

2. In order to demonstrate additive genetic variation in aphid tolerance, a breeding programme was carried out where offspring of field‐collected females of the linyphiid spiderLepthyphantes tenuiswere selected for survival on a pure diet of the aphidRhopalosiphum padithrough the first juvenile instar. Aphid tolerance was estimated as the survival in proportion to survival of a control line, fed mixed collembola. Development and reproduction were recorded in order to detect possible selection effects.

3. After only one generation of selection, survival to the first moult on an aphid diet was significantly improved. The aphid tolerance of the first instar spiderlings increased by 63% and a high heritability for the trait was found. An F2control group derived from selected parents had significantly reduced survival compared with an F2control group derived from control parents.

4. Developmental rate and reproduction were lower in the selected group than in the control line, demonstrating a cost of tolerance to aphids.

5. The background of the genetic variation and its possible implications for the natural limitation of aphid populations in agricultural systems is discussed. Consideration of the control potential of polyphagous predators must include their genetic variation in aphid tolerance. Management practices aimed at augmenting specialist aphid predators, e.g. by erecting banks or cover crops containing non‐pest aphids, may provide selection pressure for increased aphid tolerance in polyphagous predators.
Genetic introgression from distant provenances reduces fitness in local weed populations
Authors: Keller M. , Kollmann J. , Edwards P.J.
Published: March 2003

1. Seed mixtures of wildflowers are used increasingly in schemes to restore biodiversity in intensively managed farmland. Usually, the seed mixtures are produced by commercial suppliers and they may be distributed over large geographical distances. It is therefore important to ask what problems may arise from using seed that is not of local origin. The aim of this study was to evaluate one potential problem, namely the effects of genetic introgression of foreign provenances on the fitness of local weed populations.

2. The problem was investigated using the arable weed speciesAgrostemma githago,Papaver rhoeasandSilene alba, all of which are commonly included in commercial seed mixtures in Switzerland. Hybrids (F1and F2backcrosses) were made between local Swiss plants and plants of English, German and Hungarian provenance (plus F1from one US source inSilene). In a field experiment the growth of the hybrid plants was compared with that of the parents. Above‐ground dry matter after one growing season was taken as a measure of fitness. Additionally, survivorship and seed mass were determined for some of the hybrids.

3. The biomass data revealed negative outbreeding effects caused by epistasis in all four F2backcrosses ofPapaverand in the F2ofAgrostemmahybridized with plants of German provenance; no such effects were found inSilene. Survival was slightly lower in the F1hybrids ofPapaver, and considerably reduced in the F2backcrosses. ForSilene, a heterosis effect was evident in seed mass in the F1generation, while seed mass decreased in the F2. The same trend, although less strong, was also observed inAgrostemma.

4. The results suggest that only plants of relatively local origin should be used in wildflower mixtures, although it is not possible to specify precisely over what distance seed can safely be transferred. The same recommendation is also valid for schemes to reinvigorate endangered plant populations. The relevance of the fitness components that were measured, and the long‐term effects of genetic introgressions, are discussed.
Participatory research methods in environmental science: local and scientific knowledge of a limnological phenomenon in the Pantanal wetland of Brazil
Authors: Calheiros D.F. , Seidl A.F. , Ferreira C.J.A.
Published: March 2003

1. Participatory research methodologies incorporating local knowledge are important to the success of ecological research and the sustainable management of natural systems. However, methods of this type are not commonly employed in the natural sciences.

2. We adopted a scientifically rigorous ethnographic research methodology to incorporate local knowledge into understanding a natural limnological phenomenon in the Brazilian Pantanal. Known locally as ‘dequada’, it is associated with fish kills.

3. Using primarily open‐ended questions and semi‐structured interviews, 30 older head‐of‐household men were interviewed, by the same interviewer, in a small community representative of the few local riverside settlements. Their opinions were then contrasted with current scientific knowledge.

4. In concordance with the scientific community, the local community cited decomposition of organic material as the principal cause of fish mortality due to the dequada. Local people therefore can have a well‐founded understanding of their environment.

5. This study demonstrates the importance of incorporating local knowledge to corroborate and, often, to guide the process of scientific inquiry. In this case, local knowledge added to scientific knowledge by providing a more complete understanding of the management and conservation of a natural system. We recommend that ecologists should be ready to acknowledge that local understanding can be greater than that of ‘outsiders’.
The value of Collembola from agricultural soils as food for a generalist predator
Authors: Bilde Trine , Axelsen Jørgen A. , Toft Søren
Published: March 2003

1. The Collembola is one of the important prey groups for generalist arthropod predators in agro‐ecosystems. Differences in the quality of available species may play a significant role in the build‐up of a community of natural enemies. The value of some common epigeic and hemi‐edaphic Collembola as prey for adults and larvae of the carabid beetleBembidion lamproswas assessed in laboratory experiments.

2. Consumption capacity, egg production and the efficiency of converting prey into eggs were used as quality criteria for beetle adults, kept on diets of the collembolansIsotoma anglicana,Isotoma notabilis,Isotomurus prasinus,Folsomia fimetariaandLepidocyrtus cyaneus, with fruit fliesDrosophila melanogasterused as a high quality comparison prey. Survival, developmental time and teneral adult weight were used as quality criteria for beetle larvae on diets ofIsotoma anglicana,Isotoma notabilis,F. fimetaria,D. melanogasterand a starvation treatment.

3. Collembola were offered to adults in dead and live treatments to assess the cost of prey capture and handling in relation to prey quality.

4. Bembidion lamprosate more dead than live Collembola. Egg production declined over time on all collembolan diets, indicating a lower quality of all species compared withD. melanogaster, but there was considerable variation between species. The highest food conversion efficiency occurred onF. fimetaria,L. cyaneusandD. melanogaster, whileIsotoma notabiliscould not be utilized byB. lamprosfor egg production.

5. Larvae completed development with low mortality onIsotoma anglicanaandF. fimetaria, although there were differences in developmental time.The two Collembola seemed to be of relatively higher quality for larvae than for adults. Significantly higher teneral weight occurred on a diet ofD. melanogastercompared with the Collembola.

6. The effect of Collembola quality on the beetle fecundity and larval developmental time suggests that agricultural management for natural enemies, should aim to benefit the species composition of the prey population.
Responses of the willow beetle Phratora vulgatissima to genetically and spatially diverse Salix spp. plantations
Authors: Peacock L. , Herrick S.
Published: March 2003

1. Phratora vulgatissima is the most serious pest of willow grown as short‐rotation coppice in Britain. The effects of genetically diverse plantations of willow on beetle density, damage and oviposition were studied in a field trial containing monocultures of willow varieties with different willow beetle susceptibility, and mixtures which differed in number and spatial configuration of varieties. In addition, P. vulgatissima adults were introduced to potted willows in cages in a glasshouse as either a monoculture or a mixture of three varieties, and damage and oviposition were recorded.

2. Beetle density, damage and oviposition in the field were generally lower in mixtures than in monocultures, especially with five varieties rather than three and random structural composition rather than regular. In the caged experiment, where beetles could not migrate, there were no significant differences between the monoculture and the mixture for mean damage or oviposition on the two susceptible varieties.

3. Over time, the average beetle density per tree in the field increased in the monocultures of susceptible varieties, yet decreased in the mixtures. The behavioural response of P. vulgatissima to vegetational diversity was consistent with the resource concentration hypothesis, with lower colonization in, and increased emigration from, mixtures compared with monocultures.

4. Genetically and spatially diverse willow mixtures provide a sound basis for pest management due to the propensity for movement by the beetles. As each movement necessitates the location of a new host plant, it is more difficult for beetles to find favourable varieties in a genetically diverse mixture than in a monoculture.

5. Adult P. vulgatissima occur in mobile aggregations, so pest and damage surveys must be intensive and cover a wide time interval. An option for pest management is a mixture of five willow varieties, at least one of which has low susceptibility to the willow beetle, grown in a random planting of varieties. The choice of variety is important, especially the susceptibility to the rust disease, as are physiological interactions between varieties that might affect beetle ecology.
Large‐scale processes in ecology and hydrology
Authors: Caldow R.W.G. , Racey P.A.
Published: March 2003

1. Several papers published in the 1980s stressed the importance of scaling issues, the inter‐relatedness of patterns and processes at different scales of time and space, to our understanding of ecological systems. Scaling issues are of major theoretical interest and increasingly are of considerable applied importance.

2. In recognition of this, the Natural Environment Research Council, in partnership with the Scottish Executive Rural Affairs Department, funded a Thematic Programme entitled ‘Large‐scale Processes in Ecology and Hydrology’. The principal aim of this Programme was to integrate recent major developments in information resources and technologies with current theory in order to improve understanding of large‐scale patterns and processes and their relationship to patterns and processes at smaller scales.

3. The Thematic Programme, which ran from 1995 until 1999, funded six research projects that have generated a large body of published papers. This volume, dedicated to the findings of the Programme, brings together outputs from all six projects with the aim of ensuring a rapid and widespread dissemination of the Programme's findings. A brief résumé of each of the papers is presented.

4. The papers in this volume cover a wide variety of subjects ranging from ions to the flora and fauna of the United Kingdom. Nonetheless, each study has sought in various ways to quantify observed spatio‐temporal patterns at a range of scales, to determine whether those patterns are consistent across scales and to identify the interactions between small‐scale patterns and processes and those at larger scales. The importance of the spatial and temporal scales at which studies are conducted, the key role played by dispersal in spatial population dynamics, and the diversity of ways in which large‐scale patterns and processes relate to those at smaller scales are highlighted in many of the papers.

4. All of the papers presented here have direct relevance to applied issues. These issues are diverse and include the control of invasive alien species, the conservation of declining, threatened or endangered species, the development of survey techniques, strategies for farmland, woodland and forestry management, and the assessment of pollution sensitivity. Thus, the Thematic Programme has addressed issues of considerable theoretical interest and has at the same time generated results and predictive models that are of considerable practical and policy relevance.
Editors' Introduction: Birds and Agriculture
Authors: Ormerod S.J. , Watkinson A.R.
Published: March 2003

1. Around 10% of recent papers in the Journal of Applied Ecology have examined interactions between birds and agriculture. This statistic reveals the important role now played by ecologists in assessing the effects of agricultural development worldwide. It also reflects the position of birds as both indicators and targets of agricultural change: their patterns of behaviour, distribution, seasonal phenology and demography track closely onto the spatial and temporal scales of agricultural intensification.

2. Papers in this Special Profile illustrate how research in this sphere has shifted towards assessing the processes by which birds are affected ecologically by agricultural change. The works examine spatial patterns in extinction; assess long‐term trends in bird abundance and agricultural practice; reveal how foraging and breeding performance in farmland birds varies between habitats; and evaluate the role of large‐scale modelling in examining hypotheses about the influences of land management on birds. The final paper shows that birds can have intrinsically positive value in agricultural systems.

3. All the papers propose management prescriptions for agricultural areas that blend the microscopic – for example, how to modify local land structure to benefit birds – and the macroscopic – for example, by suggested inputs into land‐use policy. Perhaps most pertinent is the key conclusion that agricultural change is multivariate, so that straightforward univariate effects on birds are unlikely. Restoration of impacted populations might therefore require holistic strategies that encourage appropriately scaled agricultural extensification. Success would be most likely if farmers, conservationists and other key players were engaged collaboratively in the process.

4. Current ideas about restoring farmland bird populations share a common assumption: if agricultural practice has reduced populations hitherto, then agricultural practice can restore the losses. We suggest that this assumption carries a range of predictions that now require testing through sustainable farm management – a situation ideally suited to ‘BACI’ style experiments.

5. We reiterate the need to expand work on other groups of organisms affected negatively or positively by agricultural management to allow a broader perspective of impacts or benefits.
Habitat use and diet of skylarks Alauda arvensis wintering on lowland farmland in southern Britain
Authors: Donald P.F. , Buckingham D.L. , Moorcroft D. , Muirhead L.B. , Evans A.D. , Kirby W.B.
Published: March 2003

The habitat use and diet of skylarks wintering on lowland farms were studied to assess whether changes in agricultural practice could have reduced their most favoured wintering habitats or foods. Faecal samples were collected and soil seed densities were estimated. Skylarks in 122 cereal stubble fields in Oxfordshire were counted monthly to examine habitat use.

Cereal stubble fields were more likely to be occupied than other crops, and densities of birds in occupied fields were high. Barley stubbles were significantly more likely to be occupied than wheat stubbles. Growing cereals were weakly selected. Sugar beet stubbles held high densities of birds. Rotational set‐aside was occupied more frequently and held higher densities than non‐rotational set‐aside.

Field size affected field occupancy independently of crop type, with larger fields more likely to be occupied. Fields enclosed by hedges or trees tended to be avoided. Cereal and set‐aside fields that were occupied by skylarks in at least 1 month held significantly higher soil seed densities than fields that were not occupied.

Differences in occupancy between crops could be explained by diet. Birds in cereal stubbles fed largely on cereal grain, whereas those in winter cereals fed largely on cereal leaves. Broad‐leaved weed leaves were strongly selected as food in cereal crops and farmland grass fields. In grass fields, the proportion of the diet made up by broad‐leaved weeds was positively correlated with their availability. Broad‐leaved weed seeds did not make up a significant dietary component in any crop.

Our results show that the shift from spring to autumn sowing of cereals has led to a loss of the skylark’s most strongly selected wintering habitat and best food source. In winter cereals and in grass there was a high selectivity for relatively scarce, and probably declining, food resources. Our results suggest that the retention of weed‐rich cereal (particularly barley) and sugar beet stubbles through the winter, particularly in large open blocks, will improve conditions for skylarks in winter. Whole‐field rotational set‐aside, particularly as naturally regenerating cereal stubbles, provides good winter food resources for skylarks.
Particle selection by snail hosts of human schistosomes in relation to their survival strategies and possible control by ‘environmental antibodies’
Authors: Thomas J.D.
Published: March 2003

Experiments were undertaken withBiomphalaria glabratato (i) elucidate the mechanisms used for selecting, regulating and utilizing sand particles and (ii) evaluate particulate controlled‐release formulations (CRF), or ‘environmental antibodies’, to control target snails.

The snails selected sand particles by size, mass and density. The numbers and mass of sand particles in the guts increased with snail size, and fed snails had significantly more sand particles in their guts than deprived snails.

Snails benefited from ingesting sand particles. Increasing the weights of 63–125‐µm sand particles from 8·5 mg to 150–170 mg resulted in progressive, significant, increases in the numbers of sand particles in the various gut compartments and also enhanced snail growth.

Snails did not discriminate between sand and glass particles of the same size. When offered unwashed acidic sand there was a lag of 5–6 h before ingestion, but this could be reduced by preconditioning in media rich in base cations or chemical factors of snail origin. Under equilibrium conditions ingested sand constituted approximately 2·5% of the total snail weight but this amount was exceeded when snails were presented with large quantities of sand.

The parts of the gut involved in sorting and regulating the turnover of sand particles and food were described. The gizzard, caecal and digestive gland strings traversed the gut as far as the rectum in approximately 2·8 h, 6–8 h and 8 h, respectively.

Coprophagy by the snails facilitated the recycling of sand and its retention in the gut.

Optimally sized, 63–250‐µm, protein microcapsules containing butanoate and maltose were ingested by snails in significantly greater amounts than untreated control microcapsules. The addition of copper caused the capsules to become repellent.

These results will advance the design of effective, ecologically acceptable, environmental antibodies in the form of controlled‐release microcapsules to control schistosome snails. This work illustrates how a combination of detailed study of snail anatomy, feeding experiments and ecological understanding can contribute to the control of the intermediate hosts of a major human parasite.
The influence of management regime and altitude on the population structure of Succisapratensis: implications for vegetation monitoring
Authors: Bühler Christoph , Schmid Bernhard
Published: March 2003

Environmental change and land use may alter the vegetation typical of wetland habitats. However, commonly used techniques for vegetation monitoring that are based on species composition are often not suitable to detect gradual changes in the structure of vegetation at an early stage. In this study we tested if this methodical deficiency could be overcome by observation of the stage structure of a perennial target species.

 We studied the density and frequency distribution of four phenological stages of the perennial plant Succisapratensis in 24 calcareous fens in eastern Switzerland. These fens differed in management type (mowing, cattle‐grazing) and altitude (low, medium, high). Among grazed fens, the intensity of management was quantified by direct observation. Species composition and canopy structure of the plant community surrounding S. pratensis were also measured.

 High altitude had a positive effect on the density of adult plants of S. pratensis only in mown fens, whereas in grazed fens adult density was highest at medium altitude.

 Local densities of seedlings and vegetative adults within a fen were higher in mown than in grazed fens, and lower in fens of the lowest altitude level than of the two higher ones. However, there were no differences in the relative proportions of all four phenological stages among main factors except that significantly fewer seedlings occurred in fens of the lowest altitude level.

 It is the intensity rather than the mere type of management regime that is crucial for shaping populations of S. pratensis: for grazed fens, there is a negative relationship between intensity of grazing and density of adult plants of S. pratensis. Moreover, the number, the relative proportion of seedlings and the seed‐set are all negatively correlated with grazing intensity.

 The species composition of the plant community, but not its physical structure, was significantly related to the relative proportion of seedlings of S. pratensis, which supports the indicator qualities of the target species.

 Monitoring the population structure of one or several target species provides important indicator information about the stability of a whole plant community. For the target‐species approach we propose to use characteristic but frequently and steadily occurring species instead of rare or endangered ones.
The impact of the timing of brush management on the nutritional value of woody browse for mooseAlcesalces
Authors: Rea Roy V. , Gillingham Michael P.
Published: March 2003

We examined how the removal of above‐ground biomass (mechanical brushing) at different times of the year affected the nutritional value of regenerating shoots of Scouler’s willowSalix scoulerianafor moose for two winters after brushing.

 Brushing trials were conducted throughout the 1996 and 1997 growing seasons in central British Columbia on a 10‐year‐old regenerating clear‐cut replanted in lodgepole pinePinus contortavar.latifolia.

 We assessed the nutritional value of the browse in relation to length, diameter, mass, digestible energy, digestible protein, tannin and lignin content of current annual growth shoots in winter, as well as the phenology of plant leafing.

 One winter after brushing, willows brushed in early July had shoots that were lower in lignin, higher in digestible protein and lower or not different in tannin content compared with shoots from earlier brushed or unbrushed willows. Willows brushed in early July also had long, heavy, shoots that were high in digestible energy and delayed leaf senescence.

 In the second winter after brushing, willows that were brushed in July had larger shoots that were lower in digestible energy, digestible protein, tannin and lignin content and delayed leaf senescence compared with several other treatments. Willows brushed after July regenerated negligible shoot material in the first year after brushing. Willows brushed in September delayed leaf flush in the first post‐brushing spring.

 To increase the nutritional value of woody browse for cervids, we suggest that brushing should be performed in early to mid‐July (mid‐summer).

 Reductions in browse quality and quantity may negatively affect many mammalian species. Therefore, we recommend that the needs of other fauna potentially affected by changes in shrub architecture, shoot morphology and shoot chemistry be considered when planning the timing of brush management activities.
An evaluation of three quick methods commonly used to assess sward height in ecology
Authors: Stewart K.E.J. , Bourn N.A.D. , Thomas J.A.
Published: March 2003

Many ecological studies and applications involve measuring the height of grassland swards. An evaluation was made of the practicality, accuracy and comparability of using the sward stick, drop disc and direct methods of measurement. Each method proved to be appropriate for measuring swards that contain a wide range of heights, each was quick to perform, and recorder effects were negligible. Yet each had strengths and weaknesses.

The sward stick gave the most variable results: it was considered the best method for recording the architecture of the sward surface, and hence invertebrate niches, but was poor for measuring short turf. The drop disc was the worst method for recording microheterogeneity in sward architecture and was completely unsuitable for measuring variation in short turf. But in medium‐tall swards, it was considered to be the best method for measuring productivity, vertebrate herbivory and for large‐scale monitoring of land managed for conservation and under agri‐environment schemes. The direct method gave the most consistent and accurate results compared with an independent parameter, soil temperature. It was the only method suitable for measuring variation in short turf.

A serious problem exists when research results, recommendations and assays involve measurements made by more than one method. The sward stick consistently gave higher absolute values than either of the other methods and, apart from in short turf (for which it is unsuitable), the drop disc gave values that were 73% and up to 40% lower, respectively, than those obtained using the sward stick and direct methods. This can lead to major misapplications of ecological results and recommendations in conservation and agri‐environmental projects.
The distribution and colony size of barn swallows in relation to agricultural land use
Authors: Ambrosini Roberto , Bolzern Anna Maria , Canova Luca , Arieni Silvia , Møller Anders Pape , Saino Nicola
Published: March 2003

The barn swallowHirundo rusticais a semi‐colonial passerine that has declined in some parts of its European range, perhaps as a result of agricultural change. So far, however, swallow breeding populations have been analysed mostly in north‐western Europe. We studied their distribution, abundance, foraging habitat and breeding performance on 125 farms in Italy in relation to current and past livestock farming and agricultural practice.

 Swallows foraged within 400 m of the farms on which they bred and had a preference for feeding over hayfields. In logistic and multiple regression models, cross‐validated on independent locations, the presence of cattle or pigs in the period 2–5 years beforehand best predicted swallow presence on a farm and, in combination with the presence of stables with traditional architecture, explained 40% of the variance in colony size.

 Breeding occurred later on farms with no cattle, and fledging success declined with the number of cattle per farm.

 This study provides the first evidence from central and southern Europe that livestock farming and the architecture of rural buildings affects the distribution and abundance of barn swallows. The data also show how historical ecological information may play an important role in determining current influences on the distribution and abundance of a breeding bird.

 By augmenting perspectives on swallows at a European scale, our results have important implications for the management and conservation of their breeding populations and allow inferences about the effect of agriculture on future demographic trends.
Control of parasite burdens in wild red grouse Lagopus lagopus scoticus through the indirect application of anthelmintics
Authors: Newborn D. , Foster R.
Published: March 2003

Red grouse Lagopus lagopus scoticus populations in Britain exhibit cyclic fluctuations in abundance with periodic population crashes. Substantial evidence exists to suppose that parasitic worms are the major factor causing these population crashes.

This experimental study was undertaken between 1996 and 2000 on two areas of moorland in the north Pennines, UK, to evaluate the efficacy of the indirect application of anthelmintic drugs in the control of the caecal nematode Trichostrongylus tenuis.

On one area, grouse were given access to anthelmintic drugs incorporated into grit (medicated grit) to control T. tenuis numbers, while on the second control area the birds had access to grit without anthelmintic drugs incorporated (plain grit). In the winter of 1998–99 the treatment was reversed between the two areas.

Adult grouse from the experimentally treated area had significantly lower infections of T. tenuis than grouse from the control area. Hen grouse, which had access to anthelmintic drugs, did not produce significantly more eggs or have a greater hatching success than hens with access only to plain grit. Chick survival was significantly greater on the medicated grit areas, with a significant difference in breeding success. Hens that had access to anthelmintic drugs reared more than twice as many chicks as control hens.

No significant difference was found in red grouse survival between grit treatments.

The increase in grouse numbers arising from the use of medicated grit enhances the viability of red grouse shooting because the cost of treatment appears to be low relative to the return from an increased harvest.
A comparison between broiler chicken carcasses with and without visible faecal contamination during the slaughtering process on hazard identification of Salmonella spp.
Authors: Jiménez S.M. , Salsi M.S. , Tiburzi M.C. , Pirovani M.E.
Published: March 2003

Aims: A comparison of the prevalence of Salmonella in chicken carcasses with and without visible faecal contamination during commercial slaughter practice was made. The relationship between Enterobacteriaceae, coliform and Escherichia coli counts and Salmonella status was also evaluated to establish the likelihood of using these groups as ‘index’ organisms to predict the presence of pathogen. Methods and Results: Samples were removed immediately after evisceration, after the inside–outside shower and after chilling from the processing line for microbiological analysis. Of the carcasses visibly uncontaminated with faeces after the evisceration step 20% harboured salmonellas and 20·8% of the visibly contaminated carcasses were positive for the pathogen. When E. coli, coliforms and Enterobacteriaceae were used as predictor variables the error rates ranged from 33·3 to 60% for both sample types. Conclusions: There was no indication that any of the groups of organisms analysed could predict the incidence of salmonellas on the samples studied. Positive results for the pathogen were obtained at every tested step of the slaughtering process regardless of whether or not faecal contamination was present. Significance and Impact of the Study: The present study demonstrated that carcasses not visibly contaminated with faeces carried Salmonella as well as the visibly contaminated carcasses.
SERCA function declines with age in adrenergic nerves from the superior cervical ganglion
Authors: Pottorf W. J. , Duckles S. P. , Buchholz J. N.
Published: March 2003

1 Intracellular calcium is a universal second messenger integrating numerous cellular pathways. An age‐related breakdown in the mechanisms controlling [Ca2+]i homeostasis could contribute to neuronal degeneration. One component of neuronal calcium regulation believed to decline with age is the function of sarco/endoplasmic reticulum calcium ATPase (SERCA) pumps.

2 Therefore we investigated the impact of age on the capacity of SERCA pumps to control high (68 m
M) [K+]‐evoked [Ca2+]i‐transients in acutely dissociated superior cervical ganglion (SCG) cells from 6‐ and 20‐month‐old Fisher‐344 rats. Calcium transients were measured by fura‐2 microfluorometry in the presence of vanadate (0.1 μM) to selectively block plasma membrane calcium ATPase (PMCA) pumps, dinitrophenol (100 μM) to block mitochondrial calcium uptake and extracellular sodium replaced with tetraethylammonium to block Na+/Ca2+‐exchanger, thus forcing the neuronal cells to rely on SERCA uptake to control [Ca2+]i homeostasis.

3 In the presence of these calcium buffering blockers, the rate of recovery of [Ca2+]i was significantly slower and time to recover to approximately 90% of resting [Ca2+]i was significantly greater in SCG cells from old (20 months) compared with young (6 months) animals.

4 This age‐related change in the recovery phase of [K+]‐evoked [Ca2+]i‐transients could not be explained by differences in the sensitivity of SCG cells to the calcium buffering blockers, as no age‐related difference in basal [Ca2+]i was observed.

5 These studies illustrate that when rat SCG cells are forced to rely on SERCAs to buffer [K+]‐evoked [Ca2+]i‐transients, an age‐related decline in SERCA function is revealed. Such age‐related declines in calcium regulation coupled with neuronal sensitivity to calcium overload underscore the importance of understanding the components of [Ca2+]i homeostasis and the functional compensation that may occur with advancing age.
The geographic ranges of mammalian species in South America: spatial patterns in environmental resistance and anisotropy
Authors: Ruggiero Adriana , Lawton John H. , Blackburn Tim M.
Published: March 2003

We analyse the geographical distribution of South American mammalian species using two biogeographic indices: environmental resistance (R 50) and anisotropy (A50). R50 quantifies the loss of biotic resemblance occurring from any point in the map to the rest of the continent. A
50 quantifies the extent to which the perimeter: area ratio of the geographical ranges of all species whose distributions overlap at any particular location depart from the perimeter: area ratio of a circle. We test for the latitudinal Rapoport effect that predicts an increase in the range‐sizes of mammalian species, and hence a decrease in the values of R
50, towards the south. We test for the effect of mountains on species’ ranges, given that Janzen's argument that ‘mountain passes are higher in the tropics’ implicitly predicts greater anisotropy in the tropics. Continental spatial patterns of variation in R
50 and A50 suggest a biogeographic division of South America consistent with most classical zoogeographical classifications proposed for the continent. Rapid change in mammalian range‐sizes and shapes occurs at the limit between the Guayano‐Brazilian and Andean‐Patagonean subregions. R
50 data do not support the latitudinal Rapoport effect: the most widespread species locate in the eastern portions of Brazil, the most restricted ones are in association with the Andes. A
50 data support Janzen's prediction: the effect of mountains on species’ distributions is greater in equatorial and central regions of the Andes rather than in the south. R
50‐and A50‐contour maps reveal that, mainly due to the effects of the lie of the land and likely differences in the history of the fauna, the continent has a biogeographic texture which must have major constraints on local ecological patterns and processes. This stresses the importance of considering the role of biogeographic structure in the analyses of geographical gradients in species’ distributions.
Avifaunal diversity of five high‐altitude cloud forests on the Andean western slope of Ecuador: testing a rapid assessment method
Authors: Otto Poulsen Bent , Krabbe Niels
Published: March 2003

A standardized rapid assessment method was used to evaluate the variation in avifaunal diversity between five equal‐sized high‐altitude cloud forests on the Pacific slope of the Ecuadorian Andes. Within the limited latitudinal range (370 km) across the equator, there was little difference in avifaunal richness and α‐diversity between these sites, but moderately high differences in species compositions (β‐diversity). In this study, the latitudinal gradient comprised two biogeographically distinct areas on each side of a postulated Cañar high‐altitude corridor between the eastern and western slopes of the Andes. If our results are applicable to other places with the same environmental conditions, species compositions and names of species referred to threatened categories (e.g. endemics, restricted‐range, CITES) are the necessary data in standardized surveys for pointing out priority conservation areas. The efficiency of our standardized method was tested by comparing our results from Río Mazan with two previous detailed surveys from this site. In only 4 days, our method accounted for 85% of a forest avifauna previously assessed using an effort of thirty person‐months.
Hydroseral development in southern Ontario: patterns and controls
Authors: Bunting* M. J , Warner B. G
Published: March 2003

Palaeoecological data from a range of wetland types were synthesized in order to study the development of wetland ecosystems in southern Ontario. The present‐day nature of the wetland system occurring in a topographically defined basin was shown to be controlled in part by basin morphology. Stratigraphic and vegetational (pollen and macrofossil analysis) data were used to compare the sequence of communities occupying basins during the postglacial. In systems where terrestrial peat overlies lake sediment, the broad stages of development were relatively uniform (from a lake to a shallow open water wetland to a herbaceous marsh or fen to a woody plant‐dominated community), although the exact nature of each stage varied widely between basins. The accumulation rate of sediment within such basins varied by up to two orders of magnitude during the postglacial. Allogenic and autogenic factors have been acting on these systems throughout the postglacial, and the sensitivity of individual sites to changes in these environmental conditions will also have varied. Even the widespread land clearance associated with European settlement in the area in recent centuries has not affected some wetland systems detectably, while others have either been destroyed or profoundly changed. The patterns of hydroseral development, both timing and direction, were compared with known regional environmental changes.