bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting the long‐term acidification trends in small subarctic lakes using diatoms
Authors: Korhola Atte , Weckström Jan , Nyman Marjut 
Published: March 2003

Summary 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

Summary 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

Summary 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

Summary 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

Summary1. 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

Summary1. 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

Summary 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

Summary1. 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.