bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial synchrony in field vole Microtus agrestis abundance in a coniferous forest in northern England: the role of vole‐eating raptors
Authors: Petty S.J. , Lambin X. , Sherratt T.N. , Thomas C.J. , Mackinnon J.L. , Coles C.F. , Davison M. , Little B. 
Published: March 2003

1. The regional synchrony hypothesis (RSH) states that synchrony in microtine abundance over large geographical areas is caused by nomadic avian predators that specialize on small mammals for food. This has proved a difficult hypothesis to test because experiments at an appropriate scale are almost impossible. 2. We used the decline of the most abundant, nomadic vole‐eating raptors in an extensive conifer forest in northern England (Kielder Forest) as a natural experiment to evaluate their influence on synchronizing voles at different spatial scales. Field vole populations fluctuated on a 3–4‐year cycle of abundance, similar to the periodicity in central Fennoscandia. 3. Over a 23‐year period, the combined numbers and density of kestrels and short‐eared owls significantly declined. If these raptors were responsible for synchronizing vole abundance, the decline should have been associated with a decrease in synchrony. We could find no change in synchrony during the period of the greatest decline in kestrel and short‐eared owl numbers (1980–97). 4. In Kielder, vole abundance has been shown to change in a wave‐like manner, with synchrony in the direction of the wave being 5–10‐fold smaller than that reported in Fennoscandia. Tawny owls are sedentary and the most abundant vole‐eating raptor in our study area, and might have an equalizing influence on vole abundance over smaller areas if they foraged in a density‐dependent manner and responded functionally to increasing vole density. If this was the case, spatial variability in vole density should have been less in occupied than unoccupied owl territories, especially in years of low vole density when owls could take a larger proportion of the standing crop of voles. Even though tawny owls caught a significant proportion of the vole population, we could find no difference in variation in vole density between owl territories that were unoccupied, occupied with no breeding attempt, or occupied with a successful breeding attempt. 5. We conclude that the small‐scale synchrony in field vole abundance is unlikely to be caused by avian predators. Instead, it is more likely to be related to the pattern of clear‐cutting that has developed in Kielder, which restricts vole dispersal. If this assumption is correct, we would predict more widespread synchrony in vole abundance in first‐generation forests when extensive areas are planted over short periods of time, and this is supported by anecdotal evidence. These conclusions indicate that foresters may be able to manipulate the spatial dynamics of voles and vole predators by varying patch sizes within forests.
Testing genetically engineered potato, producing the lectins GNA and Con A, on non‐target soil organisms and processes
Authors: Griffiths B.S. , Geoghegan I.E. , Robertson W.M. 
Published: March 2003

Summary1. Two lectins, concanavalin A (Con A) andGalanthus nivalisagglutinin (GNA), have anti‐feedant properties that suggest a potential for the control of invertebrate pests of plants. We tested potato plants genetically engineered to produce each of these lectins constitutively, as well as the purified lectins, for possible non‐target effects.2. Laboratory studies with soil bacterial communities and a ciliate protozoan could detect no direct effect of either lectin over a range of concentrations. There was a significant inhibition in the host‐finding response of a bacterial‐feeding nematode when Con A or GNA was present in the medium at 0·5–50 µg ml−1.3. A number of GNA‐ and Con A‐producing potato lines had no detectable effects on the rhizosphere microbial and microfaunal populations when examined in pot trials. The incorporation of leaves from transgenic plants into soil reduced protozoan populations significantly, but there was no subsequent effect on the decomposition of added cotton strips.4. Controlled field‐release experiments demonstrated that, although GNA‐producing potato lines consistently altered the physiological profile of the rhizosphere microbial community at harvest, the effect did not persist from one season to the next over a trial period of two field seasons. There was no significant effect of the best performing GNA line on the development of a subsequent barley crop.5. A single Con A‐producing line was tested in a controlled field‐release. The only significant effects were transient reductions ofc. 40% in soil protozoan populations and ofc. 10% in potential microbial activity.
Modelling the effects of mink and habitat fragmentation on the water vole
Authors: Rushton S.P. , Barreto G.W. , Cormack R.M. , Macdonald D.W. , Fuller R. 
Published: March 2003

Summary1. The decline of the water voleArvicola terrestrisin the UK has been attributed to the spread of the introduced American minkMustela vison. Understanding the causes and dynamics of this decline is vital to water vole conservation. We investigated the dynamics of water voles in relation to habitat fragmentation and mink predation using an individual‐based spatially explicit model of population dynamics on the River Windrush, Oxfordshire, UK.2. A sensitivity analysis was undertaken using values for life‐history parameters drawn from known ranges using Latin hypercube sampling. Partial correlation coefficients were used to estimate how the predicted size of water vole population and extinction were determined by the life‐history parameters. The model was then validated by comparing model predictions with observed distributions of water voles.3. The effects of mink predation and habitat fragmentation on the future viability of water vole populations on the River Windrush were analysed after artificially manipulating habitat fragmentation on the river and running the model in the presence and absence of mink predation.4. The match between predicted and observed distributions was significantly related to home range requirement and high reproductive success. At low fragmentation, home range requirement was the most important influence on the number of populations. Reproductive output, and adult and juvenile mortality, became increasingly important with increased fragmentation. At high levels of fragmentation demographic stochasticity had a large influence on population size.5. We deduce that the importance of demography in determining population persistence will depend on the level of fragmentation. Additionally, life‐history parameters that are crucial to the viability of water vole populations can only be identified in the context of the landscape in which populations are found.6. The extinction of water vole on the River Windrush became more likely as habitat fragmentation and mink predation increased. Mink predation effectively doubled the probability of extinction over that arising from fragmentation alone.7. These simulations indicate that extant populations on the Windrush are now so fragmented that populations may not be viable even in the absence of mink predation. We assessed the extent of habitat restoration necessary to ensure population persistence on the River Windrush and considered developments of the model for use in water vole conservation.
Effects of grazing by free‐ranging cattle on vegetation dynamics in a continental north‐west European heathland
Authors: Bokdam Jan , Gleichman J. Maurits 
Published: March 2003

Summary 1. Abandonment and eutrophication are major threats to traditional pastoral landscapes and their wildlife in Europe. Social and economical developments have rendered traditional pastoralism impracticable. More knowledge is needed about the effects of grazing with free‐ranging herbivores, which is increasingly used as a substitute for the traditional herding system. 2. We studied the effects of free‐ranging cattle on the recovery of Calluna heather, tree encroachment and plant species richness in six habitats in a grass‐rich Dutch heathland during a 10‐year period. The habitats differed in soil fertility, initial heather–grass ratio and developmental stage of Calluna. 3. Despite preferential grass defoliation, cattle grazing neither reduced grass cover in grass heath nor prevented grass invasion in heather. Grass invasion failed only in a nitrogen‐poor turf‐stripped Calluna heath. Grazing induced a substantial Calluna recovery in grass heaths on podzolic soils, but its recovery failed in grass heath on a phosphorus‐rich medieval arable field. As a consequence, the grass–heather mosaics generated by free‐ranging cattle were restricted to habitats of intermediate soil fertility. 4. Grazing did not prevent encroachment by pine and birch. Removal by the site manager prevented conversion of 10–20% of the open heathland to forest. 5. During the first 5 years, grazing induced a significant increase in species richness in all habitats. During the second 5 years, species richness stabilized in grass heath and heather–grass mosaics and it declined in the pioneer Calluna heaths. 6. We found indications of various nutrient‐mediated grazing effects on the competitive balance between grass and woody pioneers. These suggest that nutrient‐mediated feedback might be an important explanatory mechanism for the described vegetation mosaic cycling in heathlands. 7. Free‐ranging grazing did not remove the high atmospheric nutrient inputs of the whole area. Substantial amounts of nutrients were redistributed from the grass lawns to the forest. 8. Free‐ranging grazing combined with tree cutting appeared to be a suitable management regime for the maintenance of species‐rich open heathlands with dynamic grass–heather mosaics. 9. Without tree cutting, free‐ranging grazing would have created dynamic tree–grass–heather mosaics in open heathland. Wood–pasture landscapes are fundamentally different from the open heather‐dominated heathlands produced by the traditional sedentary farming system. Integrated grazing of heathland, nutrient‐rich farmland and forests accelerates this change. Alternative grazing regimes are discussed.
Effects of vegetation structure, food and shelter on the home range and habitat use of an endangered wallaby
Authors: Fisher D.O. 
Published: March 2003

Summary 1. Bridled nailtail wallabies Onychogalea fraenata are medium‐sized, nocturnal, solitary macropods that persist in only one conservation reserve in central Queensland, Australia. They use shrubs, grass and logs as diurnal shelters. Factors affecting shelter choice, habitat use and home range size were interpreted in terms of habitat management, and shelter provision was assessed as a potential management tool. 2. Shelter selection, food and variation in cover were assessed at two sites that differed in vegetation density and population density. In order to determine how habitat quality and potential visibility to predators affect ranging behaviour, the relationships among home range size, grass biomass, sex, site, habitat edge availability and moon phase were determined for 37 radio‐collared wallabies during and after a severe drought. 3. Open habitats contained more food, whereas wooded habitat contained more preferred shelter. Shelter but not food availability differed between the sites. Wallabies used a higher proportion of wooded habitat, and increasingly avoided open areas, as food biomass in wooded areas increased after the drought. 4. Home range size differed between the sexes but not between the sites. It tended to be inversely related to availability of food and habitat edge. Diurnal home range size was correlated with grass biomass and was larger at the site with the lowest population density and lowest availability of cover, but it did not differ between sexes. 5. A preference for habitat edges may reflect shelter quality. Animals chose shelter sites with the densest cover at wallaby height; cover was densest at this height at the forest edge. 6. Wallabies used individual shelters repeatedly, were faithful to diurnal range areas, but did not appear to share shelter sites. They used experimentally provided shelter extensively, and more frequently than other medium‐sized mammals at the sites. 7. Increasing natural grass cover was associated with diurnal home range shifts and expansion, but experimental shelter provision had no effect on diurnal range size or location. Shelter did not explain differences in diurnal range size between the sites, which may instead be related to population density. 8. Neither vegetation type was obviously better habitat. Ongoing large‐scale manipulation of forest regrowth may be needed to increase habitat edges and maintain vegetation at the optimum height to provide shelter and food. Patchy clearing is therefore a potential strategy for habitat management for this species and other medium‐sized forest‐dwelling mammals.
Simulating the spread and management of alien riparian weeds: are they out of control?
Authors: Wadsworth R.A. , Collingham Y.C. , Willis S.G. , Huntley B. , Hulme P.E. 
Published: March 2003

1. This paper examines the circumstances under which control programmes may reduce the range of two widespread invasive weeds of riparian habitats: Impatiens glandulifera (Himalayan balsam) and Heracleum mantegazzianum (giant hogweed). 2. The spread of both species was modelled using MIGRATE, a spatially explicit model that incorporates realistic demographic parameters and multiple dispersal mechanisms. Simulations of a range of control scenarios were run within a geographical information system (GIS) using authentic landscapes based on topographic, hydrological and land cover maps of County Durham, UK. Results were interpreted at both a catchment and a regional scale. 3. Six representative strategies were explored that prioritized control as follows: at random, in relation to human population density, or by the size, age (new and old) or spatial distribution of weed populations. These strategies were assessed at different intensities of management (area treated per year) and for varying efficiencies (proportion of plants destroyed) as well as the timeliness (how long since the species became established) of implementations. 4. Strategies that prioritized control based on weed population and spatial characteristics were most effective, with plant population size and spatial distribution being the key parameters. The reduction in geographical range within a catchment or region following control was always greater for H. mantegazzianum than I. glandulifera due to its slower rate of spread. 5. Successful control of both species at a regional scale is only possible for strategies based on species distribution data, undertaken at relatively high intensities and efficiencies. The importance of understanding the spatial structure of the population and potential habitat available, as well as being able to monitor the progress of the eradication programme, is highlighted. Tentative conclusions are offered as to the feasibility of eradicating these species at a regional scale.
The responses of floodplain primary production to flood frequency and timing
Authors: Robertson A.I. , Bacon P. , Heagney G. 
Published: March 2003

Summary

River regulation and abstraction have dramatically altered the natural flow regime of many rivers world‐wide, but experimental investigations of the biological effects are infrequent. In the mid‐region of the Murray River, Australia, river regulation has reduced the frequency and duration of spring floods and increased the frequency of summer floods. We used controlled floods (treatments: no floods, spring floods, summer floods and spring + summer floods) to determine how the growth of river red gum Eucalyptus camaldulensis trees, aquatic macrophytes and biofilms varied with the seasonal timing and frequency of flooding.
After 6 years of controlled flooding, above‐ground net production of wood by river red gum trees was equal and greatest in plots receiving spring + summer floods and summer floods (mean 496 g m−2 year−1). Production was significantly lower in plots receiving spring floods or no controlled floods, which had similar rates of production (mean 330 g m−2 year−1).
During 2 years of measurement in wetlands created by flooding, production and species richness of aquatic macrophyte were both greater in spring than in summer floods. The history of flood frequency at any experimental site did not affect macrophyte production or species richness. The aquatic macrophyte community in shallow regions of wetlands differed significantly with the seasonal timing of floods, but not flood frequency.
The accumulation of chlorophyll a and total mass of biofilm on wood surfaces in wetlands created by flooding were greater in spring (mean chlorophyll a, 0·88 µg cm−2; mean mass, 0·066 mg cm−2) than in summer floods (mean chlorophyll a, 0·09 µg cm−2; mean mass, 0·034 mg cm−2). The history of flood frequency at any experimental site did not affect accumulation of either the autotrophic or heterotrophic components of biofilms.
Spring flooding, while not as beneficial for tree growth, is critical for the growth of wetland macrophytes, the maintenance of macrophyte species richness, and favours better development of autotrophic biofilms. Maintenance of both the timber harvest and wetland conservation values of these floodplains will require the return of more natural flood flows in the spring period. Restoration of floodplain rivers requires a thorough understanding of the relationships between ecological functions and the natural flow regime.
Interactions between the rust fungus Puccinia punctiformis and ectophagous and endophagous insects on creeping thistle
Authors: Stephanie Kluth , Andreas Kruess , Teja Tscharntke 
Published: March 2003

Summary

Plant–pathogen–insect interactions may have various outcomes that are of great interest when considering the combined use of insects and pathogens in the biological control of weeds. Here effects of rust infection on herbivore attack and of herbivory on rust infection were analysed to ensure that these possible control agents do not impede each other.
The system studied was the weed creeping thistle Cirsium arvense, the specialized rust fungus Puccinia punctiformis, and ectophagous and endophagous insect herbivores. On 20 sites around Göttingen, Germany, the abundance of ectophagous and endophagous insects on systemically rust‐infected and uninfected plants was quantified by suction samples and the dissection of shoots.
Abundance of ectophagous insects was not reduced by rust infection, and aphids as well as several beetle species were more abundant on systemically infected plants. Preference of endophagous insects differed between species: larvae of Apion weevils were more abundant in infected shoots, whereas Melanagromyza aeneoventris, Urophora cardui, all of them oligophagous, and some leaf miners preferred uninfected plants. In dual‐choice feeding tests, larvae of the oligophagous chrysomelid beetle Cassida rubiginosa were more likely to feed on leaf segments of uninfected thistles.
Enhancement of rust infection rate by simulated herbivory was analysed. Thistle leaves were perforated and infection rate was recorded after 2 weeks under natural Puccinia punctiformis spore concentrations. Numbers of uredosori were significantly higher in perforated leaves. Artificial inoculation resulted in an even greater increase in uredosori, both in perforated and unperforated thistles.
As the majority of ectophagous and endophagous insects did not discriminate between systemically infected and uninfected thistles, herbivore damage together with infection with Puccinia punctiformis can be expected to increase stress on creeping thistle when used in biological control of the weed. Insects may not only affect plant growth by herbivory but may also increase the susceptibility of healthy thistles to local rust infection by wounding of leaves.
Using stochastic dynamic programming to determine optimal fire management for Banksia ornata
Authors: McCarthy M.A. , Possingham H.P. , Gill A.M. 
Published: March 2003

Summary

A model of the population dynamics of Banksia ornata was developed, using stochastic dynamic programming (a state‐dependent decision‐making tool), to determine optimal fire management strategies that incorporate trade‐offs between biodiversity conservation and fuel reduction.
The modelled population of B. ornata was described by its age and density, and was exposed to the risk of unplanned fires and stochastic variation in germination success.
For a given population in each year, three management strategies were considered: (i) lighting a prescribed fire; (ii) controlling the incidence of unplanned fire; (iii) doing nothing.
The optimal management strategy depended on the state of the B. ornata population, with the time since the last fire (age of the population) being the most important variable. Lighting a prescribed fire at an age of less than 30 years was only optimal when the density of seedlings after a fire was low (< 100 plants ha−1) or when there were benefits of maintaining a low fuel load by using more frequent fire.
Because the cost of management was assumed to be negligible (relative to the value of the persistence of the population), the do‐nothing option was never the optimal strategy, although lighting prescribed fires had only marginal benefits when the mean interval between unplanned fires was less than 20–30 years.
Does host genotype diversity affect the distribution of insect and disease damage in willow cropping systems?
Authors: Peacock L. , Hunter T. , Turner H. , Brain P. 
Published: March 2003

Summary

Planting of willow genotype mixtures for biomass production has been suggested as a non‐chemical strategy for pest management. Basic information on spatial dynamics of important insects and pathogens is necessary for the effective deployment of host genotypes in a plantation. In 1998 and 1999 the degree and spatial distribution of damage by Melampsora spp. and Phratora vulgatissima were studied concurrently in a field trial containing monocultures of willow Salix genotypes with different willow rust and beetle susceptibilities, and two design mixtures (random or regular) of three or five genotypes.
For both years, there was more rust and beetle damage on plants in monocultures than in mixtures. There were significant differences in the vertical distribution of beetle damage along stems between plantation designs for the 2 years, yet only in 1999 for rust. Rust severity along stems was significantly correlated between leaves, indicating localized spread of disease. In contrast, beetle damage severity along stems was weakly correlated between alternate leaves and leaves farther apart, suggesting beetle movement from tree to tree.
In 1998, spatial distribution of rust was aggregated in 67% of plots studied and in 40% for beetles. There was no significant difference in the distribution of beetle damage between planting design, but rust was aggregated in 75% of mixtures and 33% of monocultures. While beetle damage distribution was similar between years, rust was aggregated in all monoculture plots but in only 8% of mixtures in 1999. The difference between years and design for rust was probably because of the later stage of rust development in 1999 and the delaying effect of mixtures on this development.
In 1998, there were significant negative correlations between the extent of rust and beetle damage on individual trees. However, only 20% of plots showed a significant spatial dissociation between these two types of damage. There were fewer discernible interactions in 1999.
Plantation design provides the basis for integrated control of rust and beetle damage within willow cropping systems by delaying the spread and development of both organisms. Both pest and disease can be assessed successfully simultaneously under field conditions, a major saving in human resources. Initial selection of willow mixture configuration should primarily take into account the effects of spatial design on rust development.