bluuebunny/crossref_metadata_2025_split huggingface dataset:
Living where the food is: web location by linyphiid spiders in relation to prey availability in winter wheat
Authors: Harwood J.D. , Sunderland K.D. , Symondson W.O.C. 
Published: March 2003

Summary

Spiders form a major component of the generalist predator fauna, potentially able to restrict pest population growth, but their populations may be food‐limited under current farming regimes. This study aimed to quantify food availability to spiders in winter wheat and to determine whether spider web locations are positively associated with available food resources.
Mini‐sticky traps (availability rate per 24 h, including prey falling from the crop) and mini‐quadrats (instantaneous density on the ground by day) were used, in combination, to monitor the availability of potential prey to web‐building species of money spider (Linyphiidae) in fields of winter wheat in Warwickshire, UK, 1997–98.
These methods were applied to web sites of individual spiders and to non‐web sites located randomly up to 30 cm away from each web. A total of 18 546 invertebrates were captured using these methods.
Overall, significantly more potential prey were available in web sites than in non‐web sites (both on sticky traps and in quadrats).
Prey availability in May and July was about a third of that in June (both on sticky traps and in quadrats) and may have been below that known to be necessary for spiders to realize their maximum population growth rate.
The peak rate of capture of linyphiid spiders on mini‐sticky traps was 0·6 trap−1 day−1 at web sites, and approximately half this value at non‐web sites. Numbers of spiders captured by mini‐sticky traps and mini‐quadrats increased exponentially as the season progressed. The high capture frequency in relation to population density, and the differential between web and non‐web sites, points to a dynamic and aggregated distribution of spiders in winter wheat, which is consistent with what is known about mate‐searching and web site abandonment rates by the Linyphiidae.
The combination of techniques described here is recommended for monitoring prey availability in prey‐enhancement programmes and may prove useful in quantitative studies of both intra‐ and interspecific interactions between spiders.
A model of bovine tuberculosis in the badger Melesmeles: the inclusion of cattle and the use of a live test
Authors: Smith G.C. , Cheeseman C.L. , Wilkinson D. , Clifton‐Hadley R.S. 
Published: March 2003

Summary

An individual‐based stochastic simulation model was used to investigate the control of bovine tuberculosis (TB) in the European badger Meles meles by using a live test to determine the presence of infection. The model was an extension of earlier models, and nearly all population and epidemiological parameters were derived from one study site.
This is the first TB model to examine sex differences in disease epidemiology, and the transmission of TB from badgers to cattle. The latter is an essential step if reactive badger control strategies are to be modelled.
Heterogeneity was introduced to the simulation model by the use of a carrying capacity, which defined the maximum number of breeding females per social group.
The prevalence of TB, and the number of simulated cattle herd breakdowns, was reduced for all control strategies using a live test, namely localised culling, ring culling and proactive culling. However, only proactive culling resulted in a marked reduction in these values within a few years.
If trapping efficacy was increased above its current value (80%), this did not improve the effectiveness of these culling strategies.
If the number of individual badgers caught and tested per social group was doubled from two to four animals per group, then the overall level of effectiveness of these strategies could be doubled.
The effectiveness could be improved if the sensitivity of the live test was increased, but did not continue to show an improvement above a sensitivity of about 70%.
Given the constraints of the current live test sensitivity (41%) and a trapping efficacy of 80%, proactive culling, following the testing of four individuals per group, led to an average of three cattle herd breakdowns per year in the simulation, compared with an average of 31 per year when simulating the live test trial as used between 1994 and 1996.
Measuring the range to animals at sea from boats using photographic and video images
Authors: Gordon Jonathan 
Published: March 2003

Summary

Estimating range to objects at sea by eye is notoriously difficult yet there are many occasions in management and research when accurate measures of range are required.
A new method is described in which range is calculated from the angle subtended between the horizon and the waterline of the object measured from single video or photographic images taken at a known elevation. Possible errors are explored and practical analysis methods outlined. Images can be collected and analysis performed using relatively inexpensive standard equipment.
In offshore waters, uncertainty in the height of the camera and target object due to the effects of waves and swell are likely to be the most significant sources of error. The effects of errors in camera height on ranges calculated using this method are approximately proportional to the ratio of the height error to camera height. Simulations indicate that wave‐ and swell‐induced errors in the height of both object and camera will lead to range estimates with a standard deviation (SD) of 0·5 × (error due to wave height)/(camera height).
Three trials were conducted in which ranges (out to 2000 m) measured using this method were compared with those determined using alternative methods (laser range‐finding binoculars or non‐differential global positioning system). Mean percentage discrepancies in range measurements between the two methods varied from 6·4% to 2·6%, while the SD of discrepancies in trials varied between 6·5% and 4·3%. The independent range measuring methods used here were not without error, however, and it is suggested that a mean absolute error of > 2% is an appropriate figure for the video method.
Field tests indicated that the necessary photos or video sequences could be collected from most types of cetaceans in the field. A variety of applications for the method during activities such as line transect surveys, mitigation monitoring and behavioural studies are suggested and discussed.
The effect of provenance on the performance of Crataegus monogyna in hedges
Authors: Jones A.T. , Hayes M.J. , Sackville Hamilton N.R. 
Published: March 2003

Summary

Grants for wildlife enhancement in the British Isles have supported the widespread planting of new hedges along field margins. However, much of the planted material, particularly of hawthorn Crataegus monogyna, has been obtained from the continental mainland of Europe. There is a need to assess the implications of this practice for hedgerow performance and for the conservation of indigenous genetic variation.
One local ecotype and eight commercial provenances (four British and four continental European) of hawthorn were planted in an experimental hedge at both an exposed upland site and a sheltered lowland site. Sections of hedge were planted with or without fencing and with or without mulching in all combinations. Growth and thorniness were assessed over 3 years, and phenology and disease over 2 years.
At both sites, the most locally obtained provenance had the latest bud‐burst, exhibited the least severe symptoms of mildew and was the most thorny. It also showed the greatest height increment at the upland site, but was relatively slow‐growing at the lowland site.
An imported Hungarian provenance had early bud‐burst, showed a high growth rate and suffered the most severe mildew. A commercially obtained British native provenance was aberrant in its extremely early bud‐burst and other attributes comparable with the Hungarian provenance, indicating the possibility of misidentification at some stage of production or supply.
In the absence of fencing, at the upland site hawthorn mortality was 100% compared with only 3% at the lowland site. In fenced plots there was c. 320% greater growth when mulching was used.
The results suggest that for greater establishment success and hence cost benefits in hedge planting, as well as for greater environmental benefits, there should be closer matching of hawthorn provenance to the planting site. The use of commercial material has demonstrated that locally provenanced material can be superior to any commercially available material, and that the current state of the commercial sector is insufficient to enforce the necessary controls over provenance of material used for hedge renovation.
Comparing strategies for controlling an African pest rodent: an empirically based theoretical study
Authors: Stenseth Nils Chr. , Leirs Herwig , Mercelis Saskia , Mwanjabe Patrick 
Published: March 2003

Summary

Small rodents in general and the multimammate rat Mastomys natalensis in particular cause major economic losses in Africa through damage to crops. Attempts to develop dynamic population models for this and other pest rodents are ongoing.
Demographic estimates from a capture–mark–recapture (CMR) study in Tanzania were used to parameterize a population model for this species. This model incorporated three functional age categories (juveniles, subadults and adults) of both sexes and used density‐dependent and density‐independent factors, the latter represented by rainfall.
The model was used to analyse the effect of rodent control on the population dynamics and resulting number of rats. Control measures affecting survival as well as reproduction were considered.
The model showed that control measures reducing survival will only have long‐term effects on population size if they are also applied when rodent densities are low. Control measures applied only when rodent densities are high will not have persistent effects, even at high mortality rates.
The model demonstrated that control measures reducing reproduction are likely to prevent Mastomys outbreaks, but will keep densities low over a long period only when the contraceptive effect is strong (> 75% reduction).
Provided that CMR data are available, we recommend developing Leslie‐type population models for rodent pests on the basis of CMR‐estimated demographic schedules. Such models have great potential in rodent management and allow the evaluation of different strategies.
Besides improving the ecological basis of the population modelling, economic considerations need to be incorporated into decisions about rodent control. We suggest that appropriate population models will provide important input into such decision making.
Brown locust outbreaks and climate variability in southern Africa
Authors: Todd Martin C. , Washington Richard , Cheke Robert A. , Kniveton Dominic 
Published: March 2003

Summary

The brown locust Locustana pardalina is a major agricultural pest in southern Africa, with populations periodically reaching plague proportions. Management and control would benefit from a predictive capacity at seasonal time scales, as yet unavailable.
The results of a study into the dynamics and potential predictability of locust populations in southern Africa are presented here. The number of districts reporting locust control measures was used as a proxy for swarming brown locust populations.
Spectral analysis of the annual number of brown locust infestations over southern Africa revealed dominant periodicity at 17·3 years. The data were low‐pass filtered and the low‐frequency and high‐frequency components were retained. The low‐frequency component led the observed 18‐year cycle in southern African rainfall by about 3 years, and was therefore likely to reflect endogenous controls on populations.
Variability in the interannual high‐frequency component of brown locust infestations was strongly related to rainfall over the Karoo and Eastern Cape regions of South Africa. The highest correlations were with rainfall over the 12 months prior to the locust season (r = 0·64) and in particular with rainfall during December (r = 0·55).
Evidence is presented that the high‐frequency component is related to the Pacific El Niño/Southern Oscillation (ENSO) and that high‐frequency locust activity is abnormally high (low) during La Niña (El Niño) events.
The high‐frequency component of locust activity correlates positively and negatively, respectively, with sea‐surface temperatures over the tropical western and eastern Pacific Ocean many months in advance of the locust season. Activity also correlates positively (negatively) with sea‐surface temperatures over the south‐west Indian Ocean and the Southern Ocean (west and north‐west Indian Ocean). These relationships occur later than those in the Pacific, developing in the austral winter and peaking in early summer. This pattern of correlations and the associated atmospheric circulation anomalies is consistent with ENSO‐related and non‐ENSO related patterns of climate variability.
The results suggest that there may be considerable scope for future development of models for the seasonal prediction of brown locust activity in which high‐frequency variability is related to climatic indices.
Effects of Phalaris arundinacea and nitrate‐N addition on the establishment of wetland plant communities
Authors: Green Emily K. , Galatowitsch Susan M. 
Published: March 2003

Summary

Nutrient enrichment may adversely impact plant species richness in wetlands and enhance their susceptibility to colonization and dominance by invasive species. For North American prairie wetlands, enrichment by nitrate‐N (NO3‐N) from agricultural runoff is thought to contribute to the increasing colonization and dominance of Phalaris arundinacea (reed canary grass), especially during restoration. If true, P. arundinacea might compromise the re‐establishment of sedge meadow vegetation on sites reflooded with agricultural drainage water.
We tested this hypothesis using a fertilization experiment in wetlands with controlled hydrology. A community mixture comprising 11 species from native sedge meadow was seeded in mesocosms and grown under one of three NO3‐N levels (0 g m−2 year−1, 12 g m−2 year−1, 48 g m−2 year−1) with or without P. arundinacea. Above‐ and below‐ground biomass were measured after two growing seasons to assess the response of vegetation to NO3‐N and P. arundinacea treatments.
The total shoot biomass of the native community was suppressed in the presence of P. arundinacea at all NO3‐N levels, but shoot suppression was significantly greater at the highest NO3‐N dose level (48 g m−2). Shoot growth of the native community was reduced by nearly one‐half under these conditions.
The total root biomass of the community was also suppressed by P. arundinacea when no NO3‐N was added.
As NO3‐N increased, the relative abundance (shoot biomass) of native graminoids declined while native forbs increased in communities with and without Phalaris. The most common graminoid, Glyceria grandis, was suppressed by P. arundinacea at all levels, with suppression enhanced at the 48 g m−2 NO3‐N level. Three other species were suppressed at the highest NO3‐N level, in the presence of Phalaris. The two most common forbs, Asclepias incarnata and Sium suave, exhibited a continual increase in growth with NO3‐N additions along with overall suppression by P. arundinacea.
Community diversity and evenness declined with increasing NO3‐N levels, whether or not P. arundinacea was present.
Our results demonstrate that if P. arundinacea is present, the restored sedge meadow community will not achieve levels of abundance that are possible when this species is absent, regardless of NO3‐N enrichment conditions.
At the same time, the increased suppression by P. arundinacea at the 48 g m−2 NO3‐N dose level supports the hypothesis that the dominance of this species over the native sedge meadow community is enhanced by NO3‐N inputs at levels that are common in agricultural landscapes.
Our results carry two implications for achieving biodiversity conservation in agricultural landscapes. First, reducing nitrate loads to wetland reserves is essential for minimizing declines in community diversity. Secondly, the use of P. arundinacea for soil conservation and other agri‐environmental purposes should be curtailed because of the likelihood of off‐site impacts to wetland biodiversity.
Using ants as bioindicators in land management: simplifying assessment of ant community responses
Authors: Andersen Alan N. , Hoffmann Benjamin D. , Müller Warren J. , Griffiths Anthony D. 
Published: March 2003

Summary

The indicator qualities of terrestrial invertebrates are widely recognized in the context of detecting ecological change associated with human land‐use. However, the use of terrestrial invertebrates as bioindicators remains more a topic of scientific discourse than a part of land‐management practice, largely because their inordinate numbers, taxonomic challenges and general unfamiliarity make invertebrates too intimidating for most land‐management agencies. Terrestrial invertebrates will not be widely adopted as bioindicators in land management until simple and efficient protocols have been developed that meet the needs of land managers.
In Australia, ants are one group of terrestrial insects that has been commonly adopted as bioindicators in land management, and this study examined the reliability of a simplified ant assessment protocol designed to be within the capacity of a wide range of land managers.
Ants had previously been surveyed intensively as part of a comprehensive assessment of biodiversity responses to SO2 emissions from a large copper and lead smelter at Mt Isa in the Australian semi‐arid tropics. This intensive ant survey yielded 174 species from 24 genera, and revealed seven key patterns of ant community structure and composition in relation to habitat and SO2 levels.
We tested the extent to which a greatly simplified ant assessment was able to reproduce these results. Our simplified assessment was based on ant ‘bycatch’ from bucket‐sized (20‐litre) pitfall traps used to sample vertebrates as part of the broader biodiversity survey. We also greatly simplified the sorting of ant morphospecies by considering only large (using a threshold of 4 mm) species, and we reduced sorting time by considering only the presence or absence of species at each site. In this manner, the inclusion of ants in the assessment process required less than 10% of the effort demanded by the intensive ant survey.
Our simplified protocol reproduced virtually all the key findings of the intensive survey. This puts effective ant monitoring within the capacity of a wide range of land managers.
Population dynamics of the sheep blowfly Lucilia sericata: seasonal patterns and implications for control
Authors: Cruickshank Isla , Wall Richard 
Published: March 2003

Summary

The infestation of sheep with blowfly larvae (sheep strike) is a significant animal welfare and economic problem in many regions of the world. Improved control requires greater knowledge of the population dynamics of the primary agent of strike in temperate areas, the blowfly Lucilia sericata (Diptera: Calliphoridae).
The abundance of L. sericata was recorded on two farms in south‐west England between 1990 and 2000, and the time‐series analysed to describe and explain the nature of population change within and between years.
To examine the catch time‐series for periodicity, the data were detrended, demeaned and tapered, and plotted against a day‐degree time base. Spectral analysis of periodograms showed that the clearest signal present was the low‐frequency seasonal cycle. The only other significant signal in both series had a periodicity corresponding to the day‐degree requirements for the entire life cycle of this insect species. This suggests that, within each season, the abundance pattern is composed of a series of semi‐discrete generation peaks.
Significant density‐dependence was detected in the seasonal change in fly abundance and this was shown to be approximately compensatory in action.
The results suggest that populations of L. sericata show relatively stable and predictable dynamics, with populations passing through three or four relatively discrete generations each year prior to diapause and limited by strong, apparently compensatory, density‐dependence each season.
The results have important implications for the control of this insect parasite. In general, earlier and more intense farmer intervention, to reduce sheep susceptibility and treat struck animals during the blowfly season, would result in a lower L. sericata population and reduced strike incidence. However, at the start of the season, when fly abundance may be lower than the number of susceptible hosts, direct fly control, in addition to treatment, may be a more effective strategy.
The ecology and growth patterns of Cleistogenes species in degraded grasslands of eastern Inner Mongolia, China
Authors: Liang Chen , Michalk D. L. , Millar G. D. 
Published: March 2003

Summary

Cleistogenes is an important perennial grass genus found in the pastoral steppes of eastern Inner Mongolia. Despite its dominance in many grassland types, the value of Cleistogenes as a key genus for sustainable grassland development has only recently been recognized. To understand better how to manage Cleistogenes‐dominant grasslands, an experiment was conducted in China, to characterize the growth patterns of two Cleistogenes species (C. polyphylla and C. squarrosa) in relation to environmental parameters.
Sampling exclosures were established on uniform grasslands at Mangha and Liuhe gachas. Over two growing seasons (1999–2000) vegetation cover, green and dry biomass by species, species height and tiller density of Cleistogenes were measured at about monthly intervals starting in mid‐May and ending in mid‐October. Cleistogenes polyphylla at Mangha and C. squarrosa at Liuhe accounted for > 50% of green biomass. Neither species made any significant growth before late June, even though soil moisture was available and a large number of tillers were present that had survived the subzero winter intact. In contrast, other species (Prunus sibirica, Potentilla spp. Aneurolepidium chinense) produced up to 500 kg ha−1 biomass in early spring.
A relationship between temperature and green weight (wt) tiller−1 indicated that Cleistogenes required an average air temperature > 20 °C to initiate growth, most probably due to its C4 photosynthetic pathway. In this region, temperatures above 20 °C also coincide with periods of most reliable rainfall, which may explain the success of Cleistogenes in grassland degraded by overgrazing. In contrast, competing C3 species (e.g. Stipa spp. and Aneurolepidium chinense) initiate growth earlier in spring when rainfall is highly variable and when small plants are most exposed to severe grazing pressure by livestock emerging from winter in poor condition.
Where Cleistogenes spp. completely dominated the grassland, the length of the growing season was shorter and feed shortages in early spring became more acute than for grasslands dominated by C3 species. Livestock producers can minimize this effect by adopting management tactics such as resting pastures in spring to maintain a balance between C3 and C4 perennial grasses. Further research is needed to establish when grazing and strategic rest have most impact on the stability of Cleistogenes‐dominant grasslands.