bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersal patterns in a harvested willow ptarmigan population
Authors: BRØSETH HENRIK , TUFTO JARLE , PEDERSEN HANS CHR. , STEEN HARALD , KASTDALEN LEIF 
Published: June 2005

SummaryHarvest management requires knowledge of whether the harvest is sustainable as a result of compensatory mechanisms, such as dispersal. The effect of recreational harvesting on dispersal patterns in willow ptarmiganLagopus lagopuswas assessed over four hunting seasons in central Norway.A two‐parameter Weibull model was fitted to the observed absolute dispersal distance data using maximum likelihood methods. Estimates of the scale and shape parameters for the dispersal probability distribution were calculated, describing the distribution of observed willow ptarmigan dispersal distances. From the parameter estimates of the dispersal model we estimated the standard deviation of the dispersal displacement relevant for population genetic and spatial population dynamic models.The effect of harvesting on dispersal patterns was examined by testing for differences in the scale and shape parameters of dispersal distance distributions in areas with and without harvest. No effect of harvesting was found, either in adults or juveniles.Breeding dispersal of adult birds was estimated as a dispersal probability distribution with scale parametera = 402 m and shape parameterb = 2·01, corresponding to a dispersal standard deviation of σ = 284 m. The dispersal probability distribution of adults was not significantly different from a bivariate normal distribution.Natal dispersal had a dispersal probability distribution with scale parametera = 4206 m and shape parameterb = 1·16, corresponding to a dispersal standard deviation σ = 3728 m. The dispersal probability distribution of juveniles was not significantly different from an exponential distribution.Synthesis and applications. Reduction of the population density of willow ptarmigan through harvesting at moderate densities does not seem to affect the dispersal distances. Thus, if there is little or no difference in the dispersal probability distribution in harvested and non‐harvested areas there will be only weak or no compensation for the harvest, given that natural mortality and reproduction is the same in both areas. Thus, erroneously assuming compensation of harvest by immigration into a local population can lead to overharvest.
REVIEW: Questionnaires in ecology: a review of past use and recommendations for best practice
Authors: WHITE PIRAN C. L. , JENNINGS NANCY VAUGHAN , RENWICK ANNA R. , BARKER NOLA H. L. 
Published: June 2005

SummaryQuestionnaires, or social surveys, are used increasingly as a means of collecting data in ecology. We present a critical review of their use and give recommendations for good practice.We searched for papers in which questionnaires were used in 57 ecological academic journals, published over the period 1991–2003 inclusive. This provided a total sample size of 168 questionnaires from 127 papers published in 22 academic journals.Most questionnaires were carried out in North America and western Europe, and addressed species‐level issues, principally focusing on mammals. The majority were concerned with impacts of species and/or their conservation, and just under half with human–wildlife interactions.Postal survey was the method used most frequently to carry out the questionnaires, followed by in‐person interviews. Some questionnaires were conducted by telephone, and none was web‐based.Most questionnaires were concerned with obtaining factual information or perceptions of facts. Ground‐truthing (independent verification of the facts) was carried out in less than 10% of questionnaires.The mean (± SE) sample size (number of respondents) per questionnaire was 1422 ± 261 and the average (± SE) response rate was 63 ± 3%. These figures varied widely depending on the methods used to conduct the questionnaire.The analysis of data was mostly descriptive. Simple univariate methods were the most frequently used statistical tools, and data from a third of questionnaires were not subjected to any analysis beyond simple descriptions of the results.Synthesis and applications.We provide recommendations for best practice in the future use of questionnaires in ecology, as follows: (i) the definition of the target population, any hypotheses to be tested and procedures for the selection of participants should be clearly documented; (ii) questionnaires should be piloted prior to their use; (iii) the sample size should be sufficient for the statistical analysis; (iv) the rationale for the choice of survey method should be clearly stated; (v) the number of non‐respondents should be minimized; (vi) the question and answer format should be kept as simple as possible; (vii) the structure of the questionnaire and the data emerging from it should be unambiguously shown in any publication; (viii) bias arising from non‐response should be quantified; (ix) the accuracy of data should be assessed by ground‐truthing where relevant; (x) the analysis of potentially interrelated data should be done by means of modelling. Researchers should also consider whether alternative, interpretative methods, such as in‐depth interviews or participatory approaches, may be more appropriate, for example where the focus is on elucidating motivations or perceptions rather than testing factual hypotheses.
Litterfall and nitrogen cycling following invasion byChrysanthemoides moniliferassp.rotundatain coastal Australia
Authors: LINDSAY ELIZABETH A. , FRENCH KRISTINE 
Published: June 2005

SummaryOn the south‐east coast of Australia there are extensive infestations of the environmental weed bitou bushChrysanthemoides moniliferassp.rotundata. This exotic weed is highly invasive and persistent, yet little is known about its impacts and how it dominates coastal vegetation.A field study was carried out with sites selected for having an area heavily invaded byC. moniliferaand an uninvaded native shrubland area. The mass and components of the litterfall and ground litter layer were monitored and compared over 12 months. Nutrient analysis was performed on the abscised leaves and mature green leaves. Soil properties and nitrogen content were also examined.There was a greater input of litter to the native areas (4800 ± 450 kg ha−1), which was highly seasonal, compared with theC. moniliferaareas (1690 ± 150 kg ha−1). There was also a greater mass of litter on the ground in the native areas (9600 ± 560 kg ha−1) thanC. moniliferaareas (3750 ± 170 kg ha−1), probably as a result of the higher leaf fall rate and slow decomposition rate.A large proportion of nutrients was withdrawn from the native (48–80%) andC. moniliferaleaves (38–60%) before abscission. The litterfall was estimated to contain more than twice the amount of nitrogen and phosphorous within the native areas, because of the high leaf fall rate rather than a high nutrient content.The total soil nitrogen was two to five times higher in the invaded areas (average 2570 ± 620 kg ha−1) than within the native areas (730 ± 90 kg ha−1). This was accompanied by an increase in ammonia content. The bulk density was lower in invaded areas, but there was no clear trend in the change in soil pH.Synthesis and applications.The higher soil nitrogen beneath the weed infestations could increase the competitive superiority ofC. moniliferadirectly by increasing growth rate, or indirectly by impairing the establishment of native species that are adapted to growing in nutrient‐poor soils. The control technique of sprayingC. moniliferawith herbicide, then burning and spraying seedlings again, could lead to greater regeneration success for natives species than sprayingC. moniliferawith herbicide only.
METHODOLOGICAL INSIGHTS: Increasing the value of principal components analysis for simplifying ecological data: a case study with rivers and river birds
Authors: VAUGHAN I. P. , ORMEROD S. J. 
Published: June 2005

Summary

Two priorities for applied ecologists are to (i) maintain quantitative rigour with minimal resources and (ii) ensure that multivariate results are readily understood by end users. Habitat descriptions and other complex data present particular challenges.
Principal components analysis (PCA) is often used to reduce data and stabilize subsequent statistical analyses. Interpretation can be difficult, however, and PCA is optimized for quantitative (cf. categorical) data. Moreover, future applications (e.g. in predicting species’ distributions) require the recording of all contributing variables irrespective of cost or importance.
We considered the potential benefits of two PCA variants. First, we considered whether a cluster analysis on the correlation matrix of independent variables (i.e. variable clustering), followed by a PCA within each cluster, produced a more easily interpreted output than conventional PCA, while simultaneously reducing costs. Secondly, we considered whether a generalized PCA capable of analysing qualitative data could out‐perform conventional PCA when ecological data include ordinal variables. As a case study, we used data from river habitat survey (RHS), a key applied tool in river ecology that uses more than 100 variables to describe river structure and relies heavily on three‐point ordinal scales. In distribution models that linked river birds to RHS, we compared the interpretability and efficiency of variable clustering and generalized PCA against conventional PCA.
While variable clustering gave similar predictive performance to PCA, habitat factors generated by the former were more readily interpreted than conventional principal components. Of the two cluster‐scoring methods, optimally scaled PCA explained 24% more variance in the first principal component and marginally improved the accuracy of distribution models.
Synthesis and applications. Initial variable clustering makes PCA more interpretable and will benefit the understanding of research results and their translation into management. Variable clustering should also reduce costs as variables contributing to unused clusters need not be recorded in future (cf. PCA). Optimal scaling further increases the versatility of PCA: qualitative ecological data (e.g. habitat categories) can be analysed in the same way as quantitative data, with real benefits to applied research. With cost constraints and the need for dissemination key applied issues, our results offer an important potential advance.
Modelling wildebeest population dynamics: implications of predation and harvesting in a closed system
Authors: TAMBLING CRAIG J. , DU TOIT JOHAN T. 
Published: June 2005

Summary

Predation upon ungulates is generally considered to have a stronger regulatory effect on sedentary than migratory populations, with migratory populations maintaining higher densities. The blue wildebeest Connochaetus taurinus is a migratory species that has suffered a general decline in numbers and distribution across its species range. Wildebeest suffer from a fragmented distribution together with isolation of populations in closed reserves, preventing migratory movements and potentially allowing predators to benefit from a ‘captive’ prey resource.
In Pilanesberg National Park, South Africa, the declining blue wildebeest population (from 1074 in 1995 to 594 in 2001) is sedentary because the park (50 000 ha) is completely enclosed by fencing. This population was used to model the potential effects of predation and harvesting. The Pilanesberg population was then compared with other wildebeest populations in southern Africa.
The model outputs demonstrated that increased levels of predation by lions Panthera leo on a ‘captive’ population of prey such as wildebeest, in combination with regular harvesting by park managers, can drive the population towards extinction. At lower levels of predation some other factor needs to act in combination with predation to drive the population into a decline.
During our study the lion biomass density in Pilanesberg was almost three times greater than that predicted by regression models of the stable relationship between lion and prey biomass densities across African savannas. Furthermore, the ratio of lion numbers to prey numbers was substantially higher than in most other African reserves.
Synthesis and applications. In African savannas, artificial closed systems provide advantages to large predators. If wildlife‐cropping schemes are implemented in such systems without careful monitoring and regulation of large predators, then ungulate populations can decline more rapidly than managers expect.
METHODOLOGICAL INSIGHTS: Using seismic sensors to detect elephants and other large mammals: a potential census technique
Authors: WOOD JASON D. , O'CONNELL‐RODWELL CAITLIN E. , KLEMPERER SIMON L. 
Published: June 2005

Summary

Large mammal populations are difficult to census and monitor in remote areas. In particular, elephant populations in Central Africa are difficult to census due to dense forest, making aerial surveys impractical. Conservation management would be improved by a census technique that was accurate and precise, did not require large efforts in the field, and could record numbers of animals over a period of time.
We report a new detection technique that relies on sensing the footfalls of large mammals. A single geophone was used to record the footfalls of elephants and other large mammal species at a waterhole in Etosha National Park, Namibia.
Temporal patterning of footfalls is evident for some species, but this pattern is lost when there is more than one individual present.
We were able to discriminate between species using the spectral content of their footfalls with an 82% accuracy rate.
An estimate of the energy created by passing elephants (the area under the amplitude envelope) can be used to estimate the number of elephants passing the geophone. Our best regression line explained 55% of the variance in the data. This could be improved upon by using an array of geophones.
Synthesis and applications. This technique, when calibrated to specific sites, could be used to census elephants and other large terrestrial species that are difficult to count. It could also be used to monitor the temporal use of restricted resources, such as remote waterholes, by large terrestrial species.
Evidence for post‐depletion sustainability in a mature bushmeat market
Authors: COWLISHAW GUY , MENDELSON SAMANTHA , ROWCLIFFE J. MARCUS 
Published: June 2005

Summary

The trade in wild animals for meat, or ‘bushmeat’, is perceived as one of the most important threats to wildlife in the tropics. Unsustainable bushmeat extraction also threatens the loss of livelihoods. However, the long‐term persistence of the bushmeat trade, documented in Africa over several centuries, suggests that the trade can be sustainable. In this study, we investigate sustainability in a mature bushmeat market in West Africa (Takoradi, Ghana).
Our study, conducted over January and February 2000, combined biological and socio‐economic approaches. Offtake data, including information on species identity, capture location and sales price, were collected in a market survey. Species biological data, and the historical price of bushmeat and its substitutes (fish and domestic meat), were taken from the literature. The theoretical sustainable yield for each species was estimated using standard algorithms.
We tested the hypothesis that the current trade is unsustainable with four predictions: that (1) the number of animals extracted exceeds a theoretical sustainable yield, (2) larger taxa are depleted more heavily close to the city, (3) the price of bushmeat has outstripped inflation and (4) the price of alternatives, such as domestic meat and fish, has fallen relative to the price of bushmeat. None of these predictions were supported. There was therefore no evidence of unsustainability.
Analysis of market profiles and hunter reports suggest that the present pattern of sustainability is the result of a series of non‐random extinctions from historical hunting. Vulnerable taxa (slow reproducers) have been depleted heavily in the past, so that only robust taxa (fast reproducers), such as rodents and small antelope, are now traded. These robust taxa are supplied from a predominantly agricultural landscape around the city.
Synthesis and applications. The bushmeat trade can have a severe impact on species that are vulnerable to overexploitation. However, once these species have disappeared, the remaining species may be harvested sustainably. Bushmeat management policy might therefore be improved by adopting a two‐pronged approach in which vulnerable species are protected from hunting, but robust species are allowed to supply a sustainable trade. The productivity of agricultural landscapes for many bushmeat species indicates that these areas may play an important role in supporting a sustainable bushmeat trade.
Early impacts of forest restoration treatments on the ectomycorrhizal fungal community and fine root biomass in a mixed conifer forest
Authors: SMITH JANE E. , McKAY DONARAYE , BRENNER GREG , McIVER JIM , SPATAFORA JOSEPH W. 
Published: June 2005

SummaryThe obligate symbiosis formed between ectomycorrhizal fungi (EMF) and roots of tree species in the Pinaceae influences nutrient uptake and surrounding soil structure. Understanding how EMF respond to prescribed fire and thinning will assist forest managers in selecting fuel‐reducing restoration treatments that maintain critical soil processes and site productivity.The response of EMF species richness, live fine root biomass and duff levels to various forms and combinations of thinning and burning was investigated in mixed ponderosa pine and Douglas fir stands in the Blue Mountains of Oregon. The below‐ground community composition and structure of EMF at the site was characterized using molecular methods.The EMF community consisted of a large number of infrequently detected species. The distribution of a few abundant species (Cenococcumsp.,Pilodermasp.,Rhizopogon salebrosusandWilcoxina rehmii) in a majority of the treatments both before and after treatment application demonstrates that some EMF species survive or rapidly re‐establish after disturbance.EMF species richness, live root biomass and duff levels were reduced significantly by prescribed fire treatments compared to the non‐burned treatments.Synthesis and applications.These results indicate that prescribed fire results in a short‐term reduction in EMF species richness and live root biomass and may influence whether managers can achieve the desired future condition of stands with large‐tree retention and low fuel loads. EMF mortality and complete duff reduction after fire have been implicated with poor tree survival and slow stand recovery in forest ecosystems world‐wide. The results of this study, along with the recovery potential of a site, and the impending risk of stand‐replacing wildfire in stands differing in structure from historic conditions, bear consideration when reintroducing fire.
Evaluation of the ecological restoration potential of plant communities in Norway spruce plantations using a life‐trait based approach
Authors: HÉRAULT BRUNO , HONNAY OLIVIER , THOEN DANIEL 
Published: June 2005

Summary

In Europe, intensively managed coniferous plantations rarely achieve similar nature conservation functions as deciduous woodlands. The ability to identify coniferous plantations that might be successfully converted to deciduous woodland is a key goal in forest management. The herbaceous plant community composition of mature plantations may be an accurate selection criterion for stands that are most suitable for initiating the conversion process to deciduous forest.
The herbaceous plant communities in Norway spruce plantations were analysed using a functional group approach. The analysis was conducted in three steps: (i) identification of emergent groups (EG) by multivariate classification; (ii) comparison of EG abundance between coniferous and deciduous stands (i.e. the target communities); (iii) partitioning the variation in EG abundance in coniferous plantations between forest management, local environmental and regional variables.
Seven EG were identified: two core forest groups (short geophytes and zoochoreous perennials), two groups from open habitats (annuals and helophytes) and three mixed groups (anemochoreous perennials, graminoids and short perennials).
Among the core forest groups, short geophytes were severely under‐represented in plantations (because of their low dispersal abilities and specific habitat requirements) while zoochoreous perennials were slightly more abundant (because of their good dispersal and competitive abilities).
Regional variables largely influenced the abundance of core‐forest EG. Restoration of communities rich in zoochoreous perennials is far easier than restoring short geophyte‐rich communities because of the different colonization abilities of these EG.
Forest management variables were of secondary importance for the restoration potential of plantations. Because generalist EG were favoured by low stand densities, forest practitioners should avoid large thinning operations.
Local environmental variables played a minor role in determining EG abundance. However, short geophytes preferred rather high soil pH values and were therefore negatively affected by acidification caused by coniferous litter.
Synthesis and applications. The performance of short geophytes is the key to conversion success of Norway spruce plantations to deciduous forest. Stands located on base‐rich soils and in landscapes with high forest connectivity are the most appropriate candidates for initiating the conversion process. For other types of stands, future work should explore the possibility of restoring other land‐use types, such as annually mown meadows.
Central GABAA but not GABAB Receptors Mediate Suppressive Effects of Caudal Hindbrain Glucoprivation on the Luteinizing Hormone Surge in Steroid‐Primed, Ovariectomized Female Rats
Authors: Singh S. R. , Briski K. P. 
Published: June 2005

AbstractThe neurochemical mechanisms that link caudal hindbrain glucoprivic‐‘sensitive’ neurones with the forebrain gonadotrophin‐releasing hormone (GnRH)‐pituitary luteinizing hormone (LH) axis remain unclear. Available studies indicate that the amino acid neurotransmitter, γ‐aminobutyric acid (GABA), inhibits reproductive neuroendocrine function, and that caudal fourth ventricular administration of the glucose antimetabolite, 5‐thioglucose (5TG), enhances GABA turnover within discrete septopreoptic structures that regulate LH secretion. The current experiments utilized the selective GABAA and GABAB receptor antagonists, bicuculline and phaclofen, as pharmacological tools to investigate whether one or both receptor subtypes function within neural pathways that suppress GnRH neuronal transcriptional activation and LH release during central glucose deficiency. During the ascending phase of the afternoon LH surge, groups of steroid‐primed, ovariectomized female Sprague‐Dawley rats were pretreated by lateral ventricular administration of bicuculline, phaclofen, or vehicle only, before fourth ventricular injection of 5TG or vehicle. The data indicate that, 2 h after 5TG treatment, Fos immunoexpression by rostral preoptic GnRH neurones and plasma LH levels were diminished relative to the vehicle‐treated controls, and that inhibitory effects of 5TG on these parameters were attenuated by pretreatment with bicuculline, but not phaclofen. These results demonstrate that central GABAA, but not GABAB receptor stimulation during hindbrain glucoprivation, is required for maximal inhibition of reproductive neuroendocrine function by this metabolic challenge. The current studies thus reinforce the view that central GABAergic neurotransmission mediates regulatory effects of central glucoprivic signalling on the GnRH‐pituitary LH axis.