bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of forest fertilization on the radial growth and resin exudation of insect‐defoliated Scots pines
Authors: Kytö Maarit , Niemelä Pekka , Annila Erkki , Varama Martti 
Published: March 2003

Summary 1. Scots pine trees that had been defoliated by the pine sawfly Diprion pini were fertilized with various nutrient combinations in the growing season following defoliation in order to study the possibility of accelerating tree recovery. Resin exudation, vertical resin duct density and vigour index of the trees were measured 3 years after defoliation, and radial growth 6 years after defoliation. 2. Defoliation reduced stem growth, and annual rings were missing particularly in the severely defoliated trees. Nitrogen fertilization enhanced radial growth even in the severely defoliated trees. 3. Nitrogen fertilization increased the number of vertical resin ducts in both defoliated and undefoliated trees, but resin duct density tended to be lower in the nitrogen‐fertilized trees than in trees that had not received nitrogen fertilizer. Resin duct density did not correlate with resin flow rate. 4. Resin exudation was strongest from trees that had been almost totally defoliated, intermediate from trees that had lost half of their foliage, and weakest from undefoliated trees, indicating that defoliation had induced resin production in the stem. Resin flow was not affected by fertilization. 5. There was a weak negative correlation between vigour index and resin flow. No trees with a high vigour index had strong resin exudation, while resin exudation varied from minimal to very strong in trees with a low vigour index. 6. The results indicate that nitrogen fertilization can be used to stimulate growth of defoliated trees without affecting resistance traits on infertile sites.
Can arbuscular mycorrhizal fungi be used to control the undesirable grass Poa annua on golf courses?
Authors: Gange A.C. , Lindsay D.E. , Ellis L.S. 
Published: March 2003

Summary 1.
Poa annua (annual meadow‐grass or annual bluegrass) is the most problematic weed of temperate zone golf putting greens. In the UK there are no chemicals approved for its control, although several herbicides and plant growth regulators are available in the USA. Reducing P. annua levels in fine turf would greatly reduce the heavy reliance on pesticides and water that currently exists. 2. This paper reports on an observational and a manipulative study in golf putting greens, aimed at determining whether arbuscular mycorrhizal (AM) fungi have any potential for the reduction of this weed in fine turf. 3. All 18 greens on three golf courses were sampled, and in two courses a negative relation between AM fungi and P. annua abundance was found, upholding previous results. In greens where AM fungi were relatively common (as measured by root colonization), P. annua was rare, and vice versa. Furthermore, when the fungi were common, abundance of the desirable turfgrass Agrostis stolonifera was greater. 4. Two explanations are suggested for these relations, a competitive one, in which AM fungi alter the balance of competition between the two grasses, and an antagonistic one, in which the fungi may directly reduce the growth of P. annua. 5. In a manipulative experiment, where mycorrhizal inoculum was added to a golf green, the colonization level of A. stolonifera roots was enhanced, as was the abundance of this grass. Furthermore, there was a suggestion that adding inoculum could decrease the abundance of P. annua. 6. AM fungi have the potential to be a much more environmentally sound method of P. annua control in sports turf than the currently used chemicals.
Vegetation response to grazing management in a Mediterranean herbaceous community: a functional group approach
Authors: Sternberg Marcelo , Gutman Mario , Perevolotsky Avi , Ungar Eugene D. , Kigel Jaime 
Published: March 2003

Summary 1.  A 4‐year study was conducted in a Mediterranean herbaceous community in north‐eastern Israel to investigate the effects of cattle grazing management on the structure and composition of the community. Understanding the effects of grazing on the dynamics of Mediterranean herbaceous communities is important in formulating rational management plans for both conservation and sustainable animal production. 2.  The relationships among plant functional groups were studied in the context of inter‐annual variation in rainfall. Treatments included manipulations of stocking rates (moderate, heavy and very heavy) and grazing regimes (continuous vs. seasonal), in a factorial design. 3.  The herbaceous community was rich in species, with 166 species recorded at the site, of which 74% were annuals. Plant cover was dominated by 10 species that accounted for 75% of the total cover. 4.  Inter‐seasonal rainfall variation was a dominant factor in the expression of different grazing treatments on the structure of the plant community. Grazing effects were stronger in wet years than in dry years. 5.  Paddocks under continuous grazing were higher in number of species compared with paddocks subjected to seasonal grazing, independently of grazing intensity. 6.  Functional group analyses showed that reduction in cover of tall grasses was correlated with an increase in cover of prostrate annual legumes and less palatable groups such as annual and perennial thistles, crucifers and forbs. 7.  Cover of functional groups composed of hemicryptophytic species was less variable (lower coefficient of variation) in response to grazing treatments and inter‐annual variation in climatic conditions compared with functional groups with annual species. 8.  The persistence of the dominant species and the relatively small amplitude of change in plant cover of the functional groups suggest that the community was rather stable in spite of wide variation in grazing regimes and climatic conditions. East‐Mediterranean grasslands appear to be adapted to grazing due to their long history of human association.
Predicting spatial variation in heather utilization by sheep and red deer within heather/grass mosaics
Authors: Palmer S.C.F. , Hester A.J. 
Published: March 2003

Summary 1. Recent work has shown that the dynamics of woody and herbaceous vegetation mosaics under grazing or browsing can be strongly affected by the spatial pattern of the vegetation. A suite of models is described here to predict spatial variation in the utilization of an internationally important woody species, heather Calluna vulgaris, within heather/grass mosaics when grazed by sheep or red deer Cervus elaphus. This type of information is needed for the successful management of free‐ranging herbivores grazing these extensive vegetation types. 2. The models predict: (i) heather utilization at the edge of grass patches; (ii) utilization distant from the grass edge; and (iii) the rate of change of utilization with distance from the edge of grass patches as functions of (a) the proportion by area of grass in the mosaic, (b) the length of heather/grass edge per unit area, and (c) the overall heather utilization on a site. Differences between species of grazers and seasons are also taken into account. 3. The models were fitted to data from two series of grazing experiments conducted on natural and artificial heather/grass mosaics in north‐east Scotland. 4. Overall heather utilization in the experiments was estimated using a geographical information system (GIS), taking into account higher levels of utilization in proximity to grass patches. 5. A modelling approach for predicting how the heather/grass mosaic pattern will change through time under heavy grazing is proposed. As no field data are yet available on this process, this model was developed by simulation within a GIS. 6. This work demonstrates how incorporation of spatial information can improve the accuracy of utilization predictions, and thus the design of appropriate management practices. As with many other similar systems, the paucity of data on spatial variation in heather utilization by grazing ungulates, and the effects of utilization at the heather/grass edge, particularly under high grazing pressures, is highlighted. This is considered to be a major limitation to the efficacy of currently available decision support tools to aid the management of heterogeneous grazing systems.
Habitat‐based statistical models for predicting the spatial distribution of butterflies and day‐flying moths in a fragmented landscape
Authors: Cowley Matthew J. R. , Wilson Robert J. , León‐Cortés Jorge L. , Gutiérrez David , Bulman Caroline R. , Thomas Chris D. 
Published: March 2003

1. Most species’ surveys and biodiversity inventories are limited by time and money. Therefore, it would be extremely useful to develop predictive models of animal distributions based on habitat, and to use these models to estimate species' densities and range sizes in poorly sampled regions.2. In this study, two sets of data were collected. The first set consisted of over 2000 butterfly transect counts, which were used to determine the relative density of each species in 16 major habitat types in a 35‐km2area of fragmented landscape in north‐west Wales. For the second set of data, the area was divided into 140 cells using a 500‐m grid, and the extent of each habitat and the presence or absence of each butterfly and moth species was determined for each cell.3. Logistic regression was used to model the relationship between species’ distribution and predicted density, based on habitat extent, in each grid square. The resultant models were used to predict butterfly distributions and occupancy at a range of spatial scales.4. Using a jack‐knife procedure, our models successfully reclassified the presence or absence of species in a high percentage of grid squares (mean 83% agreement). There were highly significant relationships between the modelled probability of species occurring at regional and local scales and the number of grid squares occupied at those scales.5. We conclude that basic habitat data can be used to predict insect distributions and relative densities reasonably well within a fragmented landscape. It remains to be seen how accurate these predictions will be over a wider area.
A landscape‐scale test of the predictive ability of a spatially explicit model for population viability analysis
Authors: D.B. Lindenmayer , Ball I. , Possingham H.P. , Mccarthy M.A. , Pope M.L. 
Published: March 2003

Summary

Although population viability analysis (PVA) is widely employed, forecasts from PVA models are rarely tested. This study in a fragmented forest in southern Australia contrasted field data on patch occupancy and abundance for the arboreal marsupial greater glider Petauroides volans with predictions from a generic spatially explicit PVA model. This work represents one of the first landscape‐scale tests of its type.
Initially we contrasted field data from a set of eucalypt forest patches totalling 437 ha with a naive null model in which forecasts of patch occupancy were made, assuming no fragmentation effects and based simply on remnant area and measured densities derived from nearby unfragmented forest. The naive null model predicted an average total of approximately 170 greater gliders, considerably greater than the true count (n = 81).
Congruence was examined between field data and predictions from PVA under several metapopulation modelling scenarios. The metapopulation models performed better than the naive null model. Logistic regression showed highly significant positive relationships between predicted and actual patch occupancy for the four scenarios (P = 0·001–0·006). When the model‐derived probability of patch occupancy was high (0·50–0·75, 0·75–1·00), there was greater congruence between actual patch occupancy and the predicted probability of occupancy.
For many patches, probability distribution functions indicated that model predictions for animal abundance in a given patch were not outside those expected by chance. However, for some patches the model either substantially over‐predicted or under‐predicted actual abundance. Some important processes, such as inter‐patch dispersal, that influence the distribution and abundance of the greater glider may not have been adequately modelled.
Additional landscape‐scale tests of PVA models, on a wider range of species, are required to assess further predictions made using these tools. This will help determine those taxa for which predictions are and are not accurate and give insights for improving models for applied conservation management.
The comparative demography of the pasture weed Echium plantagineum between its native and invaded ranges
Authors: Grigulis K. , Sheppard A.W. , Ash J.E. , Groves R.H. 
Published: March 2003

Summary

Echium plantagineum is native to the western Mediterranean Basin, where it is a common, but not dominant, component of species‐rich annual grasslands. Since its introduction into Australia, E. plantagineum has spread to infest vast areas of predominantly agricultural land in south‐east and south‐west Australia, where it can be the dominant pasture species.
To unravel the ecological factors responsible for the high population abundance of E. plantagineum in Australia, its demography was compared between sites in the invaded and native ranges. Demographic parameters of E. plantagineum populations were estimated at a site near Canberra in south‐eastern Australia, and at a site near Evora in southern Portugal. Identical factorial experiments were set up at each site with treatment combinations of the presence or absence of grazing and pasture competition.
The recruitment, survival, fecundity and seed bank dynamics of E. plantagineum populations were measured for each of the treatment combinations over 2 years at each site. These data allowed the estimation of demographic parameters describing the proportion of E. plantagineum individuals moving from one life‐cycle stage to the next.
Seedling establishment fractions were two to five times greater at Canberra than at Evora, and seed bank incorporation rates were three times greater at Canberra than Evora. These demographic differences were those most likely to play an important role in the greater abundance of E. plantagineum in Australia compared with Mediterranean Europe. Neither seed bank survival rates nor seed production differed between populations at Canberra and Evora, while seedling survival rates were always lower at Canberra than at Evora.
Neither grazing nor pasture competition limited the seed production or seedling survival of E. plantagineum populations at Evora more than at Canberra.
An effective approach for the control of E. plantagineum in Australia may thus be through the reduction of the seedling establishment fraction. This may be achieved by maintaining significant pasture vegetation cover and reducing the available space for E. plantagineum establishment during autumn.
Differences in the capture rate of cage‐trapped red foxesVulpes vulpesand an evaluation of rabies control measures in Britain
Authors: Baker Philip J. , Harris Stephen , Robertson Charles P.J. , Saunders Glen , White Piran C.L. 
Published: March 2003

SummaryMethods used to control canids may differ in their relative effectiveness and how they ‘sample’ age and sex classes. However, there is little information on such biases. We utilized data from a population of known size and structure to quantify differences in the seasonal capture rate of foxesVulpes vulpesof different age, sex and social status. The effects of home‐range utilization and trap experience were also investigated.The capture rate of juvenile (< 1 years) foxes was highest in spring and declined throughout the year. Adult (≥ 1 years) trap rates were equivalent to those of juveniles in winter.Neither juveniles nor adults exhibited sex differences in trappability.Adults were classified as dominant or subordinate based upon patterns of dyadic interaction. Subordinate foxes were trapped more frequently than dominants.Trappability did not differ inside or outside of core areas, after controlling for trap effort.Previous trap experience did not affect the capture rate of adult foxes.Captures of non‐resident foxes peaked in winter (52% of captures), associated with dispersing juveniles and adult males, and were lowest in summer (13%).In Britain, 75–90% of foxes would need to consume poison or vaccine baits to control a rabies epizooty. During simulated rabies control operations, where cage‐trapping was used to measure the proportion of foxes taking dummy baits containing a biomarker, < 30% of foxes consumed baits. However, non‐resident foxes present during the period of baiting but not during trapping, or vice versa, may bias these calculations. We used the frequency of capture of non‐resident foxes to re‐examine the success rate of these trials.Revised estimates still suggest that < 45% of foxes were reached during the simulated control operations. This is significantly below the levels necessary for rabies control. Further biomarker trials are required that do not rely only on trapping for sample collection and where the residency status of captured foxes has been determined.
Modelling the effects of plant species on biocontrol effectiveness in ornamental nursery crops
Authors: Skirvin David J. , De Courcy Williams Michael E. , Fenlon John S. , Sunderland Keith D. 
Published: March 2003

Summary

The development of biological control strategies for ornamental crops is challenging due to the high diversity of crops grown and zero tolerance to pest presence. In an attempt to provide a biological basis for the development of biological control, an individual‐based stochastic modelling approach was developed.
This approach has been used to examine the impact of tritrophic interactions on biological control of the spider mite Tetranychus urticae by the predatory mite Phytoseiulus persimilis. The effect of differences in the biology of T. urticae and P. persimilis on three nursery stock crops, Ceanothus thyrsiflorus var. ‘Autumnal Blue’, Choisya ternata and Euonymus japonicus, was investigated through simulation experiments.
The effect of pest aggregation and frequency of predator introduction on the control of T. urticae was examined at a range of initial pest and predator densities. Control was assumed to occur when T. urticae was driven to extinction, due to zero tolerance to pest presence on these ornamental crops.
‘One‐off’ introductions of P. persimilis rarely caused T. urticae to become extinct, but repeated weekly introductions always led to pest extinction, regardless of the plant species, at the highest introduction rate of 1000 predators (10 stem−1). Time to pest extinction was similar on all plant species with repeated introductions, but was influenced by differences in the biology of pest and predator on the three plant species.
Increased aggregation of T. urticae led to greater extinction at lower predator introduction rates, but time to extinction was increased due to the time taken for the predator to cope with the increased pest density.
These predictions highlight the importance of plant species and spatial dynamics of both pest and predator in determining the efficiency with which biological control can be achieved on ornamental crops, suggesting that prophylactic application of predatory mites may be preferable to reactive application.
Modelling the effects of an oil spill on open populations of intertidal invertebrates
Authors: Forde Samantha E. 
Published: March 2003

SummaryKnowledge of the impact of oil spills on coastal communities, in California and elsewhere, is currently limited by a lack of long‐term data, the inability to infer causality from monitoring studies, and the necessarily limited spatial and temporal scales of experimental studies.This study therefore used a modelling approach to investigate the combined effects of different intensities of an oil spill and recruitment variation on a barnacleChthamalus fissuspopulation. The methodology and results are likely to apply to any similarly open marine populations with dispersive larval forms.The model consisted of a source population comprising individuals that reproduced based on size and probability of mortality. Larvae from the source population entered a larval pool. A proportion of the larvae from the larval pool recruited to a focal population within the region.The model was used to assess the effects on recruitment to the focal population of (i) the size structure of the source population, (ii) the intensity of oil spills in the source population, and (iii) recruitment intensity to the focal population.Differences in the size structure of the source population had little effect on the reproductive output of the population relative to the intensity of the oil spill. Similarly, the intensity of the oil spill had a stronger influence on recruitment to the focal population than the size structure of the source population. Size structure of the source population was important, however, when evaluating the seasonal trajectory of the focal population.Modelling provides a format in which questions about the effects of human impacts can be addressed that would be intractable using experiments. The results of this model suggest that recruitment variation, along with the processes underlying recruitment variation, are critical to predicting the effects of disturbance on open marine populations.
Phenotypic and molecular characterization of chickpea rhizobia isolated from different areas of Morocco
Authors: Maâtallah J. , Berraho E.B. , Muñoz S. , Sanjuan J. , Lluch C. 
Published: March 2003

Aims: To determine the biodiversity of rhizobial strains nodulating Cicer arietinum L. in representative soils from various areas of Morocco.
Methods and Results: Symbiotic traits, utilization of 49 carbohydrate sources, resistance to antibiotics and heavy metals, tolerance to salinity, to extreme temperatures and pH were studied as phenotypic markers. In addition, restriction fragment length polymorphism (RFLP) of PCR-amplified 16S rDNAs were compared with those of reference strains. Numerical analysis of the phenotypic characteristics showed that the 48 strains studied fell into three distinct groups. RFLP analysis of 16S rRNA genes revealed an additional heterogeneity and four ribotypes were identified.
Conclusions: Chickpea rhizobia isolated from Moroccan soils are both phenotypically and genetically diverse. Most of these rhizobia belong to the Mesorhizobium genus. However, some strains originating from a particular soil appeared to have 16S rRNA genes similar to Sinorhizobium as well as very distinct auxanographic characteristics compared with Mesorhizo- bium isolates.
Significance and Impact of the Study: A well characterized collection of chickpea-nodulating rhizobia in representative soils of Morocco has been generated, which can be used to develop efficient inoculants for this crop. This is the first report evidencing that chickpeas may be nodulated by bacteria from the Sinorhizobium genus.