bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling possible adverse effects of marine wind farms on seabirds: developing and applying a vulnerability index
Authors: GARTHE STEFAN , HÜPPOP OMMO
Published: July 2004

Marine wind farms have attracted substantial public interest. The construction of wind facilities offshore may become Europe's most extensive technical development in marine habitats. Due to political pressure to complete construction soon, assessments of possible wind farm locations, for example in the German sectors of the North Sea and Baltic Sea, have to be based on existing knowledge.

In this study, we developed a wind farm sensitivity index (WSI) for seabirds. We applied this index to the Exclusive Economic Zone and the national waters of Germany in the North Sea. We chose nine factors, derived from species’ attributes, to be included in the WSI: flight manoeuvrability; flight altitude; percentage of time flying; nocturnal flight activity; sensitivity towards disturbance by ship and helicopter traffic; flexibility in habitat use; biogeographical population size; adult survival rate; and European threat and conservation status. Each factor was scored on a 5‐point scale from 1 (low vulnerability of seabirds) to 5 (high vulnerability of seabirds). Five of these factors could be dealt with by real data but four could only be assessed by subjective considerations based on at‐sea experience; in the latter cases, suggestions of the first author were independently modulated by experts.

Species differed greatly in their sensitivity index (SSI). Black‐throated diver Gavia arctica and red‐throated diver Gavia stellata ranked highest (= most sensitive), followed by velvet scoter Melanitta fusca, sandwich tern Sterna sandvicensis and great cormorant Phalacrocorax carbo. The lowest values were recorded for black‐legged kittiwake Rissa tridactyla, black‐headed gull Larus ridibundus and northern fulmar Fulmarus glacialis.

A WSI score for areas of the North Sea and Baltic Sea was calculated from the species‐specific sensitivity index values. Coastal waters in the south‐eastern North Sea had values indicating greater vulnerability than waters further offshore throughout the whole year.

Derived from the frequency distribution of the WSI, we suggest a ‘level of concern’ and a ‘level of major concern’ that are visualized spatially and could act as a basis for the selection of marine wind farm locations.

Synthesis and applications. The wind farm sensitivity index might be useful in strategic environmental impact assessments (EIA). Results of small‐scale EIA from wind installations should be considered within a more global perspective, provided, for example, by large mapping projects and detailed behavioural studies. This is difficult in normal EIA, particularly in highly dynamic coastal/marine habitats, and the results of this study fill an important gap by providing information on the potential sensitivity of seabirds and the importance of locations of wind installations.
Clarifying the effect of toe clipping on frogs with Bayesian statistics
Authors: MCCARTHY MICHAEL A. , PARRIS KIRSTEN M.
Published: July 2004

Toe clipping is commonly used in population ecology to identify individual amphibians, particularly frogs and toads. Toe clipping may influence the return rate of the marked animals, although results of previous studies have appeared to be contradictory.

We re‐analysed available data using Bayesian statistics to examine how the return rate of frogs may change with the number of toes removed.

Our re‐analysis indicated that toe clipping reduces the return rate by 4–11% for each toe removed after the first, assuming the effect is the same for all toes.

A second analysis allowed the effect of removing each toe to change linearly with the number removed. This indicated that when one toe had already been removed, the return rate was reduced by 3·5% (95% credibility interval of 0–7%) upon removal of a second. The reduction in return rate on removal of an additional toe was 30% (95% credibility interval of 20–39%) when seven toes had already been removed.

When considering the cumulative effect of toe clipping, the return rate of frogs with two toes removed was estimated to be 96% of those with one toe removed. This ratio decreased to 28% for frogs with eight toes removed.

Synthesis and applications. We found that the effect of toe clipping on the return rate of amphibians increases with the number of toes removed. Because this effect is reasonably consistent among studies, the estimated impact should be recognized in future work that uses toe clipping to estimate population sizes and survival rates. In addition, our study has important implications for the ethical treatment of animals, the continued use of toe clipping to mark species of conservation concern, and the removal of multiple toes from an individual frog or toad.
Response of African savanna ants to long‐term fire regimes
Authors: PARR CATHERINE L. , ROBERTSON HAMISH G. , BIGGS HARRY C. , CHOWN STEVEN L.
Published: July 2004

Despite the fact that fire is considered an important disturbance in savannas across the world and is used widely as a management tool in conservation areas, little is known about the effects of burning on their insect communities.

This study made use of a 50‐year fire experiment to investigate the responses of ant assemblages to long‐term burning regimes. The effects of fire frequency, season and time since fire (fuel age) were tested on epigaeic ants across three savanna vegetation types (Mopane woodland, Acacia savanna and Terminalia woodland) in Kruger National Park, South Africa.

There was no significant effect of burning on mean ant species richness and abundance between treatments, although there were significant differences in ant assemblage composition between burned (treatment) and unburned (control) plots. The effects of season, frequency of burn and plot age on assemblage structure were weak and often not significant.

Epigaeic ant assemblages in this savanna system appeared to be highly resistant and resilient to burning. The response of ants to fire was linked to changes in habitat cover and structure: the effect of fire on vegetation and ants was less pronounced in lower rainfall areas, where differences in vegetation structure between burnt and unburnt plots were less pronounced than in higher rainfall areas.

Synthesis and applications. The effect of fire on ant assemblages in the mid‐ to northern Kruger National Park depends on whether a patch burns or not, rather than the specifics of the burning treatment. Thus, conservation managers can focus concerns regarding the subtleties of fire regimes on other taxa or areas of particular concern.
Influence of deferred grazing on vegetation dynamics and livestock productivity in an Andean pastoral system
Authors: BUTTOLPH LITA P. , COPPOCK D. LAYNE
Published: July 2004

Management recommendations intended to reduce rangeland degradation and increase livestock productivity often assume equilibrium conditions wherein vegetation and herbivore dynamics are tightly coupled. Recent research in Africa, Asia and North America, however, suggests that the dynamics of some arid systems are driven more by precipitation, a non‐equilibrium factor. We examined the applicability of equilibrium and non‐equilibrium theory for key grazing resources within an Andean pastoral ecosystem.

Residents of Cosapa, Bolivia, recently fenced off portions of critical communal grazing areas called bofedal (wet meadow) and gramadal (dry meadow) as part of a livestock development project. Fenced exclosures were used to implement seasonally deferred grazing practices. We evaluated the effects of deferred grazing on peak standing crop (SC), above‐ground net primary production (ANPP) and plant species composition and diversity over a 4‐month growing season across 10 locations. Effects of exclosure access on the productivity of alpaca Llama pacos, llama L. glama and sheep Ovis aries were assessed through interviews with 32 herd owners.

One to three years of deferred grazing had no effect on SC or ANPP from bofedal or gramadal, but it did reduce plant species diversity for bofedal. Access to exclosures improved survival rates of young alpaca and birth rates for sheep. Llamas were typically denied access to exclosures, which negatively affected their productivity.

Our results suggest that both non‐equilibrium and equilibrium forces operate on bofedal. Stable and low rates of ANPP are largely shaped by the cold climate, a non‐equilibrium factor. Changes in plant species composition and livestock productivity, however, support equilibrium theory.

Synthesis and applications. Ecological models of rangeland dynamics often play a critical role in determining the direction of range management and pastoral development. On bofedal, we found that vegetation and herbivore dynamics are coupled to a large extent, consistent with predictions that equilibrium behaviour can occur for critical, mesic subsystems nested within arid landscapes. Seasonal grazing deferral on bofedal can thus yield benefits to livestock productivity. However, these benefits must be weighed against negative social consequences that can occur when communal resources are privatized.
Alleviating grazing damage by white‐fronted geese: an optimal foraging approach
Authors: AMANO TATSUYA , USHIYAMA KATSUMI , FUJITA GO , HIGUCHI HIROYOSHI
Published: July 2004

Agricultural damage by wildlife is a serious constraint on the coexistence of humans and wildlife. Understanding the behavioural processes involved in such agricultural damage will inform management actions. In this study, a linear programming model based on optimal foraging theory was used to formulate management strategies designed to reduce wheat damage caused by white‐fronted geese Anser albifrons around Lake Miyajimanuma in Japan.

Geese feed on rice grains or wheat leaves. Their choice of food is constrained by their daily energy requirement, daily nitrogen requirement, digestive capacity and daily maximum foraging time. With these constraints, we predicted the proportion of geese that should forage on wheat leaves under energy‐maximizing, nitrogen‐maximizing and time‐minimizing strategies, and compared the results with the observed proportion.

Our predictions for the energy‐maximizing strategy successfully explained the variation in the observed proportion of geese foraging on wheat leaves. It appeared that nitrogen constraints drove the geese to forage on wheat in autumn, but energy considerations drove the geese to forage on wheat plus rice in late spring.

Based on these results, we predicted that by increasing the harvest remains of rice by 30%, a large reduction in wheat damage could be achieved both in autumn and in spring. Damage could be reduced further by supplying protein‐rich food, such as grass on fallow fields and on ridges of rice fields in autumn, and by leaving geese foraging in rice fields undisturbed.

Synthesis and applications. Optimal foraging models that consider foraging goals and constraints have considerable potential for identifying measures for minimizing agricultural damage problems caused by grazing bird species. Specifically, for geese grazing on wheat fields in Japan, we advocate increasing the availability of alternative protein‐rich foods, such as rice harvest remains and grass, and minimizing disturbance to geese foraging on rice fields.
Assessment of ecological effects due to forest harvesting: approaches and statistical issues
Authors: BENNETT L. T. , ADAMS M. A.
Published: July 2004

Timber harvesting exemplifies many aspects of experimental manipulation in applied ecology. Evaluation of the research approaches used to assess ecological effects of harvesting thus has relevance to a diverse range of ecological questions that address large‐scale and human impacts on the environment.

We measured the frequency of approaches, and also design and statistical issues, in assessments of harvesting effects on three response variables (tree regeneration, vertebrates and water) in two major native forests of south‐east Australia. Our evaluation was based on 124 documents that contain unique, field‐based research and that represent the complete written record (published and unpublished) of relevant research prior to mid‐2002.

The dominant approach was contrasts between manipulated stands, nearly always involving mature and old‐growth stands as the reference or control. In studies of tree regeneration, focus on wood‐production objectives was apparent in the relatively frequent use of stocking standards, and in the use of between‐ and within‐stand contrasts without a control condition. Comparatively greater use of models in vertebrate and water studies suggested more frequent integration of generic principles and, in water studies, reflected strong collective knowledge based on the repeated use of BACI‐type designs (i.e. before–after, control–impact) or long‐term data sets.

Statistical issues such as poor reporting of experimental designs and of sample statistics were common. Explicit hypotheses were rare, and there was no evidence of definition of critical effect sizes, use of power analysis or use of non‐classical statistical approaches (e.g. Bayesian inference).

Lack of treatment replication was widespread in between‐stand contrasts and less frequent in within‐stand contrasts. Inappropriate interpretation of results from non‐replicated experimental designs remains an ongoing issue.

Synthesis and applications. The amount of information obtainable from stand‐level manipulations of forest would substantially increase through greater attention to data quality and experimental protocols. Studies require broader experimental contexts, including their potential place in meta‐replication frameworks. Increasingly, constraints of large‐scale manipulations necessitate the integration of data and the acknowledgement of uncertainty in formalized systems (e.g. Bayesian methods and adaptive management frameworks). Our evaluation suggests the alternative is a perpetuation of short‐term, isolated studies that repeat errors and have limited potential to refine knowledge on the ecological effects of timber harvesting and other similarly scaled disturbances.
A portable LIDAR system for rapid determination of forest canopy structure
Authors: PARKER GEOFFREY G. , HARDING DAVID J. , BERGER MICHELLE L.
Published: July 2004

The functional characteristics of forests are related to the organization of their canopies. However, understanding the relationship between canopy structure and function has been limited by a paucity of methods for determining structure at scales consistent with those of function measurements.

We describe here a portable system, assembled from commercially available components, for acquiring measurements of distances to overhead plant surfaces. These measurements can be aggregated to assess canopy structure rapidly at scales of ecological interest. Deployed from the forest floor, the system includes a narrow‐beam rapidly pulsed first‐return laser rangefinder coupled with a data recording system.

Tests in an age sequence of broad‐leaved closed‐canopy forests showed that the system provides results significantly more rapidly than previous methods, at spatial scales as small as 1 m in all dimensions. The estimated mean vertical canopy structure is consistent with that found from more laborious, manual approaches, such as the foliage height profile method. The system has some biases due to beam width and range averaging but, from a variety of tests, we found these have relatively little effect on the structure estimates.

Various field sampling schemes and methods of aggregating the measurements yield a variety of representations of structure, including mean profiles, tomographic sections, three‐dimensional distributions of canopy surface density and maximum height surfaces. Derivable summary measures include canopy cover and area index, porosity, the size distribution of overhead openings and indices of structural complexity. Moreover, the approach can provide estimates of spatial variability and covariance not previously obtainable.

Synthesis and applications.Portable light detection and ranging (LIDAR) systems, such as the one we describe here, provide a new tool for rapid measurement of small‐scale forest structure. These can contribute efficiently and relatively inexpensively to canopy research and forestry programmes, covering a range of ecological and production needs.
Determining impacts of habitat modification on diversity of tropical forest fauna: the importance of spatial scale
Authors: HILL JANE K. , HAMER KEITH C.
Published: July 2004

There is an urgent need to understand the impacts of anthropogenic habitat disturbance on biodiversity in tropical forests, but no consensus has yet emerged. We reviewed the literature for the most frequently studied taxon (birds, 37 studies) and found that increased and decreased diversity in response to disturbance (selective logging and shifting agriculture) were reported with approximately equal frequency.

The spatial scale at which studies were carried out significantly affected the reported response to disturbance: studies where disturbed and undisturbed habitats were sampled at large spatial scales were more likely to report increased diversity following disturbance, whereas studies that sampled habitats at small spatial scales were more likely to report decreased diversity. These results were not a consequence of sampling method: we divided the studies into those using capture methods and those using observation methods and the same result was obtained when the analysis was restricted to only those studies using observation methods.

Previously, we have shown that reported impacts of disturbance on Lepidoptera are also affected by the spatial scale of study. We reviewed the Lepidoptera literature published since then and showed that all 12 new studies conformed to the predicted pattern.

While sampling scale significantly affected the reported responses of both birds and Lepidoptera, there were opposite effects of scale in the two taxa: large‐scale bird studies and small‐scale Lepidoptera studies were more likely to report increased diversity following disturbance. Bird studies were generally carried out at larger spatial scales than those of Lepidoptera and these opposite impacts of scale were probably due to a non‐linear effect of habitat disturbance on habitat heterogeneity at different spatial scales.

Synthesis and applications. The rapid loss and degradation of tropical forests means that an understanding of the general patterns of responses of species to habitat disturbance is urgently needed. However, there has been little discussion of the most appropriate methods to ensure comparability of results between studies. Data presented here indicate that the spatial scale of sampling chosen in studies has a marked effect on the results obtained, and future studies need to account for this by examining explicitly the effects of disturbance at different spatial scales. The effect of spatial scale differs between taxa, and this may explain why the search for indicator taxa of disturbance effects has so far proved elusive.
The effects of disturbance on behaviour, habitat use and energy of spring staging snow geese
Authors: BÉCHET ARNAUD , GIROUX JEAN‐FRANCOIS , GAUTHIER GILLES
Published: July 2004

For many species, human‐induced disturbances can severely influence an individual's pay‐off; however, energy‐cost variations from different disturbance types have rarely been reported.

We evaluated the dynamic behavioural responses of staging greater snow geese Anser caerulescens atlanticus to different types of disturbance in southern Quebec, Canada, between 1997 and 2000. We specifically considered the impact of a unique measure, a spring conservation hunt implemented in agricultural habitats in 1999.

We tracked 237 radio‐tagged females for 2764 h and recorded 697 take‐offs following fortuitous disturbance, scaring and hunting in three regions characterized by different habitats. Geese used cornfields in south‐western Quebec, Scirpus marshes and hayfields in the upper St Lawrence estuary, and Spartina marshes and hayfields in the lower estuary.

Overall, disturbance levels increased in the upper and lower estuary during years with hunting, mostly through an increase in hunting and scaring activities.

The probability of geese returning to a refuge after disturbance in agricultural habitats increased in years with hunting except in the corn‐growing region. The short‐term energy gain of geese resuming feeding after disturbance was less than before disturbance, and this difference was greater in years with hunting. Distances flown after disturbance decreased with flock size and were longer after scaring and hunting than after fortuitous disturbances in the Scirpus region.

Overall, habitat use varied among years and associated estimated energy gain decreased markedly in both years with hunting in the Spartina and corn‐growing region, but did not change in the Scirpus region. Changes in behaviour due to disturbance, and especially those associated with hunting, probably contributed to the reduced body condition of staging greater snow geese during years with hunting.

Synthesis and applications. From a methodological viewpoint, we highlight the importance of tracking the behaviour of individual animals after disturbance to properly evaluate its impact. From a conservation perspective, we provide empirical arguments to limit the hunting of breeding waterfowl during their prenuptial migration in order to facilitate their fattening and forthcoming reproduction. From a management standpoint, we suggest that a side‐effect of disturbance induced by spring hunting to control overabundant populations may be reduced fattening and breeding output among birds that survive. Together, these data emphasize further the importance of measuring the direct and indirect effects of disturbance rather than assuming effects from the incidence of the disturbance alone.
Can we mitigate animal–vehicle accidents using predictive models?
Authors: MALO JUAN E. , SUÁREZ FRANCISCO , DÍEZ ALBERTO
Published: July 2004

Vehicle collisions with wild animals are a serious problem that justifies the widespread application of mitigation measures such as road fencing and provision of crossing structures. Models that predict the best location for mitigation measures can improve wildlife survival and road safety.

A database of 2067 records of animal–vehicle collisions was used to create two data sets at different spatial scales. The first comprised records of road sections of 1 km length with high rates of collision in combination with road sections with a low number of collisions. The second comprised records of collision and no collision incidence at points on the road system at a 0·1‐km scale. Logistic regression was used to investigate the relationship between incidence of collision and measured habitat features in each data set. The models were validated with a subset of the original data not used in developing the models.

Road sections with high collision rates were associated with areas having high forest cover, low crop cover, low numbers of buildings and high habitat diversity. The fitted model achieved a significant predictive success during validation (χ2 = 4·82, 1 d.f., P= 0·028), with more than 70% correct classification of cases.

Specific collision points typically had no guard‐rails or lateral embankments, were not near underpasses, crossroads or buildings, and featured hedges or woodland near the road. The fitted model also showed a significant predictive power in validation (64% correct classification, χ2 = 9·51, 1 d.f., P= 0·002) and accurately predicted 85·1% of collision points.

Synthesis and applications. Predictive models of animal–vehicle collision locations should be used at both a landscape level and a local scale during the process of road design and implementation of mitigation measures. Modelling of collision risk could inform decisions on road alignment and on the exact location of crossing structures for mammals, to improve wildlife survival and road safety. This is the first study integrating both landscape and local scales of analysis for the variables associated with animal–vehicle collisions.
Faecal density counts for monitoring changes in red fox numbers in rural Britain
Authors: WEBBON CHARLOTTE C. , BAKER PHILIP J. , HARRIS STEPHEN
Published: July 2004

Quantifying animal density is a fundamental requirement for the successful management of canid species. Faecal transects along linear features represent a cost‐effective means of quantifying relative density. However, it is unclear whether such counts can be utilized to estimate absolute density.

In Britain, due to proposed legislative changes in permitted culling practices, and as part of a wider monitoring programme, the current and future density of red foxes Vulpes vulpes is of applied interest. In this study, we counted fox faeces in 444 1‐km squares throughout mainland Britain to construct a baseline index of fox density against which future changes could be measured. By incorporating estimates of the defecation rate and the proportion of scats associated with linear features, we estimated absolute density in seven landscapes. These estimates were compared with existing data on fox density.

On average, captive foxes consumed 0·85 kg food day−1. Defecation rate (8 scats fox−1 day−1) was not affected by the type of food consumed.

The proportion of scats associated with linear features was determined by feeding individual free‐living foxes a known amount of food containing an indigestible marker. On average, 5·7% of scats were deposited along linear features.

Mean fox density in landscapes ranged from 0·21 to 2·23 foxes km−2. These estimates agreed closely with the limited data available on fox density in Britain. The total rural fox population was estimated to be 225 000 foxes (95% confidence interval 179 000–271 000). Including foxes in urban areas, the total national population is estimated to be approximately 258 000 individuals.

Synthesis and applications. The results suggest that faecal density counts have the potential to be used to estimate fox density over large spatial scales, although further work on estimating the proportion of scats associated with linear features and the use of faeces in territorial marking by canids is required.
Integrating herbicide and mechanical control treatments with fire and biological control to manage an invasive wetland shrub, Mimosa pigra
Authors: PAYNTER QUENTIN , FLANAGAN GRANT J.
Published: July 2004

In Australia, biological control is a promising long‐term management strategy for the woody weed mimosa Mimosa pigra but does not yet provide adequate control. Other management techniques, including herbicides and fire, can be ineffective and their impact on biological control agents is unknown. We investigated the potential of integrating control techniques, including biological control, to provide cost‐effective management.

A large‐scale (128‐ha) split‐plot experiment was performed to measure the impact of single and repeated applications of herbicide and crushing by bulldozer, either alone or in combination, on both mimosa and five introduced biological control agents that were abundant at the site. Herbicides were applied over three seasons (1997–99) and all plots were burned in 2000.

The impact of control options on mimosa cover, biomass, number of stems per ha, stand size structure and seedling regeneration was determined by aerial photography and by sampling permanent and random quadrats. Biological control agent abundance was also quantified.

In isolation, herbicide, bulldozing and fire were not effective, but several combinations of techniques cleared mimosa thickets and promoted establishment of competing vegetation that inhibited mimosa regeneration from seed.

Depending on the species, biological control agent abundance on surviving mimosa plants was either unchanged or increased following herbicide and/or bulldozing treatments. All agents recolonized regenerating mimosa within 1 year of the fire treatment, and Neurostrota gunniella increased dramatically. Carmenta mimosa abundance, however, was reduced by fire.

The abundance of N. gunniella increased in response to all treatments, which we attribute to attack by this species being most common along stand edges. Control treatments separated monocultures of mimosa into smaller patches, thereby increasing the ratio of ‘edge’ to ‘thicket’ plants. The proportion of plants susceptible to N. gunniella attack increased as a result.

Synthesis and applications. We conclude that integrating control techniques can successfully control dense mimosa thickets. Biological control integrates well with other control options and should lead to significant cost reductions for mimosa management. To maximize this benefit, integrated weed management plans should be designed to integrate biological control fully with other methods, rather than separate them spatially or temporarily.
On the loss of saltmarshes in south‐east England and the relationship with Nereis diversicolor
Authors: MORRIS R. K. A. , REACH I. S. , DUFFY M. J. , COLLINS T. S. , LEAFE R. N.
Published: July 2004

Two papers, Hughes & Paramor (2004) and Paramor & Hughes (2004), published in Journal of Applied Ecology are discussed. These papers suggest that saltmarsh erosion is linked to bioturbation, and concentrate on the role of the ragworm Nereis diversicolor. The authors also suggest that new saltmarsh will not develop in realignment sites because bioturbation will prevent the establishment of saltmarsh plants. We dispute their analysis and offer evidence that inferences derived from their experimental work are erroneous.

Experience from the current range of managed realignment sites in the UK shows that saltmarsh communities are developing, and include the lower marsh Salicornia communities that they suggest are vulnerable to the effects of bioturbation and grazing by N. diversicolor.

Further evidence of the benefits of managed realignment, even in situations where realignment sites lie below existing seaward mudflat levels, is provided by the saltmarshes that developed on sites that were not re‐enclosed after the 1953 flood in eastern England.

We highlight the importance of maintaining positive sediment budgets in order that saltmarshes may continue to adjust to sea level rise and to ensure that sufficient sediment exists to allow realignment sites to warp up to levels at which pioneer saltmarsh may develop.

We also draw attention to a range of initiatives that seek to maintain sediment levels within estuaries in south‐east England, and highlight the broader conceptual approach that looks upon dredged sediment as an important resource and not a waste material. None of these is designed to change permanently the estuarine tidal prism, as suggested by Hughes & Paramor (2004).

Synthesis and applications. We present evidence to show that coastal realignment is effective in managing and reversing saltmarsh erosion. We dispute the conclusions presented in the recent papers by Hughes & Paramor (2004) and Paramor & Hughes (2004). We suggest that infauna play an essential role in saltmarsh ecology and that N. diversicolor does not play a destructive role in saltmarsh establishment. In the broader context of coastal management, the long‐term benefits of managed realignment in sea defence and in delivering nature conservation benefit are quite clear. Sustainable sediment management will play a key role in sustaining saltmarsh habitats in the future.
Fragmented landscapes, road mortality and patch connectivity: modelling influences on the dispersal of Eurasian lynx
Authors: KRAMER‐SCHADT STEPHANIE , REVILLA ELOY , WIEGAND THORSTEN , BREITENMOSER URS
Published: July 2004

Although many reintroduction schemes for the Eurasian lynx Lynx lynx in Germany have been discussed, the implications of connectivity between suitable patches have not been assessed.

We introduce an individual‐based, spatially explicit dispersal model to assess the probability of a dispersing animal reaching another suitable patch in the complex heterogeneous German landscape, with its dense transport system. The dispersal model was calibrated using telemetric data from the Swiss Jura and based on a map of potential lynx dispersal habitat.

Most suitable patches could be interconnected by movements of dispersing lynx within 10 years of reintroduction. However, when realistic levels of mortality risks on roads were applied, most patches become isolated except along the German–Czech border. Consequently, patch connectivity is limited not so much by the distribution of dispersal habitat but by the high mortality of dispersing lynx. Accordingly, rather than solely investing in habitat restoration, management efforts should try to reduce road mortality.

Synthesis and applications. Our approach illustrates how spatially explicit dispersal models can guide conservation efforts and reintroduction programmes even where data are scarce. Clear limits imposed by substantial road mortality will affect dispersing lynx as well as other large carnivores, unless offset by careful road‐crossing management or by the careful selection of release points in reintroduction programmes.
Functional traits of graminoids in semi‐arid steppes: a test of grazing histories
Authors: ADLER PETER B. , MILCHUNAS DANIEL G. , LAUENROTH WILLIAM K. , SALA OSVALDO E. , BURKE INGRID C.
Published: July 2004

Understanding variability in ecosystem response to grazing is essential for improving management. Recent efforts have focused on the role of plant functional traits but do not identify factors influencing trait development. As traits are legacies of historical selective pressures, they may indicate the importance of a plant community's evolutionary history of grazing.

We compared grazing‐resistance traits of graminoids collected in the Patagonian steppe of Argentina, presumed to have a long evolutionary history of grazing, and the sagebrush steppe of the north‐western USA, known to have a short grazing history. The purpose of this comparison was to test the influence of grazing history and aridity on resistance traits, and to generate predictions about the vulnerability of these ecosystems to grazing impacts. We measured both morphology and leaf chemical composition on common species from an arid and a semi‐arid site in each region, then performed a principal components analysis on the species‐by‐traits matrix.

The first axis of the ordination was correlated with measures of forage quality such as leaf tensile strength, fibre and nitrogen content, while the second axis was correlated with plant stature. The dominant species from the drier Patagonia site scored significantly lower on the first axis (lower forage quality) than dominants from the sagebrush steppe. Plants from the wetter Patagonia site were intermediate in forage quality. Sagebrush steppe species scored significantly higher on the second axis (taller) but this difference was not significant when we considered only dominant species.

The intercontinental differences in plant traits are consistent with evidence indicating a longer evolutionary history of grazing in Patagonia. Differences in traits between the dry and wet sites in Patagonia are consistent with the hypothesis that aridity promotes grazing resistance, although trait contrasts between the drier and wetter sagebrush sites were not significant.

Differences in soil texture, which may influence nitrogen availability, offer an alternative explanation for differences in forage quality between Patagonia and sagebrush steppe, and between the drier and wetter sites within Patagonia.

Synthesis and applications. Our comparison of plant traits suggests that interactions between evolutionary history of grazing and abiotic covariates, especially soil texture, have selected for low forage quality in Patagonia relative to sagebrush steppe. This contrast in grazing‐resistance traits leads to the prediction that livestock grazing will have less impact on upland plant communities in Patagonian steppe compared with the sagebrush steppe of the USA, particularly if low nitrogen content limits offtake. Plant functional traits represent an easily quantified link between evolutionary grazing history and ecosystem responses to contemporary management.
Fire and competition in a southern California grassland: impacts on the rare forb Erodium macrophyllum
Authors: GILLESPIE IAN G. , ALLEN EDITH B.
Published: July 2004

The use of off‐season burns to control exotic vegetation shows promise for land managers. In California, wildfires tend to occur in the summer and autumn, when most grassland vegetation is dormant. The effects of spring fires on native bunchgrasses have been examined but their impacts on native forbs have received less attention.

We introduced Erodium macrophyllum, a rare native annual forb, by seeding plots in 10 different areas in a California grassland. We tested the hypotheses that E. macrophyllum would perform better (increased fecundity and germination) when competing with native grasses than with a mixture of exotic and native grasses, and fire would alter subsequent demography of E. macrophyllum and other species’ abundances. We monitored the demography of E. macrophyllum for two seasons in plots manually weeded so that they were free from exotics, and in areas that were burned or not burned the spring after seeding.

Weeding increased E. macrophyllum seedling emergence, survival and fecundity during both seasons. When vegetation was burned in June 2001 (at the end of the first growing season) to kill exotic grass seeds before they dispersed, all E. macrophyllum plants had finished their life cycle and dispersed seeds, suggesting that burns at this time of year would not directly impact on fecundity. In the growing season after burning (2002), burned plots had less recruitment of E. macrophyllum but more establishment of native grass seedlings, suggesting burning may differentially affect seedling recruitment.

At the end of the second growing season (June 2002), burned plots had less cover of exotic and native grasses but more cover of exotic forbs. Nevertheless, E. macrophyllum plants in burned plots had greater fecundity than in non‐burned plots, suggesting that exotic grasses are more competitive than exotic forbs.

A glasshouse study showed that exotic grasses competitively suppress E. macrophyllum to a greater extent than native grasses, indicating that the poor performance of E. macrophyllum in the non‐burned plots was due to exotic grass competition.

Synthesis and applications. This study illustrates that fire can alter the competitive environment in grasslands with differential effects on rare forbs, and that exotic grasses strongly interfere with E. macrophyllum. For land managers, the benefits of prescribed spring burns will probably outweigh the costs of decreased E. macrophyllum establishment. Land managers can use spring burns to cause a flush of native grass recruitment and to create an environment that is, although abundant with exotic forbs, ultimately less competitive compared with non‐burned areas dominated by exotic grasses.
Molecular techniques, wildlife management and the importance of genetic population structure and dispersal: a case study with feral pigs
Authors: HAMPTON JORDAN O. , SPENCER PETER B. S. , ALPERS DERYN L. , TWIGG LAURIE E. , WOOLNOUGH ANDREW P. , DOUST JEFF , HIGGS TONY , PLUSKE JOHN
Published: July 2004

Understanding the spatial structure of populations is important in developing effective management strategies for feral and invasive species, such as feral pigs Sus scrofa. World‐wide, feral pigs can act as ‘triple threat’ pests, impacting upon biodiversity, agricultural production and public health; in Australia they are a significant vertebrate pest. We utilized a molecular approach to investigate the structure of populations of feral pigs in south‐western Australia. These approaches have been underutilized in pest management.

Using 14 highly polymorphic microsatellite markers from 276 adult pigs, we identified eight inferred (K = 8) pig populations that would be difficult to define with standard ecological techniques. All populations had moderate heterozygosity (HE = 0·680) and moderate to high levels of differentiation (FST = 0·118; RST = 0·132) between populations.

The molecular approach identified feral pig groups that appeared to be acting as a source for reinvasion following control operations. It also identified populations where current control measures were less successful in reducing ‘effective population size’. Additionally, the data indicated that dispersal rates between, but not within, the inferred feral pig populations were relatively low.

The potential for the spread of directly transmitted wildlife diseases between the pig populations studied was low. However, under some circumstances, such as within major river catchments, the role of feral pigs in the transmission of endemic or exotic diseases is likely to be high.

Synthesis and applications. A molecular‐based approach allowed us to determine the genetic structure and dispersal patterns of a cryptic, destructive and invasive vertebrate pest. Our results indicated that the feral pig populations studied were unlikely to be acting as closed populations and, importantly, it identified where movement between groups was likely to occur. This should lead to more informed decisions for managing the potential risk posed by feral species, such as pigs, in the transmission of wildlife diseases. The suggested technique could help in understanding the dynamics of many other free‐ranging pest animal populations.
Application of the fire–grazing interaction to restore a shifting mosaic on tallgrass prairie
Authors: FUHLENDORF S. D. , ENGLE D. M.
Published: July 2004

Management of rangelands has long operated under the paradigm of minimizing spatially discrete disturbances, often under the objective of reducing inherent heterogeneity within managed ecosystems. Management of grazing animals has focused on uniform distribution of disturbance, so that no areas are heavily disturbed or undisturbed (i.e. management to the ‘middle’).

A model of the fire–grazing interaction argues that grazing and fire interact through a series of positive and negative feedbacks to cause a shifting mosaic of vegetation pattern across the landscape. This interaction was important in the evolution of species in the North American Great Plains grasslands. This approach has the potential to serve as an ecological‐based model for management of grasslands with a long evolutionary history of grazing.

We compared a heterogeneity‐based approach, in which fire is applied to discrete patches, with typical homogeneity‐based land management in the North American Great Plains, to determine if patch burning followed by focal grazing creates a shifting mosaic pattern of vegetation structure and composition.

Our data suggest that spatially discrete fires promote focal grazing, where grazing animals devote 75% of grazing time within the one‐third of the area that has been burned within the past year. These focal disturbances cause local changes in the plant community and increase patch‐level heterogeneity across landscapes. As the focal disturbance is shifted to other patches over time, successional processes lead to changes in local plant communities and the patchwork landscape can be described as a shifting mosaic.

A patch‐dynamic approach can be accomplished in the tallgrass prairie through applying spatially discrete fires and allowing animals free access to a diversity of landscape elements that vary in time since focal disturbance. This increases heterogeneity across the landscape, a variable that has been shown to be critical to some wildlife species as well as the structure and function of grassland ecosystems.

Synthesis and applications. Our study demonstrates that the fire‐grazing model may be useful for generating heterogeneity in grassland management. Discrete fires are applied to patches, and patchy grazing by herbivores promotes a shifting vegetation mosaic across the landscape. Furthermore, application of the model has the potential of increasing the area of rangelands under management for conservation purposes, because livestock production is maintained at a level similar to traditional management. So, by managing transient focal patches that move through the landscape, heterogeneity has the potential to be a central paradigm for managing landscapes for multiple objectives, such as biodiversity and agricultural productivity.
The problems of prediction and scale in applied ecology: the example of fire as a management tool
Authors: FRECKLETON ROBERT P.
Published: July 2004

Predicting the large‐scale consequences of novel management practices requires that we are able to accurately predict how such management will affect ecological landscapes based on short‐term datasets. In this profile we highlight the lessons learned from four studies into the large‐scale effects of fires as management tools.

Ecological interactions are key to understanding the effects of fires. Species respond differentially to processes such as competition and herbivory, as well as to fires. This means that community composition may change substantially with changing frequency of fires.

The studies highlighted in this profile reinforce the role of fire in modulating the frequency of invasion of alien species in a range of ecosystem types. In two of the studies, alien species were superior competitors to native ones in the absence of fires, but unable to regenerate following fires.

In the future, it will be necessary that the results of short‐term experiments are integrated with long‐term observational data and with theoretical models to predict long‐term dynamics. We discuss how this may be done.

Synthesis and applications. The studies of the management of ecosystems using fires as a tool are prime examples of the application of ecology. In addition to measuring the proximate effects of such management using experiments, it is necessary to understand in detail the effects of fire on the underlying interactions between species, and feedbacks between different components of ecosystems.
Ambiguous Loss Research, Theory, and Practice: Reflections After 9/11
Authors: Boss Pauline
Published: July 2004

This article contains an overview of three decades of research, theory development, and clinical application about ambiguous loss. Although the work includes both physical and psychological types of ambiguous loss, the focus is the aftermath of 9/11 (September 11, 2001), when the World Trade Center collapsed following terrorist attacks. On the basis of her previous work, the author was asked to design an intervention for families of the missing. She reflects on what she learned from this unexpected test and presents new propositions and hypotheses to stimulate further research and theory that is more inclusive of diversity. She suggests that scholars should focus more on universal family experience. Ambiguous loss is just one example. Encouraging researchers and practitioners to collaborate in theory development, she concludes that research‐based theory is essential to inform interventions in unexpected times of terror, and in everyday life.
Love and Death in Germany: The Marital Biography and Its Effect on Mortality
Authors: Brockmann Hilke , Klein Thomas
Published: July 2004

In this article, we analyze how the marital biography is affecting mortality in Germany today (N = 12,484). We find support for temporal selection into marriage for both genders, but the effect is stronger for men. In addition, protection through marriage results from long‐term accumulation of survival advantages and from the attenuation of higher mortality risks that occur immediately after a transition into or out of a marriage. Moreover, women are more likely to keep survival advantages from previous marriages and to forget about survival disadvantages from divorces and widowhood.