bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alternative models of climatic effects on sockeye salmon, Oncorhynchus nerka, productivity in Bristol Bay, Alaska, and the Fraser River, British Columbia
Authors: ADKISON MILO D. , PETERMAN RANDALL M. , LAPOINTE MICHAEL F. , GILLIS DARREN M. , KORMAN JOSH 
Published: October 2007

ABSTRACTWe compare alternative models of sockeye salmon, Oncorhynchus nerka, productivity (returns per spawner) using more than 30 years of catch and escapement data for Bristol Bay, Alaska, and the Fraser River, British Columbia. The models examined include several alternative forms of models that incorporate climatic influences as well as models not based on climate. For most stocks, a stationary stock‐recruitment relationship explains very little of the interannual variation in productivity. In Bristol Bay, productivity covaries among stocks and appears to be strongly related to fluctuations in climate. The best model for Bristol Bay sockeye involved a change in the 1970s in the parameters of the Ricker stock‐recruitment curve; the stocks generally became more productive. In contrast, none of the models of Fraser River stocks that we examined explained much of the variability in their productivity.
Concentration of pelagic organisms at mesoscale fronts in the western subarctic Pacific: small fish on long waves
Authors: ROGACHEV K. A. , SALOMATIN A. S. , CARMACK E. C. 
Published: October 2007

ABSTRACTAcoustical backscatter observations conducted off the Kuril Straits (Boussole and Vries Straits) in the western subarctic Pacific show increased concentrations of mesopelagic fish (suspected to be fish of the family Myctophidae) associated with long (4–40 km), high‐amplitude (about 100 m) internal waves. Such wave packets are thought to be generated by tidally driven flows through the deep Kuril Island straits. Because myctophids are a small, subarctic fish that must remain in cold waters, it is assumed that their increased concentration is due to an ability to sense flow direction and take advantage of the horizontal flow convergence in these long waves. Because vertical motions in waves are weak, small fish can easily maintain their preferred depth of habitat, and their concentrations tend to increase along horizontal convergence lines formed by wave orbital velocities.
Temperature as a possible factor in the increased abundance of American lobster, Homarus americanust during the 1980s and early 1990s
Authors: DRINKWATER K. F. , HARDING G. C. , MANN K. H. , TANNER N. 
Published: October 2007

ABSTRACTThrough most of the geographical range of the American lobster, Homarus americanus, from Newfoundland to the Middle Atlantic Bight, catches reached new historical maxima or near maxima in the late 1980s or early 1990s. Because of the high exploitation rates, this increase in landings is believed to reflect increased recruitment. Previous studies have shown that increased lobster landings in certain areas were linked to rising sea temperatures. This paper examines the hypothesis that the increased landings during the 1980s and early 1990s were temperature induced. When temperature‐dependent regressions of lobster landings, developed by earlier authors, were extended to the present they failed to predict the sharp rise in landings during the 1980s. In addition, the increase in lobster landings is shown to have occurred over a larger spatial scale than coherent temperature fluctuations. These results, together with an exploratory correlation analysis between sea temperatures and lobster landings, lead to the conclusion that the increase in lobster catches in the 1980s was not linked to changes in ocean temperatures.
Impact of summer warming on the thermal characteristics of a polymictic lake and consequences for oxygen, nutrients and phytoplankton
Authors: WILHELM SUSANN , ADRIAN RITA 
Published: October 2007

Summary1. The impact of long thermal stratification events on some key properties in a polymictic lake was studied by determining the mixing regime of Müggelsee, Germany, using water temperature profiles taken hourly over 4 years. The period included two exceptional summer heatwaves.2. Long thermal stratification events lasted from about 1 week to 2 months, and exhibited a high variability in thermocline depth and stratification intensity within and between events.3. During stratification events, hypolimnetic oxygen concentrations strongly decreased while hypolimnetic SRP accumulation increased, depending on the duration and intensity of stratification and on hypolimnetic water temperature.4. The impact of stratification on the functional phytoplankton composition increased with increasing stratification duration, but was rather different for the heatwaves.5. Stratification events were followed by strong nutrient pulses into the euphotic zone and intense phytoplankton growth, particularly after the heatwaves. Hence, the influence of the climate extremes counteracted effects of reduced external nutrient loading.
The significance of side‐arm connectivity for carbon dynamics of the River Danube, Austria
Authors: PREINER S. , DROZDOWSKI I. , SCHAGERL M. , SCHIEMER F. , HEIN T. 
Published: October 2007

Summary1. Side‐arms connected to the main stem of the river are key areas for biogeochemical cycling in fluvial landscapes, exhibiting high rates of carbon processing.2. This work focused on quantifying autochthonous and allochthonous carbon pools and, thereby, on comparing transport and transformation processes in a restored side‐arm system of the River Danube (Regelsbrunn). We established a carbon budget and quantified carbon processing from March to September 2003. In addition, data from previous studies during 1997 to 1999 were assessed.3. Gross primary production (GPP) and community respiration were estimated by diel oxygen time curves and an oxygen mass balance. Plankton primary production was determined to estimate its contribution to GPP under different hydrological conditions.4. Based on the degree of connectivity, three hydrological phases were differentiated. Most of the organic matter, dominated by allochthonous carbon, was transported in the main channel and through the side‐arm during floods, while at intermediate and low flows (and thus connectivity), transformation processes became more important and autochthonous carbon dominated the carbon pool. The side‐arm system functioned as a sink for particulate matter [total suspended solids and particulate organic carbon (POC)] and a source of dissolved organic carbon (DOC) and chlorophyll‐a.5. Autochthonous primary production of 4.2 t C day−1in the side‐arm was equivalent to about 20% of the allochthonous inputs of 20 t C day−1(POC and DOC) entering the area at mean flow (1% of the discharge of the main channel). Pelagic photosynthesis was generally high at mean flow (1.3–3.8 g C m−2 day−1), and contributed up to 90% of system productivity. During long stagnant periods at low discharge, the side‐arm was controlled by biological processes and a shift from planktonic to benthic activity occurred (benthic primary production of 0.4–14 g C m−2 day−1).6. The transformation of the organic matter that passes through the side‐arm under different hydrological conditions, points to the importance of these subsystems in contributing autochthonous carbon to the food web of the main channel.
Differential response of phytoplankton to additions of nitrogen, phosphorus and iron in Lake Tanganyika
Authors: WEVER AAIKE DE , MUYLAERT KOENRAAD , LANGLET DENIS , ALLEMAN LAURENT , DESCY JEAN‐PIERRE , ANDRÉ LUC , COCQUYT CHRISTINE , VYVERMAN WIM 
Published: October 2007

Summary1. In order to evaluate limitation of different phytoplankton groups by inorganic nutrients, multiple nutrient enrichment bioassays using the addition of iron (Fe) and the combined addition of nitrogen and phosphorus (NP) were carried out in the north and the south of Lake Tanganyika during the rainy and dry seasons in 2003 and 2004.2. Nutrient additions resulted in an increase in phytoplankton growth rate relative to control treatments in all experiments. HPLC pigment data and epifluorescence microscopy counts indicated differential stimulation of the dominant phytoplankton groups. Iron additions mainly stimulated prokaryotic picophytoplankton, while enrichments with nitrogen and phosphorus stimulated green algae and in some cases diatoms. Extended incubation (3 days) indicated co‐limitation of Fe and NP, in particular for picocyanobacteria.
Climate change cannot be entirely responsible for soil carbon loss observed in England and Wales, 1978–2003
Authors: SMITH PETE , CHAPMAN STEPHEN J. , SCOTT W. ANDY , BLACK HELAINA I. J. , WATTENBACH MARTIN , MILNE RONNIE , CAMPBELL COLIN D. , LILLY ALLAN , OSTLE NICK , LEVY PETER E. , LUMSDON DAVID G. , MILLARD PETER , TOWERS WILLIE , ZAEHLE SÖNKE , SMITH JO U. 
Published: October 2007

AbstractWe present results from modelling studies, which suggest that, at most, only about 10–20% of recently observed soil carbon losses in England and Wales could possibly be attributable to climate warming. Further, we present reasons why the actual losses of SOC from organic soils in England and Wales might be lower than those reported.
Impacts of bark and foliage harvest on Khaya senegalensis (Meliaceae) reproductive performance in Benin
Authors: Gaoue Orou G. , Ticktin Tamara 
Published: October 2007

Summary

Increasing concern over the sustainability of harvesting non‐timber forest products (NTFP) has led to a growing literature on the ecological impacts of NTFP extraction. A large proportion of NTFP are harvested for multiple plant parts, but few studies have assessed the impacts of harvesting multi‐use species. In addition, few studies have assessed how harvest effects may vary across space. This information is necessary for designing effective conservation plans for the many NTFP species that are harvested from variable ecological contexts.
This study assessed the impacts of combined bark and foliage harvest on Khaya senegalensis (Meliaceae) reproductive performance in Benin. K. senegalensis bark is an important medicine for malaria, the leaves are pruned by indigenous Fulani herders as a critical source of fodder for their livestock, and the timber is highly prized. Data on reproductive characteristics were collected from 12 populations spread across two ecological regions (Sudanian and Sudano–Guinean). Half the populations had a history of high harvest intensity and half were subject to low/no harvest.
Trees produced more fruit and began fruiting at a significantly smaller size in the drier Sudanian region than in the wetter Sudano–Guinean region. However, pruning decreased fruit production significantly in the Sudanian region but not in the Sudano–Guinean region. Pruning had a significantly greater impact on fruit production in larger trees than in smaller trees. High harvest populations in the Sudano–Guinean region had significantly higher rates of seed production than low harvest populations, although the seeds were significantly lighter. There were no significant effects of debarking or combined debarking and pruning on reproductive performance.
Synthesis and applications. This study illustrates that heavy rates of foliage harvest can decrease rates and patterns of reproduction in K. senegalensis, and that the impacts may vary across environmental contexts. Lowered rates of reproduction may lead to decreases in K. senegalensis population size over the long term. Effective ex situ conservation strategies for K. senegalensis include increasing the availability of its fodder and bark by promoting K. senegalensis plantations programmes involving Fulani harvesters.
Trapping and vaccination of endangered Ethiopian wolves to control an outbreak of rabies
Authors: Knobel D. L. , Fooks A. R. , Brookes S. M. , Randall D. A. , Williams S. D. , Argaw K. , Shiferaw F. , Tallents L. A. , Laurenson M. K. 
Published: October 2007

Summary

As outbreaks of infectious diseases have emerged as a threat to small populations, conservation managers are increasingly making decisions regarding whether and how to intervene in such situations. Past controversies and lack of knowledge and firm guidelines may inhibit this process. We present data on a vaccination campaign against a rabies outbreak in endangered Ethiopian wolves as a case study of a disease‐control intervention in a threatened population.
Ethiopian wolves on the periphery of the outbreak area were trapped to administer a dose of injectable rabies vaccine and to assess the magnitude and duration of the immune response. The expansion of an established population monitoring programme allowed us to assess the factors influencing the probability of capturing particular animals and to evaluate the overall success of the intervention.
All wolves sampled 1 month after vaccination had protective levels of serum antibody titres. A booster dose administered within 1–6 months appeared to be necessary to maintain these levels. Females were less likely to be trapped than expected, if dispersing females were included in the population. Animals captured in the first trapping session were more likely to be recaptured if the pack was trapped again.
The intervention was successful in halting the spread of the rabies outbreak and had few short‐term impacts on the population of wolves and non‐target species.
Synthesis and applications. Demographic, spatial and behavioural heterogeneities within populations may affect vaccine uptake or delivery and thus the efficacy of vaccine‐based interventions. Managers of populations of threatened species should ensure that disease‐control programmes are carefully designed to maximize information gained on all aspects of an intervention, and thus to evaluate its outcome and impact. Dissemination and discussion of results is crucial in order to apply what has been learnt to similar scenarios in the same or related populations.
Avifaunal changes as a consequence of large‐scale livestock exclusion in the mountains of Central Argentina
Authors: García César , Renison Daniel , Cingolani Ana M. , Fernández‐Juricic Esteban 
Published: October 2007

SummaryIn the high Mountains of Córdoba (Central Argentina) large native herbivores were replaced completely by domestic livestock early in the 20th century. Recently, livestock were excluded in a large portion of the mountains to reduce alarming soil erosion rates, leading to an unnatural situation as the area has a long evolutionary history of large herbivore grazing. Many of the birds living in this area are endemic subspecies. Lack of large herbivore grazing can reduce plant diversity, but the response of birds is unknown.We surveyed birds in 46 1·8‐ha transects distributed across eight vegetation units under (a) traditional livestock rearing and (b) 4 years of livestock exclusion. We described bird communities per transect using density and richness. The effects of grazing situation and vegetation units on these parameters were analysed by two‐way analysis of variance (anova). Additionally, we analysed bird composition through detrended correspondence analysis (DCA).Livestock exclusion caused, in all vegetation units, significant reductions in observed bird density and richness when all species were included in the analysis, and when the 12 endemic subspecies were considered separately. An analysis for each guild showed a similar pattern but differences were significant only for richness of insectivorous and granivorous birds. Vegetation units always showed significant differences in bird density and richness, with no significant interactions between vegetation and grazing situations. Community composition described through DCA was different between vegetation units but not between grazing situations. Endemic birds were associated mainly with rocky areas.Synthesis and applications. In areas where large native herbivores are locally extinct, extensive exclusion of domestic livestock is not recommended where bird conservation is also a priority. Where possible, we suggest reintroducing native large herbivores. Where reintroductions are not feasible, livestock must be excluded only from those sites where it is most necessary, and maintained elsewhere at reduced stocking rates. To mimic past natural grazing regimes more effectively, livestock grazing regimes should incorporate temporal fluctuations at seasonal, yearly and decade scales.
Ecological correlates of vulnerability to fragmentation in Neotropical bats
Authors: Meyer Christoph F. J. , Fründ Jochen , Lizano Willy Pineda , Kalko Elisabeth K.V. 
Published: October 2007

Summary

In the face of widespread human‐induced habitat fragmentation, identification of those ecological characteristics that render some species more vulnerable to fragmentation than others is vital for understanding, predicting and mitigating the effects of habitat alteration on biodiversity. We compare hypotheses on the causes of interspecific differences in fragmentation sensitivity using distribution and abundance data collected on 23 species of Neotropical bats.
Bats were captured over a 2‐year period on 11 land‐bridge islands in Gatún Lake, Panama, and on the adjacent mainland. We derived a series of explanatory variables from our capture data and from the literature: (1) natural abundance in continuous forest, (2) body mass, (3) trophic level, (4) dietary specialization, (5) vertical stratification, (6) edge‐sensitivity, (7) mobility, (8) wing morphology (aspect ratio and relative wing loading) and (9) ecologically scaled landscape indices (ESLIs). After phylogenetic correction, these variables were used separately and in combination to assess their association with two indices of fragmentation sensitivity, species prevalence (proportion of islands occupied) as well as an index of change in abundance.
Model selection based on Akaike's information criterion identified edge‐sensitivity as the best correlate of vulnerability to fragmentation. Natural abundance and mobility or traits linked to mobility (relative wing loading and ESLI) received limited support as predictors. Vulnerability of gleaning animalivorous bats is probably caused by a combination of these traits.
Synthesis and applications. Our findings emphasize the importance of a local‐scale approach in developing predictive models of species fragmentation sensitivity and indicate that risk assessments of Neotropical bats could be based on species tolerance to habitat edges and mobility‐related traits. We suggest that, in order to be effective, management efforts should aim to minimize the amount of edge‐habitat and reduce the degree of fragment‐matrix contrast. Moreover, if high bat diversity is to be preserved in fragmented Neotropical landscapes, conservation measures regarding reserve design should assure spatial proximity to source populations in larger tracts of continuous forest and a low degree of remnant isolation.
Indicators for biodiversity in agricultural landscapes: a pan‐European study
Authors: Billeter R. , Liira J. , Bailey D. , Bugter R. , Arens P. , Augenstein I. , Aviron S. , Baudry J. , Bukacek R. , Burel F. , Cerny M. , De Blust G. , De Cock R. , Diekötter T. , Dietz H. , Dirksen J. , Dormann C. , Durka W. , Frenzel M. , Hamersky R. , Hendrickx F. , Herzog F. , Klotz S. , Koolstra B. , Lausch A. , Le Coeur D. , Maelfait J. P. , Opdam P. , Roubalova M. , Schermann A. , Schermann N. , Schmidt T. , Schweiger O. , Smulders M.J.M. , Speelmans M. , Simova P. , Verboom J. , Van Wingerden W.K.R.E. , Zobel M. , Edwards P.J. 
Published: October 2007

Summary

In many European agricultural landscapes, species richness is declining considerably. Studies performed at a very large spatial scale are helpful in understanding the reasons for this decline and as a basis for guiding policy. In a unique, large‐scale study of 25 agricultural landscapes in seven European countries, we investigated relationships between species richness in several taxa, and the links between biodiversity and landscape structure and management.
We estimated the total species richness of vascular plants, birds and five arthropod groups in each 16‐km2 landscape, and recorded various measures of both landscape structure and intensity of agricultural land use. We studied correlations between taxonomic groups and the effects of landscape and land‐use parameters on the number of species in different taxonomic groups. Our statistical approach also accounted for regional variation in species richness unrelated to landscape or land‐use factors.
The results reveal strong geographical trends in species richness in all taxonomic groups. No single species group emerged as a good predictor of all other species groups. Species richness of all groups increased with the area of semi‐natural habitats in the landscape. Species richness of birds and vascular plants was negatively associated with fertilizer use.
Synthesis and applications. We conclude that indicator taxa are unlikely to provide an effective means of predicting biodiversity at a large spatial scale, especially where there is large biogeographical variation in species richness. However, a small list of landscape and land‐use parameters can be used in agricultural landscapes to infer large‐scale patterns of species richness. Our results suggest that to halt the loss of biodiversity in these landscapes, it is important to preserve and, if possible, increase the area of semi‐natural habitat.
Experimental or precautionary? Adaptive management over a range of time horizons
Authors: Hauser Cindy E , Possingham Hugh P 
Published: October 2007

SummaryMany studies of adaptive harvest management already exist in the literature, but most (if not all) use long, sometimes infinite, time horizons. Such long‐term objectives provide an opportunity to manage experimentally, so that poorly understood dynamics are learned and any returns sacrificed for experimentation are repaid by improved management over the remaining time horizon.However, a manager is unlikely to weight outcomes in the distant future equally against outcomes in the present. Furthermore, the most appropriate model of system dynamics may not remain constant over the time‐frame required to experiment, learn and improve management. In these cases the use of discounting and/or a finite time horizon fit the manager's assumptions and goals more effectively, and the value of experimentation is likely to be diminished.In this paper we construct a simple model of a hypothetical population and compare optimal passive and active adaptive harvest strategies over a range of time horizons. This allows us to determine the optimal level of experimentation for short‐, medium‐ and long‐term goals.We discover that the optimal active adaptive harvest strategy may be precautionary over short to medium time horizons, rather than experimental. That is, an action with known moderate benefits is preferred over an action with uncertain but marginally larger expected benefits. This runs counter to the widespread assumption in the adaptive management literature that incorporating learning into an optimization of management will encourage experimentation.Synthesis and applications. The general results of this paper have potential application to any environmental management problem where adaptive management might be applied; for example, conservation, pest control, harvesting and management of water flows. We examine adaptive management over a range of finite time horizons to reflect a variety of possible management goals and assumptions. Our simple example demonstrates that in the face of model uncertainty, the management strategy that maximizes benefits does not necessarily include deliberate experimentation and learning. Optimal active adaptive management weighs experimentation against all its potential consequences, and this can yield a precautionary approach.