bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships between carbon turnover and bioavailable energy fluxes in two temperate forest soils
Authors: CURRIE WILLIAM S. 
Published: May 2003

AbstractRecent research has shown that the broad empirical relationships used in many ecosystem models to predict carbon turnover and stabilization in soils can fail to capture differences across vegetation types or climates. Theoretically, because energy flow is fundamental to the function of decomposer organisms and ecosystems, energetics could provide complimentary fundamental constraints on soil C dynamics. Often, however, C is considered as a surrogate for energy in studies of detrital decay and C turnover in soil. Bomb calorimetry has long been used to measure stored energy in organic matter, but in detritus not all of the energy is bioavailable. Here I outline an approach to quantify the flux of bioavailable energy dissipated by resident heterotrophic communities in soil organic horizonsin situ. I used the principle of energy balance together with a biogeochemical process model parameterized through calorimetric analysis of field samples. I also tested relationships between C and energy across samples of forest detritus (foliar and fine root litter, well‐decayed Oea material, and woody debris), across decay stages, and between a deciduous and coniferous forest at the Harvard Forest, MA, USA. As a first approximation, energy and C concentrations were closely related (within ca. 10%), as were ratios of heterotrophic energy dissipation to C mineralization across types of detritus (within 16%). Differences in energy content and energy : C ratios were measurable in forest detritus (particularly woody vs nonwoody), but did not vary reliably enough between forest types or through detrital stages to indicate that soil C models could be improved by including energetics. Model results indicated that there are strong similarities in energy flows and storage in the O horizons of the contrasting forest types studied at this location. Future research could focus on broader patterns across climates or biomes.
The input and fate of new C in two forest soils under elevated CO2
Authors: HAGEDORN FRANK , SPINNLER DIETER , BUNDT MAYA , BLASER PETER , SIEGWOLF ROLF 
Published: May 2003

AbstractThe aim of this study was to estimate (i) the influence of different soil types on the net input of new C into soils under CO2 enrichment and (ii) the stability and fate of these new C inputs in soils. We exposed young beech–spruce model ecosystems on an acidic loam and calcareous sand for 4 years to elevated CO2. The added CO2 was depleted in 13C, allowing to trace new C inputs in the plant–soil system. We measured CO2‐derived new C in soil C pools fractionated into particle sizes and monitored respiration as well as leaching of this new C during incubation for 1 year. Soil type played a crucial role in the partitioning of C. The net input of new C into soils under elevated CO2 was about 75% greater in the acidic loam than in the calcareous sand, despite a 100% and a 45% greater above‐ and below‐ground biomass on the calcareous sand. This was most likely caused by a higher turnover of C in the calcareous sand as indicated by 30% higher losses of new C from the calcareous sand than from the acidic loam during incubation. Therefore, soil properties determining stabilization of soil C were apparently more important for the accumulation of C in soils than tree productivity. Soil fractionation revealed that about 60% of the CO2‐derived new soil C was incorporated into sand fractions. Low natural 13C abundance and wide C/N ratios show that sand fractions comprise little decomposed organic matter. Consistently, incubation indicated that new soil C was preferentially respired as CO2. During the first month, evolved CO2 consisted to 40–55% of new C, whereas the fraction of new C in bulk soil C was 15–23% only. Leaching of DOC accounted for 8–23% of the total losses of new soil C. The overall effects of CO2 enrichment on soil C were small in both soils, although tree growth increased significantly on the calcareous sand. Our results suggest that the potential of soils for C sequestration is limited, because only a small fraction of new C inputs into soils will become long‐term soil C.
Spatial variation in regional CO2 exchange for the Kuparuk River Basin, Alaska over the summer growing season
Authors: VOURLITIS GEORGE L. , VERFAILLIE JOSEPH , OECHEL WALTER C. , HOPE ALLEN , STOW DOUGLAS , ENGSTROM RYAN 
Published: May 2003

AbstractThe spatial and temporal patterns in CO2 flux for the Kuparuk River Basin, a 9200‐km2 watershed located in NE Alaska were estimated using the Regional Arctic CO2 Exchange Simulator (RACES) for the 1994–1995 growing seasons. RACES uses non‐linear models and a Geographical Information System database (GIS) consisting of the normalized difference vegetation index (NDVI) and dynamic temperature and radiation maps. The spatial and temporal patterns in the NDVI during both growing seasons suggest that ecosystem development occurred 2–4 weeks earlier and was relatively more rapid in the southern portion of the Kuparuk River Basin. Rates of gross primary production (GPP) and whole‐ecosystem respiration (R) were 2–4 fold higher in the southern basin than along the arctic coastal plain depending on time of year. The higher rate of GPP estimated for the southern basin was primarily due to higher NDVI values, while the higher R estimated for the southern basin was due in part to higher temperature and the NDVI. While GPP and R showed strong latitudinal trends, spatial and temporal trends in net ecosystem CO2 exchange (NEE) were much more variable. Thus, while spatial trends in carbon gain (GPP) and loss (R) were highly correlated, small spatial and temporal differences in these large fluxes (GPP and/or R) lead to corresponding large spatial variations in the NEE.
Seasonal changes in the effects of elevated CO2 on rice at three levels of nitrogen supply: a free air CO2 enrichment (FACE) experiment
Authors: KIM HAN‐YONG , LIEFFERING MARK , KOBAYASHI KAZUHIKO , OKADA MASUMI , MIURA SHU 
Published: May 2003

AbstractOver time, the stimulative effect of elevated CO2 on the photosynthesis of rice crops is likely to be reduced with increasing duration of CO2 exposure, but the resultant effects on crop productivity remain unclear. To investigate seasonal changes in the effect of elevated CO2 on the growth of rice (Oryza sativa L.) crops, a free air CO2 enrichment (FACE) experiment was conducted at Shizukuishi, Iwate, Japan in 1998–2000. The target CO2 concentration of the FACE plots was 200 µmol mol−1 above that of ambient. Three levels of nitrogen (N) were supplied: low (LN, 4 g N m−2), medium [MN, 8 (1998) and 9 (1999, 2000) g N m−2] and high N (HN, 12 and 15 g N m−2). For MN and HN but not for LN, elevated CO2 increased tiller number at panicle initiation (PI) but this positive response decreased with crop development. As a result, the response of green leaf area index (GLAI) to elevated CO2 greatly varied with development, showing positive responses during vegetative stages and negative responses after PI. Elevated CO2 decreased leaf N concentration over the season, except during early stage of development. For MN crops, total biomass increased with elevated CO2, but the response declined linearly with development, with average increases of 32, 28, 21, 15 and 12% at tillering, PI, anthesis, mid‐ripening and grain maturity, respectively. This decline is likely to be due to decreases in the positive effects of elevated CO2 on canopy photosynthesis because of reductions in both GLAI and leaf N. Up to PI, LN‐crops tended to have a lower response to elevated CO2 than MN‐ and HN‐crops, though by final harvest the total biomass response was similar for all N levels. For MN‐ and HN‐crops, the positive response of grain yield (ca. 15%) to elevated CO2 was slightly greater than the response of final total biomass while for LN‐crops it was less. We conclude that most of the seasonal changes in crop response to elevated CO2 are directly or indirectly associated with N uptake.
Changing Childbirth: a pilot project
Authors: Hicks Carolyn , Spurgeon Peter , Barwell Fred 
Published: June 2003

Objective. To compare the outcomes of an adapted pilot Changing Childbirth initiative providing continuity of care by a group of known midwives with traditional maternity care. Design. Between‐groups trial to compare levels of satisfaction and clinical outcomes for two groups of women, cared for either under this Changing Childbirth scheme or the traditional model of care. Method. Of the 200 women who agreed to participate in the project, 100 were randomly allocated to the pilot scheme and 100 to the traditional care package. During the postpartum period, information was collected via a questionnaire about participants’ levels of satisfaction with a variety of aspects of care provided during the antenatal, delivery and postpartum periods. Data about clinical outcomes for the two groups were also obtained. Results. Women in the pilot group had significantly more continuity of care throughout each of the three periods, were generally more satisfied with their care, felt that they had more choice over a variety of aspects of care and experienced no compromise in clinical outcomes (P = 0·05 or less in each case). Implications for practice. Many previous attempts to introduce the Changing Childbirth initiative have revealed significant problems, particularly with regard to the continuity of carer requirement. Taking account of local health care needs and existing provision, the present study adapted this concept to continuity of care. This did not apparently affect any of the guiding principles contained in the original document, and yet enhanced satisfaction. It would appear that the Changing Childbirth agenda can be adapted and integrated with local health care situations without sacrificing any of the overarching principles.
Sexual harassment of nurses and nursing students
Authors: Bronner Gila , Peretz Chava , Ehrenfeld Mally 
Published: June 2003

Background. Nursing has dealt with sexual harassment long before the term was coined during the 1970s. The current study investigated sexual harassment of nurses and nursing students in Israel following new legislation against sexual harassment in the workplace. Methods. A self‐report questionnaire was administered to 281 nurses and 206 nursing students (80% women) from five medical centres in Israel. Seven types of sexual harassment behaviour patterns were evaluated. Findings. Frequency of sexual harassment decreased as the behaviour became more intimate and offensive. Ninety percent of subjects reported experiencing at least one type of sexual harassment and 30% described at least four types. A significant difference was found between nurses and nursing students. Furthermore, ‘severe’ types of behaviour were experienced by 33% of nurses, in comparison with 23% of nursing students. Women were significantly more exposed than men to ‘mild’ and ‘moderate’ types of sexual harassment, while 35% of men vs. 26% of women were exposed to ‘severe’ types of harassment. However, women responded significantly more assertively than men to ‘severe’ sexual harassment. Conclusions. Particular attention is needed when sexual harassment occurs to male students and nurses because they may be subjected to the more offensive sexual conducts and at the same time may lack the ability to respond assertively.
Reducing the density of breeding gulls influences the pattern of recruitment of immature Atlantic puffinsFratercula arcticato a breeding colony
Authors: Finney S. K. , Harris M. P. , Keller L. F. , Elston D. A. , Monaghan P. , Wanless S. 
Published: June 2003

SummaryBy acting as both competitors and predators, gulls (Larusspp.) are generally considered to reduce significantly the attractiveness of potential breeding sites for other birds. This perceived threat posed by gulls to other breeding birds has led to the implementation of gull control procedures at many seabird colonies. However, the extent to which reducing gull numbers benefits other species has received little rigorous scientific investigation.During a gull control programme (1972–89), gull nest density on the Isle of May, south‐east Scotland, was reduced by between 30% and 100% in different sections of the island. Following termination of the original programme in 1989, several sections were maintained as gull‐free by repeated removal of nests.We used data collected over a 23‐year period to determine the extent to which the spatial variation in puffinFratercula arcticarecruitment was influenced by changes in the density and spatial distribution of breeding gulls resulting from the control programme.The presence of breeding gulls significantly affected the pattern of recruitment of puffins to the colony. Puffin recruitment rate was highest in the sections of the island where gull nest density was low. Gull density explained 21% of the variation in puffin recruitment rate.These results suggest that the reduction in the number of breeding gulls substantially increased the attractiveness of areas of the colony as breeding sites for puffins, and is thus likely to have played an important role in the pattern of expansion of the puffin population on the island.Synthesis and applications.Following a recent increase in the conservation status of both herringL. argentatusand lesser black‐backed gullsL. fuscus, there has been a move to make management decisions more objective. This has highlighted the need for studies such as this, aimed at assessing the impact of gulls and their removal on other breeding birds, to ensure that any future control programmes are both necessary and effective.
Population dynamics in European hare: breeding parameters and sustainable harvest rates
Authors: Marboutin E. , Bray Y. , Péroux R. , Mauvy B. , Lartiges A. 
Published: June 2003

Summary

Hares are considered to be a valuable game species in most European countries. Hunting needs to be sustainable and sound management of hare populations requires some knowledge of the species’ demographic variability, especially regarding the breeding output, which is highly time‐ and space‐dependent and may govern the population size and exploitability.
Using shooting bag analysis and placental scar counts, mean fecundity and leveret survival were estimated at four study sites with contrasting hare numbers and density trends. These demographic parameters, harvest rates and adult natural survival rates (from the literature) were incorporated into a matrix projection model to analyse the population growth rate (λ) sensitivity and to derive indices of sustainable harvest rate (ISHR, i.e. rates compatible with λ≥ 1).
The age structure comprised 48–69% young; fecundity varied between 12·2 and 15·0 leverets per breeding female; and 85–100% of adult females bred. These data combined gave a birth‐to‐autumn leveret survival index of 0·14–0·29 and, when loaded into the matrix model, resulted in simulated λs that matched the density changes observed in the study areas. The model structure, although simple, accounted for most of the relevant biological information.
ISHR was 30% when derived iteratively as a function of mean values of those parameters with largest elasticities (leveret survival and doe fecundity). When environmental and demographic stochasticity were included in the model, the proportion of endangered trajectories where the density threshold was < 1 km2 over 50 km2 varied sharply, with small changes in harvest rate or initial population size. Small populations could only sustain ≤ 20% harvest rates.
Demographic parameters derived from killed animals during year t can be used a posteriori to understand the species’ dynamics and as a baseline to modulate the shooting scheme in year t+ 1. An actual sustainable shooting scheme would require an additional real‐time local process that, automatically, would take all sources of change in numbers into account. A two‐stage management strategy (e.g. first computing a catch‐effort estimator of population size based on numbers killed very early in the shooting period, then defining flexible harvest quotas) would help managers to cope with the unpredictable dynamics of the species and resulting fluctuations in hare numbers.
Synthesis and applications. The results of this exploratory study suggest that sustainable shooting of hares is possible provided some local data about their dynamics are available and slightly conservative quotas are used. Modelling approaches have potential in assessing the latter, but also as a check on the coherence of the estimates of the former (comparison of observed and modelled λ).
Changes in the rhizome system of bracken subjected to long‐term experimental treatment
Authors: Duc M. G. LE , Pakeman R. J. , Marrs R. H. 
Published: June 2003

Summary

Bracken Pteridium aquilinum is a serious weed of upland and marginal land. Its extensive rhizome system and large carbohydrate reserves make control difficult. This paper reports the results of seven long‐term experiments, established in four diverse UK locations, to test control and vegetation restoration treatments.
Samples were obtained from 580 rhizome pits between 1998 and 2000. Total dry mass per unit area (M, a measure of performance) and ratio of frond‐bearing to total rhizome dry mass (R, a relative measure of investment in frond production) were measured.
The range of means for M in untreated bracken was 1·8–5·1 kg m−2, greater than that reported by others (1·2–3·0 kg m−2). Measured values for R were 0·24–0·42, again differing from other reports (0·10–0·38), probably due to our policy of avoiding advancing bracken fronts.
Randomization tests were used to check for non‐independence of sampling units. They confirmed the general adequacy of the anova results; there was little detectable interference between plots. Two regions contained matching pairs of experiments, thus variation within region was tested and differences were found in one region.
Five bracken control treatments (cutting, herbicide application and combinations) were employed at all but one experiment. Cutting once or twice per year generally gave the best results, reducing M by c. 60% after ≤ 5 years. Some subtreatments designed mainly for vegetation restoration, notably surface disturbance, also affected M.
R was reduced by herbicide treatment, for example from 0·30 to 0·16. Such low values of R are typical of invading bracken and are thought to represent rejuvenated and invasive rhizomes. Follow‐up treatments are needed in such situations. Despite large differences between untreated M at matching experiments on Cannock Chase (Staffordshire), treatment effects were similar at both sites (cutting twice per year or cutting together with herbicide application were best). At Sourhope (Cheviot Hills) a different pattern of response was obtained, with cutting alone giving better results than treatments involving herbicide.
The ratio of rhizome to frond dry mass per unit area was 10 : 1 in good conditions for growth, but the proportionate size of rhizomes could be reduced in poor growing conditions such as wet summers.
Synthesis and applications. In order to develop a national control strategy the following must be considered: rhizome mass differs between sites and in response to control treatments; cutting twice per year is generally most effective; where cutting is impossible, herbicide treatment should be applied. Weather may affect rhizome mass, with wet years being detrimental. This raises the possibility that bracken may increase under the drier conditions that may occur with global warming.
Independent evolution of migration on the South American landscape in a long‐distance temperate‐tropical migratory bird, Swainson's flycatcher (Myiarchus swainsoni)
Authors: Joseph Leo , Wilke Thomas , Alpers Deryn 
Published: May 2003

AbstractAim  To understand the evolution of long‐distance temperate–tropical migration in a South American bird, Swainson's flycatcher (Myiarchus swainsoni).Methods  A total of 842 base pairs of the mitochondrial DNA genes ATPase 8 and 6 were sequenced from forty‐nine individuals of the M. swainsoni complex from most of its range. Analyses measured the phylogenetic signal in the data, and tools of population genetics, phylogeography and phylogeny were used to interpret the evolution of the bird and its migration on the South American landscape.Results  Migratory populations in the M. swainsoni complex are not each other's closest relatives. The migratory subspecies M. s. swainsoni, which breeds in south‐eastern South America, is not closely related to the rest of the complex. The remaining migratory populations of the subspecies M. s. ferocior and two intergrade populations are extremely closely related to non‐migratory populations with which they form a well‐supported clade despite substantial morphological differentiation from each other. Within this clade of migrants and non‐migrants, net divergence across 4000 km of lowland South America is zero and most diversity is distributed among individuals not populations. Mismatch analyses and significant values of Tajima's D and Fu's Fs suggest the clade has undergone a very recent range expansion. Migration and the shifts of breeding distribution that accompanied its evolution evolved twice within what has recently been considered the polytypic species M. swainsoni. Furthermore, these shifts of range probably occurred at very different times as parts of different southward ‘pulses’ of humid, Amazonian taxa.Main conclusions  Evolution of temperate‐tropical migration in the M. swainsoni complex has been spatio‐temporally layered on the South American landscape. The analysis cautions that the historical biogeography underlying a single present‐day migration system need not have been driven by a single set of environmental factors operating at one time. We suggest directions for further study of ecology and demography in zones of apparent contact between various migratory and non‐migratory populations.
Critique of parsimony analysis of endemicity as a method of historical biogeography
Authors: Brooks Daniel R. , Van Veller Marco G. P. 
Published: May 2003

AbstractAim Assess the value of parsimony analysis of endemism as either ana priori(cladistic) and ana posteriori(phylogenetic) method of historical biogeography.Location World‐wide.Methods Parsimony analysis of endemicity (PAE) and Brooks parsimony analysis (BPA).Results Parsimony analysis of endemicity is capable of finding correct and unambiguous area relationships only under scenarios of vicariance in combination with non‐response to vicariance or extinction. An empirical comparison between PAE and BPA, using the poeciliid fish generaHeterandriaandXiphophorus, demonstrates that PAE fails to document much of the historical complexity in this relatively simple system.Main conclusions Thea prioriassumptions of PAE are far more restrictive than those made by othera priorimethods, limiting its utility as a method of cladistic biogeography. The inability of PAE to detect perfect vicariance or biogeographical histories involving dispersal, renders it unsuitable as a method of phylogenetic biogeography.