bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and analysis of peatlands as dynamical systems
Authors: Hilbert David W. , Roulet Nigel , Moore Tim 
Published: March 2003

Summary 1 A general model of peatland dynamics is presented that emphasizes the interaction between water table depth and peat production. The model consists of two coupled, non‐linear differential equations representing change in depth of peat and depth to the water table. Several simplified models are also considered to show the logical development of this model from previously published ones. The model provides an integrated view of how peatlands function over long time scales, by focusing on the non‐linear interactions among peat production, decomposition and hydrology. 2 Analysis of the model shows that equilibrium peat accumulation and water table depth depend on the net water input to the peatland. In drier sites, peatlands with relatively deep water tables develop and the equilibrium peat depth increases with increasing water input. In very wet conditions, peatlands have water tables near the surface, peat accumulation is limited by low production rates, and equilibrium peat depth is lower than is possible in comparatively drier sites. Over a range of intermediate water balances, there are two simultaneous equilibrium states where deep, dry peatlands and shallower, wet peatlands can both occur. This sensitivity to water balance suggests that small changes in precipitation regime, such as are expected with climate variability and change, could rapidly convert peatlands that are now in equilibrium into either sources or sinks of carbon.
Short‐term effects of cyclone impact and long‐term recovery of tropical rain forest on Kolombangara, Solomon Islands
Authors: Burslem D. F. R. P. , Whitmore T. C. , Brown G. C. 
Published: March 2003

Summary1 We evaluate the effects of large‐scale disturbance on tropical tree communities by examining the population dynamics of all individuals > 4.9 cm in diameter at breast height (d.b.h.) of 12 tree species over 30 years (1964–94) in lowland tropical rain forest on Kolombangara, Solomon Islands.2 During the study period Kolombangara was struck by four cyclones between 1967 and 1970. The last cyclone caused most damage to canopy structure. Mortality in the 6‐month interval spanning the first cyclone was 7.0% of all trees, while mean annual mortality for all other intervals (including those spanning other cyclones) was 1.4–2.2% year−1. Mortality varied between species but was independent of topography and geographical location.3 Recruitment increased from very low rates (median 0.0% year−1) before the first cyclone to median values of 1.6–3.2% year−1during 1971–79, i.e. following a lag period of 3.5–8 years after the first cyclone. Recruitment rates were higher on plots showing greater mortality rates during this cyclone. Recruitment and mortality rates were still higher in 1994 than they had been before the 1967–70 cyclones.4 Mean annual mortality rates were positively correlated with mean annual recruitment rates across species. This relationship reflects a continuum of life‐history characteristics and contributes to constancy in the relative abundance of the 12 species when the same sets of plots are compared over all measurement intervals up to 30 years.5 We conclude that cyclone impacts have only short‐term effects on the relative abundance of common tree species on Kolombangara, and do not therefore prevent the establishment of an equilibrium rank abundance hierarchy or create spatial variation in tree species composition. Differences in forest composition across Kolombangara are more likely to have been caused by differential anthropogenic disturbance linked to settlement patterns.
Effects of elevated carbon dioxide and increased nitrogen deposition on bog vegetation in the Netherlands
Authors: Heijmans Monique M. P. D. , Berendse Frank , Arp Wim J. , Masselink Ab K. , Klees Herman , De Visser Willem , Van Breemen Nico 
Published: March 2003

Summary We studied the effects of elevated atmospheric CO2and increased N deposition on the plant species composition of aSphagnum‐dominated bog ecosystem in the Netherlands. Large peat monoliths (surface area 1 m2, depth 0.6 m) with intact bog vegetation were kept outdoors in large containers and were exposed to elevated CO2or increased N deposition for three growing seasons. Elevated CO2conditions (target concentration 560 µmol CO2 mol−1) were created using MiniFACE technology. In a separate experiment, N deposition was increased by 5 g N m−2year−1by adding dissolved NH4NO3at 3 week intervals during the growing season. Elevated atmospheric CO2increased height growth ofSphagnum magellanicum, the dominantSphagnumspecies, in the second and third growing seasons. Vascular plant biomass was not significantly affected by elevated CO2, but growth of species growing close to the moss surface was influenced negatively by the increasedSphagnumheight growth. Elevated CO2did not change allocation to below‐ground plant parts. Adding N increased above‐ground vascular plant biomass. The shallow‐rooted speciesVaccinium oxycoccusresponded most to the increased N deposition.Sphagnumgrowth was significantly reduced in the third growing season. This reduction was likely the result of the increased vascular plant cover, given the observed negative relation between vascular plant cover andSphagnumgrowth. The observed shifts in species composition as a result of species‐specific responses to treatments, and interactions between peat mosses and vascular plants will have important consequences for the sequestration of carbon in the bog ecosystem.
Competitive effects of grasses and woody plants in mixed‐grass prairie
Authors: Peltzer Duane A. , Köchy Martin 
Published: March 2003

Summary Variation in the competitive ability of plant species may determine their persistence and abundance in communities. We quantified the competitive effects of grasses and woody plants in native mixed‐grass prairie on the performance of transplant species and on resources. We separated the effects of grasses, shrubs and intact vegetation containing both grasses and shrubs by manipulating the natural vegetation using selective herbicides to create four neighbourhood treatments: no neighbours (NN), no shrubs (NS), no grasses (NG) and all neighbours (AN). Treatments were applied to 2 × 2 m experimental plots located in either grass‐ or shrub‐dominated habitats. The effects of grasses and shrubs on resource availability (light, soil moisture, soil available nitrogen) and on the growth of transplants ofBouteloua gracilis, a perennial tussock grass, andElaeagnus commutata, a common shrub, were measured over two growing seasons. Resource availability was two‐ to fivefold higher in no neighbour (NN) plots than in vegetated plots (NS, NG, AN) with grasses and shrubs having similar effects. Light penetration declined linearly with increasing grass or shrub biomass, to a minimum of about 30% incident light at 500 g m−2shoot mass. Soil resources did not decline with increasing neighbour shoot or root mass for either grasses or shrubs, suggesting that the presence of neighbours was more important than their abundance. Transplant growth was significantly suppressed by the presence of neighbours, but not by increasing neighbour shoot or root biomass, except for a linear decline inBoutelouagrowth with increasing neighbour shoot mass in plots containing only shrubs. Competition intensity, calculated as the reduction in transplant growth by neighbours, was similar in both grass‐ and shrub‐dominated habitats for transplants ofBouteloua, but was less intense in shrub‐dominated habitats for the shrubElaeagnus. Variation in the persistence and abundance of plants in communities may therefore be more strongly controlled by variation in the competitive effects exerted by neighbours than by differences in competitive response ability.
Grazing history versus current grazing: leaf demography and compensatory growth of three alpine plants in response to a native herbivore (Ochotona collaris)
Authors: McIntire Eliot J. B. , Hik David S. 
Published: March 2003

Summary1 We measured leaf births, leaf deaths and leaf length of three alpine perennial species, Kobresia myosuroides, Erigeron humilis and Oxytropis nigrescens, from sites with different grazing histories (strong or weak) in response to two levels of current season grazing (present or absent) by collared pikas (Ochotona collaris), a small lagomorph, in the south‐west Yukon.2 All three species appeared to tolerate the removal of 58–61% of summer leaf production under natural conditions. Grazing history, which was defined by the location of plants located either < 2 m or > 6 m from boulderfields with a history of occupation by pikas, was the most significant factor determining shifts in leaf births and leaf deaths following herbivory.3 The only detectable influence of current season herbivory for any measured species was a reduction of leaf length of Kobresia.4 A comparison of historically grazed with historically ungrazed plants indicated several changes in leaf demography and morphology. Kobresia leaves were generally shorter and had higher rates of production of new leaves. Oxytropis had higher rates of new leaf production. Erigeron had fewer leaf births throughout the summer, but showed a large and highly significant delay in the timing of leaf senescence.5 These responses can be largely understood as strategies to avoid the predictable intensive late season foraging that is characteristic of pikas. Morphological mechanisms allow these species to tolerate and, more importantly for the herbivore, persist under heavy and chronic grazing.
Pinus sylvestris treeline development and movement on the Kola Peninsula of Russia: pollen and stomate evidence
Authors: Gervais Bruce R. , MacDonald Glen M. , Snyder Jeffrey A. , Kremenetski Constantine V. 
Published: March 2003

Summary

A sediment core recovered from Poteryanny Zub Lake on the Kola Peninsula of Russia (68°48′91″ N, 35°19′32″ E) provides fossil pollen and stomate evidence for Pinus sylvestris treeline development and movement. The site today lies in birch forest tundra, approximately 25 km north of the pine treeline and 90 km south of the Murman Coast.
The record begins approximately 10 050 14C years before present (bp). The post‐glacial tundra, typified by various herbaceous taxa and Artemisia, was followed by Betula‐dominated woodland forest with Polypodiaceae‐Gramineae pollen types. Such vegetation assemblages are not analogous to any in the western Kola Peninsula today.
Stomate evidence demonstrates that Pinus sylvestris immigrated to the study site as early as 8150 14C bp. Pine forest probably expanded northwards from sparse or small disjunct populations, which established c. 1000 14C bp before the expansion evident in the pollen and wood macrofossil records (7200 14C bp). Betula and other shrub and herb taxa declined at this time, possibly as a result of shading by the pine canopy.
The presence of fossil Pinus sylvestris stomates and wood, together with AP : NAP ratios, indicates that the pine treeline was some 100 km north of its present position by the end of the middle Holocene warming (7000–6000 14C bp). This places it near the Barents Sea coast, currently tundra vegetation. An approximate 2 °C increase in regional summer temperatures would be necessary to move the treeline to the present‐day coastline.
From 6000 14C bp the pine treeline gradually retreated southward to its present modern position. Birch woodland has grown at the site since c. 3000 14C bp.
Tree‐life history prior to death: two fungal root pathogens affect tree‐ring growth differently
Authors: Cherubini Paolo , Fontana Giovanni , Rigling Daniel , Dobbertin Matthias , Brang Peter , Innes John L. 
Published: March 2003

Summary

This paper assesses whether tree‐ring patterns found in recently dead mountain pines (Pinus mugo Turra) infected by Armillaria spp. differ from those infected by Heterobasidion annosum, and determines whether and to what extent tree rings may be used as indicators of tree‐decline history (i.e. tree health conditions in relation to disease history) prior to death.
Dendroecological and phytopathological analyses were undertaken in the Swiss National Park. The calendar year of death of the standing dead trees was determined by cross‐dating ring‐width patterns of dead trees to reference chronologies from living trees. This procedure is not, however, exact as there may be multiple intermittent missing rings.
A remarkable discrepancy (up to 31 years) was found between the tree‐death year estimated through crown condition assessment (i.e. the presence or lack of green needles) and the date of the outermost tree ring (when tree‐ring production ceased). New needles may form and existing ones remain green for some years after the cambium at different heights along the stem has ceased activity and no new wood cells are being formed.
Ring‐patterns in trees infected by Armillaria differ from those in trees infected by H. annosum. All dead trees infected by Armillaria had a slow growth decrease indicating suppression for several decades, and suggesting that Armillaria attacked trees that were already weakened by competition. In contrast, trees infected by H. annosum died over a very short period of time, although they may have been infected a long time previously. Nevertheless H. annosum seems to infect and kill trees directly , whereas Armillaria, at this site, is a secondary pathogen.
This study demonstrates that tree rings may be used as indicators of the history of tree decline prior to tree death. However, the history of tree disease is difficult to reconstruct fully, e.g. tree rings do not enable the onset of infection to be dated.
Habitat configuration, species traits and plant distributions
Authors: Dupré Cecilia , Ehrlén Johan 
Published: March 2003

SummaryIn a metapopulation context, the distribution of a species in a patchy landscape is interpreted as the equilibrium outcome of extinction and colonization processes. Populations are thus more likely to occur in larger, better connected habitat fragments.To test whether metapopulation models explain distribution patterns of plant species with different life histories we investigated the incidence of herbaceous species in deciduous forests in four provinces of south Sweden.These data were correlated with habitat quality (soil pH, nitrogen mineralization and organic matter) and habitat configuration (patch area and distance to the nearest deciduous forest patch). We also examined whether habitat configuration affected the distribution of species with different life history attributes.All ground layer plant species at 81 sites were recorded, and distribution patterns of 57 species were tested against seed mass, seed number, presence of a seed bank, plant height, life span, mode of pollination, dispersal mode and habitat preference.Habitat quality, especially pH, was more important for the incidence of species than habitat configuration with patch area and isolation significantly affecting only 11 and four species, respectively. Species favoured by larger area were also disadvantaged by greater isolation.The importance of habitat configuration to a species varied with life history. Species that were more negatively affected by patch isolation tended to be habitat specialists and clonal perennials and to produce fewer seeds. Animal‐dispersed species were more negatively affected by small stand size.Habitat configuration may be less important for vascular plant distributions than habitat quality or the effects of land use history.
Effects of plant size on reproductive output and offspring performance in the facultative biennial Digitalis purpurea
Authors: Sletvold Nina 
Published: March 2003

Summary

Monocarpy in facultative biennials can be favoured by selection when there is a more than proportional increase in fitness with size. The possible contributions of larger reproductive output and higher offspring quality to such an increase were investigated in the facultative biennial plant Digitalis purpurea. Straw mass (rosette leaves and flowering stem excluding fruits and seeds) was determined for 100 individuals of varying size and correlated with the number of flowers and seeds per flower to examine whether sex‐allocation is size dependent.
To determine whether maternal size influences offspring growth, and whether this effect is more pronounced in the presence of competition, seeds from 32 maternal plants were grown alone, and with one, two or four competitors.
Total seed number increased proportionally with size. Seed quality, measured as seed size, germination percentage and speed also increased with maternal size. The combined fitness measures of total seed mass (seed number × seed size), number of seedlings (seed number × germination percentage) and total female fitness (seed number × germination percentage × mean offspring dry mass after 14 weeks) all increased disproportionally with size.
Sex‐allocation was size dependent, with large plants emphasizing the female function.
Offspring dry mass after both 8 and 14 weeks of growth was strongly influenced by competition, whereas the effect of maternal size was significant only at the first harvest date. Competition did not accentuate the effects of maternal size.
The results support that monocarpy exists in D. purpurea because of increased offspring quality rather than a disproportionate advantage in seed output of large individuals.
Comparative dispersal effectiveness of wigeongrass seeds by waterfowl wintering in south‐west Spain: quantitative and qualitative aspects
Authors: Figuerola Jordi , Green Andy J. , Santamaría Luis 
Published: March 2003

Summary

The effectiveness of a seed disperser depends on the quantity of seed dispersed and the quality of dispersal provided to each seed. Relationships between the quantity and quality components and their dependence on characteristics of the dispersers remain largely uninvestigated.
The effectiveness of different waterfowl species at dispersing seeds of Ruppia maritima was evaluated in a wetland in south‐west Spain. Droppings were collected during autumn and spring waterfowl migrations and the number of seeds ingested (estimated from seed fragments), undigested and viable in germination trials were determined.
Ingestion by waterfowl enhanced the rate of germination and, for several duck species, it also had a positive effect on germinability. Both the presence of seeds in the diet and the effects of gut passage showed high interspecific and temporal variance. Some of the interspecific variation in dispersal quality was related to gut structure: species with heavier gizzards destroyed a higher proportion of seeds and undigested seeds ingested by species with more grit in the gizzard germinated better.
In the waterfowl community studied, the quantity and quality components of seed dispersal effectiveness were positively correlated across species.
Measuring outcomes with tools of proven feasibility and utility: the example of a patient‐focused asthma measure
Authors: Georgiou Andrew , Pearson Michael 
Published: March 2003

AbstractBest quality care is clearly desirable and instituting quality assurance should be logical and simple. However, the practicality of setting standards for a product or service, and designing systems to measure against the standards, is more difficult. In the health service it is only likely to be feasible if data can be generated from efficient and reliable information systems. The ideal measure of quality is an outcome measure that evaluates whether or not the quality of care has achieved the desired standard of outcome. Direct measures of outcome are not easy to construct and the information systems required to provide data are not widely available. The National Centre for Health Outcomes Development (NCHOD) has produced a series of indicators in 10 areas of health care, where an indicator is a pointer to, rather than a direct measure of, a desired outcome. Feasibility studies measuring their sensitivity and reliability have drawn attention to their possible utility within different health care settings. This paper reports on an investigation into a patient‐focused outcome indicator for asthma. There is broad agreement about the need to measure the outcome of disease. However, when outcome indicators are defined there are major obstacles to their successful uptake. A key challenge for outcomes measurement is to ensure that the cost of collecting the data and ensuring completeness, accuracy and standardization are justified by the benefits derived. Health outcome indicators should not be treated as a panacea, but as a part of the clinical and health care tool kit.
Critical incident reporting in UK intensive care units: a postal survey
Authors: Thomas A. N. , Pilkington C. E. , Greer R. 
Published: March 2003

AbstractRationale, aims and objectives To review critical incident reporting in UK intensive care units (ICUs).Methods We conducted a postal survey of clinical directors of UK ICUs to ask if critical incident reporting was used in their ICU. Using a structured questionnaire, we also asked for details of critical incident reporting systems and for changes introduced as a result of incident reporting.Results and conclusions Eighty‐six of a total of 256 questionnaires were returned. Sixty‐one units had been using a critical incident reporting system for a median duration of 3 years (interquartile range 2–5 years). There were wide variations in the structures of reporting systems between units. A median of four (interquartile range 3–8) critical incidents were reported per unit per month. In 141 changes, the development of protocols and guidelines (18) and changes in drug prescription and checking (20) were most common. A more consistent approach to reporting could improve patient care and 65 responders felt that a national reporting system was potentially useful.
Reduction of stress response in carp,Cyprinus carpioL., held under deteriorating environmental conditions, by oral administration of bovine lactoferrin
Authors: Kakuta I 
Published: March 2003

AbstractBovine lactoferrin (LF) was evaluated for its ability to suppress stress reactions in carp, Cyprinus carpio L., held under deteriorating environmental conditions. Three test diets containing different levels of LF (0.01, 0.1 and 1%) were fed at 2% of fish body weight per day, i.e. LF at 2, 20 and 200 mg kg–1 body weight day–1 was administered orally to carp for 14 days at 20 °C. In the fish reared at a density of 2 individuals 10 l–1, plasma cortisol, adrenaline and noradrenaline decreased in the groups fed with 0.1 and 1% LF content diets. In the fish held at a density of 10 individuals 10 l–1 for 3 days, plasma cortisol, adrenaline, noradrenaline, dopamine and glucose were higher than those at 2 individuals 10 l–1 in both the control and LF‐treated groups. The extent to which these parameters were elevated in the fish held at the same density was reduced with increasing LF content of the diet. Twenty‐four hours after exposure to hypoxic conditions (dissolved oxygen level, 2.5 mg l–1), haemoglobin, haematocrit, plasma cortisol, adrenaline, noradrenaline and dopamine increased significantly in all groups. The responses of hypoxic fish fed with 0.1 and 1% LF diets for 14 days were smaller than those of the controls. These results suggest that LF has an ability to reduce the stress response of carp held under deteriorating environmental conditions.