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Terms modified by Fen Selected AbstractsDifferences in the interaction between aryl propionic acid derivatives and poly(vinylpyrrolidone) K30: A multi-methodological approachJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2009Zehadin Gashi Abstract The present work aims at the application of several methods to explain differences in the physical interaction of some aryl propionic acid derivatives (ibuprofen [IBP], ketoprofen [KET], flurbiprofen [FLU], naproxen [NAP], fenbufen [FEN]) with poly(vinylpyrrolidone) (PVP) K30, stored together at 298,±,0.5 K and 22% RH. X-ray powder diffractometry and 13C-solid state NMR demonstrated that IBP was able to strongly interact with the polymer, while weak interaction was observed for KET, FLU, NAP, and the least for FEN. The interaction of comelted drug and PVP was studied by differential scanning calorimetry by applying the Gordon,Taylor equation, which revealed that small molar drug volumes may favour the drug diffusion through the PVP amorphous chains increasing the polymer free volume and decreasing the mixture Tg. The molecular docking study revealed that intermolecular energy is mainly due to the contribution of van der Waals energy component, causing the differences among the drugs, and is related to the drug,PVP surface contact area in the complex formed. Solid-state kinetic study demonstrated that IBP molecules are involved in a three-dimensional diffusion mechanism within the polymer favoured by its low molar volume that reduces molecular hindrance, and by the weakness of its crystal lattice, which facilitates crystallinity loss and stabilisation of the amorphous phase. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4216,4228, 2009 [source] Serotonin, Impulsivity, and Alcohol Use Disorders in the Older Adolescent: A Psychobiological StudyALCOHOLISM, Issue 11 2000Paul H. Soloff Background: Alcohol use disorders (AUDs) among adolescents are associated with a high prevalence of conduct disorder (CD), much as type II alcoholism in adults is associated with impulsive-aggressive behavior and antisocial personality traits. Adults with impulsive personality disorders and AUD demonstrate diminished central serotonergic responsiveness to serotonergic agonists. Dysregulation of central serotonergic function may contribute to a vulnerability to impulsive-aggressive behavior, CD, and AUD. We studied older adolescents, both male and female, to examine the relationships between sex, dispositional impulsivity, aggressivity, CD, and responsiveness to serotonergic challenge with d,l fenfluramine (FEN) early in the development of AUD. Methods: Thirty-six adolescents between the ages of 16 and 21 years were assessed for DSM-IV AUD and other Axis I disorders by using the Psychoactive Substance Use Disorders section of the Structured Clinical Interview for DSM III-R, the Schedule for Affective Disorders and Schizophrenia for School-Age Children,Present and Lifetime Version, and CD interviews. Impulsivity and aggressivity were assessed by the Barratt Impulsiveness Scale, Lifetime History of Aggression, Buss-Durkee Hostility Inventory, Eysenck Impulsiveness Questionnaire, Youth Self Report, and Multidimensional Personality Questionnaires. FEN was administered as 0.8 mg/kg to a maximum of 60 mg, and blood was sampled at fixed intervals for prolactin, cortisol, fenfluramine, and norfenfluramine levels. Results: Eighteen adolescents (12 male, 6 female) with AUD scored significantly higher on all measures of impulsivity and aggressivity compared with 18 healthy controls (12 male, 6 female). There were no significant differences between groups in peak prolactin or cortisol responses (minus baseline), or area-under-the-curve determinations (AUC); however, 9 subjects with AUD and comorbid CD had significantly elevated cortisol AUC levels compared with subjects with AUD and no CD or with normal controls. In the total sample, cortisol AUC was associated positively with measures of aggression. Conclusions: Adolescents with early-onset AUD are characterized by impulsivity and aggressivity compared with healthy peers but do not demonstrate the diminished prolactin or cortisol responses to FEN characteristic of adult alcoholics with impulsive-aggression. [source] Fragmentation of the (Cyclam-acetato)iron Azide Cation in the Gas PhaseEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2007Detlef Schröder Abstract Mass spectrometry is used to investigate the fragmentation of the ligated azidoiron cation [(cyclam-acetato)Fe(N3)]+, which is accessible in the gas phase by electrospray ionization of a solution of its hexafluorophosphate salt in methanol/water. Upon collisional activation, mass-selected [(cyclam-acetato)Fe(N3)]+ undergoes competing loss of dinitrogen or HN3 as the prevailing fragmentations. The former dissociation pathway is investigated in detail in order to determine whether or not the free, high-valent iron nitride [(cyclam-acetato)FeN]+ is formed. The evidence obtained indeed supports the formation of the iron nitride species as an intermediate, although the long-lived ion sampled after mass selection may also have undergone further rearrangements.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] The electronic structure and magnetism of a rocksalt FeN(001) surface: A density functional studyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007J. I. Lee Abstract We investigated the electronic structure and magnetism of the rocksalt FeN(001) surface. We considered both the ferromagnetic and antiferromagnetic configurations. We calculated the electronic structure using the full-potential linearized augmented plane wave method within generalized gradient approximation. We found that the antiferromagnetic phase is more stable than the ferromagnetic one, as in bulk, with an energy difference of 0.14 eV per the considered slab. The magnetic moments of the Fe atoms in the antiferromagnetic phase slab are 2.90 ,B, ,2.26 ,B and 2.37 ,B for the surface, subsurface, and center layers, respectively, while the values for the ferromagnetic one are 2.85 ,B, 1.81 ,B, and 2.37 ,B, respectively. The detailed electronic structures for ferromagnetic and antiferromagnetic phases are compared and discussed with the calculated spin-densities and density of states. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rehabilitation of Acidified Floating Fens by Addition of Buffered Surface WaterRESTORATION ECOLOGY, Issue 1 2002M. C. Bootsma Abstract Floating fens are species-rich succession stages in fen areas in the Netherlands. Many of these fens are deteriorating due to acidification; Sphagnum species and Polytrichum commune build 10,25 cm thick moss carpets, and the species diversity decreases. Earlier experiments in wet ecosystems indicate that successful restoration of circum-neutral and mesotrophic conditions requires a combination of hydrological measures and sod removal. In an acidified fen recharged by rainwater in the nature reserve Ilperveld (The Netherlands), a ditch/trench system was dug for the purpose of creating a run-off channel for acid rainwater in wet periods and to enable circum-neutral surface water to enter the fen in dry periods. Moreover, the sod was removed in part of the fen. Ditch/trench creation or sod cutting had no effect individually, but a combination of the two measures led to a change in the abiotic conditions (higher pH and Ca), and in turn to an increase of species-richness and the reestablishment of a number of characteristic species. Reestablishment of rare vascular plant species and characteristic bryophytes might be a long-term process because of incomplete recovery of site conditions and constraints in seed dispersal. [source] Fens and floodplains of the temperate zone: Present status, threats, conservation and restorationAPPLIED VEGETATION SCIENCE, Issue 2 2006Rudy van Diggelen Abstract. This Special Feature focuses on lowland fens and flood plains. In this introduction we discuss the most important mire-related terms, present status, threats and conservation and restoration attempts. Floodplains and especially lowland fens are rare and vulnerable ecosystems. They are highly threatened all over the world because of direct conversion to agricultural land and especially the lack of appropriate management and altered catchment hydrology. Finally we present a framework for the conservation and restoration of these ecosystems. This consists of (1) optimising abiotic conditions; (2) safeguarding propagule availability of the target species; (3) creating and maintaining conditions for (re)establishment of these species, and (4) appropriate management to keep the conditions suitable. [source] Vertical profiles of methanogenesis and methanogens in two contrasting acidic peatlands in central New York State, USAENVIRONMENTAL MICROBIOLOGY, Issue 8 2006Hinsby Cadillo-Quiroz Summary Northern acidic peatlands are important sources of atmospheric methane, yet the methanogens in them are poorly characterized. We examined methanogenic activities and methanogen populations at different depths in two peatlands, McLean bog (MB) and Chicago bog (CB). Both have acidic (pH 3.5,4.5) peat soils, but the pH of the deeper layers of CB is near-neutral, reflecting its previous existence as a neutral-pH fen. Acetotrophic and hydrogenotrophic methanogenesis could be stimulated in upper samples from both bogs, and phylotypes of methanogens using H2/CO2 (Methanomicrobiales) or acetate (Methanosarcinales) were identified in 16S rRNA gene clone libraries and by terminal restriction fragment length polymorphism (T-RFLP) analyses using a novel primer/restriction enzyme set that we developed. Particularly dominant in the upper layers was a clade in the Methanomicrobiales, called E2 here and the R10 or fen group elsewhere, estimated by quantitative polymerase chain reaction to be present at ,108 cells per gram of dry peat. Methanogenic activity was considerably lower in deeper samples from both bogs. The methanogen populations detected by T-RFLP in deeper portions of MB were mainly E2 and the uncultured euryarchaeal rice cluster (RC)-II group, whereas populations in the less acidic CB deep layers were considerably different, and included a Methanomicrobiales clade we call E1-E1,, as well as RC-I, RC-II, marine benthic group D, and a new cluster that we call the subaqueous cluster. E2 was barely detectable in the deeper samples from CB, further evidence for the associations of most organisms in this group with acidic habitats. [source] Microsite-dependent changes in methanogenic populations in a boreal oligotrophic fenENVIRONMENTAL MICROBIOLOGY, Issue 11 2003Pierre E. Galand Summary Wetlands, including peatlands, are the main source of natural methane emission. Well-defined fen microsites have different methane emissions rates, but it is not known whether the methane-producing Archaea communities vary at these sites. Possible horizontal variations of communities, in a natural oligotrophic fen, were analysed by characterizing the methanogens from two well-defined microsites: Eriophorum lawn and Hummock. Community structures were studied at two different layers of the fen, showing, respectively, high and low methane production. The structure of methanogen populations was determined using molecular techniques targeting the 16SrRNA gene and combined denaturing gradient gel electrophoresis (DGGE) and restriction fragment length polymorphism (RFLP) analysis. Results subjected to non-metric multidimensional scaling (MDS), diversity indices calculation and phylogenetic analysis revealed that upper layer communities changed with site while deeper layer communities remained the same. Phylogenetic analyses revealed six different clusters of sequences grouping with only two known orders of methanogens. Upper layers of Hummock were dominated by sequences clustering with members of Methanomicrobiales and sequences dominating the upper part of the Eriophorum lawn were related to members of the order Methanosarcinales. Novel methanogenic sequences were found at both sites at both depths. Vegetation characterizing the microsites probably influences the microbial communities in the layers of the fen where methane is produced. [source] Comparison of greenhouse gas fluxes and nitrogen budgets from an ombotrophic bog in Scotland and a minerotrophic sedge fen in FinlandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2010J. Drewer Northern peatlands cover approximately 4% of the global land surface area. Those peatlands will be particularly vulnerable to environmental and climate change and therefore it is important to investigate their total greenhouse gas (GHG) budgets, to determine the feedback on the climate. Nitrogen (N) is known to influence the GHG budget in particular by affecting the methane (CH4) balance. At two peatland sites in Scotland and Finland GHG fluxes of carbon dioxide (CO2), methane and nitrous oxide (N2O) and nitrogen fluxes were measured as part of the European project ,NitroEurope'. The Scottish site, Auchencorth Moss, was a GHG sink of ,321, ,490 and ,321 g CO2 eq m,2 year,1 in 2006, 2007 and 2008, respectively, with CO2 as the dominating GHG. In contrast, the dominating GHG at the Finnish site, Lompolojänkkä, was CH4, resulting in the site being a net GHG source of +485 and +431 g CO2 eq m,2 year,1 in 2006 and 2007, respectively. Therefore, Auchencorth Moss had a negative global warming potential (GWP) whilst Lompolojänkkä had a positive GWP over the investigated time period. Initial results yielded a positive N budget for Lompolojänkkä of 7.1 kg N ha,1 year,1, meaning the site was gaining nitrogen, and a negative N budget for Auchencorth Moss of ,2.4 kg N ha year,1, meaning the site was losing nitrogen. [source] Connecting Atmosphere and Wetland: Energy and Water Vapour ExchangeGEOGRAPHY COMPASS (ELECTRONIC), Issue 4 2008Peter M. Lafleur Wetlands are ubiquitous over the globe, comprise a vast array of ecosystem types and are of great ecological and social importance. Their functioning is intimately tied to the atmosphere by the energy and mass exchanges that take place across the wetland,atmosphere boundary. This article examines recent research into these exchanges, with an emphasis on the water vapour exchange. Although broad classes of wetland type, such as fen, bog and marsh, can be defined using ecological or hydrologic metrics, distinct difference in energy exchanges between the classes cannot be found. This arises because there are many factors that control the energy exchanges and interplay of these factors is unique to every wetland ecosystem. Wetlands are more similar in their radiation balances than in the partitioning of this energy into conductive and turbulent heat fluxes. This is especially true of evapotranspiration (ET) rates, which vary considerably among and within wetland classes. A global survey of wetland ET studies shows that location has little to do with ET rates and that variation in rates is largely determined by local climate and wetland characteristics. Recent modelling studies suggest that although wetlands occupy a small portion of the global land surface, their water and energy exchanges may be important in regional and global climates. Although the number of studies of wetland,atmosphere interactions has increased in recent years more research is needed. Five key areas of study are identified: (i) the importance of moss covers, (ii) lack of study in tropical systems, (iii) inclusion of wetlands in global climate models, (iv) importance of microforms in wetlands and their scaling to the whole ecosystem, and (v) the paucity of annual ET measurements. [source] Diurnal and seasonal variation in methane emissions in a northern Canadian peatland measured by eddy covarianceGLOBAL CHANGE BIOLOGY, Issue 9 2010KEVIN D. LONG Abstract Eddy covariance measurements of methane (CH4) net flux were made in a boreal fen, typical of the most abundant peatlands in western Canada during May,September 2007. The objectives of this study were to determine: (i) the magnitude of diurnal and seasonal variation in CH4 net flux, (ii) the relationship between the temporally varying flux rates and associated changes in controlling biotic and abiotic factors, and (iii) the contribution of CH4 emission to the ecosystem growing season carbon budget. There was significant diurnal variation in CH4 emission during the peak of the growing season that was strongly correlated with associated changes in solar radiation, latent heat flux, air temperature and ecosystem conductance to water vapor. During days 181,215, nighttime average CH4 efflux was only 47% of the average midday values. The peak value for daily average CH4 emission rate was approximately 80 nmol m,2 s,1 (4.6 mg CH4 m,2 h,1), and seasonal variation in CH4 flux was strongly correlated with changes in soil temperature. Integrated over the entire measurement period [days 144,269 (late May,late September)], the total CH4 emission was 3.2 g CH4 m,2, which was quite low relative to other wetland ecosystems and to the simultaneous high rate of ecosystem net CO2 sequestration that was measured (18.1 mol CO2 m,2 or 217 g C m,2). We estimate that the negative radiative forcing (cooling) associated with net carbon storage over the life of the peatland (approximately 2200 years) was at least twice the value of positive radiative forcing (warming) caused by net CH4 emission over the last 50 years. [source] Solar UVB and warming affect decomposition and earthworms in a fen ecosystem in Tierra del Fuego, ArgentinaGLOBAL CHANGE BIOLOGY, Issue 10 2009JOHANN G. ZALLER Abstract Combined effects of co-occurring global climate changes on ecosystem responses are generally poorly understood. Here, we present results from a 2-year field experiment in a Carex fen ecosystem on the southernmost tip of South America, where we examined the effects of solar ultraviolet B (UVB, 280,315 nm) and warming on above- and belowground plant production, C : N ratios, decomposition rates and earthworm population sizes. Solar UVB radiation was manipulated using transparent plastic filter films to create a near-ambient (90% of ambient UVB) or a reduced solar UVB treatment (15% of ambient UVB). The warming treatment was imposed passively by wrapping the same filter material around the plots resulting in a mean air and soil temperature increase of about 1.2 °C. Aboveground plant production was not affected by warming, and marginally reduced at near-ambient UVB only in the second season. Aboveground plant biomass also tended to have a lower C : N ratio under near-ambient UVB and was differently affected at the two temperatures (marginal UVB × temperature interaction). Leaf decomposition of one dominant sedge species (Carex curta) tended to be faster at near-ambient UVB than at reduced UVB. Leaf decomposition of a codominant species (Carex decidua) was significantly faster at near-ambient UVB; root decomposition of this species tended to be lower at increased temperature and interacted with UVB. We found, for the first time in a field experiment that epigeic earthworm density and biomass was 36% decreased by warming but remained unaffected by UVB radiation. Our results show that present-day solar UVB radiation and modest warming can adversely affect ecosystem functioning and engineers of this fen. However, results on plant biomass production also showed that treatment manipulations of co-occurring global change factors can be overridden by the local climatic situation in a given study year. [source] Carbon dioxide balance of a fen ecosystem in northern Finland under elevated UV-B radiationGLOBAL CHANGE BIOLOGY, Issue 4 2009JAANA K. HAAPALA Abstract The effect of elevated UV-B radiation on CO2 exchange of a natural flark fen was studied in open-field conditions during 2003,2005. The experimental site was located in Sodankylä in northern Finland (67°22,N, 26°38,E, 179 m a.s.l.). Altogether 30 study plots, each 120 cm × 120 cm in size, were randomly distributed between three treatments (n=10): ambient control, UV-A control and UV-B treatment. The UV-B-treated plots were exposed to elevated UV-B radiation level for three growing seasons. The instantaneous net ecosystem CO2 exchange (NEE) and dark respiration (RTOT) were measured during the growing season using a closed chamber method. The wintertime CO2 emissions were estimated using a gradient technique by analyzing the CO2 concentration in the snow pack. In addition to the instantaneous CO2 exchange, the seasonal CO2 balances during the growing seasons were modeled using environmental data measured at the site. In general, the instantaneous NEE at light saturation was slightly higher in the UV-B treatment compared with the ambient control, but the gross photosynthesis was unaffected by the exposure. The RTOT was significantly lower under elevated UV-B in the third study year. The modeled seasonal (June,September) CO2 balance varied between the years depending on the ground water level and temperature conditions. During the driest year, the seasonal CO2 balance was negative (net release of CO2) in the ambient control and the UV-B treatment was CO2 neutral. During the third year, the seasonal CO2 uptake was 43±36 g CO2 -C m,2 in the ambient control and 79±45 g CO2 -C m,2 in the UV-B treatment. The results suggest that the long-term exposure to high UV-B radiation levels may slightly increase the CO2 accumulation to fens resulting from a decrease in microbial activity in peat. However, it is unlikely that the predicted development of the level of UV-B radiation would significantly affect the CO2 balance of fen ecosystems in future. [source] Long-term ozone effects on vegetation, microbial community and methane dynamics of boreal peatland microcosms in open-field conditionsGLOBAL CHANGE BIOLOGY, Issue 8 2008SAMI K. MÖRSKY Abstract To study the effects of elevated ozone concentration on methane dynamics and a sedge species, Eriophorum vaginatum, we exposed peatland microcosms, isolated by coring from an oligotrophic pine fen, to double ambient ozone concentration in an open-air ozone exposure field for four growing seasons. The field consists of eight circular plots of which four were fumigated with elevated ozone concentration and four were ambient controls. At the latter part of the first growing season (week 33, 2003), the methane emission was 159±14 mg CH4 m,2 day,1 (mean±SE) in the ozone treatment and 214±8 mg CH4 m,2 day,1 under the ambient control. However, towards the end of the experiment the ozone treatment slightly, but consistently, enhanced the methane emission. At the end of the third growing season (2005), microbial biomass (estimated by phospholipid fatty acid biomarkers) was higher in peat exposed to ozone (1975±108 nmol g,1 dw) than in peat of the control microcosms (1589±115 nmol g,1 dw). The concentrations of organic acids in peat pore water showed a similar trend. Elevated ozone did not affect the shoot length or the structure of the sedge E. vaginatum leaves but it slightly increased the total number of sedge leaves towards the end of the experiment. Our results indicate that elevated ozone concentration enhances the general growth conditions of microbes in peat by increasing their substrate availability. However, the methane production did not reflect the increase in the concentration of organic acids, probably because hydrogenotrophic methane production dominated in the peat studied. Although, we used isolated peatland microcosms with limited size as study material, we did not find experimental factors that could have hampered the basic conclusions on the effects of ozone. [source] Effects of short- and long-term water-level drawdown on the populations and activity of aerobic decomposers in a boreal peatlandGLOBAL CHANGE BIOLOGY, Issue 2 2007KRISTA JAATINEN Abstract We analysed the response of microbial communities, characterized by phospholipid fatty acids (PLFAs), to changing hydrological conditions at sites with different nutrient levels in a southern boreal peatland. Although PLFAs of Gram-negative bacteria were characteristic of the peatland complex, microbial communities differed among sites (ombrotrophic bog, oligotrophic fen, mesotrophic fen) and sampling depths (0,5, 5,10, 10,20, 20,30 cm). The microbial communities in each site changed significantly following water-level drawdown. The patterns of change varied among sites and sampling depths. The relative proportion of Gram-negative bacteria decreased in the upper 10 cm but increased in deeper layers of the fen sites. Fungi benefited from water-level drawdown in the upper 5 cm of the mesotrophic fen, but suffered in the drier surfaces of the ombrotrophic bog, especially in the 5,10 cm layer. In contrast, actinobacteria suffered from water-level drawdown in the mesotrophic fen, but benefited in the drier surfaces of the ombrotrophic bog. Basal respiration rate correlated positively with pH and fungal PLFA, and negatively with depth. We suggest that the changes in microbial community structure after persistent water-level drawdown follow not only the hydrological conditions but also the patterns of vegetation change. Our results imply that changes in structure and activity of the microbial community in response to climate change will be strongly dependent on the type of peatland. [source] Potential effects of warming and drying on peatland plant community compositionGLOBAL CHANGE BIOLOGY, Issue 2 2003Jake F. Weltzin Abstract Boreal peatlands may be particularly vulnerable to climate change, because temperature regimes that currently constrain biological activity in these regions are predicted to increase substantially within the next century. Changes in peatland plant community composition in response to climate change may alter nutrient availability, energy budgets, trace gas fluxes, and carbon storage. We investigated plant community response to warming and drying in a field mesocosm experiment in northern Minnesota, USA. Large intact soil monoliths removed from a bog and a fen received three infrared warming treatments crossed with three water-table treatments (n = 3) for five years. Foliar cover of each species was estimated annually. In the bog, increases in soil temperature and decreases in water-table elevation increased cover of shrubs by 50% and decreased cover of graminoids by 50%. The response of shrubs to warming was distinctly species-specific, and ranged from increases (for Andromeda glaucophylla) to decreases (for Kalmia polifolia). In the fens, changes in plant cover were driven primarily by changes in water-table elevation, and responses were species- and lifeform-specific: increases in water-table elevation increased cover of graminoids , in particular Carex lasiocarpa and Carex livida, as well as mosses. In contrast, decreases in water-table elevation increased cover of shrubs, in particular A. glaucophylla and Chamaedaphne calyculata. The differential and sometimes opposite response of species and lifeforms to the treatments suggest that the structure and function of both bog and fen plant communities will change , in different directions or at different magnitudes , in response to warming and/or changes in water-table elevation that may accompany regional or global climate change. [source] Modelling the interannual variability of net ecosystem CO2 exchange at a subarctic sedge fenGLOBAL CHANGE BIOLOGY, Issue 5 2001Timothy J. Griffis Abstract This paper presents an empirical model of net ecosystem CO2 exchange (NEE) developed for a subarctic fen near Churchill, Manitoba. The model with observed data helps explain the interannual variability in growing season NEE. Five years of tower-flux data are used to test and examine the seasonal behaviour of the model simulations. Processes controlling the observed interannual variability of CO2 exchange at the fen are examined by exploring the sensitivity of the model to changes in air temperature, precipitation and leaf area index. Results indicate that the sensitivity of NEE to changing environmental controls is complex and varies interannually depending on the initial conditions of the wetland. Changes in air temperature and the timing of precipitation events have a strong influence on NEE, which is largely manifest in gross ecosystem photosynthesis (GEP). Climate change scenarios indicate that warmer air temperatures will increase carbon acquisition during wet years but may act to reduce wetland carbon storage in years that experience a large water deficit early in the growing season. Model simulations for this subarctic sedge fen indicate that carbon acquisition is greatest during wet and warm conditions. This suggests therefore that carbon accumulation was greatest at this subarctic fen during its early developmental stages when hydroclimatic conditions were relatively wet and warm at approximately 2500 years before present. [source] Modelling hydrological management for the restoration of acidified floating fensHYDROLOGICAL PROCESSES, Issue 20 2005Stefan C. Dekker Abstract Wetlands show a large decline in biodiversity. To protect and restore this biodiversity, many restoration projects are carried out. Hydrology in wetlands controls the chemical and biological processes and may be the most important factor regulating wetland function and development. Hydrological models may be used to simulate these processes and to evaluate management scenarios for restoration. HYDRUS2D, a combined saturated,unsaturated groundwater flow and transport model, is presented. This simulates near-surface hydrological processes in an acidified floating fen, with the aim to evaluate the effect of hydrological restoration in terms of conditions for biodiversity. In the acidified floating fen in the nature reserve Ilperveld (The Netherlands), a trench system was dug for the purpose of creating a runoff channel for acid rainwater in wet periods and to enable circum-neutral surface water to enter the fen in dry periods. The model is calibrated against measured conductivity values for a 5 year period. From the model simulations, it was found that lateral flow in the floating raft is limited. Furthermore, the model shows that the best management option is a combination of trenches and inundation, which gave the best soil water quality in the root zone. It is concluded that hydrological models can be used for the calculation of management scenarios in restoration projects. The combined saturated,unsaturated model concept used in this paper is able to incorporate the governing hydrological processes in the wetland root zones. Copyright © 2005 John Wiley & Sons, Ltd. [source] The influence of management regime and altitude on the population structure of Succisapratensis: implications for vegetation monitoringJOURNAL OF APPLIED ECOLOGY, Issue 4 2001Christoph Bühler Summary 1,Environmental change and land use may alter the vegetation typical of wetland habitats. However, commonly used techniques for vegetation monitoring that are based on species composition are often not suitable to detect gradual changes in the structure of vegetation at an early stage. In this study we tested if this methodical deficiency could be overcome by observation of the stage structure of a perennial target species. 2,We studied the density and frequency distribution of four phenological stages of the perennial plant Succisapratensis in 24 calcareous fens in eastern Switzerland. These fens differed in management type (mowing, cattle-grazing) and altitude (low, medium, high). Among grazed fens, the intensity of management was quantified by direct observation. Species composition and canopy structure of the plant community surrounding S. pratensis were also measured. 3,High altitude had a positive effect on the density of adult plants of S. pratensis only in mown fens, whereas in grazed fens adult density was highest at medium altitude. 4,Local densities of seedlings and vegetative adults within a fen were higher in mown than in grazed fens, and lower in fens of the lowest altitude level than of the two higher ones. However, there were no differences in the relative proportions of all four phenological stages among main factors except that significantly fewer seedlings occurred in fens of the lowest altitude level. 5,It is the intensity rather than the mere type of management regime that is crucial for shaping populations of S. pratensis: for grazed fens, there is a negative relationship between intensity of grazing and density of adult plants of S. pratensis. Moreover, the number, the relative proportion of seedlings and the seed-set are all negatively correlated with grazing intensity. 6,The species composition of the plant community, but not its physical structure, was significantly related to the relative proportion of seedlings of S. pratensis, which supports the indicator qualities of the target species. 7,Monitoring the population structure of one or several target species provides important indicator information about the stability of a whole plant community. For the target-species approach we propose to use characteristic but frequently and steadily occurring species instead of rare or endangered ones. [source] Spatial and temporal analysis of vegetation mosaics for conservation: poor fen communities in a Cornish valley mireJOURNAL OF BIOGEOGRAPHY, Issue 9 2003E. J. Southall Abstract Aim Biogeographers increasingly realize the importance of seeing plant communities as spatial mosaics and understanding the spatial and temporal heterogeneity of a site is often a key to successful conservation. The aim of this paper is to examine the approaches to the description and analysis of spatial and temporal variation in sub-communities within patch mosaics of vegetation in order to inform conservation management. The activities of the tin streaming industry in Cornwall over the last century have created a highly varied mosaic of poor fen vegetation on Goss Moor National Nature Reserve (NNR). The wetland mosaics comprise dry hummocks and different sized wet pools. The size and depth of the pools determines the rate and type of vegetation that develops, as does the nature of boundary or edge. The ergodic hypothesis is used to describe the various plant sub-communities and their boundaries to identify pathways of hydroseral succession. A further aim was to test the use of Ellenberg Indicator (EI) values as a tool for the rapid description of spatial and temporal environmental change on wetland sites with a view to their management. Location Goss Moor National Nature Reserve, Cornwall, UK. Methods An extensive survey of the whole wetland complex was undertaken to identify patches of poor fen vegetation containing Potentilla palustris (L.) Scop. and Menyanthes trifoliata L. At each patch, species abundance data were collected as well as associated environmental information such as depth of the organic layer and standing water depth, patch location, patch size and boundary type. The plant sub-communities present were defined using techniques of numerical classification [two-way indicator species analysis (twinspan)] and ordination [detrended correspondence analysis (DCA)] and these were ordered using the ergodic hypothesis in order to characterize the stages of the hydrosere. Floristic and environmental relationships were examined using canonical correspondence analysis (CCA). Further environmental differences between the poor fen sub-community types were characterized by weighted EI values for acidity (R), moisture (F), nitrogen (N) and light (L). Results and conclusions Twelve poor fen sub-community types were described and found to be distributed along a primary environmental gradient of organic matter depth, surface water height and bare substrate. Separation of the poor fen communities by a moisture gradient was considered as spatial evidence for hydroseral succession, which begins with the colonization of open-water pools created by tin excavations. High water levels were associated with the swamp communities, increased organic depth was associated with poor fen, and the type of boundary was shown to affect the resulting community composition. Weighted Community Ellenberg Indicator values for nitrogen, light, reaction and moisture are recommended as an effective tool for indicating differences between plant (sub-)communities. The importance of examining sub-community mosaics in the study of hydroseral development is stressed and the manner in which both sets of information may be used to underpin the conservation management of the site is demonstrated. [source] Rejecting the mean: Estimating the response of fen plant species to environmental factors by non-linear quantile regressionJOURNAL OF VEGETATION SCIENCE, Issue 4 2005Henning K. Schröder Abstract Question: Is quantile regression an appropriate statistical approach to estimate the response of fen species to single environmental factors? Background: Data sets in vegetation field studies are often characterized by a large number of zeros and they are generally incomplete in respect to the factors which possibly influence plant species distribution. Thus, it is problematic to relate plant species abundance to single environmental factors by the ordinary least squares regression technique of the conditional mean. Location: Riparian herbaceous fen in central Jutland (Denmark). Methods: Semi-parametric quantile regression was used to estimate the response of 18 plant species to six environmental factors, 95% regression quantiles were chosen to reduce the impact of multiple unmeasured factors on the regression analyses. Results of 95% quantile regression and ordinary least squares regression were compared. Results: The standard regression of the conditional mean underestimated the rates of change of species cover due to the selected factor in comparison to 95% regression quantiles. The fitted response curves indicated a general broad tolerance of the studied fen species to different flooding durations but a narrower range concerning groundwater amplitude. The cover of all species was related to soil exchangeable phosphate and base-richness. A relationship between soil exchangeable potassium and species cover was only found for 11 species. Conclusion: Considering the characteristics of data sets in vegetation science, non-linear quantile regression is a useful method for gradient analyses. [source] Plant communities along environmental gradients of high-arctic mires in Sassendalen, SvalbardJOURNAL OF VEGETATION SCIENCE, Issue 6 2002Archibald W. Vanderpuye Elvebakk & Prestrud (1996) for species; Elvebakk (1994) for syntaxa Abstract. The wet to moist bryophyte-dominated vegetation of Sassendalen, Svalbard, was classified into seven communities. These communities were grouped into (1) Cardamino nymanii-Saxifragion foliolosae marsh; (2) Caricion stantis fen; (3) Luzulion nivalis snowbed , including manured vegetation corresponding to moss tundras. All communities have a basically arctic distribution. Marshes are developed in habitats with a water table above the bryophyte vegetation surface and fens on sites with a water table level high above the permafrost but below the bryophyte surface. Moss tundras normally have no standing water table, but in Sassendalen they have a low water table due to their development on less steep slopes than in their normal habitat near bird cliffs. CCA confirms that the standing water level is the prime differentiating factor between the alliances, while aspect favourability and permafrost depth differentiate between the fen communities and temporary desiccation is important for the Catoscopium nigritum community. Carex subspathacea is a characteristic fen species in the absence of other Carex species dominating elsewhere in the Arctic. Arctic marshes are linked to an extremely cold environment. They have a very low species diversity with a few species dominating; Arctophila fulva, Pseudocalliergon trifarium, Scorpidium scorpioides and Warnstorfia tundrae are character species. Moss tundra as defined here appears to be restricted to Svalbard and, probably, neighbouring Novaya Zemlya. This may be due to the absence of rodents and the high seabird density, which is related to the mild sea currents reaching further to the north here and which implies manuring of surrounding ecosystems. Manuring in a very cold environment produces moss carpets with a thin active layer and accumulation of thick peat layers without a standing water level. In Sassendalen the role of arctic seabirds is replaced by Svalbard reindeer which are nonmigratory and are concentrated to favourable grazing areas where their manuring effect is intense. Their long-term manuring effect probably explains the occurrence of moss tundras in this weakly rolling landscape where seabird colonies are absent. [source] Nutrient limitation and morphological plasticity of the carnivorous pitcher plant Sarracenia purpurea in contrasting wetland environmentsNEW PHYTOLOGIST, Issue 3 2008Terry Bott Summary ,,Plasticity of leaf nutrient content and morphology, and macronutrient limitation were examined in the northern pitcher plant, Sarracenia purpurea subsp. purpurea, in relation to soil nutrient availability in an open, neutral pH fen and a shady, acidic ombrotrophic bog, over 2 yr following reciprocal transplantation of S. purpurea between the wetlands. ,,In both wetlands, plants were limited by nitrogen (N) but not phosphorus (P) (N content < 2% DW,1, N : P < 14) but photosynthetic quantum yields were high (FV/FM > 0.79). Despite carnivory, leaf N content correlated with dissolved N availability to plant roots (leaf N vs , r2 = 0.344, P < 0.0001); carnivorous N acquisition did not apparently overcome N limitation. ,,Following transplantation, N content and leaf morphological traits changed in new leaves to become more similar to plants in the new environment, reflecting wetland nutrient availability. Changes in leaf morphology were faster when plants were transplanted from fen to bog than from bog to fen, possibly reflecting a more stressful environment in the bog. ,,Morphological plasticity observed in response to changes in nutrient supply to the roots in natural habitats complements previous observations of morphological changes with experimental nutrient addition to pitchers. [source] Nitrogen and phosphorus in mire plants: variation during 50 years in relation to supply rate and vegetation typeOIKOS, Issue 3 2005Nils Malmer Southern Sweden has long been exposed to an increasing atmospheric nitrogen deposition. We investigated the effects of this supply on the Sphagnum mire vegetation in SW Götaland by comparing above-ground tissue concentrations of N and P and biomass variables in five vascular plant and two Sphagnum species collected during three periods since 1955 at 81 sites representing three vegetation types, viz. ombrotrophic bog, extremely poor fen and moderately poor fen, within two areas differing in annual N deposition. The N:P ratios in the plants were rarely below 17, suggesting P as the growth-limiting mineral nutrient. In the vascular plants both growth and concentrations of N and P were highest in the moderately poor fen sites because of a higher mineralization rate, the differences between the extremely poor fen and bog sites being smaller in these respects. In the extremely poor fen and bog sites the N concentrations were slightly higher in the area with the highest N deposition. From 1955 to 2002 the concentration of N in the Sphagnum spp. increased proportionally to the supply rate while P remained constant. In the vascular plants the concentrations of P remained constant while N showed slightly decreasing trends in the bog and extremely poor fen sites, but since the size of the plants increased the biomass content of N and P increased, too. The increased N deposition has had its greatest effects on the site types with the highest Sphagnum biomass and peat accumulation rate. The high N concentration in the Sphagnum mosses probably reduced their competitiveness and facilitated the observed expansion of vascular plants. However, the increased N deposition might also have triggered an increased mineralization in the acrotelm increasing the supply of P to the vascular plants and thus also their productivity. This may also explain the slightly higher productivity among the vascular plants in the area with the highest N deposition rate. In conclusion, it seems as the increased N deposition has directly influenced only the growth of the Sphagnum mosses and that the effects on the growth of the vascular plants are indirect. [source] Rehabilitation of Acidified Floating Fens by Addition of Buffered Surface WaterRESTORATION ECOLOGY, Issue 1 2002M. C. Bootsma Abstract Floating fens are species-rich succession stages in fen areas in the Netherlands. Many of these fens are deteriorating due to acidification; Sphagnum species and Polytrichum commune build 10,25 cm thick moss carpets, and the species diversity decreases. Earlier experiments in wet ecosystems indicate that successful restoration of circum-neutral and mesotrophic conditions requires a combination of hydrological measures and sod removal. In an acidified fen recharged by rainwater in the nature reserve Ilperveld (The Netherlands), a ditch/trench system was dug for the purpose of creating a run-off channel for acid rainwater in wet periods and to enable circum-neutral surface water to enter the fen in dry periods. Moreover, the sod was removed in part of the fen. Ditch/trench creation or sod cutting had no effect individually, but a combination of the two measures led to a change in the abiotic conditions (higher pH and Ca), and in turn to an increase of species-richness and the reestablishment of a number of characteristic species. Reestablishment of rare vascular plant species and characteristic bryophytes might be a long-term process because of incomplete recovery of site conditions and constraints in seed dispersal. [source] On inference for a semiparametric partially linear regression model with serially correlated errorsTHE CANADIAN JOURNAL OF STATISTICS, Issue 4 2007Jinhong You Abstract The authors consider a semiparametric partially linear regression model with serially correlated errors. They propose a new way of estimating the error structure which has the advantage that it does not involve any nonparametric estimation. This allows them to develop an inference procedure consisting of a bandwidth selection method, an efficient semiparametric generalized least squares estimator of the parametric component, a goodness-of-fit test based on the bootstrap, and a technique for selecting significant covariates in the parametric component. They assess their approach through simulation studies and illustrate it with a concrete application. L'inférence dans le cadre d'un modèle de régression semiparamétrique partiellement linéaire à termes d'erreur corrélés en série Les auteurs s'intéressent à un modèle de régression semiparamétrique partiellement linéaire à termes d'erreur corrélés en série. Ils proposent une façon originale d'estimer la structure d'erreur qui a l'avantage de ne faire intervenir aucune estimation non paramétrique. Ceci leur permet de développer une procédure d'inférence comportant un choix de fen,tre, l'emploi de la méthode des moindres carrés généralisés pour l'estimation semiparamétrique efficace de la composante paramétrique, un test d'adéquation fondé sur le rééchantillonnage et une technique de sélection des covariables significatives de la composante paramétrique. Ils évaluent leur approche par voie de simulation et en donnent une illustration concrète. [source] Ecological gradients, subdivisions and terminology of north-west European miresJOURNAL OF ECOLOGY, Issue 2 2000B. D. Wheeler Summary 1,The historical development of mire ecology and terminology is reviewed in relation to evolving concepts and perceptions, and the diverse schools and traditions of vegetation and habitat description and research. 2,Most ecological and floristic variation within north-west European mire vegetation is accounted for by three ecological gradients: the acid base-poor vs. neutral, base- and bicarbonate-rich gradient; the gradient in fertility related to availability of the limiting nutrient elements N and P; and the water level gradient. Effects of salinity and the spring,flush,fen gradients are of more local significance, usually easily recognized. Land use is an important additional factor. 3,The mineral-soil-water limit between ombrotrophic and minerotrophically influenced sites is not sharp, and cannot be related to consistent differences in either vegetation or water chemistry. It should be abandoned as a general main division within mires. 4,The most important natural division is between ,bog', with pH generally < 5.0, low Ca2+, and Cl, and SO42, as the main inorganic anions, typically dominated by sphagna, ericoids and calcifuge Cyperaceae, and ,fen', with pH generally > 6.0, high Ca2+ and HCO3,, vegetation rich in dicotyledonous herbs and ,brown mosses'. This division is reflected in a bimodal distribution of pH. 5,The terms oligotrophic, mesotrophic and eutrophic should refer only to nutrient richness (fertility, mainly N and P), not to base richness (metallic cations and pH). 6,It is recommended that ,mire' should embrace both wetlands on peat and related communities on mineral soils, that ,bog' (unqualified) should encompass both ombrotrophic and weakly minerotrophic mires, including ,bog woodland', and that ,fen' should be restricted to base-rich mires but include both herbaceous and wooded vegetation (,fen carr'). 7,Definitions are given for a range of broadly defined categories that should cover most vegetation types commonly encountered. The relation of these to British national vegetation classification types and to major units in European phytosociology is outlined. [source] The effects of fire, local environment and time on ant assemblages in fens and forestsDIVERSITY AND DISTRIBUTIONS, Issue 6 2005Jaime S. Ratchford ABSTRACT We investigated the effects of the abiotic environment, plant community composition and disturbance by fire on ant assemblages in two distinct habitat types in the Siskiyou Mountains in northern California and southern Oregon, USA. Sampling over 2 years in burned and unburned Darlingtonia fens and their adjacent upland forests, we found that the effects of disturbance by fire depended on habitat type. In forests, fire intensity predicted richness in ant assemblages in both years after the fire, and plant community composition predicted richness 2 years after the fire. No factors were associated with richness in the species-poor fen ant assemblages. Species-specific responses to both habitat type and disturbance by fire were idiosyncratic. Assemblage composition depended on habitat type, but not disturbance by fire, and the composition of each assemblage between years was more dissimilar in burned than unburned sites. [source] Carbon dioxide balance of a fen ecosystem in northern Finland under elevated UV-B radiationGLOBAL CHANGE BIOLOGY, Issue 4 2009JAANA K. HAAPALA Abstract The effect of elevated UV-B radiation on CO2 exchange of a natural flark fen was studied in open-field conditions during 2003,2005. The experimental site was located in Sodankylä in northern Finland (67°22,N, 26°38,E, 179 m a.s.l.). Altogether 30 study plots, each 120 cm × 120 cm in size, were randomly distributed between three treatments (n=10): ambient control, UV-A control and UV-B treatment. The UV-B-treated plots were exposed to elevated UV-B radiation level for three growing seasons. The instantaneous net ecosystem CO2 exchange (NEE) and dark respiration (RTOT) were measured during the growing season using a closed chamber method. The wintertime CO2 emissions were estimated using a gradient technique by analyzing the CO2 concentration in the snow pack. In addition to the instantaneous CO2 exchange, the seasonal CO2 balances during the growing seasons were modeled using environmental data measured at the site. In general, the instantaneous NEE at light saturation was slightly higher in the UV-B treatment compared with the ambient control, but the gross photosynthesis was unaffected by the exposure. The RTOT was significantly lower under elevated UV-B in the third study year. The modeled seasonal (June,September) CO2 balance varied between the years depending on the ground water level and temperature conditions. During the driest year, the seasonal CO2 balance was negative (net release of CO2) in the ambient control and the UV-B treatment was CO2 neutral. During the third year, the seasonal CO2 uptake was 43±36 g CO2 -C m,2 in the ambient control and 79±45 g CO2 -C m,2 in the UV-B treatment. The results suggest that the long-term exposure to high UV-B radiation levels may slightly increase the CO2 accumulation to fens resulting from a decrease in microbial activity in peat. However, it is unlikely that the predicted development of the level of UV-B radiation would significantly affect the CO2 balance of fen ecosystems in future. [source] Potential effects of warming and drying on peatland plant community compositionGLOBAL CHANGE BIOLOGY, Issue 2 2003Jake F. Weltzin Abstract Boreal peatlands may be particularly vulnerable to climate change, because temperature regimes that currently constrain biological activity in these regions are predicted to increase substantially within the next century. Changes in peatland plant community composition in response to climate change may alter nutrient availability, energy budgets, trace gas fluxes, and carbon storage. We investigated plant community response to warming and drying in a field mesocosm experiment in northern Minnesota, USA. Large intact soil monoliths removed from a bog and a fen received three infrared warming treatments crossed with three water-table treatments (n = 3) for five years. Foliar cover of each species was estimated annually. In the bog, increases in soil temperature and decreases in water-table elevation increased cover of shrubs by 50% and decreased cover of graminoids by 50%. The response of shrubs to warming was distinctly species-specific, and ranged from increases (for Andromeda glaucophylla) to decreases (for Kalmia polifolia). In the fens, changes in plant cover were driven primarily by changes in water-table elevation, and responses were species- and lifeform-specific: increases in water-table elevation increased cover of graminoids , in particular Carex lasiocarpa and Carex livida, as well as mosses. In contrast, decreases in water-table elevation increased cover of shrubs, in particular A. glaucophylla and Chamaedaphne calyculata. The differential and sometimes opposite response of species and lifeforms to the treatments suggest that the structure and function of both bog and fen plant communities will change , in different directions or at different magnitudes , in response to warming and/or changes in water-table elevation that may accompany regional or global climate change. [source] | ||||||||||||||||||||||||||||||||||