bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon storage and fluxes in ponderosa pine forests at different developmental stages
Authors: Law B.E. , Thornton P.E. , Irvine J. , Anthoni P.M. , Van Tuyl S. 
Published: March 2003

AbstractWe compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, eddy flux estimates of net ecosystem exchange (NEE), and Biome‐BGC simulations of fluxes. The young forest (Y site) was previously an old‐growth ponderosa pine forest that had been clearcut in 1978, and the old forest (O site), which has never been logged, consists of two primary age classes (50 and 250 years old). Total ecosystem carbon content (vegetation, detritus and soil) of the O forest was about twice that of the Y site (21 vs. 10 kg C m−2ground), and significantly more of the total is stored in living vegetation at the O site (61% vs. 15%). Ecosystem respiration (Re) was higher at the O site (1014 vs. 835 g C m−2 year−1), and it was largely from soils at both sites (77% of Re). The biological data show that above‐ground net primary productivity (ANPP),NPPand net ecosystem production (NEP) were greater at the O site than the Y site. Monte Carlo estimates ofNEPshow that the young site is a source of CO2to the atmosphere, and is significantly lower thanNEP(O)byc. 100 g C m−2 year−1. Eddy covariance measurements also show that the O site was a stronger sink for CO2than the Y site. Across a 15‐km swath in the region,ANPPranged from 76 g C m−2 year−1at the Y site to 236 g C m−2 year−1(overall mean 158 ± 14 g C m−2 year−1). The lowestANPPvalues were for the youngest and oldest stands, but there was a large range ofANPPfor mature stands. Carbon, water and nitrogen cycle simulations with the Biome‐BGC model suggest that disturbance type and frequency, time since disturbance, age‐dependent changes in below‐ground allocation, and increasing atmospheric concentration of CO2all exert significant control on the net ecosystem exchange of carbon at the two sites. Model estimates of major carbon flux components agree with budget‐based observations to within ± 20%, with larger differences forNEPand for several storage terms. Simulations showed the period of regrowth required to replace carbon lost during and after a stand‐replacing fire (O) or a clearcut (Y) to be between 50 and 100 years. In both cases, simulations showed a shift from net carbon source to net sink (on an annual basis) 10–20 years after disturbance. These results suggest that the net ecosystem production of young stands may be low because heterotrophic respiration, particularly from soils, is higher than the NPP of the regrowth. The amount of carbon stored in long‐term pools (biomass and soils) in addition to short‐term fluxes has important implications for management of forests in the Pacific North‐west for carbon sequestration.
Monoterpene emission and monoterpene synthase activities in the Mediterranean evergreen oak Quercus ilex L. grown at elevated CO2 concentrations
Authors: Loreto Francesco , Fischbach Robert J. , Schnitzler Jörg‐Peter , Ciccioli Paolo , Brancaleoni ENZO , Calfapietra Carlo , Seufert Guenther 
Published: March 2003

AbstractMonoterpene emissions, monoterpene synthase activities, photosynthesis, fluorescence yield in the dark and drought stress indicators (stomatal conductance and mid‐day water potential) were concurrently measured under similar temperature and illumination in current‐year leaves of Quercus ilex L. of plants grown in open‐top chambers at ambient (350 ppm) and elevated (700 ppm) CO2. The study was undertaken to understand the effect of CO2 on monoterpene biosynthesis, and to predict and parameterize the biogenic emissions at growing CO2 concentrations. The results of the 1998 and 1999 studies show that at elevated CO2, and in the absence of persistent environmental stresses, photosynthesis was stimulated with respect to ambient CO2, but that the emission of the three most abundantly emitted monoterpenes (α‐pinene, sabinene and β‐pinene) was inhibited by approximately 68%. The enzyme activities of the monoterpene synthases catalysing the formation of the three monoterpenes were also inhibited at elevated CO2 and an excellent relationship was found between monoterpene emission and activity of the corresponding enzyme both at ambient and elevated CO2. Interestingly, however, limonene emission was enhanced in conditions of elevated CO2 as it was also the corresponding synthase. The ratio between enzyme activity and emission of the three main monoterpenes was high (above 20) at ambient CO2 but it was below 10 at elevated CO2 and, for limonene, on both treatments. Our results indicate that the overall emission of monoterpenes at elevated CO2 will be inhibited because of a concurrent, strong down‐regulation of monoterpene synthase activities. When the enzyme activity does not change, as for limonene, the high photosynthetic carbon availability at elevated CO2 conditions may even stimulate emission. The results of the 1997 study show that severe and persistent drought, as commonly occurs in the Mediterranean, may inhibit both photosynthesis and monoterpene (α‐pinene) emission, particularly at ambient CO2. Thus, emission is probably limited by photosynthetic carbon availability; the effect of elevated CO2per se is not apparent if drought, and perhaps other environmental stresses, are also present.
Modelling night‐time ecosystem respiration by a constrained source optimization method
Authors: Lai Chun‐Ta , Katul Gabriel , Butnor John , Ellsworth David , Oren Ram 
Published: March 2003

AbstractOne of the main challenges to quantifying ecosystem carbon budgets is properly quantifying the magnitude of night‐time ecosystem respiration. Inverse Lagrangian dispersion analysis provides a promising approach to addressing such a problem when measured mean CO2 concentration profiles and nocturnal velocity statistics are available. An inverse method, termed ‘Constrained Source Optimization’ or CSO, which couples a localized near‐field theory (LNF) of turbulent dispersion to respiratory sources, is developed to estimate seasonal and annual components of ecosystem respiration. A key advantage to the proposed method is that the effects of variable leaf area density on flow statistics are explicitly resolved via higher‐order closure principles. In CSO, the source distribution was computed after optimizing key physiological parameters to recover the measured mean concentration profile in a least‐square fashion. The proposed method was field‐tested using 1 year of 30‐min mean CO2 concentration and CO2 flux measurements collected within a 17‐year‐old (in 1999) even‐aged loblolly pine (Pinus taeda L.) stand in central North Carolina. Eddy‐covariance flux measurements conditioned on large friction velocity, leaf‐level porometry and forest‐floor respiration chamber measurements were used to assess the performance of the CSO model. The CSO approach produced reasonable estimates of ecosystem respiration, which permits estimation of ecosystem gross primary production when combined with daytime net ecosystem exchange (NEE) measurements. We employed the CSO approach in modelling annual respiration of above‐ground plant components (c. 214 g C m−2 year−1) and forest floor (c. 989 g C m−2 year−1) for estimating gross primary production (c. 1800 g C m−2 year−1) with a NEE of c. 605 g C m−2 year−1 for this pine forest ecosystem. We conclude that the CSO approach can utilise routine CO2 concentration profile measurements to corroborate forest carbon balance estimates from eddy‐covariance NEE and chamber‐based component flux measurements.
The effects of long‐term elevated UV‐B on the growth and phenolics of field‐grown silver birch (Betula pendula)
Authors: Tegelberg Riitta , Julkunen‐Tiitto Riitta , Aphalo Pedro J. 
Published: March 2003

AbstractThe effects of long‐term elevated UV‐B radiation on silver birch (Betula pendula Roth) seedlings were studied over three growing seasons in an outdoor experiment in Finland started 64 days after germination. One group of seedlings was exposed to a constant 50% increase in UV‐BCIE radiation, which corresponds to 20–25% of ozone depletion; another group received a small increase in UV‐A radiation and a third (the control group) received ambient solar radiation. Changes in growth appeared during the third growing season; the stems of the UV‐B treated seedlings were thinner and their height tended to be shorter compared with that of the control seedlings. In contrast, there were no UV‐B effects on biomass, bud burst, bud dry weights, leaf area, rust frequency index or chlorophyll concentrations in any of the summers. During the three‐year study, the flavonols were significantly increased by the elevated UV‐B only in the first growing season. The responses varied greatly among individual compounds; the most induced were the quercetin glycosides, while the main flavonols, myricetins, were reduced by the UV‐A control treatment. In the second summer phenolic acids, such as 3,4′‐dihydroxypropiophenone‐3‐glucoside, neochlorogenic acid and 5‐coumarylquinic acid, were increased by the UV‐B treatment. In the third year, the constitutive concentrations of phenolics were not affected by the UV‐B treatment.
The influence of elevated atmospheric CO2 on fine root dynamics in an intact temperate forest
Authors: Pritchard Seth G. , Rogers Hugo H. , Davis Micheal A. , Van Santen Edzard , Prior Stephen A. , Schlesinger William H. 
Published: March 2003

AbstractRoot dynamics are important for plant, ecosystem and global carbon cycling. Changes in root dynamics caused by rising atmospheric CO2 not only have the potential to moderate further CO2 increases, but will likely affect forest function. We used FACE (Free‐Air CO2 Enrichment) to expose three 30‐m diameter plots in a 13‐year‐old loblolly pine (Pinus taeda) forest to elevated (ambient + 200 µL L−1) atmospheric CO2. Three identical fully instrumented plots were implemented as controls (ambient air only). We quantified root dynamics from October 1998 to October 1999 using minirhizotrons. In spite of 16% greater root lengths and 24% more roots per minirhizotron tube, the effects of elevated atmospheric CO2 on root lengths and numbers were not statistically significant. Similarly, production and mortality were also unaffected by the CO2 treatment, even though annual root production and mortality were 26% and 46% greater in elevated compared to ambient CO2 plots. Average diameters of live roots present at the shallowest soil depth were, however, significantly enhanced in CO2‐enriched plots. Mortality decreased with increasing soil depth and the slopes of linear regression lines (mortality vs. depth) differed between elevated and ambient CO2 treatments, reflecting the significant CO2 by depth interaction. Relative root turnover (root flux/live root pool) was unchanged by exposure to elevated atmospheric CO2. Results from this study suggest modest, if any, increases in ecosystem‐level root productivity in CO2‐enriched environments.
Assessing effects of forecasted climate change on the diversity and distribution of European higher plants for 2050
Authors: Bakkenes M. , Alkemade J. R. M. , Ihle F. , Leemans R. , Latour J. B. 
Published: March 2003

AbstractThe rapidly increasing atmospheric concentrations of greenhouse gases may lead to significant changes in regional and seasonal climate patterns. Such changes can strongly influence the diversity and distribution of species and, therefore, affect ecosystems and biodiversity. To assess these changes we developed a model, called euromove. The model uses climate data from 1990 to 2050 as compiled from the image 2 model, and determines climate envelopes for about 1400 plant species by multiple logistic regression analysis. The climate envelopes were applied to the projected climate to obtain predictions about plant diversity and distributions by 2050. For each European grid cell, euromove calculates which species would still occur in forecasted future climate conditions and which not. The results show major changes in biodiversity by 2050. On average, 32% of the European plant species that were present in a cell in 1990 would disappear from that cell. The area, in which 32% or more of the 1990 species will disappear, takes up 44% of the modelled European area. Individual responses of the plant species to the forecasted climate change were diverse. In reviewing possible future trends, we found that plant species, in general, would find their current climate envelopes further northeast by 2050, shifting ranges that were comparable with those ranges in other studies.
Interacting elevated CO2 and tropospheric O3 predisposes aspen (Populus tremuloides Michx.) to infection by rust (Melampsora medusae f. sp. tremuloidae)
Authors: Karnosky D. F. , Percy Kevin E. , Xiang Bixia , Callan Brenda , Noormets Asko , Mankovska Blanka , Hopkin Anthony , Sober Jaak , Jones Wendy , Dickson R. E. , Isebrands J. G. 
Published: March 2003

AbstractWe investigated the interaction of elevated CO2 and/or (Ozone) O3 on the occurrence and severity of aspen leaf rust (Melampsora medusae Thuem. f. sp. tremuloidae) on trembling aspen (Populus tremuloides Michx.). Furthermore, we examined the role of changes in leaf surface properties induced by elevated CO2 and/or O3 in this host–pathogen interaction. Three‐ to five‐fold increases in levels of rust infection index were found in 2 consecutive years following growing‐season‐long exposures with either O3 alone or CO2 + O3 depending on aspen clone. Examination of leaf surface properties (wax appearance, wax amount, wax chemical composition, leaf surface and wettability) suggested significant effects by O3 and CO2 + O3. We conclude that elevated O3 is altering aspen leaf surfaces in such a way that it is likely predisposing the plants to increased infection by aspen leaf rust.
Steps towards justice for people with learning disabilities as victims of crime: the important role of the police
Authors: Sharp Hannah 
Published: March 2003

SummaryDuring 1999, Mencap, Values Into Action and Enable jointly conducted the first UK‐wide inquiry into the harassment, victimization and bullying of people with learning disabilities (LDs). Only 17% of participants in the inquiry reported incidents of crimes against them to the police according to a 1999 Mencap report. Values Into Action has continued its involvement in this project on crime, harassment and people with LDs. Since the UK inquiry, the project has examined the developmental work required by the police to respond adequately to the reports which they receive from people with LDs who may be victims. The present paper outlines: (1) the key findings of the Mencap inquiry; (2) some of the difficulties experienced by people with LDs in reporting possible crimes to the police; and (3) the recent changes in policy and law which have the potential to improve radically how people with LDs experience contact with the police and thereby improve their access to the criminal justice system.
Movement of yeast 1,3‐β‐glucan synthase is essential for uniform cell wall synthesis
Authors: Utsugi Takahiko , Minemura Masayo , Hirata Aiko , Abe Mitsuhiro , Watanabe Daisuke , Ohya Yoshikazu 
Published: March 2003

AbstractBackground:  The cell wall has an important role in maintaining cell shape. In the budding yeast Saccharomyces cerevisiae, the major filamentous component of the cell wall responsible for its rigidity is 1,3‐β‐glucan and is synthesized by 1,3‐β‐glucan synthase (GS), localized on the plasma membrane.Results:  Observations of green fluorescent protein (GFP)‐conjugated Fks1p, a catalytic subunit of GS, revealed that it is co‐localized with cortical actin patches and moves on the cell surface at the sites of cell wall remodelling. Mutants with impaired actin patch movement show immobility of Fks1p‐GFP spots, indicating that actin patch motility is required for the movement of Fks1p. Cells with immobilized Fks1p exhibit defective cell wall structure and function. The cell wall thickness of the mutants becomes irregular, eventually leading to cell lysis.Conclusion:  We propose that GS movement is necessary for proper cell wall remodelling.
Hyperploidy induced by drugs that inhibit formation of microtubule promotes chromosome instability
Authors: Nitta Masayuki , Tsuiki Hiromasa , Arima Yoshimi , Harada Kei , Nishizaki Takahumi , Sasaki Kousuke , Mimori Tatsuyuki , Ushio Yukitaka , Saya Hideyuki 
Published: March 2003

AbstractBackground: Antimicrotubule drugs (AMDs), such as taxol and vincristine, are the most important addition to the chemotherapeutic armamentarium against human cancers. It has been shown that prolonged AMD treatment induces hyperploidy in G1‐checkpoint‐defective cancer cells and that these hyperploid cells subsequently undergo apoptosis. However, a fraction of these hyperploid cells are able to survive the prolonged mitotic stress and resume cell‐cycle progression.Results: We established hyperploid clones that escaped from cell death after AMD treatment from two glioma cell lines, U251MG and U87MG. Subtractive comparative genomic hybridization (CGH) analysis revealed that clones derived from U87MG mainly had chromosome number changes, but that those from U251MG showed both numerical and structural chromosomal changes. Furthermore, numerous aberrations identified in U251MG clones were remarkably chromosome‐specific, which may have been due to clonal selection for cells that have an advantage in growth and/or survival. All clones derived from both cell lines had abnormalities in chromosome segregation, and karyotypes of clones were more heterogeneous than those of parental cells, suggesting that cells having a higher chromosome number are subject to asymmetric chromosome segregation, resulting in a heterogeneous karyotype. All clones derived from U87MG and U251MG increased both centric and acentromeric micronuclei, suggesting the presence of chromosome structural abnormality.Conclusions: AMD treatment induces hyperploid formation and chromosome instability in checkpoint‐deficient cancer cells.
Phosphatidylinositol 3‐phosphate 5‐kinase is required for the cellular response to nutritional starvation and mating pheromone signals in Schizosaccharomyces pombe
Authors: Morishita Masayo , Morimoto Fusako , Kitamura Kenji , Koga Takako , Fukui Yasuhisa , Maekawa Hiromi , Yamashita Ichiro , Shimoda Chikashi 
Published: March 2003

AbstractBackground: Phosphatidylinositol (3,5) bisphosphate, which is converted from phosphatidylinositol 3‐phosphate by phosphatidylinositol 3‐phosphate 5‐kinase, is implicated in vacuolar functions and the sorting of cell surface proteins within endosomes in the endocytic pathway of budding yeast. A homologous protein, SpFab1p, has been found in the fission yeast Schizosaccharomyces pombe, but its role is not known.Results: Here we report that SpFab1p is encoded by ste12+ known as a fertility gene in S. pombe. The ste12 mutant grew normally under stress‐free conditions, but was highly vacuolated and swelled at high temperatures and under starvation conditions. In nitrogen‐free medium, ste12 cells were arrested in G1 phase, but partially defective in the expression of genes responsible for mating and meiosis. The ste12 mutant was defective both in the production of, and in the response to, mating pheromones. The amount of the pheromone receptor protein Map3p, was substantially decreased in ste12 cells. Map3p was transported to the cell surface, then internalized and eventually transported to the vacuolar lumen, even in the ste12 mutant.Conclusion: The results indicate that phosphatidylinositol(3,5)bisphosphate is essential for cellular responses to various stresses and for the mating pheromone signalling under starvation conditions.
The cystic fibrosis transmembrane conductance regulator is not a base transporter in isolated duodenal epithelial cells
Authors: PRAETORIUS J. , FRIIS U. G. , AINSWORTH M. A. , SCHAFFALITZKY DE MUCKADELL O. B. , JOHANSEN T. 
Published: March 2003

ABSTRACTDuodenal epithelial bicarbonate secretion has previously been shown to be greatly impaired in mice deficient of the cystic fibrosis transmembrane conductance regulator (CFTR). It has been proposed that transmembranal bicarbonate transport occurs through the CFTR channel itself. In the present study, the transport of acid/base equivalents across the plasma membrane of proximal duodenal epithelial cells from CFTR deficient mice was compared with that of cells from normal littermates. Mixed epithelial cells from both villi and crypts were isolated from proximal duodenum and intracellular pH was assessed by cuvette‐based fluorescence spectrometry using the pH sensitive dye 2′,7′‐bis‐(2‐carboxyethyl)‐5‐(and‐6)‐carboxyfluorescein. The steady state intracellular pH, the acid extrusion rate and the alkaline extrusion rate were unaffected by CFTR deficiency in the presence of CO2/HCO3–. Forskolin had no effect on acid extrusion or alkaline extrusion rates. In control experiments without CO2/HCO3–, the intrinsic buffering capacities, the steady state intracellular pH and the acid extrusion rates were equivalent in the cells from CFTR deficient mice and normal littermates. The results are consistent with a model where acid/base transport is almost exclusively mediated by the previously described transporters in the murine duodenum (i.e. Na+/H+ exchange, Cl–/HCO3– exchange and Na+ : HCO3– cotransport). There were no evidence for significant CFTR dependent HCO3– transport in proximal duodenal epithelial cells of mixed villus and crypt origin.
Dopamine‐induced inhibition of Na+‐K+‐ATPase activity requires integrity of actin cytoskeleton in opossum kidney cells
Authors: GOMES P. , SOARES‐DA‐SILVA P. 
Published: March 2003

ABSTRACTThe present study evaluated the importance of the association between Na+‐K+‐ATPase and the actin cytoskeleton on dopamine‐induced inhibition of Na+‐K+‐ATPase activity. The approach used measures the transepithelial transport of Na+ in monolayers of opossum kidney (OK) cells, when the Na+ delivered to Na+‐K+‐ATPase was increased at the saturating level by amphotericin B. The maximal amphotericin B (1.0 μg mL–1) induced increase in short‐circuit current (Isc) was prevented by ouabain (100 μM) or removal of apical Na+. Dopamine (1 μM) applied from the apical side significantly decreased (29 ± 5% reduction) the amphotericin B‐induced increase in Isc, this being prevented by the D1‐like receptor antagonist SKF 83566 (1 μM) and the protein kinase C (PKC) inhibitor chelerythrine (1 μM). Exposure of OK cells to cytochalasin B (1 μM) or cytochalasin D (1 μM), inhibitors of actin polymerization, from both cell sides reduced by 31 ± 4% and 36 ± 3% the amphotericin B‐induced increase in Isc and abolished the inhibitory effect of apical dopamine (1 μM), but not that of the PKC activator phorbol‐12,13‐dibutyrate (PDBu; 100 nM). Colchicine (1 μM) failed to alter the inhibitory effects of dopamine. The relationship between Na+‐K+‐ATPase and the concentration of extracellular Na+ showed a Michaelis–Menten constant (Km) of 44.1 ± 13.7 mM and a Vmax of 49.6 ± 4.8 μA cm–2 in control monolayers. In the presence of apical dopamine (1 μM) or cytochalasin B (1 μM) Vmax values were significantly (P < 0.05) reduced without changes in Km values. These results are the first, obtained in live cells, showing that the PKC‐dependent inhibition of Na+‐K+‐ATPase activity by dopamine requires the integrity of the association between actin cytoskeleton and Na+‐K+‐ATPase.