bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone mineral density in acromegaly: the effect of gender, disease activity and gonadal status
Authors: Scillitani Alfredo , Battista Claudia , Chiodini Iacopo , Carnevale Vincenzo , Fusilli Saverio , Ciccarelli Enrica , Terzolo Massimo , Oppizzi Giuseppe , Arosio Maura , Gasperi Maurizio , Arnaldi Giorgio , Colao Annamaria , Baldelli Roberto , Ghiggi Maria Rosaria , Gaia Daniela , Di Somma Carolina , Trischitta Vincenzo , Liuzzi Antonio 
Published: June 2003

Summaryobjective Data on bone mineral density (BMD) in acromegaly are conflicting as most previous studies collectively evaluated eugonadal and hypogonadal patients of both sexes, with or without active disease. We have evaluated BMD in 152 acromegalic patients of both sexes with varying disease activity and gonadal status.design Cross‐sectional, retrospective.patients We studied 152 acromegalic patients (99 women aged 26–72 years, and 53 men aged 21–75 years), 107 with active and 45 with controlled disease. Eighty‐five patients had normal gonadal status and 67 were hypogonadal.measurements In all patients we measured serum GH levels by immunoenzimometric assay, and serum IGF‐I levels by radioimmunoassay. BMD was assessed at spine L2–L4 (LS) and at femoral neck (FN) by dual energy X‐ray absorptiometry; results are expressed as Z‐values.results We evaluated the effect of GH excess on bone at different sites in relation to gonadal status, disease activity and gender. At LS, in respect to the reference population, BMD (mean ± SE) values were higher in eugonadal patients (active: 0·71 ± 0·29, P < 0·02; controlled: 0·65 ± 0·28, P < 0·05) and lower in hypogonadal ones (active: −0·64 ± 0·35, 0·1 < P < 0·05; controlled: −1·05 ± 0·36, P < 0·01), regardless of disease activity. On the contrary, at FN, BMD was higher than in the reference population, both in eugonadal (1·01 ± 0·22, P < 0·001) and hypogonadal (0·63 ± 0·17, P < 0·001) patients only in subjects with active disease, but not in those in which the disease was controlled (eugonadal: 0·31 ± 0·23, P = ns; hypogonadal 0·04 ± 0·28, P = ns). We did not observe any difference in BMD values according to gender both at LS (males vs. females −0·02 ± 0·30 vs. 0·01 ± 0·24, P = ns) or at FN (0·77 ± 0·19 vs. 0·63 ± 0·15, P = ns).conclusions The anabolic effect of GH excess on bone in acromegalic patients is: (i) gender‐independent; (ii) evident at the spine only in eugonadal regardless of disease activity; (iii) evident at femoral neck only in the presence of active disease regardless of gonadal status.
Seed production and seed quality in a calcareous grassland in elevated CO2
Authors: THÜRIG BARBARA , KÖRNER CHRISTIAN , STÖCKLIN JÜRG 
Published: May 2003

AbstractIn diverse plant communities the relative contribution of species to community biomass may change considerably in response to elevated CO2. Along with species‐specific biomass responses, reproduction is likely to change as well with increasing CO2 and might further accelerate shifts in species composition. Here, we ask if, after 5 years of CO2 exposure, seed production and seed quality in natural nutrient‐poor calcareous grassland are affected by elevated CO2 (650 μL L−1 vs 360 μL L−1) and how this might affect long‐term community dynamics. The effect of elevated CO2 on the number of flowering shoots (+ 24%, P < 0.01) and seeds (+ 29%, P = 0.06) at the community level was similar to above ground biomass responses in this year, suggesting that the overall allocation to sexual reproduction remained unchanged. Compared among functional groups of species we found a 42% increase in seed number (P < 0.01) of graminoids, a 33% increase (P = 0.07) in forbs, and no significant change in legumes (− 38%, n.s.) under elevated CO2. Large responses particularly of two graminoid species and smaller responses of many forb species summed up to the significant or marginally significant increase in seed number of graminoids and forbs, respectively. In several species the increase in seed number resulted both from an increase in flowering shoots and an increase in inflorescence size. In most species, seeds tended to be heavier (+ 12%, P < 0.01), and N‐concentration of seeds was significantly reduced in eight out of 13 species. The fraction of germinating seeds did not differ between seeds produced in ambient and elevated CO2, but time to germination was significantly shortened in two species and prolonged in one species when seeds had been produced in elevated CO2. Results suggest that species specific increases in seed number and changes in seed quality will exert substantial cumulative effects on community composition in the long run.
Production, turnover and mycorrhizal colonization of root systems of three Populus species grown under elevated CO2 (POPFACE)
Authors: LUKAC MARTIN , CALFAPIETRA CARLO , GODBOLD DOUGLAS L. 
Published: May 2003

AbstractA fast growing high density Populus plantation located in central Italy was exposed to elevated carbon dioxide for a period of three years. An elevated CO2 treatment (550 ppm), of 200 ppm over ambient (350 ppm) was provided using a FACE technique. Standing root biomass, fine root turnover and mycorrhizal colonization of the following Populus species was examined: Populus alba L., Populus nigra L., Populus x euramericana Dode (Guinier). Elevated CO2 increased belowground allocation of biomass in all three species examined, standing root biomass increased by 47–76% as a result of FACE treatment. Similarly, fine root biomass present in the soil increased by 35–84%. The FACE treatment resulted in 55% faster fine root turnover in P. alba and a 27% increase in turnover of roots of P. nigra and P. x euramericana. P. alba and P. nigra invested more root biomass into deeper soil horizon under elevated CO2. Response of the mycorrhizal community to elevated CO2 was more varied, the rate of infection increased only in P. alba for both ectomycorrhizal (EM) and arbuscular mycorrhizas (AM). The roots of P. nigra showed greater infection only by AM and the colonization of the root system of P. x euramericana was not affected by FACE treatment. The results suggest that elevated atmospheric CO2 conditions induce greater belowground biomass investment, which could lead to accumulation of assimilated C in the soil profile. This may have implications for C sequestration and must be taken into account when considering long‐term C storage in the soil.
Thermal acclimation of leaf and root respiration: an investigation comparing inherently fast‐ and slow‐growing plant species
Authors: LOVEYS B. R. , ATKINSON L. J. , SHERLOCK D. J. , ROBERTS R. L. , FITTER A. H. , ATKIN O. K. 
Published: May 2003

AbstractWe investigated the extent to which leaf and root respiration (R) differ in their response to short‐ and long‐term changes in temperature in several contrasting plant species (herbs, grasses, shrubs and trees) that differ in inherent relative growth rate (RGR, increase in mass per unit starting mass and time). Two experiments were conducted using hydroponically grown plants. In the long‐term (LT) acclimation experiment, 16 species were grown at constant 18, 23 and 28 °C. In the short‐term (ST) acclimation experiment, 9 of those species were grown at 25/20 °C (day/night) and then shifted to a 15/10 °C for 7 days. Short‐term Q10 values (proportional change in R per 10 °C) and the degree of acclimation to longer‐term changes in temperature were compared. The effect of growth temperature on root and leaf soluble sugar and nitrogen concentrations was examined. Light‐saturated photosynthesis (Asat) was also measured in the LT acclimation experiment. Our results show that Q10 values and the degree of acclimation are highly variable amongst species and that roots exhibit lower Q10 values than leaves over the 15–25 °C measurement temperature range. Differences in RGR or concentrations of soluble sugars/nitrogen could not account for the inter‐specific differences in the Q10 or degree of acclimation. There were no systematic differences in the ability of roots and leaves to acclimate when plants developed under contrasting temperatures (LT acclimation). However, acclimation was greater in both leaves and roots that developed at the growth temperature (LT acclimation) than in pre‐existing leaves and roots shifted from one temperature to another (ST acclimation). The balance between leaf R and Asat was maintained in plants grown at different temperatures, regardless of their inherent relative growth rate. We conclude that there is tight coupling between the respiratory acclimation and the temperature under which leaves and roots developed and that acclimation plays an important role in determining the relationship between respiration and photosynthesis.
Reduction of forest floor respiration by fertilization on both carbon dioxide‐enriched and reference 17‐year‐old loblolly pine stands
Authors: BUTNOR JOHN R. , JOHNSEN KURT H. , OREN RAM , KATUL GABRIEL G. 
Published: May 2003

AbstractElevated atmospheric carbon dioxide (CO2e) increases soil respiration rates in forest, grassland, agricultural and wetland systems as a result of increased growth, root biomass and enhanced biological activity of soil microorganisms. Less is known about how forest floor fluxes respond to the combined effects of elevated CO2and nutrient amendments; until now no experiments have been in place with large forest trees to allow even preliminary investigations. We investigated changes in forest floor respiration (Sff) in aPinus taedaL. plantation fumigated with CO2by using free‐air CO2enrichment (FACE) technology and given nutrient amendments. The prototype FACE apparatus (FACEp; 707 m2) was constructed in 1993, 10 years after planting, on a moderate fertility site in Duke Forest, North Carolina, USA, enriching the stand to 55 Pa (CO2e). A nearby ambient CO2(CO2a) plot (117 m2) was designated at the inception of the study as a reference (Ref). Both FACEp and Ref plot were divided in half and urea fertilizer was applied to one half at an annual rate of 11.2 g N m−2in the spring of 1998, 1999 and 2000. Forest floor respiration was monitored continuously for 220 days – March through November 2000 – by using two Automated Carbon Efflux Systems. Thirty locations (491 cm2each) were sampled in both FACEp and Ref, about half in each fertility treatment. Forest floor respiration was strongly correlated with soil temperature at 5 cm. Rates ofSffwere greater in CO2erelative to CO2a(an enhancement of ∼178 g C m−2) during the measurement period. Application of fertilizer resulted in a statistically significant depression of respiration rates in both the CO2aand CO2eplots (a reduction of ∼186 g C m−2). The results suggest that closed canopy forests on moderate fertility sites cycle back to the atmosphere more assimilated carbon (C) than similar forests on sites of high fertility. We recognize the limitations of this non‐replicated study, but its clear results offer strong testable hypotheses for future research in this important area.
Conversion of hardwood forests to spruce and pine plantations strongly reduced soil methane sink in Germany
Authors: BORKEN WERNER , XU YI‐JUN , BEESE FRIEDRICH 
Published: May 2003

AbstractWell‐drained forest soils are thought to be a significant sink for atmospheric methane. Recent research suggests that land use change reduces the soil methane sink by diminishing populations of methane oxidizing bacteria. Here we report soil CH4 uptake from ‘natural’ mature beech forests and from mature pine and spruce plantations in two study areas of Germany with distinct climate and soils. The CH4 uptake rates of both beech forests at Solling and Unterlüß were about two–three times the CH4 uptake rates of the adjacent pine and spruce plantations, indicating a strong impact of forest type on the soil CH4 sink. The CH4 uptake rates of sieved mineral soils from our study sites confirmed the tree species effect and indicate that methanotrophs were mainly reduced in the 0–5 cm mineral soil depth. The reasons for the reduction are still unknown. We found no site effect between Solling and Unterlüß, however, CH4 uptake rates from Solling were significantly higher at the same effective CH4 diffusivity. This potential site effect was masked by higher soil water contents at Solling. Soil pH (H2O) explained 71% of the variation in CH4 uptake rates of sieved mineral soils from the 0–5 cm depth, while cation exchange capacity, soil organic carbon, soil nitrogen and total phosphorous content were not correlated with CH4 uptake rates. Comparing 1998–99, annual CH4 uptake rates increased by 69–111% in the beech and spruce stands and by 5–25% in the pine stands, due primarily to differences in growing season soil moisture. Cumulative CH4 uptake rates from November throughout April were rather constant in both years. The CH4 uptake rates of each stand were separately predicted using daily average soil matric potential and a previously developed empirical model. The model results revealed that soil matric potential explains 53–87% of the temporal variation in CH4 uptake. The differences between measured and predicted annual CH4 uptake rates were less than 10%, except for the spruce stand at Solling in 1998 (17%). Based on data from this study and from the literature, we calculated a total reduction in the soil CH4 sink of 31% for German forests due in part to conversion of deciduous to coniferous forests.
Long‐term changes in phytoplankton, zooplankton and salmon related to climate
Authors: BEAUGRAND GRÉGORY , REID PHILIP C. 
Published: May 2003

AbstractRecently, large‐scale changes in the biogeography of calanoid copepod crustaceans have been detected in the northeastern North Atlantic Ocean and adjacent seas. Strong biogeographical shifts in all copepod assemblages were found with a northward extension of more than ° in latitude of warm‐water species associated with a decrease in the number of colder‐water species. These changes were attributed to regional increase in sea surface temperature. Here, we have extended these studies to examine long‐term changes in phytoplankton, zooplankton and salmon in relation to hydro‐meteorological forcing in the northeast Atlantic Ocean and adjacent seas. We found highly significant relationships between (1) long‐term changes in all three trophic levels, (2) sea surface temperature in the northeastern Atlantic, (3) Northern Hemisphere temperature and (4) the North Atlantic Oscillation. The similarities detected between plankton, salmon, temperature and hydro‐climatic parameters are also seen in their cyclical variability and in a stepwise shift that started after a pronounced increase in Northern Hemisphere Temperature anomalies at the end of the 1970s. All biological variables show a pronounced change which started after circa 1982 for euphausiids (decline), 1984 for the total abundance of small copepods (increase), 1986 for phytoplankton biomass (increase) and Calanus finmarchicus (decrease) and 1988 for salmon (decrease). This cascade of biological events led to an exceptional period, which is identified after 1986 to present and followed another shift in large‐scale hydro‐climatic variables and sea surface temperature. This regional temperature increase therefore appears to be an important parameter that is at present governing the dynamic equilibrium of northeast Atlantic pelagic ecosystems with possible consequences for biogeochemical processes and fisheries.
Accumulation of carbon and nitrogen by old arable land reverting to woodland
Authors: POULTON P. R. , PYE E. , HARGREAVES P. R. , JENKINSON D. S. 
Published: May 2003

AbstractThe accumulation of carbon (C) and nitrogen (N) was measured on two sites on Rothamsted Farm that had been fenced off some 120 years ago and allowed to revert naturally to woodland. The sites had previously been arable for centuries. One had been chalked and was still calcareous; the other had never been chalked and the pH fell from 7.1 in 1883 to 4.4 in 1999. The acidic site (Geescroft wilderness) is now a deciduous wood, dominated by oak (Quercus robor); the calcareous site (Broadbalk wilderness) is now dominated by ash (Fraxinus excelsior), with sycamore (Acer pseudoplatanus) and hawthorn (Craetagus monogyna) as major contributors. The acidic site gained 2.00 t C ha−1 yr−1 over the 118‐year period (0.38 t in litter and soil to a depth of 69 cm, plus an estimated 1.62 t in trees and their roots); the corresponding gains of N were 22.2 kg N ha−1 year−1 (15.2 kg in the soil, plus 6.9 kg in trees and their roots). The calcareous site gained 3.39 t C ha−1 year−1 over the 120‐year period (0.54 t in the soil, plus an estimated 2.85 t in trees and roots); for N the gains were 49.6 kg ha−1 yr−1 (36.8 kg in the soil, plus 12.8 kg in trees and roots). Trees have not been allowed to grow on an adjacent part of the calcareous site. There is now a little more C and N in the soil from this part than in the corresponding soil under woodland. We argue from our results that N was the primary factor limiting plant growth and hence accumulation of C during the early stages of regeneration in these woodlands. As soil organic N accumulates and the sites move towards N saturation, other factors become limiting. Per unit area of woodland, narrow strips; that is, wide hedges with trees, are the most efficient way of sequestering C – provided that they are not short of N.
Stoichiometric impacts of increased carbon dioxide on a planktonic herbivore
Authors: URABE JOTARO , TOGARI JUN , ELSER JAMES J. 
Published: May 2003

AbstractThe partial pressure of carbon dioxide (pCO2) in lake ecosystems varies over four orders of magnitude and is affected by local and global environmental perturbations associated with both natural and anthropogenic processes. Little is known, however, about how changes in pCO2 extend into the function and structure of food webs in freshwater ecosystems. To fill this gap, we performed laboratory experiments using the ecologically important planktonic herbivore Daphnia and its algal prey under a natural range of pCO2 with low light and phosphorus supplies. The experiment showed that increased pCO2 stimulated algal growth but reduced algal P : C ratio. When feeding on algae grown under high pCO2, herbivore growth decreased regardless of algal abundance. Thus, high CO2‐raised algae were poor food for Daphnia. Short‐term experimental supplementation of PO4 raised the P content of the high CO2‐raised algae and improved Daphnia growth, indicating that low Daphnia growth rates under high pCO2 conditions were due to lowered P content in the algal food. These results suggest that, in freshwater ecosystems with low nutrient supplies, natural processes as well as anthropogenic perturbations resulting in increased pCO2 enhance algal production but reduce energy and mass transfer efficiency to herbivores by decreasing algal nutritional quality.
Changes in flowering and abundance of Delphinium nuttallianum (Ranunculaceae) in response to a subalpine climate warming experiment
Authors: SAAVEDRA FRANCISCA , INOUYE DAVID W. , PRICE MARY V. , HARTE JOHN 
Published: May 2003

AbstractHigh‐altitude and high‐latitude sites are expected to be very sensitive to global warming, because the biological activity of most plants is restricted by the length of the short snow‐free season, which is determined by climate. Long‐term observational studies in subalpine meadows of the Colorado Rocky Mountains have shown a strong positive correlation between snowpack and flower production by the forb Delphinium nuttallianum. If a warmer climate reduces annual snowfall in this region then global warming might reduce fitness in D. nuttallianum. In this article we report effects of experimental warming on the abundance and flower production of D. nuttallianum. Plant abundance (both flowering and vegetative plants) was slightly greater on warmed than control plots prior to initiation of the warming treatment in 1991. Since 1994 experimental warming has had a negative effect on D. nuttallianum flower production, reducing both the abundance of flowering plants and the total number of flowers per plant. Flower bud abortion was higher in the heated plots than the controls only in 1994 and 1999. Results from both the warming experiment and analyses of unmanipulated long‐term plots suggest that global warming may affect the fecundity of D. nuttallianum, which may have cascading effects on the pollinators that depend on it and on the fecundity of plants that share similar pollinators.
Large seasonal changes in Q10 of soil respiration in a beech forest
Authors: JANSSENS IVAN A. , PILEGAARD KIM 
Published: May 2003

AbstractWe analyzed one year of continuous soil respiration measurements to assess variations in the temperature sensitivity of soil respiration at a Danish beech forest. A single temperature function derived from all measurements across the year (Q10 = 4.2) was adequate for estimating the total annual soil respiration and its seasonal evolution. However, Q10's derived from weekly datasets ranged between three in summer (at a mean soil temperature of 14 °C) and 23 in winter (at 2 °C), indicating that the annual temperature function underestimated the synoptic variations in soil respiration during winter. These results highlight that empirical models should be parameterized at a time resolution similar to that required by the output of the model. If the objective of the model is to simulate the total annual soil respiration rate, annual parameterization suffices. If however, soil respiration needs to be simulated over time periods from days to weeks, as is the case when soil respiration is compared to total ecosystem respiration during synoptic weather patterns, more short‐term parameterization is required.Despite the higher wintertime Q10's, the absolute response of soil respiration to temperature was smaller in winter than in summer. This is mainly because in absolute numbers, the temperature sensitivity of soil respiration depends not only on Q10, but also on the rate of soil respiration, which is highly reduced in winter. Nonetheless, the Q10 of soil respiration in winter was larger than can be explained by the decreasing respiration rate only. Because the seasonal changes in Q10 were negatively correlated with temperature and positively correlated with soil moisture, they could also be related to changing temperature and/or soil moisture conditions.