bluuebunny/crossref_metadata_2025_split huggingface dataset:
UV‐B radiation causes early ripening and reduction in size of fruits in two lines of tomato (Lycopersicon esculentum Mill.)
Authors: Bacci L. , Grifoni D. , Sabatini F. , Zipoli G. 
Published: March 2003

SummaryAn open‐air experiment was performed in Pistoia (Italy) to investigate the possible protective role played by different contents of UV‐B absorbing compounds to realistic UV‐B supplementation and to study its effect on plant fruit production. A mutant line and its normal counterpart of Lycopersicon esculentum Mill, which differ in the content of UV‐B absorbing compounds, were used. Additional UV‐B radiation in the field was supplied to simulate a 20% stratospheric ozone depletion. Two groups of plants were grown: ‘control’, where plants received only natural solar UV‐B radiation, and ‘UV‐B’ treatment, where plants were grown under supplemental UV‐B. The results of the experiment showed that the content of UV‐B absorbing compounds of treated plants did not differ from that of the control in both lines. This indicates that natural sunlight, in Mediterranean areas, is saturating for synthesis of these compounds also in plants with normal content of UV‐B absorbing compounds. Consequently, plants are not able to produce significant additional amounts of them, in response to a realistic UV‐B supplementation, in order to protect the plant from additional UV‐B radiation. No different responses to the UV‐B supplementation were found between the two lines. The most significant UV‐B effect was an earlier reddening of fruits in comparison with the ‘control’ accompanied by a reduction in the size of mature fruits. No significant effects of UV‐B treatment were observed in biomass accumulation, leaf ontogeny, flowering or productivity.
Carbon dioxide and temperature effects on forage establishment: tissue composition and nutritive value
Authors: Fritschi Felix B. , Boote Kenneth J. , Sollenberger LynN. E. , Hartwell L. 
Published: March 2003

SummaryAtmospheric CO2 concentration ([CO2]) and temperature are likely to increase in the future and may change plant growth and composition characteristics. Rhizoma peanut (Arachis glabrata Benth.) and bahiagrass (Paspalum notatum Flügge) were grown on a natural field soil in temperature‐gradient greenhouses to evaluate the effects of elevated [CO2] and temperature on tissue composition and digestibility during the establishment year. Carbon dioxide levels were maintained at 365 (ambient) and 640 μL CO2 L–1 air. The temperature‐gradient greenhouses were regulated to obtain air temperature sectors of 0.2, 1.5, 2.9, and 4.5 °C above ambient. Samples were taken of previously undefoliated herbage at 57, 86, 121, 148, and 217 days after planting and entire plots were harvested at 218 days after planting. Elevated [CO2] increased total nonstructural carbohydrate concentration in rhizoma peanut leaves by almost 50%. Rhizoma peanut leaf N concentration was 6% lower at elevated than at ambient [CO2]. The N concentration in new rhizomes of rhizoma peanut was increased by high [CO2], while the N concentration in bahiagrass was not affected by temperature or [CO2]. No effects of [CO2] and temperature were found on neutral detergent fibre in rhizoma peanut leaves or stems; however, elevated [CO2] increased neutral detergent fibre in bahiagrass leaves. Only at season end was in vitro organic matter digestion of rhizoma peanut higher at ambient (623 g kg–1) than at elevated [CO2] (609 g kg–1). Elevated [CO2] had a greater effect on tissue composition of rhizoma peanut than of bahiagrass. These data suggest that elevated temperature and CO2‐induced changes in chemical composition of forage species adapted to humid subtropics will be relatively small, particularly for C4 species.
Decomposition of Metrosideros polymorpha leaf litter along elevational gradients in Hawaii
Authors: Scowcroft Paul. G. , Turner Douglas R. , Vitousek Peter M. 
Published: March 2003

SummaryWe examined interactions between temperature, soil development, and decomposition on three elevational gradients, the upper and lower ends of each being situated on a common lava flow or ash deposit. We used the reciprocal transplant technique to estimate decomposition rates of Metrosideros polymorpha leaf litter during a three‐year period at warm and cool ends of each gradient. Litter quality was poorest early in soil development or where soils were most intensely leached and waterlogged. In situ litter decomposition was slowest on the young 1855 flow (k=  0.26 and 0.14 at low and high elevation, respectively). The more fertile Laupahoehoe gradient also supported more rapid in situ decay at the warmer low elevation site (k=  0.90) than at high elevation (k=  0.51). The gradient with the most advanced soil development showed no difference for in situ decay at low and high elevations (k=  0.88 and 0.99, respectively) probably due to low soil nutrient availability at low elevation, which counteracted the effect of warmer temperature. Comparisons of in situ, common litter, and common site experiments indicated that site factors influenced decomposition more than litter quality did. The effect of temperature, however, could be over‐ridden by soil fertility or other site factors. Field gradient studies of this sort yield variable estimates of apparent Q10, even under the best conditions, due to interactions among temperature, moisture, nutrient availability, decomposer communities and litter quality. Such interactions may be as likely to occur with changing climate as they are along elevational gradients.
Carbon and nitrogen pools and mineralization in a grassland gley soil under elevated carbon dioxide at a natural CO2 spring
Authors: Ross D. J. , Tate K. R. , Newton P. C. D. , Wilde R. H. , Clark H. 
Published: March 2003

SummaryThe growth and chemical composition of most plants are influenced by elevated CO2, but accompanying effects on soil organic matter pools and mineralization are less clearly defined, partly because of the short‐term nature of most studies. Herein we describe soil properties from a naturally occurring cold CO2 spring (Hakanoa) in Northland, New Zealand, at which the surrounding vegetation has been exposed to elevated CO2 for at least several decades. The mean annual temperature at this site is ≈ 15.5 °C and rainfall ≈ 1550 mm. The site was unfertilized and ungrazed, with a vegetation of mainly C3 and C4 grasses, and had moderate levels of ‘available’ P. Two soils were present − a gley soil and an organic soil – but only the gley soil is examined here. Average atmospheric CO2 concentrations at 17 sampling locations in the gley soil area ranged from 372 to 670 ppmv.In samples at 0–5 cm depth, pH averaged 5.4; average values for organic C were 150 g, total N 11 g, microbial C 3.50 g, and microbial N 0.65 g kg−1, respectively. Under standardized moisture conditions at 25 °C, average rates of CO2‐C production (7–14 days) were 5.4 mg kg−1 h−1 and of net mineral‐N production (14 −42 days) 0.40 mg kg−1 h−1. These properties were all correlated positively and significantly (P < 0.10) with atmospheric CO2 concentrations, but not with soil moisture (except for CO2‐C production) or with clay content; they were, however, correlated negatively and mainly significantly with soil pH. In spite of uncertainties associated with the uncontrolled environment of naturally occurring springs, we conclude that storage of C and N can increase under prolonged exposure to elevated CO2, and may include an appreciable labile fraction in mineral soil with an adequate nutrient supply.
A global prognostic scheme of leaf onset using satellite data
Authors: Botta A. , Viovy N. , Ciais P. , Friedlingstein P. , Monfray P. 
Published: March 2003

SummaryLeaf phenology describes the seasonal cycle of leaf functioning. Although it is essential for understanding the interactions between the biosphere, the climate, and biogeochemical cycles, it has received little attention in the modelling community at global scale. This article focuses on the prediction of spatial patterns of the climatological onset date of leaf growth for the decade 1983–93. It examines the possibility of extrapolating existing local models of leaf onset date to the global scale. Climate is the main variable that controls leaf phenology for a given biome at this scale, and satellite observations provide a unique means to study the seasonal cycle of canopies. We combine leaf onset dates retrieved from NOAA/AVHRR satellite NDVI with climate data and the DISCover land‐cover map to identify appropriate models, and determine their new parameters at a 0.5° spatial resolution. We define two main regions: at temperate and high latitudes leaf onset models are mainly dependent on temperature; at low latitudes they are controlled by water availability. Some local leaf onset models are no longer relevant at the global scale making their calibration impossible. Nevertheless, we define our unified model by retaining the model that best reproduced the spatial distribution of leaf onset dates for each biome. The main spatial patterns of leaf onset date are well simulated, such as the Sahelian gradient due to aridity and the high latitude gradient due to frost. At temperate and high latitudes, simulated onset dates are in good agreement with climatological observations; 62% of treated grid‐cells have a simulated leaf onset date within 10 days of the satellite observed onset date (which is also the temporal resolution of the NDVI data). In tropical areas, the subgrid heterogeneity of the phenology is larger and our model's predictive power is diminished. The difficulties encountered in the tropics are due to the ambiguity of the satellite signal interpretation and the low reliability of rainfall and soil moisture fields.
Photosynthesis, respiration, and net primary production of sunflower stands in ambient and elevated atmospheric CO2 concentrations: an invariant NPP:GPP ratio?
Authors: Cheng Weixin , Sims Daniel A. , Luo Yiqi , Coleman James S. ,   and, Johnson Dale W. 
Published: March 2003

SummaryThe effect of elevated CO2 on photosynthesis, respiration, and growth efficiency of sunflower plants at the whole‐stand level was investigated using a whole‐system gas exchange facility (the EcoCELLs at the Desert Research Institute) and a 13C natural tracer method. Total daily photosynthesis (GPP), net primary production (NPP), and respiration under the elevated CO2 treatment were consistently higher than under the ambient CO2 treatment. The overall level of enhancement due to elevated CO2 was consistent with published results for a typical C3 plant species. The patterns of daily GPP and NPP through time approximated logistic curves under both CO2 treatments. Regression analysis indicated that both the rate of increase (the parameter ‘r’) and the maximum value (the parameter ‘k’) of daily GPP and NPP under the elevated CO2 treatment were significantly higher than under the ambient CO2 treatment. The percentage increase in daily GPP due to elevated CO2 varied systematically through time according to the logistic equations used for the two treatments. The GPP increase due to elevated CO2 ranged from approximately 10% initially to 73% at the peak, while declining to about 33%, as predicted by the ratio of the two maximum values. Different values of percentage increase in GPP and NPP were obtained at different sampling times. This result demonstrated that one‐time measurements of percentage increases due to elevated CO2 could be misleading, thereby making interpretation difficult. Although rhizosphere respiration was substantially enhanced by elevated CO2, no effect of elevated CO2 on R:P (respiration:photosynthesis) was found, suggesting an invariant NPP:GPP ratio during the entire experiment. Further validation of the notion of an invariant NPP:GPP ratio may significantly simplify the process of quantifying terrestrial carbon sequestration by directly relating total photosynthesis to net primary production.
Partitioning net ecosystem carbon exchange with isotopic fluxes of CO2
Authors: Bowling David R. , Tans Pieter P. , Monson Russell K. 
Published: March 2003

SummaryBecause biological and physical processes alter the stable isotopic composition of atmospheric CO2, variations in isotopic content can be used to investigate those processes. Isotopic flux measurements of13CO2above terrestrial ecosystems can potentially be used to separate net ecosystem CO2exchange (NEE) into its component fluxes, net photosynthetic assimilation (FA) and ecosystem respiration (FR). In this paper theory is developed to partition measured NEE intoFAandFR, using measurements of fluxes of CO2and13CO2, and isotopic composition of respired CO2and forest air. The theory is then applied to fluxes measured (or estimated, for13CO2) in a temperate deciduous forest in eastern Tennessee (Walker Branch Watershed). It appears that there is indeed enough additional information in13CO2fluxes to partition NEE into its photosynthetic and respiratory components. Diurnal patterns inFAandFRwere obtained, which are consistent in magnitude and shape with patterns obtained from NEE measurements and an exponential regression between night‐time NEE and temperature (a standard technique which provides alternate estimates ofFRandFA). The light response curve for photosynthesis (FAvs. PAR) was weakly nonlinear, indicating potential for saturation at high light intensities. Assimilation‐weighted discrimination against13CO2for this forest during July 1999 was 16.8–17.1‰, depending on canopy conductance. The greatest uncertainties in this approach lie in the evaluation of canopy conductance and its effect on whole‐canopy photosynthetic discrimination, and thus the indirect methods used to estimate isotopic fluxes. Direct eddy covariance measurements of13CO2flux are needed to assess the validity of the assumptions used and provide defensible isotope‐based estimates of the component fluxes of net ecosystem exchange.
Productivity overshadows temperature in determining soil and ecosystem respiration across European forests
Authors: Janssens I. A. , Lankreijer H. , Matteucci G. , Kowalski A. S. , Buchmann N. , Epron D. , Pilegaard K. , Kutsch W. , Longdoz B. , Grünwald T. , Montagnani L. , Dore S. , Rebmann C. , Moors E. J. , Grelle A. , Rannik Ü. , Morgenstern K. , Oltchev S. , Clement R. , Guðmundsson J. , Minerbi S. , Berbigier P. , Ibrom A. , Moncrieff J. , Aubinet M. , Bernhofer C. , Jensen N. O. , Vesala T. , Granier A. , Schulze E. ‐D. , Lindroth A. , Dolman A. J. , Jarvis P. G. , Ceulemans R. , Valentini R. 
Published: March 2003

SummaryThis paper presents CO2flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1(mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil respiration (SR) was 760 ± 340 gC m−2 y−1(55% of GPP and 69% of TER).Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature.At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated fromthe relationship between annual SR (and TER) and GPP observed among the less‐disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.
The cost of living for freshwater fish in a warmer, more polluted world
Authors: Morgan Ian J. , McDonald D. Gord , Wood Chris M. 
Published: March 2003

SummaryLittle of the vast literature on the temperature physiology of freshwater fish is useful in predicting the effects of global warming. In the present review a series of laboratory experiments is reviewed in which rainbow trout (Oncorhynchus mykiss) were exposed to simulated global warming, a 2 °C increment superimposed upon the natural thermal regime, in the presence and absence of two common freshwater pollutants, ammonia and acidity (low pH). Simulated global warming had little effect on the growth and physiology of trout fed to satiation over much of the summer. However, in late summer, when ambient water temperature was at its highest, the addition of 2 °C caused a marked inhibition of appetite and growth, although this impact was not exacerbated by a reduction in food availability. In winter, + 2 °C stimulated metabolism, appetite and growth by approximately 30–60%.Exposure of satiation‐fed trout to low levels of pollutants produced unexpected results. Ammonia (NH3 + NH4+ = 70 μm) stimulated summer growth and energy conversion efficiency, whilst acidification (pH 5.2) increased appetite and growth but caused no disturbance of electrolyte balance. These pollutant effects were additive upon, but not synergistic with, the effects of + 2 °C. The ability of the fish to acclimate to the experimental conditions was tested with acute lethal temperature and/or toxicant challenges. Fish exposed to + 2 °C had a slightly (0.2–1.0 °C) but significantly higher lethal temperature than those exposed to ambient temperature when fed to satiation. However, there was no evidence of acclimation to either ammonia or low pH. It is concluded that the impact of global warming on freshwater fish will vary seasonally. The additional temperature may provide growth benefits in winter, but may threaten fish populations living towards the upper end of their thermal tolerance zone in (late) summer.
Organic carbon and carbon isotopes in modern and 100‐year‐old‐soil archives of the Russian steppe
Authors: Torn Margaret S. , Lapenis Andrei G. , Timofeev Anatoly , Fischer Marc L. , Babikov Boris V. , Harden Jennifer W. 
Published: March 2003

AbstractArchived soils can provide valuable information about changes in the carbon and carbon isotope content of soils during the past century. We characterized soil carbon dynamics in a Russian steppe preserve using a 100‐year‐old‐soil archive and modern samples collected from the same site. The site has been protected since 1885 to the present, during which time the region has experienced widespread conversion to cultivation, a decrease in fire frequency, and a trend of increasing precipitation. In the preserve, the amount of organic carbon did not change appreciably between the 1900 and 1997 sampling dates, with 32 kg C/m2 in the top meter and a third of that in the top 20 cm. Carbon and nitrogen stocks varied by less than 6% between two replicate modern soil pits or between the modern sites and the archive. Radiocarbon content decreased with depth in all sites and the modern SOM had positive Δ values near the surface due to nuclear weapons testing in the early 1960s. In the upper 10 cm, most of the SOM had a turnover time of 6–10 years, according to a model fit to the radiocarbon content. Below about 10 cm, the organic matter was almost all passive material with long (millennial) turnover times. Soil respiration Δ14CO2 on a summer day was 106–109‰, an isotopic disequilibrium of about 9‰ relative to atmospheric 14CO2. In both the modern and archive soil, the relative abundance of 13C in organic matter increased with depth by 2‰ in the upper meter from δ13C = ‐‐26‰ at 5 cm to ‐‐24‰ below a meter. In addition, the slope of δ13C vs. depth below 5 cm was the same for both soils. Given the age of the soil archive, these results give clear evidence that the depth gradients are not due to depletion of atmospheric 13CO2 by fossil fuel emissions but must instead be caused by isotopic fractionation between plant litter inputs and preservation of SOM. Overall, the data show that these soils have a large reservoir of recalcitrant C and stocks had not changed between sampling dates 100 years apart.
A meta‐analysis of elevated [CO2] effects on soybean (Glycine max) physiology, growth and yield
Authors: Ainsworth Elizabeth A. , Davey Phillip A. , Bernacchi Carl J. , Dermody Orla C. , Heaton Emily A. , Moore David J. , Morgan Patrick B. , Naidu Shawna L. , Yoo Ra Hyung‐shim , Zhu Xin‐guang , Curtis Peter S. , Long Stephen P. 
Published: March 2003

AbstractThe effects of elevated [CO2] on 25 variables describing soybean physiology, growth and yield are reviewed using meta‐analytic techniques. This is the first meta‐analysis to our knowledge performed on a single crop species and summarizes the effects of 111 studies. These primary studies include numerous soybean growth forms, various stress and experimental treatments, and a range of elevated [CO2] levels (from 450 to 1250 p.p.m.), with a mean of 689 p.p.m. across all studies. Stimulation of soybean leaf CO2 assimilation rate with growth at elevated [CO2] was 39%, despite a 40% decrease in stomatal conductance and a 11% decrease in Rubisco activity. Increased leaf CO2 uptake combined with an 18% stimulation in leaf area to provide a 59% increase in canopy photosynthetic rate. The increase in total dry weight was lower at 37%, and seed yield still lower at 24%. This shows that even in an agronomic species selected for maximum investment in seed, several plant level feedbacks prevent additional investment in reproduction, such that yield fails to reflect fully the increase in whole plant carbon uptake. Large soil containers (> 9 L) have been considered adequate for assessing plant responses to elevated [CO2]. However, in open‐top chamber experiments, soybeans grown in large pots showed a significant threefold smaller stimulation in yield than soybeans grown in the ground. This suggests that conclusions about plant yield based on pot studies, even when using very large containers, are a poor reflection of performance in the absence of any physical restriction on root growth. This review supports a number of current paradigms of plant responses to elevated [CO2]. Namely, stimulation of photosynthesis is greater in plants that fix N and have additional carbohydrate sinks in nodules. This supports the notion that photosynthetic capacity decreases when plants are N‐limited, but not when plants have adequate N and sink strength. The root : shoot ratio did not change with growth at elevated [CO2], sustaining the charge that biomass allocation is unaffected by growth at elevated [CO2] when plant size and ontogeny are considered.