bluuebunny/crossref_metadata_2025_split huggingface dataset:
Canopy radiation‐ and water‐use efficiencies as affected by elevated [CO2]
Authors: Hui Dafeng , Luo Yiqi , Cheng Weixin , Coleman J. S. , Johnson Dale W. , Sims Daniel A. 
Published: March 2003

SummaryThis study used an environmentally controlled plant growth facility, EcoCELLs, to measure canopy gas exchanges directly and to examine the effects of elevated [CO2] on canopy radiation‐ and water‐use efficiencies. Sunflowers (Helianthus annus var. Mammoth) were grown at ambient (399 μmol mol−1) and elevated [CO2] (746 μmol mol−1) for 53 days in EcoCELLs. Whole canopy carbon‐ and water‐fluxes were measured continuously during the period of the experiment. The results indicated that elevated [CO2] enhanced daily total canopy carbon‐ and water‐fluxes by 53% and 11%, respectively, on a ground‐area basis, resulting in a 54% increase in radiation‐use efficiency (RUE) based on intercepted photosynthetic active radiation and a 26% increase in water‐use efficiency (WUE) by the end of the experiment. Canopy carbon‐ and water‐fluxes at both CO2 treatments varied with canopy development. They were small at 22 days after planting (DAP) and gradually increased to the maxima at 46 DAP. When canopy carbon‐ and water‐fluxes were expressed on a leaf‐area basis, no effect of CO2 was found for canopy water‐flux while elevated [CO2] still enhanced canopy carbon‐flux by 29%, on average. Night‐time canopy carbon‐flux was 32% higher at elevated than at ambient [CO2]. In addition, RUE and WUE displayed strong diurnal variations, high at noon and low in the morning or afternoon for WUE but opposite for RUE. This study provided direct evidence that plant canopy may consume more, instead of less, water but utilize both water and radiation more efficiently at elevated than at ambient [CO2], at least during the exponential growth period as illustrated in this experiment.
The influence of elevated O3 and CO2 concentrations on secondary metabolites of Scots pine (Pinus sylvestris L. ) seedlings
Authors: Sallas Leena , Kainulainen Pirjo , Utriainen Jarkko , Holopainen Toini , Holopainen Jarmo K. 
Published: March 2003

SummaryTerpene, resin acid and total phenolic concentrations in five‐year‐old Scots pine (Pinus sylvestris L.) seedlings were analysed after exposure to ambient and realistically elevated (2 × ambient) O3 and CO2 concentrations and their combination in open‐top chambers during two growing seasons. Under O3 exposure, limonene concentration in needles and isopimaric concentration in stems decreased significantly. As a response to elevated CO2, α‐pinene and total phenolic concentrations in needles increased significantly, while bornyl acetate concentration in needles and palustric + levopimaric and neoabietic acid concentrations in stems decreased significantly. Some terpenes and resin acids were found at lower concentrations in the combined O3 and CO2 treatment than in O3 exposure or elevated CO2. A negative chamber effect was found: seedlings growing inside the chambers with ambient air had significantly lower concentrations of some terpenes and resin acids than seedlings growing outside the chambers. There was a lot of between‐tree variation in terpene and resin acid concentrations, which is typical of open‐pollinated populations. The results of this study suggest that, at least in short‐term experiments, Scots pine secondary metabolites are relatively insensitive to climate change factors. Total phenolics in the needles were the most responsive group showing about 25% increase in elevated CO2, and O3 exposure did not mitigate this CO2 effect. Terpenes and resin acids were less responsive, although some individual compounds showed notable responses, e.g. α‐pinene in needles, which increased about 50% in response to elevated CO2. As a consequence, although there were only slight effects on total pools of needle secondary metabolites, considerable O3 and CO2 effects on certain individual compounds might have ecological significance via trophic amplification, e.g. in decomposing processes of needle litter.
Stress synergy between drought and a common environmental contaminant: studies with the collembolanFolsomia candida
Authors: Højer Rikke , Bayley Mark , And Christian F. Damgaard , Holmstrup Martin 
Published: March 2003

SummaryThe term global change is used predominantly in connection with the global temperature increase and associated changes in weather patterns over the next century. In a broader sense it also covers other anthropogenic impacts on the environment such as habitat fragmentation and pollution. The individual effects of each of these stress types have been extensively studied in the biota. However, organisms will frequently encounter these stress types in combination rather than alone and there is little information available on the effects of stress combinations.Here an examination is made of the interaction between realistic levels of summer drought and a common contaminant of agricultural soil (4‐nonylphenol, NP), on a widespread soil invertebrate, the collembolanFolsomia candida.These stress factors were tested individually and in combination using a full factorial design. This approach revealed the existence of highly significant Bliss type synergistic interaction between the two stress types. Thus, exposure to NP significantly reduced the drought tolerance of this organism and, reciprocally, the toxicity of NP (LC50) during realistic summer drought was more than doubled in comparison to the value obtained under optimal soil moisture conditions. Furthermore, it is shown that NP has a detrimental effect on the physiological mechanisms underlying this animal's drought tolerance, thus providing some explanation for the mechanisms involved in the synergy. It is argued that this type of synergy is unlikely to be confined to this particular combination of stresses and thus there is a need to study the interactions between dominant natural stresses and pollution. The most important implication of these results is that some of the effects of global climate changes can be predicted to be most severe in polluted areas.
Herbivory in global climate change research: direct effects of rising temperature on insect herbivores
Authors: Bale Jeffery S. , Masters Gregory J. , Hodkinson Ian D. , Awmack Caroline , Bezemer T. Martijn , Brown Valerie K. , Butterfield Jennifer , Buse Alan , Coulson John C. , Farrar John , Good John E. G. , Harrington Richard , Hartley Susane , Jones T. Hefin , Lindroth Richard L. , Press Malcolm C. , Symrnioudis Ilias , Watt Allan D. , Whittaker John B. 
Published: March 2003

AbstractThis review examines the direct effects of climate change on insect herbivores. Temperature is identified as the dominant abiotic factor directly affecting herbivorous insects. There is little evidence of any direct effects of CO2 or UVB. Direct impacts of precipitation have been largely neglected in current research on climate change. Temperature directly affects development, survival, range and abundance. Species with a large geographical range will tend to be less affected. The main effect of temperature in temperate regions is to influence winter survival; at more northerly latitudes, higher temperatures extend the summer season, increasing the available thermal budget for growth and reproduction. Photoperiod is the dominant cue for the seasonal synchrony of temperate insects, but their thermal requirements may differ at different times of year. Interactions between photoperiod and temperature determine phenology; the two factors do not necessarily operate in tandem. Insect herbivores show a number of distinct life‐history strategies to exploit plants with different growth forms and strategies, which will be differentially affected by climate warming. There are still many challenges facing biologists in predicting and monitoring the impacts of climate change. Future research needs to consider insect herbivore phenotypic and genotypic flexibility, their responses to global change parameters operating in concert, and awareness that some patterns may only become apparent in the longer term.
Climatic regime shifts and decadal‐scale variability in calanoid copepod populations off southern California
Authors: Rebstock Ginger A. 
Published: March 2003

AbstractDecadal‐scale climatic regimes and the shifts between them have important impacts on marine ecosystems. Climatic regime shifts have been observed or hypothesized in the North Pacific basin in 1976–77 and 1989. This paper examines long‐term (1951–99) trends in calanoid copepod populations off southern California, and the evidence for responses to regime shifts.    Most of the species of calanoid copepod that were analysed underwent one or more step changes during the 49 years covered by the study. All but one of these changes occurred in five periods: the late 1950s, late 1960s, mid‐1970s, early 1980s and around 1990. The late 1960s changes are considered to be artifacts of an increase in sampling depth. Strong El Niño conditions affected California waters during the late 1950s and early 1980s. The step changes of the mid‐1970s and late 1980s to early 1990s may have been responses to regime shifts or other climatic events. 28% of the species and subspecies responded to the 1976–77 event, all increasing in abundance. Another 28% of the copepod categories underwent step changes around 1990, most decreasing.    Evidence for regime shifts in the hydrographic variables that were examined is mixed. The 10‐m temperature increased in the mid‐1970s. Abrupt changes in variables around 1990 were short‐lived. However, the population responses around 1990 and to the El Niños of the late 1950s and early 1980s indicate that some species of calanoid copepods may respond on longer time scales to environmental conditions that persist only a few years.
Changed plant and animal life cycles from 1952 to 2000 in the Mediterranean region
Authors: Peñuelas Josep , Filella Iolanda , Comas PerE. 
Published: March 2003

AbstractThe available data on climate over the past century indicate that the earth is warming. Important biological effects, including changes of plant and animal life cycle events, have already been reported. However, evidence of such effects is still scarce and has been mostly limited to northern latitudes. Here we provide the first long‐term (1952–2000) evidence of altered life cycles for some of the most abundant Mediterranean plants and birds, and one butterfly species. Average annual temperatures in the study area (Cardedeu, NE Spain) have increased by 1.4 °C over the observation period while precipitation remained unchanged. A conservative linear treatment of the data shows that leaves unfold on average 16 days earlier, leaves fall on average 13 days later, and plants flower on average 6 days earlier than in 1952. Fruiting occurs on average 9 days earlier than in 1974. Butterflies appear 11 days earlier, but spring migratory birds arrive 15 days later than in 1952. The stronger changes both in temperature and in phenophases timing occurred in the last 25 years. There are no significant relationships among changes in phenophases and the average date for each phenophase and species. There are not either significant differences among species with different Raunkiaer life‐forms or different origin (native, exotic or agricultural). However, there is a wide range of phenological alterations among the different species, which may alter their competitive ability, and thus, their ecology and conservation, and the structure and functioning of ecosystems. Moreover, the lengthening of plant growing season in this and other northern hemisphere regions may contribute to a global increase in biospheric activity.
The influence of plants grown under elevated CO2and N fertilization on soil nitrogen dynamics
Authors: Martín‐Olmedo Piedad , Rees Robert M. , Grace John 
Published: March 2003

AbstractWe investigated the effects of spring barley growth on nitrogen (N) transformations and rhizosphere microbial processes in a controlled system under elevated carbon dioxide (CO2) at two levels of N fertilization (applied with15N labelling). After 25 d, elevated CO2(twice ambient) increased plant growth (dry weight, DW) by 141% at low‐N fertilization and by 60% at high‐N fertilization, but its positive effect on the root‐to‐shoot ratio was only significant at low‐N input. As a result of this plant response, elevated CO2caused a greater soil CO2efflux, rhizosphere soil DW, and soil microbial biomass under N‐limiting conditions than under high N availability. Elevated CO2also caused a significant (P < 0.001) increase in the N recovered by the plant from both the labelled (Nf) and unlabelled (Ns + Nuf) N pools. The dynamics of N in the system as affected by elevated CO2were driven principally by mineralization–immobilization turnover, with little loss by denitrification. Under N‐limiting conditions, there is evidence to suggest enhanced nutrient release from soil organic matter (SOM) pools—a process which could be defined as priming. The results of our experiment did not indicate a direct plant‐mediated effect of elevated CO2on nitrous oxide (N2O) fluxes or denitrification activity.
Effects of nutrition and soil warming on stemwood production in a boreal Norway spruce stand
Authors: STRÖMGREN MONIKA , LINDER SUNE 
Published: March 2003

AbstractThe boreal forest is expected to experience the greatest warming of all forest biomes. The extent of the boreal forest, the large amount of carbon contained in the soil, and the expected climate warming, make the boreal forest a key biome to understand and represent correctly in global carbon models. It has been suggested that an increase in temperature could stimulate the release of CO2 caused by an increased decomposition rate, more than biomass production, which could convert current carbon sinks into carbon sources. Most boreal forests are currently carbon sinks, but it is unclear for how long in the future the carbon sink capacity of the boreal forest is likely to be maintained. The impact of soil warming on stem volume growth was studied during 6 years, in irrigated (I) and irrigated‐fertilized (IL) stands of 40‐year‐old Norway spruce in Northern Sweden. From May to October heating cables were used to maintain the soil temperature on heated‐irrigated plots (Ih and ILh) 5 °C above that on unheated control plots (Ic and ILc). After six seasons' warming, stem volume production (m3 ha−1 a−1) was 115% higher on Ih than on unheated (Ic) plots, and on heated and irrigated‐fertilized plots (ILh) it was 57% higher than on unheated plots (ILc). The results indicate that in a future warmer climate, an increased availability of nitrogen, combined with a longer growing season, may increase biomass production substantially, on both low‐ and high‐fertility sites. It is, however, too early to decide whether the observed responses are transitory or long lasting. It is therefore crucial to gain a better understanding of the responses of boreal forest ecosystems to climate change, and to provide data to test and validate models used in predicting the impact of climate change.
Acute seasonal drought does not permanently alter mass loss and nitrogen dynamics during decomposition of red maple (Acer rubrumL.) litter
Authors: O'Neill E. G. , Johnson D. W. , Ledford J. , Todd D. E. 
Published: March 2003

AbstractLitter decomposition is a major component of nutrient cycling in forest ecosystems and is known to be sensitive to both temperature and moisture. A drought during periods of the year when moisture is normally abundant may impact decomposition more than moisture limitation during seasons that are routinely dry. We excluded precipitation for a 3‐month period during each of four seasons and measured mass loss and nitrogen (N) dynamics inAcer rubrumleaf litter by using a litterbag approach. We hypothesized that rainfall exclusion would retard mass loss during the exclusion period, with the maximum effect occurring during the spring and summer months when moisture was normally adequate and temperatures optimum for decomposition, and that exclusion during these two periods would have the greatest impact on subsequent timing of decomposition events, particularly N mineralization. Mass loss in litterbags was initially reduced by precipitation exclusion in the spring treatment only. For each season, a set of bags exposed to drying in the same way and allowed to remain in the field under ambient conditions for an additional 9 months no longer showed a difference in mass loss relative to control bags. Nitrogen accumulation was immediately and significantly reduced in the exclusion treatments in all seasons; however, like mass loss, there was no difference 9 months later. We conclude that short‐term effects of drought do occur, especially with regard to N accumulation, and that these effects do not persist and are unlikely to have any substantial effect on nutrient cycling.
A global change‐induced biome shift in the Montseny mountains (NE Spain)
Authors: Peñuelas Josep , Boada Martí 
Published: March 2003

AbstractShifts in plant species and biome distribution in response to warming have been described in past climate changes. However, reported evidence of such shifts under current climate change is still scarce. By comparing current and 1945 vegetation distribution in the Montseny mountains (Catalonia, NE Spain), we report here a progressive replacement of cold‐temperate ecosystems by Mediterranean ecosystems. Beech (Fagus sylvatica) forest has shifted altitudinally upwards by ca. 70 m at the highest altitudes (1600–1700 m). Both the beech forests and the heather (Calluna vulgaris) heathlands are being replaced by holm oak (Quercus ilex) forest at medium altitudes (800–1400 m). This beech replacement has been observed to occur through a progressive isolation and degradation of beech stands. In ‘isolated’ (small and surrounded by holm oaks) beech stands, beech trees are 30% more defoliated, beech recruitment is 41% lower, and holm oak recruitment is three times higher than in ‘continental’ (large and continuous) beech stands. The progressively warmer conditions, complemented by the land use changes (mainly the cessation of traditional land management) are the apparent causes, providing a paradigmatic example of global change affecting distributions of plant species and biomes.
Seasonal characteristics of nitric oxide emission from a typical Chinese rice–wheat rotation during the non‐waterlogged period
Authors: Zheng Xunhua , Huang Yao , Wang Yuesi , Wang Mingxing 
Published: March 2003

AbstractNitric oxide emissions from a typical rice–wheat rotation system in southeastern China were continuously measured with an automatic system in 1996–1997. The seasonal pattern of the NO emissions was characterized for the non‐waterlogged period of a rotation cycle. Nitric oxide emissions during the period from March through June were 3.9–6.3 folds for the fertilized plots and 1.6 folds for the unfertilized plot larger than those from November through December. Nitric oxide emissions were not detectable during the winter period from January through February. Amendment of synthetic fertilizer N significantly enhanced the NO emission by a factor of 6.5, but the enhancement was significantly mitigated by 25% through substituting ca. 16% of the synthetic fertilizer N with organic N from fermented crop residues or by 21% through deep tillage. The NO–N emission factor, defined as the amount of NO–N released per unit of synthetic fertilizer N input, was determined to be 0.025 kg NO–N kg−1 of N applied for the non‐waterlogged period, which was reduced by 32% through substituting part of the synthetic N fertilizer with fermented crop residues or by 24% through deep tillage. In addition, the NO emission factor, defined as the amount of NO–N emitted from unit unfertilized area per day, was observed to be ca. 3.8 g N ha−1 d−1. Approximately 0.55 Tg N yr−1 was likely released as NO from Chinese cultivated lands.
Effects of elevated CO2, nitrogen and fungal endophyte‐infection on tall fescue: growth, photosynthesis, chemical composition and digestibility
Authors: NEWMAN J. A. , ABNER M. L. , DADO R. G. , GIBSON D. J. , BROOKINGS A. , PARSONS A. J. 
Published: March 2003

AbstractRising global carbon dioxide levels may lead to profound changes in plant composition, regardless of the degree of global warming that may result from the accumulation of this greenhouse gas. We studied the interaction of a CO2 doubling and two levels of nitrogen fertilizer on the growth and chemical composition of tall fescue (Festuca arundinacea Schreber cv. KY‐31) when infected and uninfected with the mutualistic fungal endophyte Neotyphodium coenophialum Morgan‐Jones and Gams. Two‐year‐old plants were harvested to 5 cm every 4 weeks, and after 12 weeks of growth plants grown in twice ambient CO2 concentrations: photosynthesized 15% more; produced tillers at a faster rate; produced 53% more dry matter (DM) yield under low N conditions and 61% more DM under high N conditions; the % organic matter (OM) was little changed except under elevated CO2 and high N when %OM increased by 3%; lignin decreased by 14%; crude protein (CP) concentrations (as %DM) declined by 21%; the soluble CP fraction (as %CP) increased by 13%; the acid detergent insoluble CP fraction (as %CP) increased by 12%, and in vitro neutral detergent fiber digestibility declined by 5% under high N conditions but not under low N. Plants infected with the endophytic fungus: photosynthesized 16% faster in high N compared with under low N; flowered earlier than uninfected plants; had 28% less lignin in high N compared with under low N; and had much smaller reductions in CP concentration (as %DM) and smaller increases in the soluble CP fraction (as %CP) and the acid detergent insoluble CP fraction (as %CP) under elevated CO2. Such large and varied changes in plant quality are likely to have large and significant effects on the herbivore populations that feed from these plants.
Effects of elevated CO2, nitrogen deposition, and decreased species diversity on foliar fungal plant disease
Authors: MITCHELL CHARLES E. , REICH PETER B. , TILMAN DAVID , GROTH JAMES V. 
Published: March 2003

AbstractThree components of global change, elevated CO2, nitrogen addition, and decreased plant species richness (‘diversity’), increased the percent leaf area infected by fungi (pathogen load) for much to all of the plant community in one year of a factorial grassland experiment. Decreased plant diversity had the broadest effect, increasing pathogen load across the plant community. Decreased diversity increased pathogen load primarily by allowing remaining plant species to increase in abundance, facilitating spread of foliar fungal pathogens specific to each plant species. Changes in plant species composition also strongly influenced community pathogen load, with communities that lost less disease prone plant species increasing more in pathogen load. Elevated CO2 increased pathogen load of C3 grasses, perhaps by decreasing water stress, increasing leaf longevity, and increasing photosynthetic rate, all of which can promote foliar fungal disease. Decreased plant diversity further magnified the increase in C3 grass pathogen load under elevated CO2. Nitrogen addition increased pathogen load of C4 grasses by increasing foliar nitrogen concentration, which can enhance pathogen infection, growth, and reproduction. Because changes in foliar fungal pathogen load can strongly influence grassland ecosystem processes, our study suggests that increased pathogen load can be an important mechanism by which global change affects grassland ecosystems.