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1.
Leena Sallas Pirjo Kainulainen Jarkko Utriainen Toini Holopainen Jarmo K. Holopainen† 《Global Change Biology》2001,7(3):303-311
Terpene, 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. 相似文献
2.
Fitzgerald L. Booker † Stephen A. Prior‡ H. Allen Torbert‡ Edwin L. Fiscus † Walter A. Pursley † Shuijin Hu§ 《Global Change Biology》2005,11(4):685-698
A critical global climate change issue is how increasing concentrations of atmospheric CO2 and ground‐level O3 will affect agricultural productivity. This includes effects on decomposition of residues left in the field and availability of mineral nutrients to subsequent crops. To address questions about decomposition processes, a 2‐year experiment was conducted to determine the chemistry and decomposition rate of aboveground residues of soybean (Glycine max (L.) Merr.) grown under reciprocal combinations of low and high concentrations of CO2 and O3 in open‐top field chambers. The CO2 treatments were ambient (370 μmol mol?1) and elevated (714 μmol mol?1) levels (daytime 12 h averages). Ozone treatments were charcoal‐filtered air (21 nmol mol?1) and nonfiltered air plus 1.5 times ambient O3 (74 nmol mol?1) 12 h day?1. Elevated CO2 increased aboveground postharvest residue production by 28–56% while elevated O3 suppressed it by 15–46%. In combination, inhibitory effects of added O3 on biomass production were largely negated by elevated CO2. Plant residue chemistry was generally unaffected by elevated CO2, except for an increase in leaf residue lignin concentration. Leaf residues from the elevated O3 treatments had lower concentrations of nonstructural carbohydrates, but higher N, fiber, and lignin levels. Chemical composition of petiole, stem, and pod husk residues was only marginally affected by the elevated gas treatments. Treatment effects on plant biomass production, however, influenced the content of chemical constituents on an areal basis. Elevated CO2 increased the mass per square meter of nonstructural carbohydrates, phenolics, N, cellulose, and lignin by 24–46%. Elevated O3 decreased the mass per square meter of these constituents by 30–48%, while elevated CO2 largely ameliorated the added O3 effect. Carbon mineralization rates of component residues from the elevated gas treatments were not significantly different from the control. However, N immobilization increased in soils containing petiole and stem residues from the elevated CO2, O3, and combined gas treatments. Mass loss of decomposing leaf residue from the added O3 and combined gas treatments was 48% less than the control treatment after 20 weeks, while differences in decomposition of petiole, stem, and husk residues among treatments were minor. Decreased decomposition of leaf residues was correlated with lower starch and higher lignin levels. However, leaf residues only comprised about 20% of the total residue biomass assayed so treatment effects on mass loss of total aboveground residues were relatively small. The primary influence of elevated atmospheric CO2 and O3 concentrations on decomposition processes is apt to arise from effects on residue mass input, which is increased by elevated CO2 and suppressed by O3. 相似文献
3.
Effects of elevated O3 and CO2 concentrations on photosynthesis and stomatal conductance in Scots pine 总被引:1,自引:0,他引:1
Naturally regenerated Scots pines (Pinus sylvestris L.), aged 28–30 years old, were grown in open-top chambers and subjected in situ to three ozone (O3) regimes, two concentrations of CO2, and a combination of O3 and CO2 treatments From 15 April to 15 September for two growing seasons (1994 and 1995). The gas exchanges of current-year and 1-year-old shoots were measured, along with the nitrogen content of needles. In order to investigate the factors underlying modifications in photosynthesis, five parameters linked to photosynthetic performance and three to stomatal conductance were determined. Elevated O3 concentrations led to a significant decline in the CO2 compensation point (Г*), maximum RuP2-saturated rate of carboxylation (Vcmax), maximum rate of electron transport (Jmax), maximum stomatal conductance (gsmax), and sensitivity of stomatal conductance to changes in leaf-to-air vapour pressure difference (?gs/?Dv) in both shoot-age classes. However, the effect of elevated O3 concentrations on the respiration rate in light (Rd) was dependent on shoot age. Elevated CO2(700 μmol mol?1) significantly decreased Jmax and gsmax but increased Rd in 1-year-old shoots and the ?gs/?Dv in both shoot-age classes. The interactive effects of O3 and CO2 on some key parameters (e.g. Vcmax and Jmax) were significant. This may be closely related to regulation of the maximum stomatal conductance and stomatal sensitivity induced by elevated CO2. As a consequence, the injury induced by O3 was reduced through decreased ozone uptake in 1-year-old shoots, but not in the current-year shoots. Compared to ambient O3 concentration, reduced O3 concentrations (charcoal-filtered air) did not lead to significant changes in any of the measured parameters. Compared to the control treatment, calculations showed that elevated O3 concentrations decreased the apparent quantum yield by 15% and by 18%, and the maximum rate of photosynthesis by 21% and by 29% in the current-year and 1-year-old shoots, respectively. Changes in the nitrogen content of needles resulting from the various treatments were associated with modifications in photosynthetic components. 相似文献
4.
Decomposition of Betula papyrifera leaf litter under the independent and interactive effects of elevated CO2 and O3 总被引:1,自引:0,他引:1
William F. J. Parsons †‡ Richard L. Lindroth James G. Bockheim† 《Global Change Biology》2004,10(10):1666-1677
Litter decay dynamics of paper birch (Betula papyrifera) were assessed at the Aspen free‐air CO2 enrichment (FACE) facility in northern Wisconsin, USA. Leaf litter was decomposed for 12 months under factorial combinations of 360 vs. 560 μL CO2 L?1, crossed with 36 vs. 55 nL O3 L?1. To differentiate between substrate quality and environment effects, litterbags were placed in their Native Plots of origin or transplanted into the other treatments. CO2 enrichment, regardless of O3 concentration, produced poorer quality litter (high C/N, lignin/N and condensed tannins) than did ambient CO2 (low C/N, lignin/N and condensed tannins). Substrate quality differences were reflected in the mass loss rates (k‐values), which were high for litter generated under ambient CO2 (0.887 year?1) and low for litter generated under elevated CO2 (0.674 year?1). The rate‐retarding effects of CO2 enrichment were neither alleviated nor exacerbated by O3 exposure. Decay rates varied, however, depending on whether litter was placed back into its plot of origin or transplanted to Common Gardens. The results of this study are species specific, but they have important implications for understanding the processes regulating storage of fixed C and the release of CO2 from northern forest ecosystems. 相似文献
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6.
E.-M. LUOMALA K. LAITINEN S. KELLOMÄKI & E. VAPAAVUORI 《Plant, cell & environment》2003,26(5):645-660
In this experiment, the photosynthetic acclimation of successive needle cohorts of Scots pine were studied during 3 years of growth at elevated CO2 and temperature. Naturally regenerated Scots pine (Pinus sylvestris L.) trees were subjected to elevated CO2 concentration (+CO2, 700 p.p.m), elevated temperature (+T, ambient +2 to +6 °C) and to a combination of elevated CO2 and temperature (+CO2 + T) in closed‐top chambers, starting in August 1996. Trees growing in chambers with ambient CO2 and ambient temperature served as controls (AmbC). Elevated CO2 influenced the dark reactions more than the light reactions of photosynthesis, as in the 1996 and 1997 cohorts the carboxylation capacity of Rubisco was reduced in the first and second year of exposure, but there was no consistent change in chlorophyll fluorescence. Net photosynthesis measured at growth concentration of CO2 was higher at +CO2 than at AmbC on only one measuring occasion, was generally lower at +T and was not changed at +CO2 + T. However, trees grown at +T tended to invest more nitrogen (N) in Rubisco, as Rubisco/chlorophyll and the proportion of the total needle N bound to Rubisco occasionally increased. The interaction of +CO2 and +T on Rubisco was mostly negative; consequently, in the second and third year of the experiment the carboxylation capacity decreased at +CO2 + T. In the 1996, 1997 and 1998 cohorts, the structural N concentration of needles was lower at +CO2 than at AmbC. Elevated CO2 and elevated temperature generally had a positive interaction on N concentration; consequently, N concentration in needles decreased less at +CO2 + T than at +CO2. At +CO2 + T, the acclimation response of needles varied between years and was more pronounced in the 1‐year‐old needles of the 1997 cohort than in those of the 1998 cohort. Thus, acclimation was not always greater in 1‐year‐old needles than in current‐year needles. In the +CO2 + T treatment, elevated temperature had a greater effect on acclimation of needles than elevated CO2. 相似文献
7.
KATRI KOSTIAINEN HANNA JALKANEN SEIJA KAAKINEN PEKKA SARANPÄĆ ELINA VAPAAVUORI 《Global Change Biology》2006,12(7):1230-1240
Effects of elevated carbon dioxide (CO2) and ozone (O3) on wood properties of two initially 7‐year‐old silver birch (Betula pendula Roth) clones were studied after a fumigation during three growing seasons. Forty trees, representing two fast‐growing clones (4 and 80), were exposed in open‐top chambers to the following treatments: outside control, chamber control, 2 × ambient [CO2], 2 × ambient [O3] and 2 × ambient [CO2]+2 × ambient [O3]. After the 3‐year exposure, the trees were felled and wood properties were analyzed. The treatments affected both stem wood structure and chemistry. Elevated [CO2] increased annual ring width, and concentrations of extractives and starch, and decreased concentrations of cellulose and gravimetric lignin. Elevated O3 decreased vessel percentage and increased cell wall percentage in clone 80. In vessel percentage, elevated CO2 ameliorated the O3‐induced decrease. In clone 4, elevated O3 decreased nitrogen concentration of wood. The two clones had different wood properties. In clone 4, the concentrations of extractives, starch, soluble sugars and nitrogen were greater than in clone 80, while in clone 80 the concentrations of cellulose and acid‐soluble lignin were higher. Clone 4 also had slightly longer fibres, greater vessel lumen diameter and vessel percentage than clone 80, while in clone 80 cell wall percentage was greater. Our results show that wood properties of young silver birch trees were altered under elevated CO2 in both clones, whereas the effects of O3 depended on clone. 相似文献
8.
Edward B. Mondor Michelle N. Tremblay Caroline S. Awmack Richard L. Lindroth 《Global Change Biology》2005,11(11):1990-1996
Environmental change is anticipated to negatively affect both plant and animal populations. As abiotic factors rapidly change habitat suitability, projections range from altered genetic diversity to wide-spread species loss. Here, we assess the degree to which changes in atmospheric composition associated with environmental change will influence not only the abundance, but also the genotypic/phenotypic diversity, of herbivore populations. Using free-air CO2 and O3 enrichment (FACE) technology, we assess numerical responses of pea aphids (Acyrthosiphon pisum) exhibiting a pink–green genetic polymorphism and an environmentally determined wing polyphenism on broad bean plants (Vicia faba) under enriched CO2 and/or O3 atmospheres, over multiple generations. We show that these two greenhouse gases alter not only aphid population sizes, but also genotypic and phenotypic frequencies. As the green genotype was positively influenced by elevated CO2 levels, but the pink genotype was not, genotypic frequencies (pink morph : green morph) ranged from 1 : 1 to 9 : 1. These two genotypes also displayed marked differences in phenotypic frequencies. The pink genotype exhibited higher levels of wing induction under all atmospheric treatments, however, this polyphenism was negatively influenced by elevated O3 levels. Resultantly, frequencies of winged phenotypes (pink morph : green morph) varied from 10 : 1 to 332 : 1. Thus, atmospheric conditions associated with environmental change may alter not just overall population sizes, but also genotypic and phenotypic frequencies of herbivore populations, thereby influencing community and ecosystem functioning. 相似文献
9.
Effects of elevated O3 , alone and in combination with elevated CO2 , on tree leaf chemistry and insect herbivore performance: a meta-analysis 总被引:1,自引:0,他引:1
We reviewed the effects of elevated ozone (O3), alone and in combination with elevated carbon dioxide (CO2) on primary and secondary metabolites of trees and performance of insect herbivores by means of meta‐analysis. Our database consisted of 63 studies conducted on 22 species of trees and published between 1990 and 2005. Ozone alone had no overall effect on concentrations of carbohydrates or nutrients, whereas in combination with CO2, elevated O3 reduced nutrient concentrations and increased carbohydrate concentrations. In contrast to primary metabolites, concentrations of phenolics and terpenes were significantly increased by 16% and 8%, respectively, in response to elevated O3. Effects of ozone in combination with elevated CO2 were weaker than those of ozone alone on phenolics, but stronger than those of ozone alone on terpenes. The magnitude of secondary metabolite responses depended on the type of ozone exposure facility and increased in the following order: indoor growth chamber 3 than gymnosperms, as shifts in concentrations of carbohydrate and phenolics were observed in the former, but not in the latter. Elevated O3 had positive effects on some indices of insect performance: pupal mass increased and larval development time shortened, but these effects were counteracted by elevated CO2. Therefore, despite the observed increase in secondary metabolites, elevated O3 tends to increase tree foliage quality for herbivores, but elevated CO2 may alleviate these effects. Our meta‐analysis clearly demonstrated that effects of elevated O3 alone on leaf chemistry and some indices of insect performance differed from those of O3+CO2, and therefore, it is important to study effects of several factors of global climate change simultaneously. 相似文献
10.
Species control variation in litter decomposition in a pine forest exposed to elevated CO2 总被引:1,自引:0,他引:1
Net primary production and the flux of dry matter and nutrients from vegetation to soils has increased following four years of exposure to elevated CO2 in a southern pine forest in NC, USA. This has increased the demand for nutrients to support enhanced rates of NPP and altered the conditions for litter decomposition on the forest floor. We quantified the chemistry and decomposition dynamics of leaf litter produced by five of the most abundant tree species in this ecosystem during the third and fourth growing seasons under elevated CO2. The objectives of this study were to determine (i) if there were systemic or species‐specific changes in leaf litter chemistry associated with a sustained enhancement of plant growth under elevated CO2; and (ii) whether the process of litter decomposition was altered by increased inputs of energy and nutrients to the forest floor in the plots under elevated CO2. Leaf litter chemistry, including various C fractions and N concentration, was virtually unchanged by elevated CO2. With few exceptions, plant litter produced under elevated CO2 lost mass or N at the same relative rate as that produced under ambient CO2. The relationship between initial litter chemistry and decomposition was not altered by elevated CO2. The greater forest floor mass and nutrient content in the plots under elevated CO2 had no consistent or long‐term effect on litter decomposition. Thus, we found no evidence that plant and microbial processes under elevated CO2 resulted in systemic changes in mass loss or N dynamics during decomposition. In contrast to the limited effects of elevated CO2 on litter chemistry and decomposition, there were large differences among species in initial litter chemistry, mass loss and N dynamics during decomposition. If the species composition of this forest community is altered by elevated CO2, the indirect effect of a change in species composition will exert greater control over the long‐term rate of nutrient cycling than the direct effect of elevated CO2 on litter chemistry and decomposition dynamics alone. 相似文献
11.
The ongoing increase in atmospheric CO2 concentration ([CO2]) can potentially alter litter decomposition rates by changing: (i) the litter quality of individual species, (ii) allocation patterns of individual species, (iii) the species composition of ecosystems (which could alter ecosystem‐level litter quality and allocation), (iv) patterns of soil moisture, and (v) the composition and size of microbial communities. To determine the relative importance of these mechanisms in a California annual grassland, we created four mixtures of litter that differed in species composition (the annual legume Lotus wrangelianus Fischer & C. Meyer comprised either 10% or 40% of the initial mass) and atmospheric [CO2] during growth (ambient or double‐ambient). These mixtures decomposed for 33 weeks at three positions (above, on, and below the soil surface) in four types of grassland microcosms (fertilized and unfertilized microcosms exposed to elevated or ambient [CO2]) and at a common field site. Initially, legume‐rich litter mixtures had higher nitrogen concentrations ([N]) than legume‐poor mixtures. In most positions and environments, the different litter mixtures decomposed at approximately the same rate. Fertilization and CO2 enrichment of microcosms had no effect on mass loss of litter within them. However, mass loss was strongly related to litter position in both microcosms and the field. Nitrogen dynamics of litter were significantly related to the initial [N] of litter on the soil surface, but not in other positions. We conclude that changes in allocation patterns and species composition are likely to be the dominant mechanisms through which ecosystem‐level decomposition rates respond to increasing atmospheric [CO2]. 相似文献
12.
Interannual climatic variation mediates elevated CO2 and O3 effects on forest growth 总被引:1,自引:0,他引:1
MARK E. KUBISKE VANESSA S. QUINN WARREN E. HEILMAN† EVAN P. McDONALD PAULA E. MARQUARDT RON M. TECLAW ALEXANDER L. FRIEND‡ DAVID F. KARNOSKY§ 《Global Change Biology》2006,12(6):1054-1068
We analyzed growth data from model aspen (Populus tremuloides Michx.) forest ecosystems grown in elevated atmospheric carbon dioxide ([CO2]; 518 μL L?1) and ozone concentrations ([O3]; 1.5 × background of 30–40 nL L?1 during daylight hours) for 7 years using free‐air CO2 enrichment technology to determine how interannual variability in present‐day climate might affect growth responses to either gas. We also tested whether growth effects of those gasses were sustained over time. Elevated [CO2] increased tree heights, diameters, and main stem volumes by 11%, 16%, and 20%, respectively, whereas elevated ozone [O3] decreased them by 11%, 8%, and 29%, respectively. Responses similar to these were found for stand volume and basal area. There were no growth responses to the combination of elevated [CO2+O3]. The elevated [CO2] growth stimulation was found to be decreasing, but relative growth rates varied considerably from year to year. Neither the variation in annual relative growth rates nor the apparent decline in CO2 growth response could be explained in terms of nitrogen or water limitations. Instead, growth responses to elevated [CO2] and [O3] interacted strongly with present‐day interannual variability in climatic conditions. The amount of photosynthetically active radiation and temperature during specific times of the year coinciding with growth phenology explained 20–63% of the annual variation in growth response to elevated [CO2] and [O3]. Years with higher photosynthetic photon flux (PPF) during the month of July resulted in more positive growth responses to elevated [CO2] and more negative growth responses to elevated [O3]. Mean daily temperatures during the month of October affected growth in a similar fashion the following year. These results indicate that a several‐year trend of increasingly cloudy summers and cool autumns were responsible for the decrease in CO2 growth response. 相似文献
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14.
Soil CO2 efflux in a boreal pine forest under atmospheric CO2 enrichment and air warming 总被引:3,自引:0,他引:3
The response of forest soil CO2 efflux to the elevation of two climatic factors, the atmospheric concentration of CO2 (↑CO2 of 700 μmol mol−1 ) and air temperature (↑ T with average annual increase of 5°C), and their combination (↑CO2 +↑ T ) was investigated in a 4-year, full-factorial field experiment consisting of closed chambers built around 20-year-old Scots pines ( Pinus sylvestris L.) in the boreal zone of Finland. Mean soil CO2 efflux in May–October increased with elevated CO2 by 23–37%, with elevated temperature by 27–43%, and with the combined treatment by 35–59%. Temperature elevation was a significant factor in the combined 4-year efflux data, whereas the effect of elevated CO2 was not as evident. Elevated temperature had the most pronounced impact early and late in the season, while the influence of elevated CO2 alone was especially notable late in the season. Needle area was found to be a significant predictor of soil CO2 efflux, particularly in August, a month of high root growth, thus supporting the assumption of a close link between whole-tree physiology and soil CO2 emissions. The decrease in the temperature sensitivity of soil CO2 efflux observed in the elevated temperature treatments in the second year nevertheless suggests the existence of soil response mechanisms that may be independent of the assimilating component of the forest ecosystem. In conclusion, elevated atmospheric CO2 and air temperature consistently increased forest soil CO2 efflux over the 4-year period, their combined effect being additive, with no apparent interaction. 相似文献
15.
Caroline S. Awmack † Richard Harrington† Richard L. Lindroth 《Global Change Biology》2004,10(8):1414-1423
Changes in atmospheric composition affect plant quality and herbivore performance. We used the Aspen Free Air CO2 Enrichment (FACE) facility to investigate the impacts of elevated carbon dioxide (CO2) and ozone (O3) on the performance of the aphid Cepegillettea betulaefoliae Granovsky feeding on paper birch (Betula papyrifera Marsh.). In Year 1, we simultaneously measured individual performance and population growth rates, and in Year 2 we surveyed natural aphid, predator and parasitoid populations throughout the growing season. Aphid growth and development (relative growth rate (RGR), development time, adult weight, embryo number and the birth weight of newborn nymphs) were unaffected by CO2 and O3. Aphid fecundity decreased on trees grown at elevated CO2, O3 and CO2+O3. Neither nymphal performance nor adult size were reliable indicators of future fecundity at elevated CO2 and/or O3. Aphid populations protected from natural enemies were unaffected by elevated CO2, but increased significantly at elevated O3. Individual fecundity in elevated CO2 and O3 atmospheres did not predict population growth rates, probably because of changes in the strength of intraspecific competition or the ability of the aphids to induce nutrient sinks. Natural aphid, predator and parasitoids populations (Year 2) showed few significant responses to CO2 and O3, although CO2 and O3 did affect the timing of aphid and natural enemy peak abundance. Elevated CO2 and O3 affected aphid and natural enemy populations independently: no CO2× O3 interactions were observed. We conclude that: (1) aphid individual performance did not predict population responses to CO2 and O3 and (2) elevated CO2 and O3 atmospheres are unlikely to affect C. betulaefoliae populations in the presence of natural enemy communities. 相似文献
16.
Lewis H. Ziska 《Global Change Biology》2000,6(8):899-905
Soybean (Glycine max) was grown at ambient and enhanced carbon dioxide (CO2, + 250 μL L?1 above ambient) with and without the presence of a C3 weed (lambsquarters, Chenopodium album L.) and a C4 weed (redroot pigweed, Amaranthus retroflexus L.), in order to evaluate the impact of rising atmospheric carbon dioxide concentration [CO2] on crop production losses due to weeds. Weeds of a given species were sown at a density of two per metre of row. A significant reduction in soybean seed yield was observed with either weed species relative to the weed‐free control at either [CO2]. However, for lambsquarters the reduction in soybean seed yield relative to the weed‐free condition increased from 28 to 39% as CO2 increased, with a 65% increase in the average dry weight of lambsquarters at enhanced [CO2]. Conversely, for pigweed, soybean seed yield losses diminished with increasing [CO2] from 45 to 30%, with no change in the average dry weight of pigweed. In a weed‐free environment, elevated [CO2] resulted in a significant increase in vegetative dry weight and seed yield at maturity for soybean (33 and 24%, respectively) compared to the ambient CO2 condition. Interestingly, the presence of either weed negated the ability of soybean to respond either vegetatively or reproductively to enhanced [CO2]. Results from this experiment suggest: (i) that rising [CO2] could alter current yield losses associated with competition from weeds; and (ii) that weed control will be crucial in realizing any potential increase in economic yield of agronomic crops such as soybean as atmospheric [CO2] increases. 相似文献
17.
Few studies have investigated how tree species grown under elevated CO2 and elevated temperature alter the performance of leaf‐feeding insects. The indirect effects of an elevated CO2 concentration and temperature on leaf phytochemistry, along with potential direct effects on insect growth and consumption, may independently or interactively affect insects. To investigate this, we bagged larvae of the gypsy moth on leaves of red and sugar maple growing in open‐top chambers in four CO2/temperature treatment combinations: (i) ambient temperature, ambient CO2; (ii) ambient temperature, elevated CO2 (+ 300 μL L?1 CO2); (iii) elevated temperature (+ 3.5°C), ambient CO2; and (iv) elevated temperature, elevated CO2. For both tree species, leaves grown at elevated CO2 concentration were significantly reduced in leaf nitrogen concentration and increased in C: N ratio, while neither temperature nor its interaction with CO2 concentration had any effect. Depending on the tree species, leaf water content declined (red maple) and carbon‐based phenolics increased (sugar maple) on plants grown in an enriched CO2 atmosphere. The only observed effect of elevated temperature on leaf phytochemistry was a reduction in leaf water content of sugar maple leaves. Gypsy moth larval responses were dependent on tree species. Larvae feeding on elevated CO2‐grown red maple leaves had reduced growth, while temperature had no effect on the growth or consumption of larvae. No significant effects of either temperature or CO2 concentration were observed for larvae feeding on sugar maple leaves. Our data demonstrate strong effects of CO2 enrichment on leaf phytochemical constituents important to folivorous insects, while an elevated temperature largely has little effect. We conclude that alterations in leaf chemistry due to an elevated CO2 atmosphere are more important in this plant–folivorous insect system than either the direct short‐term effects of temperature on insect performance or its indirect effects on leaf chemistry. 相似文献
18.
William J. Mattson Kari Kuokkanen† Pekka Niemelä† Riitta Julkunen-Tiitto‡ Seppo Kellomäki† Jorma Tahvanainen‡ 《Global Change Biology》2004,10(8):1402-1413
We studied the three‐way interaction of elevated CO2, nitrogen (N), and temperature (T), and the two‐way interaction of elevated CO2 and early‐season defoliation on the secondary chemistry and resistance of Eurasian silver birch (Betula pendula) and North American paper birch (B. papyrifera) against the Eurasian hare (Lepus timidus) and the North American eastern cottontail rabbit (Sylvilagus floridanus), respectively. Elevated CO2 decreased the palatability of winter‐dormant silver and paper birch stems to both hares and rabbits, respectively. But the effect on hares was only apparent at intermediate levels of N fertilization. Elevated T had no effect on palatability. The effects of elevated CO2, N, and T on levels of silver birch bark phenolics and terpenoids were dominated by two‐way interactions between N and CO2, and N and T. Generally, however, N amendments elicited a parabolic response in carbon partitioning to most biosynthetic classes of silver birch phenolics (i.e. highest concentrations occurring at intermediate N). CO2 elevation was most enhancing at highest levels of N. On the other hand, T increases, more often than not, elicited reductions in phenolics, but especially so at the highest N level. In the case of B. papyrifera, elevated CO2 increased carbon partitioning to Folin‐Denis stem and branch phenolics and condensed tannins. Early‐season defoliation, on the other hand, had no effect on phenolics and tannins but lowered both N and energy levels of branches. Elevated CO2 substantially ameliorated the negative effects of severe defoliation on tree growth. These results support the hypothesis that continuing anthropogenic alterations of the atmosphere may trigger significant changes in plant phenotypic resistance to mammalian herbivores owing to an increasing net carbon balance between the highly vagile supply and demand capacities of plant carbon sources and sinks. 相似文献
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20.
The influence of elevated CO2 and O3 on fine roots and mycorrhizas of naturally growing young Scots pine trees during three exposure years 总被引:2,自引:0,他引:2
Young Scots pine trees naturally established at a pine heath were exposed to two concentrations of CO2 (ambient and doubled ambient) and two O3 regimes (ambient and doubled ambient) and their combination in open-top field chambers during growing seasons 1994, 1995 and 1996 (late May to 15 September). Filtered ozone treatment and chamberless control trees were also included in the treatment comparisons. Root ingrowth cores were inserted to the undisturbed soil below the branch projection of each tree at the beginning of the fumigation period in 1994 and were harvested at the end of the fumigation periods in 1995 and 1996. Root biomasses were determined from different soil layers in the ingrowth cores, and the infection levels of different mycorrhizal types were calculated. Elevated O3 and CO2 did not have significant effects on the biomass production of Scots pine coarse (Ø > 2 mm) or fine roots (Ø < 2 mm) and roots of grasses and dwarf shrubs. Elevated O3 caused a transient stimulation, observable in 1995, in the proportion of tuber-like mycorrhizas, total mycorrhizas and total short roots but this stimulation disappeared during the last study year. Elevated CO2 did not enhance carbon allocation to root growth or mycorrhiza formation, although a diminishing trend in the mycorrhiza formation was observed. In the combination treatment increased CO2 inhibited the transient stimulating effect of ozone, and a significant increase of old mycorrhizas was observed. Our conclusion is that doubled CO2 is not able to increase carbon allocation to growth of fine roots or mycorrhizas in nutrient poor forest sites and realistically elevated ozone does not cause a measurable limitation to roots within a period of three exposure years. 相似文献