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1.
Three model communities of trembling aspen (monoculture, and mixed with either paper birch or sugar maple) were grown for seven years in elevated atmospheric CO(2) and O(3) using Free Air CO(2) Enrichment (FACE) technology. We utilized trends in species' importance, calculated as an index of volume growth and survival, as indications of shifting community composition. For the pure aspen communities, different clones emerged as having the highest change in relative importance values depending on the pollutant exposure. In the control and elevated CO(2) treatments, clone 42E was rapidly becoming the most successful clone while under elevated O(3), clone 8 L emerged as the dominant clone. In fact, growth of clone 8 L was greater in the elevated O(3) treatment compared to controls. For the mixed aspen-birch community, importance of aspen and birch changed by - 16 % and + 62 %, respectively, in the controls. In the treatments, however, importance of aspen and birch changed by - 27 % and + 87 %, respectively, in elevated O(3), and by - 10 % and + 45 %, respectively, in elevated CO(2). Thus, the presence of elevated O(3) hastened conversion of stands to paper birch, whereas the presence of elevated CO(2) delayed it. Relative importance of aspen and maple changed by - 2 % and + 3 %, respectively, after seven years in the control treatments. But in elevated O(3), relative importance of aspen and maple changed by - 2 % and + 5 %, respectively, and in elevated CO(2) by + 9 and - 20 %, respectively. Thus, elevated O(3) slightly increases the rate of conversion of aspen stands to sugar maple, but maple is placed at a competitive disadvantage to aspen under elevated CO(2). 相似文献
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The long‐term effects of rising atmospheric carbon dioxide (CO2) and tropospheric O3 concentrations on fungal communities in soil are not well understood. Here, we examine fungal community composition and the activities of cellobiohydrolase and N‐acetylglucosaminidase (NAG) after 10 years of exposure to 1.5 times ambient levels of CO2 and O3 in aspen and aspen–birch forest ecosystems, and compare these results to earlier studies in the same long‐term experiment. The forest floor community was dominated by saprotrophic fungi, and differed slightly between plant community types, as did NAG activity. Elevated CO2 and O3 had small but significant effects on the distribution of fungal genotypes in this horizon, and elevated CO2 also lead to an increase in the proportion of Sistotrema spp. within the community. Yet, although cellobiohydrolase activity was lower in the forest floor under elevated O3, it was not affected by elevated CO2. NAG was also unaffected. The soil community was dominated by ectomycorrhizal species. Both CO2 and O3 had a minor effect on the distribution of genotypes; however, phylogenetic analysis indicated that under elevated O3Cortinarius and Inocybe spp. increased in abundance and Laccaria and Tomentella spp. declined. Although cellobiohydrolase activity in soil was unaffected by either CO2 or O3, NAG was higher (~29%) under CO2 in aspen–birch, but lower (~18%) under aspen. Time series analysis indicated that CO2 increased cellulolytic enzyme activity during the first 5 years of the experiment, but that the magnitude of this effect diminished over time. NAG activity also showed strong early stimulation by elevated CO2, but after 10 years this effect is no longer evident. Elevated O3 appears to have variable stimulatory and repressive effects depending on the soil horizon and time point examined. 相似文献
4.
KATRI KOSTIAINEN SEIJA KAAKINEN PEKKA SARANPÄĆ BJARNI D. SIGURDSSON‡ SVEN-OLOF LUNDQVIST§ SUNE LINDER¶ ELINA VAPAAVUORI 《Global Change Biology》2009,15(2):368-379
The objective of the study was to investigate the interactive effects of elevated atmospheric carbon dioxide concentration, [CO2 ], and temperature on the wood properties of mature field-grown Norway spruce ( Picea abies (L.) Karst.) trees. Material for the study was obtained from an experiment in Flakaliden, northern Sweden, where trees were grown for 3 years in whole-tree chambers at ambient (365 μmol mol−1 ) or elevated [CO2 ] (700 μmol mol−1 ) and ambient or elevated air temperature (ambient +5.6 °C in winter and ambient +2.8 °C in summer). Elevated temperature affected both wood chemical composition and structure, but had no effect on stem radial growth. Elevated temperature decreased the concentrations of acetone-soluble extractives and soluble sugars, while mean and earlywood (EW) cell wall thickness and wood density were increased. Elevated [CO2 ] had no effect on stem wood chemistry or radial growth. In wood structure, elevated [CO2 ] decreased EW cell wall thickness and increased tracheid radial diameter in latewood (LW). Some significant interactions between elevated [CO2 ] and temperature were found in the anatomical and physical properties of stem wood (e.g. microfibril angle, and LW cell wall thickness and density). Our results show that the wood material properties of mature Norway spruce were altered under exposure to elevated [CO2 ] and temperature, although stem radial growth was not affected by the treatments. 相似文献
5.
Anthropogenic activities are altering levels of greenhouse gases to the extent that multiple and diverse ecosystem processes are being affected. Two gases that substantially influence forest health are atmospheric carbon dioxide (CO2) and tropospheric ozone (O3). Plant chemistry will play an important role in regulating ecosystem processes in future environments, but little information exists about the longitudinal effects of elevated CO2 and O3 on phytochemistry, especially for long‐lived species such as trees. To address this need, we analysed foliar chemical data from two genotypes of trembling aspen, Populus tremuloides, collected over 10 years of exposure to levels of CO2 and O3 predicted for the year 2050. Elevated CO2 and O3 altered both primary and secondary chemistry, and the magnitude and direction of the responses varied across developmental stages and between aspen genotypes. Our findings suggest that the effects of CO2 and O3 on phytochemical traits that influence forest processes will vary over tree developmental stages, highlighting the need to continue long‐term, experimental atmospheric change research. 相似文献
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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
8.
DONALD R. ZAK † WILLIAM E. HOLMES KURT S. PREGITZER‡ JOHN S. KING§ DAVID S. ELLSWORTH MARK E. KUBISKE¶ 《Global Change Biology》2007,13(10):2230-2238
As human activity continues to increase CO2 and O3, broad expanses of north temperate forests will be simultaneously exposed to elevated concentrations of these trace gases. Although both CO2 and O3 are potent modifiers of plant growth, we do not understand the extent to which they alter competition for limiting soil nutrients, like nitrogen (N). We quantified the acquisition of soil N in two 8‐year‐old communities composed of trembling aspen genotypes (n= 5) and trembling aspen–paper birch which were exposed to factorial combinations of CO2 (ambient and 560 μL L−1) and O3 (ambient = 30–40 vs. 50–60 nL L−1). Tracer amount of 15NH4+ were applied to soil to determine how these trace gases altered the competitive ability of genotypes and species to acquire soil N. One year after isotope addition, we assessed N acquisition by measuring the amount of 15N tracer contained in the plant canopy (i.e. recent N acquisition), as well as the total amount of canopy N (i.e. cumulative N acquisition). Exposure to elevated CO2 differentially altered recent and cumulative N acquisition among aspen genotypes, changing the rank order in which they obtained soil N. Elevated O3 also altered the rank order in which aspen genotypes obtained soil N by eliciting increases, decreases and no response among genotypes. If aspen genotypes respond similarly under field conditions, then rising concentrations of CO2 and O3 could alter the structure of aspen populations. In the aspen–birch community, elevated CO2 increased recent N (i.e. 15N) acquisition in birch (68%) to a greater extent than aspen (19%), suggesting that, over the course of this experiment, birch had gained a competitive advantage over aspen. The response of genotypes and species to rising CO2 and O3 concentrations, and how these responses are modified by competitive interactions, has the potential to change the future composition and productivity of northern temperate forests. 相似文献
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Calfapietra C Wiberley AE Falbel TG Linskey AR Mugnozza GS Karnosky DF Loreto F Sharkey TD 《Plant, cell & environment》2007,30(5):654-661
Emission of hydrocarbons by trees has a crucial role in the oxidizing potential of the atmosphere. In particular, isoprene oxidation leads to the formation of tropospheric ozone and other secondary pollutants. It is expected that changes in the composition of the atmosphere will influence the emission rate of isoprene, which may in turn feedback on the accumulation of pollutants and greenhouse gases. We investigated the isoprene synthase (ISPS) gene expression and the ISPS protein levels in aspen trees exposed to elevated ozone (O(3)) and/or elevated carbon dioxide (CO(2)) in field-grown trees at the Aspen Free-Air Carbon Dioxide Enrichment (FACE) experimental site. Elevated O(3) reduced ISPS mRNA and the amount of ISPS protein in aspen leaves, whereas elevated CO(2) had no significant effect. Aspen clones with different O(3) sensitivity showed different levels of inhibition under elevated O(3) conditions. The drop in ISPS protein levels induced a drop in the isoprene emission rate under elevated O(3). However, the data indicated that other mechanisms also contributed to the observed strong inhibition of isoprene emission under elevated O(3). 相似文献
10.
DUNCAN C. McKINLEY JULIO C. ROMERO BRUCE A. HUNGATE† BERT G. DRAKE JAMES P. MEGONIGAL 《Global Change Biology》2009,15(8):2035-2048
A scrub‐oak woodland has maintained higher aboveground biomass accumulation after 11 years of atmospheric CO2 enrichment (ambient +350 μmol CO2 mol?1), despite the expectation of strong nitrogen (N) limitation at the site. We hypothesized that changes in plant available N and exploitation of deep sources of inorganic N in soils have sustained greater growth at elevated CO2. We employed a suite of assays performed in the sixth and 11th year of a CO2 enrichment experiment designed to assess soil N dynamics and N availability in the entire soil profile. In the 11th year, we found no differences in gross N flux, but significantly greater microbial respiration (P≤0.01) at elevated CO2. Elevated CO2 lowered extractable inorganic N concentrations (P=0.096) considering the whole soil profile (0–190 cm). Conversely, potential net N mineralization, although not significant in considering the entire profile (P=0.460), tended to be greater at elevated CO2. Ion‐exchange resins placed in the soil profile for approximately 1 year revealed that potential N availability at the water table was almost 3 × greater than found elsewhere in the profile, and we found direct evidence using a 15N tracer study that plants took up N from the water table. Increased microbial respiration and shorter mean residence times of inorganic N at shallower depths suggests that enhanced SOM decomposition may promote a sustained supply of inorganic N at elevated CO2. Deep soil N availability at the water table is considerable, and provides a readily available source of N for plant uptake. Increased plant growth at elevated CO2 in this ecosystem may be sustained through greater inorganic N supply from shallow soils and N uptake from deep soil. 相似文献
11.
Michael L. Hillstrom Leanne M. Vigue David R. Coyle Kenneth F. Raffa Richard L. Lindroth 《Agricultural and Forest Entomology》2010,12(3):285-292
- 1 Natural forest systems constitute a major portion of the world's land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects. A suite of invasive weevils has become established in the northern hardwood forests of North America. How these insects will respond to increasing CO2 or O3 is unknown.
- 2 The present study examined the effects of elevated atmospheric CO2 and O3 on the invasive weevil Polydrusus sericeus Schaller at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, Wisconsin. A performance assay was conducted in the laboratory during the summer of 2007 using mated pairs of P. sericeus fed a combination of aspen, birch and maple foliage. We recorded leaf area consumption, oviposition and adult longevity. We also conducted visual abundance surveys in the field from 2004 to 2007 on aspen and birch at Aspen FACE.
- 3 Elevated CO2, but not O3, significantly affected P. sericeus performance. Female, but not male, longevity was reduced under elevated CO2. Polydrusus sericeus also produced fewer eggs under elevated CO2 conditions compared with ambient conditions. Adult P. sericeus strongly preferred birch over both aspen and maple, regardless of fumigation treatment.
- 4 The effects of elevated CO2 on P. sericeus populations at Aspen FACE were minimal, and varied among years and host tree species. Polydrusus sericeus abundance was significantly greater on birch than aspen. Over the long term, elevated CO2 may reduce adult female longevity and fecundity of P. sericeus. Further studies are needed to evaluate how this information may scale to ecosystem impacts.
12.
- 1 Trembling aspen Populus tremuloides Michaux is an important forest species in the Great Lakes region and displays tremendous genetic variation in foliar chemistry. Elevated carbon dioxide (CO2) and ozone (O3) may also influence phytochemistry and thereby alter the performance of insect herbivores such as the aspen leaf beetle Chrysomela crotchi Brown.
- 2 The present study aimed to relate genetic‐ and atmospheric‐based variation in aspen phytochemistry to C. crotchi performance (larval development time, adult mass, survivorship). The experiment was conducted at the Aspen Free‐Air CO2 Enrichment (FACE) site in northern Wisconsin. Beetles were reared on three aspen genotypes under elevated CO2 and/or O3. Leaves were collected to determine chemical characteristics.
- 3 The foliage exhibited significant variation in nitrogen, condensed tannins and phenolic glycosides among genotypes. CO2 and O3, however, had little effect on phytochemistry. Nonetheless, elevated CO2 decreased beetle performance on one aspen genotype and had inconsistent effects on beetles reared on two other genotypes. Elevated O3 decreased beetle performance, especially for beetles reared on an O3‐sensitive genotype. Regression analyses indicated that phenolic glycosides and nitrogen explain a substantial amount (27–45%) of the variation in herbivore performance.
- 4 By contrast to the negative effects that are typically observed with generalist herbivores, aspen leaf beetles appear to benefit from phenolic glycosides, chemical components that are largely genetically‐determined in aspen. The results obtained in the present study indicate that host genetic variation and atmospheric concentrations of greenhouse gases will be important factors in the performance of specialist herbivores, such as C. crotchi, in future climates.
13.
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
14.
Chris Van Kessel Jennifer Nitschelm William R. Horwath David Harris Frances Walley Andreas Lüscher Ueli Hartwig 《Global Change Biology》2000,6(1):123-135
The impact of elevated CO2 and N‐fertilization on soil C‐cycling in Lolium perenne and Trifolium repens pastures were investigated under Free Air Carbon dioxide Enrichment (FACE) conditions. For six years, swards were exposed to ambient or elevated CO2 (35 and 60 Pa pCO2) and received a low and high rate of N fertilizer. The CO2 added in the FACE plots was depleted in 13C compared to ambient (Δ? 40‰) thus the C inputs could be quantified. On average, 57% of the C associated with the sand fraction of the soil was ‘new’ C. Smaller proportions of the C associated with the silt (18%) and clay fractions (14%) were derived from FACE. Only a small fraction of the total C pool below 10 cm depth was sequestered during the FACE experiment. The annual net input of C in the FACE soil (0–10 cm) was estimated at 4.6 ± 2.2 and 6.3 ± 3.6 (95% confidence interval) Mg ha? 1 for T. repens and L. perenne, respectively. The maximum amount of labile C in the T. repens sward was estimated at 8.3 ± 1.6 Mg ha? 1 and 7.1 ± 1.0 Mg ha? 1 in the L. perenne sward. Mean residence time (MRT) for newly sequestered soil C was estimated at 1.8 years in the T. repens plots and 1.1 years for L. perenne. An average of 18% of total soil C in the 0–10 cm depth in the T. repens sward and 24% in the L. perenne sward was derived from FACE after 6 years exposure. The majority of the change in soil δ13C occurred in the first three years of the experiment. No treatment effects on total soil C were detected. The fraction of FACE‐derived C in the L. perenne sward was larger than in the T. repens sward. This suggests a priming effect in the L. perenne sward which led to increased losses of the old C. Although the rate of C cycling was affected by species and elevated CO2, the soil in this intensively managed grassland ecosystem did not become a sink for additional new C. 相似文献
15.
MARIA OLSRUD BENGT Å. CARLSSON BRITA M. SVENSSON ANDERS MICHELSEN JERRY M. MELILLO 《Global Change Biology》2010,16(6):1820-1829
Responses of the mycorrhizal fungal community in terrestrial ecosystems to global change factors are not well understood. However, virtually all land plants form symbiotic associations with mycorrhizal fungi, with approximately 20% of the plants' net primary production transported down to the fungal symbionts. In this study, we investigated how ericoid mycorrhiza (ErM), fine endophytes (FE) and dark septate endophytes (DSE) in roots responded to elevated atmospheric CO2 concentrations and warming in the dwarf shrub understory of a birch forest in the subarctic region of northern Sweden. To place the belowground results into an ecosystem context we also investigated how plant cover and nutrient concentrations in leaves responded to elevated atmospheric CO2 concentrations and warming. The ErM colonization in ericaceous dwarf shrubs increased under elevated atmospheric CO2 concentrations, but did not respond to warming following 6 years of treatment. This suggests that the higher ErM colonization under elevated CO2 might be due to increased transport of carbon belowground to acquire limiting resources such as N, which was diluted in leaves of ericaceous plants under enhanced CO2. The elevated CO2 did not affect total plant cover but the plant cover was increased under warming, which might be due to increased N availability in soil. FE colonization in grass roots decreased under enhanced CO2 and under warming, which might be due to increased root growth, to which the FE fungi could not keep up, resulting in proportionally lower colonization. However, no responses in aboveground cover of Deschampsia flexuosa were seen. DSE hyphal colonization in grass roots significantly increased under warmer conditions, but did not respond to elevated CO2. This complex set of responses by mycorrhizal and other root‐associated fungi to global change factors of all the fungal types studied could have broad implications for plant community structure and biogeochemistry of subarctic ecosystems. 相似文献
16.
Jennifer L Mansfield Peter S Curtis Donald R Zak Kurt S Pregitzer 《American journal of botany》1999,86(8):1154-1159
The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO2 partial pressure and high- and low-fertility soil in field open-top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO2 and low soil fertility compared to ambient CO2 and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO2, while others showed no CO2 response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO2, and fertility treatments. These results suggest that with rising atmospheric CO2, plant secondary compound production may vary within species. This could have consequences for plant–herbivore and plant–microbe interactions and for the evolutionary response of this species to global climate change. 相似文献
17.
William E. Holmes Donald R. Zak Kurt S. Pregitzer† John S. King† 《Global Change Biology》2003,9(12):1743-1750
Increases in atmospheric CO2 and tropospheric O3 may affect forest N cycling by altering plant litter production and the availability of substrates for microbial metabolism. Three years following the establishment of our free‐air CO2–O3 enrichment experiment, plant growth has been stimulated by elevated CO2 resulting in greater substrate input to soil; elevated O3 has counteracted this effect. We hypothesized that rates of soil N cycling would be enhanced by greater plant productivity under elevated CO2, and that CO2 effects would be dampened by O3. We found that elevated CO2 did not alter gross N transformation rates. Elevated O3 significantly reduced gross N mineralization and microbial biomass N, and effects were consistent among species. We also observed significant interactions between CO2 and O3: (i) gross N mineralization was greater under elevated CO2 (1.0 mg N kg?1 day?1) than in the presence of both CO2 and O3 (0.5 mg N kg?1 day?1) and (ii) gross NH4+ immobilization was also greater under elevated CO2 (0.8 mg N kg?1 day?1) than under CO2 plus O3 (0.4 mg N kg?1 day?1). We used a laboratory 15N tracer method to quantify transfer of inorganic N to organic pools. Elevated CO2 led to greater recovery of NH4+‐15N in microbial biomass and corresponding lower recovery in the extractable NO3? pool. Elevated CO2 resulted in a substantial increase in NO3?‐15N recovery in soil organic matter. We observed no O3 main effect and no CO2 by O3 interaction effect on 15N recovery in any soil pool. All of the above responses were most pronounced beneath Betula papyrifera and Populus tremuloides, which have grown more rapidly than Acer saccharum. Although elevated CO2 has increased plant productivity, the resulting increase in plant litter production has yet to overcome the influence of the pre‐existing pool of soil organic matter on soil microbial activity and rates of N cycling. Ozone reduces plant litter inputs and also appears to affect the composition of plant litter in a way that reduces microbial biomass and activity. 相似文献
18.
YOKO WATANABE TAKAMI SATOMURA KAICHIRO SASA RYO FUNADA TAKAYOSHI KOIKE 《Plant, cell & environment》2010,33(7):1101-1111
To determine whether an elevated carbon dioxide concentration ([CO2]) can induce changes in the wood structure and stem radial growth in forest trees, we investigated the anatomical features of conduit cells and cambial activity in 4‐year‐old saplings of four deciduous broadleaved tree species – two ring‐porous (Quercus mongolica and Kalopanax septemlobus) and two diffuse‐porous species (Betula maximowicziana and Acer mono) – grown for three growing seasons in a free‐air CO2 enrichment system. Elevated [CO2] had no effects on vessels, growth and physiological traits of Q. mongolica, whereas tree height, photosynthesis and vessel area tended to increase in K. septemlobus. No effects of [CO2] on growth, physiological traits and vessels were seen in the two diffuse‐porous woods. Elevated [CO2] increased larger vessels in all species, except B. maximowicziana and number of cambial cells in two ring‐porous species. Our results showed that the vessel anatomy and radial stem growth of Q. mongolica, B. maximowicziana and A. mono were not affected by elevated [CO2], although vessel size frequency and cambial activity in Q. mongolica were altered. In contrast, changes in vessel anatomy and cambial activity were induced by elevated [CO2] in K. septemlobus. The different responses to elevated [CO2] suggest that the sensitivity of forest trees to CO2 is species dependent. 相似文献
19.
Elevated CO(2) and ozone effects were studied singly and in combination on the crown structure of two Betula pendula clones. Measurements were made at the end of the second fumigation period in an open-top-chamber experiment with 9-year-old trees. Shoot ramification (number of long and short daughter shoots), shoot length, and number of metamers, leaves and buds were measured at four positions in every tree. As a result of increased temperature, trees in chambers had longer shoots and more frequent shoot ramification than control trees not enclosed in chambers. Ozone treatment decreased shoot ramification significantly. Additionally, ozone treatment resulted in an increased number of metamers in one clone. There was no statistically significant interaction between ozone effect and crown position; however, there was a slight tendency for the lower crown to be more affected by ozone. Elevated CO(2) caused a significant increase in the number of long-shoot metamers. Therefore, 2x ambient CO(2) concentration partly ameliorated the negative effect of ozone because the increased number of leaves per shoot counteracted the decreased branching. Although the main effects of elevated ozone and CO(2) were similar in the two clones, slight, statistically insignificant, differences appeared in their responses when interactions with crown position were considered. 相似文献
20.
Irena Ma
ek Dave R. Clark Nataa ibanc Gerald Moser Dominik Vodnik Christoph Müller Alex J. Dumbrell 《Molecular ecology》2019,28(14):3445-3458
The ecological impacts of long‐term elevated atmospheric CO2 (eCO2) levels on soil microbiota remain largely unknown. This is particularly true for the arbuscular mycorrhizal (AM) fungi, which form mutualistic associations with over two‐thirds of terrestrial plant species and are entirely dependent on their plant hosts for carbon. Here, we use high‐resolution amplicon sequencing (Illumina, HiSeq) to quantify the response of AM fungal communities to the longest running (>15 years) free‐air carbon dioxide enrichment (FACE) experiment in the Northern Hemisphere (GiFACE); providing the first evaluation of these responses from old‐growth (>100 years) semi‐natural grasslands subjected to a 20% increase in atmospheric CO2. eCO2 significantly increased AM fungal richness but had a less‐pronounced impact on the composition of their communities. However, while broader changes in community composition were not observed, more subtle responses of specific AM fungal taxa were with populations both increasing and decreasing in abundance in response to eCO2. Most population‐level responses to eCO2 were not consistent through time, with a significant interaction between sampling time and eCO2 treatment being observed. This suggests that the temporal dynamics of AM fungal populations may be disturbed by anthropogenic stressors. As AM fungi are functionally differentiated, with different taxa providing different benefits to host plants, changes in population densities in response to eCO2 may significantly impact terrestrial plant communities and their productivity. Thus, predictions regarding future terrestrial ecosystems must consider changes both aboveground and belowground, but avoid relying on broad‐scale community‐level responses of soil microbes observed on single occasions. 相似文献