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1.
Frank Hagedorn Werner Landolt David Tarjan Philipp Egli Jürg B. Bucher 《Oecologia》2002,132(1):109-117
The objectives of this study were to investigate how different soil types and elevated N deposition (0.7 vs 7 g N m-2a-1) influence the effects of elevated CO2 (370 vs 570 µmol CO2 mol-1) on soil nutrients and net accumulation of N, P, K, S, Ca, Mg, Fe, Mn, and Zn in spruce (Picea abies) and beech (Fagus sylvatica). Model ecosystems were established in large open-top chambers on two different forest soils: a nutrient-poor acidic loam and a nutrient-rich calcareous sand. The response of net nutrient accumulation to elevated atmospheric CO2 depended upon soil type (interaction soil 2 CO2, P<0.05 for N, P, K, S, Ca, Mg, Zn) and differed between spruce and beech. On the acidic loam, CO2 enrichment suppressed net accumulation of all nutrients in beech (P<0.05 for P, S, Zn), but stimulated it for spruce (P<0.05 for Fe, Zn) On the nutrient-rich calcareous sand, increased atmospheric CO2 enhanced nutrient accumulation in both species significantly. Increasing the N deposition did not influence the CO2 effects on net nutrient accumulation with either soil. Under elevated atmospheric CO2, the accumulation of N declined relative to other nutrients, as indicated by decreasing ratios of N to other nutrients in tree biomass (all ratios: P<0.001, except the N to S ratio). In both the soil and soil solution, elevated CO2 did not influence concentrations of base cations and available P. Under CO2 enrichment, concentrations of exchangeable NH4+ decreased by 22% in the acidic loam and increased by 50% in the calcareous sand (soil 2 CO2, P<0.001). NO3- concentrations decreased by 10-70% at elevated CO2 in both soils (P<0.01). 相似文献
2.
To elucidate how atmospheric CO2 enrichment, enhanced nutrient supply and soil quality interact to affect regrowth of temperate forests, young Fagus sylvatica and Picea abies trees were grown together in large model ecosystems. Identical communities were established on a nutrient-poor acidic and on a more fertile calcareous soil and tree growth, leaf area index, fine root density and soil respiration monitored over four complete growing seasons. Biomass responses to CO2 enrichment and enhanced N supply at the end of the experiment reflected compound interest effects of growth stimulation during the first two to three seasons rather than persistent stimulation over the whole duration of the experiment. Whereas biomass of Picea was enhanced in elevated CO2 on both soils, Fagus responded negatively to CO2 on acidic but positively on calcareous soil. Biomass of both species profited from enhanced N supply on the poor acidic soil only. Leaf area index on both soils was greater in high N supply as a consequence of a stimulation early in the experiment, but was unaffected by CO2 enrichment. Fine root density on acidic soil was increased in high N supply, but this did not stimulate soil respiration rate. In contrast, elevated CO2 stimulated both fine root density and soil CO2 efflux on calcareous soil, especially towards the end of the experiment. Our experiment suggests that future species dominance in beech-spruce forests is likely to change in response to CO2 enrichment, but this response is subject to complex interactions with environmental factors other than CO2, particularly soil type. 相似文献
3.
The long-term effects of elevated CO2 and CO2+O3 concentrations on the growth allocation in northern provenances of Norway spruce [Picea abies (L.) Karst.], Scots pine [Pinus sylvestris (L.)] and pubescent birch clones (Betula pubescens Ehrh.) were examined in open-top chambers after a 4-year-long experiment. The total biomass responses of the tree seedlings to increased CO2 and CO2+O3 concentrations were not statistically significant and varied between the provenances and species. The seedlings of northern origin were the least sensitive in their response to treatments. The total biomass of the Norway spruce seedlings slightly decreased in response to CO2 in three provenances. Scots pine from the local provenance had a slight biomass increase after elevated CO2+O3 treatment. The slower-growing birch clone seemed to benefit from elevated CO2, whereas in the faster-growing clone, reductions in biomass accumulation were seen. The combined CO2+O3 treatment reduced the positive effects of elevated CO2, especially in the slower-growing birches. Observations of significant effects were limited to a few parameters. Carbon dioxide treatment decreased needle dry weight of Norway spruce in one northern provenance. The needle and wood dry weight increased (CO2 + O3) in local Scots pine. Significant birch response was limited to increased fine root density (O3 + CO2) in the inland clone. The diverse effects of elevated CO2 and CO2 +O3 on seedling growth and biomass provide evidence that exposure of northern trees to the enhanced variable CO2 and O3 concentrations of the future will have varied effects on the growth of these species. The direction and magnitude of those effects will differ depending on species and origins. 相似文献
4.
Philipp Egli Stefan Maurer Dieter Spinnler Werner Landolt Madeleine S. Günthardt‐Goerg Christian Krner 《Oikos》2001,92(2):279-290
Young beech (Fagus sylvatica) and spruce (Picea abies) trees from different provenances or genotypes were grown in competition in large model ecosystems and were exposed to two concentrations of atmospheric CO2 (370 vs 570 μmol mol?1), two levels of wet nitrogen deposition (7 vs 70 kg N ha?1 yr?1), and two native forest soils (acidic vs calcareous) for four years in open‐top chambers. The 2×2×2 factorial experimental design was fully replicated (n=4) with each CO2×N combination applied to each soil type. Exposure to atmospheric CO2 enrichment stimulated daytime net ecosystem CO2 flux (NEC) as measured during sunny days in the middle of the third growing season. Nevertheless, we observed substantial down‐regulation of NEC, with larger adjustments on acidic than on calcareous soil. NEC adjustment was associated with slightly reduced leaf area index (LAI) on the acidic soil (no response on calcareous soil), enhanced soil CO2 efflux from both substrate types, and, most importantly, with down‐regulation of CO2 uptake at the leaf scale. Downward adjustment of light‐saturated single‐leaf photosynthesis (A) and of Rubisco was more pronounced in beech than in spruce and these species‐specific differences increased over time. By year four, A adjustment (except in one specific treatment combination in each species) had become complete in beech but had disappeared in spruce. At no time did we observe a genotype or provenance effect on the downward adjustment of carbon fluxes, and nitrogen deposition rate generally had little effect as well. Overall, our results suggest that tree species and soil quality will have profound effects on ecosystem CO2 fluxes under continued atmospheric CO2 enrichment. 相似文献
5.
This study examined the effects of elevated CO2 on secondary metabolites for saplings of tropical trees. In the first experiment, nine species of trees were grown in the ground in open-top chambers in central Panama at ambient and elevated CO2 (about twice ambient). On average, leaf phenolic contents were 48% higher under elevated CO2. Biomass accumulation was not affected by CO2, but starch, total non-structural carbohydrates and C/N ratios all increased. In a second experiment with Ficus, an early successional species, and Virola, a late successional species, treatments were enriched for both CO2 and nutrients. For both species, nutrient fertilization increased plant growth and decreased leaf carbohydrates, C/N ratios and phenolic contents, as predicted by the carbon/nutrient balance hypothesis. Changes in leaf C/N levels were correlated with changes in phenolic contents for Virola (r=0.95, P<0.05), but not for Ficus. Thus, elevated CO2, particularly under conditions of low soil fertility, significantly increased phenolic content as well as the C/N ratio of leaves. The magnitude of the changes is sufficient to negatively affect herbivore growth, survival and fecundity, which should have impacts on plant/herbivore interactions. 相似文献
6.
Genotypic variation in the response of two perennial grass species to elevated carbon dioxide 总被引:3,自引:0,他引:3
Shoot and reproductive biomass of genotypes of Bromus erectus and Dactylis glomerata grown in competition at ambient and elevated CO2 were examined for 2 consecutive years in order to test whether genetic variation in those traits exists and whether it is maintained over time. At the species level, a positive CO2 response of shoot biomass of both species was only found in the first year of treatment. At the genotype level, no significant CO22genotype interaction was found at any single harvest either for vegetative or reproductive biomass of either species. Analysis over time, however, indicated that there is a potential for evolutionary adaptation only for D. glomerata: (1) repeated measures ANOVA detected a marginally significant CO22genotype2time interaction for shoot biomass, because the range of the genotypes CO2 response increased over time; (2) genotypes that displayed the highest response during the first year under elevated CO2 also showed the highest response the second year. Null (B. erectus) or weak (D. glomerata) selective potentials of elevated CO2 were detected in this experiment, but short time series could underestimate this potential with perennial species. 相似文献
7.
Genotypic variation in response of quaking aspen (Populus tremuloides) to atmospheric CO2 enrichment 总被引:2,自引:0,他引:2
Enriched atmospheric CO2 alters the quantity and quality of plant production, but how such effects vary among plant genotypes is poorly known. We evaluated the independent and interactive effects of CO2 and nutrient availability on growth, allocation and phytochemistry of six aspen (Populus tremuloides Michx.) genotypes. One-year-old trees, propagated from root cuttings, were grown in CO2-controlled glasshouses for 64 days, then harvested. Foliage was analyzed for levels of water, nitrogen, starch, phenolic glycosides and condensed tannins. Of seven plant growth/allocation variables measured, four (biomass production, stem growth, relative growth rate and root:shoot ratio) exhibited marginally to highly significant CO2 2 genotype interactions. CO2 enrichment stimulated growth of some genotypes more than others, and this interaction was itself influenced by soil nutrient availability. In addition, enriched CO2 increased the magnitude of the among-genotype variance for four of the growth/allocation variables. Of six foliar chemical constituents analyzed, CO2-mediated responses of two (the phenolic glycoside tremulacin and condensed tannins) varied among genotypes. Moreover, enriched CO2 increased the magnitude of among-genotype variance for four of the chemical variables. Given the importance of these growth and chemical characteristics to the biological fitness of aspen, this research suggests that projected atmospheric CO2 increases are likely to alter the genetic structures and evolutionary trajectories of aspen populations. 相似文献
8.
Fernando Valladares José Chico Ismael Aranda Luis Balaguer Pierre Dizengremel Esteban Manrique Erwin Dreyer 《Trees - Structure and Function》2002,16(6):395-403
The responses of Quercus robur (oak) and Fagus sylvatica (beech) seedlings to four different light environments (full, 50%, 40% and 15% sunlight) and to a rapid increase in irradiance were explored during the summer, after 2 years of growth in a forest nursery at Nancy (France). Significant differences between the two species were found for most variables. Phenotypic plasticity for morphological variables (root-shoot ratio, leaf size, leaf weight ratio) was higher in beech than in oak, while the reverse was true for anatomical (stomatal density, epidermis thickness, exchange surface area of the palisade parenchyma) and physiological (maximum photosynthetic rate, stomatal conductance, Rubisco activity) variables. Predawn photochemical efficiency (Fv/Fm) was higher in oak than in beech in all light environments except in 15% sunlight. Fv/Fm was significantly lower in 100% sunlight than in the other light environments in beech but not in oak. Maximum photosynthetic rates (Amax) increased with increasing light availability in the two species but they were always higher in oak than in beech. Oak exhibited higher Rubisco activity than beech in full sunlight. The transfer of shade-adapted seedlings to the open caused a decrease of Fv/Fm, which was larger for beech than for oak. Transferred oak but not beech plants recovered gradually to the control Fv/Fm values. The decreased chlorophyll content and the increased non-photochemical quenching observed in high-light beech seedlings were not enough to avoid photoinhibition. The results suggest that a greater tolerance of strong irradiance is linked to an enhanced physiological plasticity (variables related to photosynthesis), while shade tolerance relies on an enhanced plasticity in light-harvesting variables (crown morphology and chlorophyll content). 相似文献
9.
Seed production and seedling recruitment were measured over 2 years under ambient (360 ppm) and elevated (475 ppm) atmospheric CO2 in a free air carbon dioxide enrichment (FACE) experiment, carried out in a sheep-grazed pasture on dry, sandy soil in New Zealand. In both years elevated CO2 led to more dispersed seeds of the grasses Anthoxanthum odoratum, Lolium perenne and Poa pratensis, the legumes Trifolium repens and T. subterraneum and the herbs Hypochaeris radicata and Leontodon saxatilis. The increased seed dispersal in A. odoratum, H. radicata, Leontodon saxatilis and T. repens reflected both more inflorescences per unit area and more seeds per inflorescence under elevated CO2. The increased seed dispersal in Lolium perenne, P. pratensis and T. subterraneum was due solely to more inflorescences per unit area. The number of seedlings that emerged and survived to at least 7 months of age was increased by elevated CO2 for H. radicata, Leontodon saxatilis, T. repens and T. subterraneum in both years and for A. odoratum and Lolium perenne in the first year. For species where increased seedling recruitment was noted, there was a significant positive correlation between seed production in summer and seedling emergence in the following autumn and winter, and sowing 200 extra seeds per species m-2 resulted in more seedlings compared to unsown controls. Elevated CO2 did not affect seedling survival in any species. There was no measurable effect of elevated CO2 on canopy and soil surface conditions or soil moisture at the time of seedling emergence. The results suggest the dominant effect of elevated CO2 on seedling recruitment in this pasture was an indirect one, reflecting effects on the number of seeds produced. The biomass of H. radicata, Leontodon saxatilis, T. repens and T. subterraneum in the above-ground vegetation was greater under elevated than ambient CO2. However, the size of individual seedlings and mature plants of these four species was unaffected by elevated CO2. The results indicate an important way elevated CO2 influenced plant species composition in this pasture was through changes in the pattern of seedling recruitment. 相似文献
10.
Ten pairs of secondary pure spruce (Picea abies) and adjacent mixed spruce-beech (Fagus sylvatica) stands on comparable sites were selected on two different bedrocks for soil formation (Flysch: nutrient rich and high soil pH; Molasse: poor nutrient supply and acidic) to study how an admixture of beech to spruce stands affects nutrient cycling and consequently soil chemistry. Soil analyses indicated accumulation of Ca under the mixed stands while the top soil under pure spruce was acidified. It was hypothesized that changes of soil chemical properties due to species composition over the last six decades are reflected in the stem wood of spruce. Three healthy dominant spruce trees per plot were selected for coring. Cores were crossdated and half-decadal samples were analyzed for Ca, Mg, Mn and Al. Calcium and Mg concentrations in stem wood of spruce were significantly higher for the pure spruce than for the mixed stands in spite of lower Ca and Mg stores in the soil. We assume that acidification caused by pure spruce mobilized these cations temporarily, increasing soil solution contents and consequently stem wood concentrations. It was possible to reconstruct soil pH from the element ratios Ca/Al (pure stands) and Ca/Mg (mixed stands), since these ratios in the stem wood of the last half-decade did correlate with soil pH for selected soil depths. Reconstructed soil pH showed a decline over the last 60 years under both species compositions due to accumulation of base cations in the increasing biomass. Comparisons of reconstructed soil pH in 0–5 and 10–20 cm soil depth indicated more pronounced top soil acidification (lower soil pH in 0–5 cm) by spruce on the nutrient rich soil (Flysch) than on the acidic soil (Molasse). However, admixture of beech caused higher pH values in 0–5 cm than in 10–20 cm soil depth on Flysch due to the observed Ca-pump effect of beech (uptake of Ca from deeper soil horizons). 相似文献
11.
Kari Kuokkanen Riitta Julkunen-Tiitto Markku Keinänen Pekka Niemelä Jorma Tahvanainen 《Trees - Structure and Function》2001,15(6):378-384
The effect of elevated atmospheric CO2 and temperature on resource allocation and secondary chemistry of white birch (Betula pendula Roth) under a non-limiting nutrient and water supply was investigated. Birch seedlings were grown in closed-top chambers exposed to ambient CO2 and temperature, elevated atmospheric CO2 (700 ppm), elevated temperature (2°C above ambient) and a combination of elevated CO2 and temperature for one growing season. Elevated CO2 significantly increased the total biomass of the seedlings. The combined effect of the elevated CO2 and temperature treatments further increased the total biomass, but not significantly. The content of nitrogen and water decreased, while some secondary compounds (such as condensed tannins and flavonol glycosides) increased in leaves subjected to CO2 enrichment. Elevated temperature increased the concentration of total flavone aglycones and decreased that of total HPLC-phenolics in the leaves, due to the decrease in individual flavonol glycosides, cinnamoylquinic acids and (+)-catechin. There were no significant interactive effects between CO2 and temperature in the phenolic concentrations of the leaves and in the stems, while the number of resin droplets in the top part of the stems showed significant interaction. This clearly implies that carbon allocation into secondary metabolites in the leaves and stems differ under enhanced CO2 and temperature, and the combined effect of CO2 and temperature on the herbivore resistance of birches, is lower than that of CO2 and temperature alone. 相似文献
12.
The stomatal characteristics, length and dry weight as well as stable carbon isotope composition (i13C) of needles and tree rings of Qinghai spruce (Picea crassifolia) at different altitudes in the Qilian mountains were investigated. The results showed that stomatal density, distribution pattern on epidermis, and length and dry weight of needles all increased with altitude below 3,000 m. In contrast, these parameters all decreased with increasing altitude above 3,000 m. Furthermore an assay of tree rings showed that near 3,000 m in altitude was the optimum zone for growth and development of Qinghai spruce. Although atmospheric CO2 concentration influences stomatal density, the effects of many environmental factors, such as temperature, light and rainfall, could obscure the effects of changes in atmospheric CO2 concentration on stomatal density at altitudes higher than the optimum for growth. The correlation of stomatal density with atmospheric CO2 concentration and i13C of Qinghai spruce needles was significant below 3,000 m, but was insignificant above 3,000 m altitude. The i13C value of needles, however, was negatively correlated with atmospheric CO2 concentrations. Therefore, the influence of altitude should be considered in research on plant physiological ecology and the relationship of stomatal density with i13C value or atmospheric CO2 concentration. 相似文献
13.
Microbial community composition and function beneath temperate trees exposed to elevated atmospheric carbon dioxide and ozone 总被引:11,自引:0,他引:11
We hypothesized that changes in plant growth resulting from atmospheric CO2 and O3 enrichment would alter the flow of C through soil food webs and that this effect would vary with tree species. To test this idea, we traced the course of C through the soil microbial community using soils from the free-air CO2 and O3 enrichment site in Rhinelander, Wisconsin. We added either 13C-labeled cellobiose or 13C-labeled N-acetylglucosamine to soils collected beneath ecologically distinct temperate trees exposed for 3 years to factorial CO2 (ambient and 200 µl l-1 above ambient) and O3 (ambient and 20 µl l-1 above ambient) treatments. For both labeled substrates, recovery of 13C in microbial respiration increased beneath plants grown under elevated CO2 by 29% compared to ambient; elevated O3 eliminated this effect. Production of 13C-CO2 from soils beneath aspen (Populus tremuloides Michx.) and aspen-birch (Betula papyrifera Marsh.) was greater than that beneath aspen-maple (Acer saccharum Marsh.). Phospholipid fatty acid analyses (13C-PLFAs) indicated that the microbial community beneath plants exposed to elevated CO2 metabolized more 13C-cellobiose, compared to the microbial community beneath plants exposed to the ambient condition. Recovery of 13C in PLFAs was an order of magnitude greater for N-acetylglucosamine-amended soil compared to cellobiose-amended soil, indicating that substrate type influenced microbial metabolism and soil C cycling. We found that elevated CO2 increased fungal activity and microbial metabolism of cellobiose, and that microbial processes under early-successional aspen and birch species were more strongly affected by CO2 and O3 enrichment than those under late-successional maple. 相似文献
14.
A. Mena-Petite A. Robredo S. Alcalde M. Duñabeitia M. González-Moro M. Lacuesta A. Muñoz-Rueda 《Trees - Structure and Function》2003,17(2):133-143
Post-storage gas exchange parameters like CO2 assimilation, stomatal conductance, transpiration, water use efficiency and intercellular CO2 concentrations, together with several chlorophyll a fluorescence parameters: Fo, Fv, Fv/Fm, Fm/Fo and Fv/Fo were examined in radiata pine (Pinus radiata D. Don) seedlings that were stored for 1, 8 or 15 days at 4° or 10°C with or without soil around the roots. Results were analysed in relation to post-storage water potential and electrolyte leakage in order to forecast their vitality (root growth potential) following cold storage, and post-planting survival potential under optimal conditions. During storage at 4° and 10°C, photosynthesis was reduced, being more pronounced in bare-root seedlings than in seedlings with soil around the roots. The depletion of CO2 assimilation seemed not to be solely a stomatal effect as effects on chloroplasts contributed to this photosynthetic inhibition. Thus, the fall in the ratios Fv/Fm, Fv/Fo and Fm/Fo indicated photochemical apparatus damage during storage. Photosynthetic rate was positively correlated with the root growth index and new root length showing that new root growth is dependent primarily on current photosynthesis. Pre-planting exposure of bare-root radiata pine seedlings to temperatures of 10°C for more than 24 h during transportation or storage is not recommended. 相似文献
15.
Annual and short-lived perennial plant performance during wet years is important for long-term persistence in the Mojave Desert. Additionally, the effects of elevated CO2 on desert plants may be relatively greater during years of high resource availability compared to dry years. Therefore, during an El Niño year at the Nevada Desert FACE Facility (a whole-ecosystem CO2 manipulation), we characterized photosynthetic investment (by assimilation rate-internal CO2 concentration relationships) and evaluated the seasonal pattern of net photosynthesis (Anet) and stomatal conductance (gs) for an invasive annual grass, Bromus madritensis ssp. rubens and a native herbaceous perennial, Eriogonum inflatum. Prior to and following flowering, Bromus showed consistent increases in both the maximum rate of carboxylation by Rubisco (VCmax) and the light-saturated rate of electron flow (Jmax) at elevated CO2. This resulted in greater Anet at elevated CO2 throughout most of the life cycle and a decrease in the seasonal decline of maximum midday Anet upon flowering as compared to ambient CO2. Eriogonum showed significant photosynthetic down-regulation to elevated CO2 late in the season, but the overall pattern of maximum midday Anet was not altered with respect to phenology. For Eriogonum, this resulted in similar levels of Anet on a leaf area basis as the season progressed between CO2 treatments, but greater photosynthetic activity over a typical diurnal period. While gs did not consistently vary with CO2 in Bromus, it did decrease in Eriogonum at elevated CO2 throughout much of the season. Since the biomass of both plants increased significantly at elevated CO2, these patterns of gas exchange highlight the differential mechanisms for increased plant growth. The species-specific interaction between CO2 and phenology in different growth forms suggests that important plant strategies may be altered by elevated CO2 in natural settings. These results indicate the importance of evaluating the effects of elevated CO2 at all life cycle stages to better understand the effects of elevated CO2 on whole-plant performance in natural ecosystems. 相似文献
16.
Jean-Fran?ois David Nathalie Malet Marie-Madeleine Co?teaux Jacques Roy 《Oecologia》2001,127(3):343-349
The consumption and assimilation rates of the woodlouse Armadillidium vulgare were measured on leaf litters from five herb species grown and naturally senesced at 350 and 700 µl l-1 CO2. Each type of litter was tested separately after 12, 30 and 45 days of decomposition at 18°C. The effects of elevated CO2 differed depending on the plant species. In Medicago minima (Fabaceae), the CO2 treatment had no significant effect on consumption and assimilation. In Tyrimnus leucographus (Asteraceae), the CO2 treatment had no significant effect on consumption, but the elevated CO2 litter was assimilated at a lower rate than the ambient CO2 litter after 30 days of decomposition. In the three other species, Galactites tomentosa (Asteraceae), Trifolium angustifolium (Fabaceae) and Lolium rigidum (Poaceae), the elevated CO2 litter was consumed and/or assimilated at a higher rate than the ambient CO2 litter. Examination of the nitrogen contents in these three species of litter did not support the hypothesis of compensatory feeding, i.e. an increase in woodlouse consumption to compensate for low nitrogen content of the food. Rather, the results suggest that in herbs that were unpalatable at the start of the experiment (Galactites, Trifolium and Lolium), more of the the litter produced at 700 µl l-1 CO2 was consumed than of that produced at 350 µl l-1 because inhibitory factors were eliminated faster during decomposition. 相似文献
17.
Does elevated atmospheric CO2 concentrations affect wood decomposition? 总被引:10,自引:0,他引:10
This study was conducted to test the hypothesis that wood tissues generated under elevated atmospheric [CO2] have lower quality and subsequent reduced decomposition rates. Chemical composition and subsequent field decomposition rates
were studied for beech (Fagus sylvatica L.) twigs grown under ambient and elevated [CO2] in open top chambers. Elevated [CO2] significantly affected the chemical composition of beech twigs, which had 38% lower N and 12% lower lignin concentrations
than twigs grown under ambient [CO2]. The strong decrease in N concentration resulted in a significant increase in the C/N and lignin/N ratios of the beech wood
grown at elevated [CO2]. However, the elevated [CO2] treatment did not reduce the decomposition rates of twigs, neither were the dynamics of N and lignin in the decomposing
beech wood affected by the [CO2] treatment, despite initial changes in N and lignin concentrations between the ambient and elevated [CO2] beech wood.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Hagedorn Frank Bucher Jürg B. Tarjan David Rusert Peter Bucher-Wallin Inga 《Plant and Soil》2000,224(2):273-286
The objectives of this study were to estimate how soil type, elevated N deposition (0.7 vs. 7 g N m–2y–1) and tree species influence the potential effects of elevated CO2 (370 vs. 570 mol CO2 mol–1) on N pools and fluxes in forest soils. Model spruce-beech forest ecosystems were established on a nutrient-rich calcareous sand and on a nutrient-poor acidic loam in large open-top chambers. In the fourth year of treatment, we measured N concentrations in the soil solution at different depths, estimated N accumulation by ion exchange resin (IER) bags, and quantified N export in drainage water, denitrification, and net N uptake by trees. Under elevated CO2, concentrations of N in the soil solution were significantly reduced. In the nutrient-rich calcareous sand, CO2 enrichment decreased N concentrations in the soil solution at all depths (–45 to –100%). In the nutrient-poor acidic loam, the negative CO2 effect was restricted to the uppermost 5 cm of the soil. Increasing the N deposition stimulated the negative impact of CO2 enrichment on soil solution N in the acidic loam at 5 cm depth from –20% at low N inputs to –70% at high N inputs. In the nutrient-rich calcareous sand, N additions did not influence the CO2 effect on soil solution N. Accumulation of N by IER bags, which were installed under individual trees, was decreased at high CO2 levels under spruce in both soil types. Under beech, this decrease occurred only in the calcareous sand. N accumulation by IER bags was negatively correlated with current-years foliage biomass, suggesting that the reduction of soil N availability indices was related to a CO2-induced growth enhancement. However, the net N uptake by trees was not significantly increased by elevated CO2. Thus, we suppose that the reduced N concentrations in the soil solution at elevated CO2 concentrations were rather caused by an increased N immobilisation in the soil. Denitrification was not influenced by atmospheric CO2 concentrations. CO2 enrichment decreased nitrate leaching in drainage by 65%, which suggests that rising atmospheric CO2 potentially increases the N retention capacity of forest ecosystems. 相似文献
19.
Carbon isotope discrimination in photosynthetic bark 总被引:1,自引:0,他引:1
Lucas A. Cernusak John D. Marshall Jonathon P. Comstock Nick J. Balster 《Oecologia》2001,128(1):24-35
We developed and tested a theoretical model describing carbon isotope discrimination during photosynthesis in tree bark. Bark photosynthesis reduces losses of respired CO2 from the underlying stem. As a consequence, the isotopic composition of source CO2 and the CO2 concentration around the chloroplasts are quite different from those of photosynthesizing leaves. We found three lines of evidence that bark photosynthesis discriminates against 13C. First, in bark of Populus tremuloides, the '13C of CO2 efflux increased from -24.2 in darkness to -15.8 in the light. In Pinus monticola, the '13C of CO2 efflux increased from -27.7 in darkness to -10.2 in the light. Observed increases in '13C were generally in good agreement with predictions from the theoretical model. Second, we found that '13C of dark-respired CO2 decreased following 2-3 h of illumination (P<0.01 for Populus tremuloides, P<0.001 for Pinus monticola). These decreases suggest that refixed photosynthate rapidly mixes into the respiratory substrate pool. Third, a field experiment demonstrated that bark photosynthesis influenced whole-tissue '13C. Long-term light exclusion caused a localized increase in the '13C of whole bark and current-year wood in branches of P. monticola (P<0.001 and P<0.0001, respectively). Thus bark photosynthesis was shown to discriminate against 13C and create a pool of photosynthate isotopically lighter than the dark respiratory pool in all three experiments. Failure to account for discrimination during bark photosynthesis could interfere with interpretation of the '13C in woody tissues or in woody-tissue respiration. 相似文献
20.
Carbon dioxide flux from coarse woody debris (CWD) is an important source of CO2 in forests with moderate to large amounts of CWD. A process-based understanding of environmental controls on CWD CO2 flux (RCWD) is needed to accurately model carbon exchange between forests and the atmosphere. The objectives of this study were to: (1) use a laboratory incubation factorial experiment to quantify the effect of temperature (TCWD), water content (WC), decay status, and their interactions on RCWD for black spruce [Picea mariana (Mill.) BSP] CWD; (2) measure and model spatial and temporal dynamics in TCWD for a boreal black spruce fire chronosequence; and (3) validate the RCWD model with field measurements, and quantify potential errors in estimating annual RCWD from this model on various time steps. The RCWD was positively correlated to TCWD (R2=0.37, P<0.001) and WC (R2=0.18, P<0.001), and an empirical RCWD polynomial model that included TCWD and WC interactions explained 74% of the observed variation of RCWD. The RCWD estimates from the RCWD model excellently matched the field measurements. Decay status of CWD significantly (P<0.001) affected RCWD. The temperature coefficient (Q10) averaged 2.5, but varied by 141% across the 5-42°C temperature range, illustrating the potential shortcomings of using a constant Q10. The CWD temperature was positively correlated to air temperature (R2=0.79, P<0.001), with a hysteresis effect that was correlated to CWD decay status and stand leaf area index . Ignoring this temperature hysteresis introduced errors of -1% to +32% in annual RCWD estimates. Increasing TCWD modeling time step from hourly to daily or monthly introduced a 5-11% underestimate in annual RCWD. The annual RCWD values in this study were more than two-fold greater than those in a previous study, illustrating the need to incorporate spatial and temporal responses of RCWD to temperature and water content into models for long-term RCWD estimation in boreal forest ecosystems. 相似文献