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1.
Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years on leaves of 24 sour orange ( Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO 2 concentration of 400 microliters per liter, and 16 growing in air enriched with CO 2 to concentrations approaching 1000 microliters per liter. Over this CO 2 concentration range, net photosynthesis increased linearly with CO 2 by more than 200%, whereas dark respiration decreased linearly to only 20% of its initial value. These results, together with those of a comprehensive fine-root biomass determination and two independent aboveground trunk and branch volume inventories, suggest that a doubling of the air's current mean CO 2 concentration of 360 microliters per liter would enhance the growth of the trees by a factor of 3.8. 相似文献
2.
Pinus eldarica L. trees, rooted in the natural soil of an agricultural field at Phoenix, Arizona, were grown from the seedling stage in clear-plastic-wall open-top enclosures maintained at four different atmospheric CO 2 concentrations for 15 months. Light response functions were determined for one tree from each treatment by means of whole-tree net CO 2 exchange measurements at the end of this period, after which rates of carbon assimilation of an ambient-treatment tree were measured across a range of atmospheric CO 2 concentrations. The first of these data sets incorporates the consequences of both the CO 2-induced enhancement of net photosynthesis per unit needle area and the CO 2-induced enhancement of needle area itself (due primarily to the production of more needles), whereas the second data set reflects only the first of these effects. Hence the division of the normalized results of the first data set by the normalized results of the second set yields a representation of the increase in whole-tree net photosynthesis due to enhanced needle production caused by atmospheric CO 2 enrichment. In the solitary trees we studied, the relative contribution of this effect increased rapidly with the CO 2 concentration of the air to increase whole-tree net photosynthesis by nearly 50% at a CO 2 concentration approximately 300 μmol mol −1 above ambient. 相似文献
3.
Numerous photosynthesis and growth measurements of sour orange ( Citrus aurantium L.) trees maintained in ambient air and air enriched with an extra 300 microliters per liter of CO 2 have revealed the CO 2-enriched trees to have consistently sequestered approximately 2.8 times more carbon than the control trees over a period of three full years. Under field conditions in the natural environment, plants may not experience the downward regulation of photosynthetic capacity typically observed in long-term CO 2 enrichment experiments with plants growing in pots. 相似文献
4.
Evidence of an atmospheric CO 2‐fertilization effect on radial growth rates was uncovered for open‐grown white spruce in a mixed‐grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite that a similar amount (61%) of the total variation in radial growth index was explained by climate for both young and old trees, residuals from young trees for the period of 1955–1999 demonstrated a stronger upward trend ( R2=0.551, P<0.0001) than old trees for the period of 1900–1996 ( R2=0.020, P=0.167). Similar to young trees, the residuals from the early growth period (1900–1929) of old trees also demonstrated a stronger upward trend ( R2=0.480, P<0.0001) than the period of 1900–1996. Likewise, a comparable period (1970–1999) of young trees also demonstrated a stronger upward trend ( R2=0.619, P<0.0001) than the early growth period (1900–1929) of old trees. In addition, postdrought growth response was much stronger for young trees (1970–1999) compared with old trees at the same development stage (1900–1929) ( P=0.011) or within the same time period (1970–1999) ( P=0.014). There was no difference ( P=0.221) in drought recovery between the early (1900–1929) period and the late (1970–1999) period within old trees. Together, our results suggest that (1) open‐grown white spruce trees improved their growth with time at the early developmental stage, and (2) at the same developmental stage, a greater growth response occurred in the late period when atmospheric CO 2 concentration, and the rate of atmospheric CO 2 increase were both relatively high. While it is impossible to rule out other factors, these results are consistent with expectations for CO 2‐fertilization effects. 相似文献
5.
Rising atmospheric carbon dioxide (CO 2) concentration is expected to change plant tissue quality with important implications for plant–insect interactions. Taking advantage of canopy access by a crane and long‐term CO 2 enrichment (530 μ mol mol ?1) of a natural old‐growth forest (web‐free air carbon dioxide enrichment), we studied the responses of a generalist insect herbivore feeding in the canopy of tall trees. We found that relative growth rates (RGR) of gypsy moth ( Lymantria dispar) were reduced by 30% in larvae fed on high CO 2‐exposed Quercus petraea, but increased by 29% when fed on high CO 2‐grown Carpinus betulus compared with control trees at ambient CO 2 (370 μ mol mol ?1). In Fagus sylvatica, there was a nonsignificant trend for reduced RGR under elevated CO 2. Tree species‐specific changes in starch to nitrogen ratio, water, and the concentrations of proteins, condensed and hydrolyzable tannins in response to elevated CO 2 were identified to correlate with altered RGR of gypsy moth larvae. Our data suggest that rising atmospheric CO 2 will have strong species‐specific effects on leaf chemical composition of canopy trees in natural forests leading to contrasting responses of herbivores such as those reported here. A future change in host tree preference seems likely with far‐ranging consequences for forest community dynamics. 相似文献
6.
Pedunculate oak ( Quercus robur L.) was germinated and grown at ambient CO 2 level and 650 ppmv CO 2 in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 6 month under nutrient non-limiting conditions. Mycorrhization and elevated atmospheric CO 2 each supported the growth of the trees. Stem height, stem diameter, and dry matter accumulation of pedunculate oak were increased by mycorrhization. Elevated atmospheric CO 2 enhanced stem height, stem diameter, fresh weight and dry weight, as well as lateral root formation of the trees. In combination, mycorrhization and elevated atmospheric CO 2 had a more than additive, positive effect on tree height and biomass accumulation, and further improved lateral root formation of the trees. From these findings it is suggested that the efficiency of the roots in supporting the growth of the shoot is increased in mycorrhized oak trees at elevated atmospheric CO 2.Abbreviations DW
dry weight
- FW
fresh weight
- RWC
relative water content 相似文献
7.
The course of respiration of attached maize ( Zea mays L.) leaves was measured by infrared gas analysis of CO 2 efflux in the dark following illumination in atmospheres of 300 microliters of CO 2 per liter of air, CO 2-free air, and CO 2-free N 2 containing 400 microliters of O 2 per liter. CO 2 efflux from control leaves started 3 to 4 minutes after darkening, increased to a maximum after about 20 minutes, and returned to a steady minimum after 2 to 3 hours. Respiration was quantitatively related to prior illumination, independent of net CO 2 fixation in the light, and depressed by N 2. Light, but not air, was required to produce a substrate for respiration in the subsequent dark period; air was required for oxidation of the substrate to CO 2. The stimulation of respiration by prior illumination in maize leaves differs in its slower onset and greater duration from the postillumination burst of photorespiration. 相似文献
8.
Long‐term population effects of changes in atmospheric CO 2 will be largely determined by reproductive effort. Our research objectives were to quantify variability in seed production and rate of maturation among individual Pinus taeda L. (Pinaceae) trees growing in elevated CO 2 (ambient plus 200 μL L ?1) since 1996. Estimating tree fecundity in nature is frustrated by the difficulty of counting seeds from individual trees and the need for long‐term data. We have used a hierarchical Bayes approach to model individual tree fecundity, accounting for the complexity of experimentation in a natural setting over multiple years. The study presented here demonstrates large variability in natural fecundity rates and contributes to our understanding of how both interannual variation and population heterogeneity influence elevated CO 2 effects. We found that trees growing under elevated CO 2 matured earlier and produced more seeds and cones per unit basal area than ambient grown trees. By 2004, trees grown in high CO 2 had produced an average 300 more seeds per tree than ambient grown trees. Although there was a trend toward decreasing mean CO 2 effect (difference in fecundity between elevated and ambient treatments) over time, the hierarchical analysis indicates that this decrease comes from the emergence of a few highly fecund ambient grown trees by 2002, rather than acclimation or downregulation among the fumigated trees. The most important effect of increased CO 2 in forest ecosystems may be the increase in fecundity reported here. Although biomass responses can sometimes be large, the increase in fecundity can have long‐term impacts on forest dynamics that transcend the current generation. 相似文献
9.
For herbaceous species, elevated CO 2 often increases seed production but usually leads to decreased seed quality. However, the effects of increased atmospheric CO 2 on tree fecundity remain uncertain, despite the importance of reproduction to the composition of future forests. We determined how seed quantity and quality differed for pine trees grown for 12 years in ambient and elevated (ambient+200 μL L ?1) CO 2, at the Duke Forest free‐air CO 2 enrichment (FACE) site. We also compared annual reproductive effort with yearly measurements of aboveground net primary productivity (ANPP), precipitation (P), potential evapotranspiration (PET) and water availability [precipitation minus potential evapotranspiration (P?PET)] to investigate factors that may drive interannual variation in seed production. The number of mature, viable seeds doubled per unit basal area in high‐CO 2 plots from 1997 to 2008 ( P<0.001), but there was no CO 2 effect on mean seed mass, viability, or nutrient content. Interannual variation in seed production was positively related to ANPP, with a similar percentage of ANPP diverted to reproduction across years. Seed production was negatively related to PET ( P<0.005) and positively correlated with water availability ( P<0.05), but showed no relationship with precipitation ( P=0.88). This study adds to the few findings that, unlike herbaceous crops, woody plants may benefit from future atmospheric CO 2 by producing larger numbers of seeds without suffering degraded seed quality. Differential reproductive responses between functional groups and species could facilitate woody invasions or lead to changes in forest community composition as CO 2 rises. 相似文献
10.
Diurnal and seasonal patterns of CO 2 concentration ([CO 2]) in leaf gas spaces were measured to better understand the relationship of sediment-derived CO 2 to photosynthesis in the emergent wetland species, Typha latifolia L. (cattail). Leaf [CO 2] was above 2,000 μl/liter at dawn on all but the first sampling date. At all sampling dates, leaf [CO 2] declined to near atmospheric [CO 2] at midday and rose to well above atmospheric [CO 2] in the late afternoon. The maximum leaf [CO 2] varied with sampling date and was over 18 times atmospheric levels (over 6,300 μl/liter) in August. Based on measurement of photon flux density and temperature, the diurnal pattern in leaf [CO 2] may be generally controlled by expected photosynthetic rates. It is hypothesized that seasonal variation in leaf [CO 2] may be a function of variation in microbial (soil) respiration. Using dye and slight pressurization, it was confirmed that gas spaces in rhizomes were interconnected with the gas spaces in leaves through the rhizome-shoot transition. From anatomical measurements, it was also estimated that over 50% of total leaf volume was occupied by gas spaces and that most of the total gas-space volume in plants was in the shoot. Photosynthetic rate in C3 plants, like cattail, can increase with increasing [CO 2] under natural conditions. For this reason, cattail and other emergent wetland plants possessing continuous gas-space pathways appear to have a significant carbon supplement as compared to other C3 plants growing in well-aerated soils. 相似文献
11.
The RIVERSTRAHLER model, an idealized biogeochemical model of the river system, has been coupled to MIRO‐CO 2, a complex biogeochemical model describing diatom and Phaeocystis blooms and carbon and nutrient cycles in the marine domain, to assess the dual role of changing nutrient loads and increasing atmospheric CO 2 as drivers of air–sea CO 2 exchanges in the Southern North Sea with a focus on the Belgian coastal zone (BCZ). The whole area, submitted to the influence of two main rivers (Seine and Scheldt), is characterized by variable diatom and Phaeocystis colonies blooms which impact on the trophic status and air–sea CO 2 fluxes of the coastal ecosystem. For this application, the MIRO‐CO 2 model is implemented in a 0D multibox frame covering the eutrophied Eastern English Channel and Southern North Sea and receiving loads from the rivers Seine and Scheldt. Model simulations are performed for the period between 1951 and 1998 using real forcing fields for sea surface temperature, wind speed and atmospheric CO 2 and RIVERSTRAHLER simulations for river carbon and nutrient loads. Model results suggest that the BCZ shifted from a source of CO 2 before 1970 (low eutrophication) towards a sink during the 1970–1990 period when anthropogenic DIN and P loads increased, stimulating C fixation by autotrophs. In agreement, a shift from net annual heterotrophy towards autotrophy in BCZ is simulated from 1980. The period after 1990 is characterized by a progressive decrease of P loads concomitant with a decrease of primary production and of the CO 2 sink in the BCZ. At the end of the simulation period, the BCZ ecosystem is again net heterotroph and acts as a source of CO 2 to the atmosphere. R‐MIRO‐CO 2 scenarios testing the relative impact of temperature, wind speed, atmospheric CO 2 and river loads variability on the simulated air–sea CO 2 fluxes suggest that the trend in air–sea CO 2 fluxes simulated between 1951 and 1998 in the BCZ was mainly controlled by the magnitude and the ratio of inorganic nutrient river loads. Quantitative nutrient changes control the level of primary production while qualitative changes modulate the relative contribution of diatoms and Phaeocystis to this flux and hence the sequestration of atmospheric CO 2. 相似文献
12.
Although elevated atmospheric CO 2 has been shown to increase growth of tree seedlings and saplings, the response of intact forest ecosystems and established trees is unclear. We report results from the first large-scale experimental system designed to study the effects of elevated CO 2 on an intact forest with the full complement of species interactions and environmental stresses. During the first year of exposure to ^ 1.5 Ë ambient CO 2, canopy loblolly pine ( Pinus taeda, L.) trees increased basal area growth rate by 24% but understorey trees of loblolly pine, sweetgum ( Liquidambar styraciflua L.), and red maple ( Acer rubrum L.) did not respond. Winged elm ( Ulmus alata Michx.) had a marginally significant increase in growth rate ( P = 0.069). These data suggest that this ecosystem has the capacity to respond immediately to a step increase in atmospheric CO 2; however, as exposure time increases, nutrient limitations may reduce this initial growth stimulation. 相似文献
13.
The effect of elevated atmospheric CO 2 on water distribution in the intact roots of Vicia faba L. bean seedlings grown in natural soil was studied noninvasively with proton ( 1H) nuclear magnetic resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric CO 2-enriched air at 650 cm 3 m ?3 produced significant increases in water imaged in upper roots, hypogeal cotyledons and lower stems in response to a short-term drying-stress cycle. Above ground, drying produced negligible stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion of water imaged in the same upper root structures in control plants subject to ambient CO 2 (350 m 3 m ?3), and stem shrinkage and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO 2 does not necessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper roots and lower stem in elevated CO 2 environments may be a mitigating factor in assessing deleterious effects of greenhouse changes on crops during periods of dry climate. 相似文献
14.
Foliar spray applications of 40% aqueous methanol were made to sunlit leaves of sour orange trees that had been grown continuously in clear-plastic-wall open-top enclosures maintained out-of-doors at Phoenix, Arizona, for over 5.5 years in ambient air of approximately 400 μmol mol -1 CO 2 and in air enriched with CO 2 to a concentration of approximately 700 μmol mol -1. No unambiguous effects of the methanol applications were detected in net photosynthesis measurements made on foliage in either of the two CO 2 treatments. The 75% increase in CO 2, however, raised the upper-limiting leaf temperature for positive net photosynthesis by approximately 7 C, which resulted in a 75% enhancement in net photosynthesis at a leaf temperature of 31 C, a 100% enhancement at a leaf temperature of 35 C, and a 200% enhancement at 42 C. 相似文献
15.
Nitrogen‐fixing plant species growing in elevated atmospheric carbon dioxide concentration ([CO 2]) should be able to maintain a high nutrient supply and thus grow better than other species. This could in turn engender changes in internal storage of nitrogen (N) and remobilisation during periods of growth. In order to investigate this one‐year‐old‐seedlings of Alnus glutinosa (L.) Gaertn and Pinus sylvestris (L.) were exposed to ambient [CO 2] (350 µ mol mol ? 1) and elevated [CO 2] (700 µ mol mol ? 1) in open top chambers (OTCs). This constituted a main comparison between a nitrogen‐fixing tree and a nonfixer, but also between an evergreen and a deciduous species. The trees were supplied with a full nutrient solution and in July 1994, the trees were given a pulse of 15N‐labelled fertiliser. The allocation of labelled N to different tissues (root, leaves, shoots) was followed from September 1994 to June 1995. While N allocation in P. sylvestris (Scots pine) showed no response to elevated [CO 2], A. glutinosa (common alder) responded in several ways. During the main nutrient uptake period of June–August, trees grown in elevated [CO 2] had a higher percentage of N derived from labelled fertiliser than trees grown in ambient [CO 2]. Remobilisation of labelled N for spring growth was significantly higher in A. glutinosa grown in elevated [CO 2] (9.09% contribution in ambient vs. 29.93% in elevated [CO 2] leaves). Exposure to elevated [CO 2] increased N allocation to shoots in the winter of 1994–1995 (12.66 mg in ambient vs. 43.42 mg in elevated 1993 shoots; 4.81 mg in ambient vs. 40.00 mg in elevated 1994 shoots). Subsequently significantly more labelled N was found in new leaves in April 1995. These significant increases in movement of labelled N between tissues could not be explained by associated increases in tissue biomass, and there was a significant shift in C‐biomass allocation away from the leaves towards the shoots (all above‐ground material except leaves) in A. glutinosa. This experiment provides the first evidence that not only are shifts in C allocation affected by elevated [CO 2], but also internal N resource utilisation in an N 2‐fixing tree. 相似文献
16.
The unabated rise in atmospheric [CO 2] is associated with increased air temperature. Yet, few CO 2‐enrichment studies have considered pre‐industrial [CO 2] or warming. Consequently, we quantified the interactive effects of growth [CO 2] and temperature on photosynthesis of faster‐growing Eucalyptus saligna and slower‐growing E. sideroxylon. Well‐watered and ‐fertilized tree seedlings were grown in a glasshouse at three atmospheric [CO 2] (290, 400, and 650 µL L ?1), and ambient (26/18 °C, day/night) and high (ambient + 4 °C) air temperature. Despite differences in growth rate, both eucalypts responded similarly to [CO 2] and temperature treatments with few interactive effects. Light‐saturated photosynthesis ( Asat) and light‐ and [CO 2]‐saturated photosynthesis ( Amax) increased by ~50% and ~10%, respectively, with each step‐increase in growth [CO 2], underpinned by a corresponding 6–11% up‐regulation of maximal electron transport rate ( Jmax). Maximal carboxylation rate ( Vcmax) was not affected by growth [CO 2]. Thermal photosynthetic acclimation occurred such that Asat and Amax were similar in ambient‐ and high‐temperature‐grown plants. At high temperature, the thermal optimum of Asat increased by 2–7 °C across [CO 2] treatments. These results are the first to suggest that photosynthesis of well‐watered and ‐fertilized eucalypt seedlings will remain strongly responsive to increasing atmospheric [CO 2] in a future, warmer climate. 相似文献
17.
Stands of groundnut ( Arachis hypogaea L. cv. Kadiri‐3) were grown in controlled environment glasshouses at mean atmospheric CO 2 concentrations of 375 or 700 μmol mol ?1 and daily mean air temperatures of 28 or 32°C on irrigated or drying soil profiles. Leaf water (Ψ l) and solute potential (Ψ s), relative water content (RWC), stomatal conductance (g l) and net photosynthesis (P n) were measured at midday for the youngest mature leaf throughout the growing season. Elevated CO 2 and temperature had no detectable effect on the water relations of irrigated plants, but higher values of RWC, Ψ l and Ψ s were maintained for longer under elevated CO 2 during progressive drought. Turgor potential (Ψ p) reached zero when Ψ l declined to ?1.6 to ?1.8 MPa in all treatments; turgor was lost sooner when droughted plants were grown under ambient CO 2. A 4°C increase in mean air temperature had no effect on Ψ s in droughted plants, but elicited a small increase in Ψ l; midday g l values were lower under elevated than under ambient CO 2, and Ψ l and g l declined below ?1.5 MPa and 0.25 cm s ?1, respectively, as the soil dried. Despite the low g l values recorded for droughted plants late in the season, P n was maintained under elevated CO 2, but declined to zero 3 weeks before final harvest under ambient CO 2. Concurrent reductions in g l and increases in water use efficiency under elevated CO 2 prolonged photosynthetic activity during drought and increased pod yields relative to plants grown under ambient CO 2. The implications of future increases in atmospheric CO 2 for the productivity of indeterminate C 3 crops grown in rainfed subsistence agricultural systems in the semi‐arid tropics are discussed. 相似文献
18.
The saturating photon flux density (400 to 700 nanometers) for induction of flowering of the long day plant Anagallis arvensis L. was 1,900 micromoles per square meter per second (6,000 foot-candles) when an 8-hour daylength was extended to 24 hours by a single period of supplementary irradiation. The saturating photon flux density for photosynthetic CO 2 uptake during the same single supplementary light period was lower, at about 1,000 to 650 micromoles per square meter per second (3,000 to 2,000 foot-candles). The per cent flowering and mean number of floral buds per plant were significantly reduced when the light extension treatment was given in CO2-free air, and glucose (10 kilograms per cubic meter in water) relieved this effect. Glucose solution also significantly increased flowering of plants given supplementary light treatment in atmospheric air under a photon flux density of 80 micromoles per square meter per second. Increasing the CO2 concentration to 1.27 grams per cubic meter of CO2 in air during the supplementary light period did not increase flowering. It is concluded that high photon flux densities promote flowering of Anagallis through both increased photosynthesis and the photomorphogenic action of high irradiance. 相似文献
19.
The effects of atmospheric CO 2 enrichment on mature trees in their natural environment are largely unknown. Here we present a new, and inexpensive technique which can be used in situ to address some key physiological questions related to the CO 2 problem. Small, light-weight cups mounted on the lower side of rigid leaves at the top of tall tropical forest trees were supplied with CO 2-enriched air derived from a low-technology air mixing device utilizing forest floor CO 2 evolution. We present the scientific rationale for such field experiments, technical details, an assessment of potential cup artifacts and first results illustrating effects of elevated CO 2 on stomata and carbohydrate accumulation in the canopies of mature trees. 相似文献
20.
The long‐term effect of elevated atmospheric CO 2 on isoprenoid emissions from adult trees of two Mediterranean oak species (the monoterpene‐emitting Quercus ilex L. and the isoprene‐emitting Quercus pubescens Willd.) native to a high‐CO 2 environment was investigated. During two consecutive years, isoprenoid emission was monitored both at branch level, measuring the actual emissions under natural conditions, and at leaf level, measuring the basal emissions under the standard conditions of 30 °C and at light intensity of 1000 µmol m ?2 s ?1. Long‐term exposure to high atmospheric levels of CO 2 did not significantly affect the actual isoprenoid emissions. However, when leaves of plants grown in the control site were exposed for a short period to an elevated CO 2 level by rapidly switching the CO 2 concentration in the gas‐exchange cuvette, both isoprene and monoterpene basal emissions were clearly inhibited. These results generally confirm the inhibitory effect of elevated CO 2 on isoprenoid emission. The absence of a CO 2 effect on actual emissions might indicate higher leaf temperature at elevated CO 2, or an interaction with multiple stresses some of which (e.g. recurrent droughts) may compensate for the CO 2 effect in Mediterranean ecosystems. Under elevated CO 2, isoprene emission by Q. pubescens was also uncoupled from the previous day's air temperature. In addition, pronounced daily and seasonal variations of basal emission were observed under elevated CO 2 underlining that correction factors may be necessary to improve the realistic estimation of isoprene emissions with empirical algorithms in the future. A positive linear correlation of isoprenoid emission with the photosynthetic electron transport and in particular with its calculated fraction used for isoprenoid synthesis was found. The slope of this relationship was different for isoprene and monoterpenes, but did not change when plants were grown in either ambient or elevated CO 2. This suggests that physiological algorithms may usefully predict isoprenoid emission also under rising CO 2 levels. 相似文献
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