首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 750 毫秒
1.
Increases in growth temperature have been observed to affect photosynthesis differently under long-term exposure to ambient- and twice ambient-air CO2 concentrations. This study investigates the causes of this interaction in wheat (Triticum aestivum L.) grown in the field over two consecutive years under temperature gradient chambers in ambient (370 μmol mol−1) or elevated (700 μmol mol−1) atmospheric CO2 concentrations and at ambient or ambient +4°C temperatures, with either a low or a high nitrogen supply. The photosynthesis-internal CO2 response curves and the activity, activation state, kcat and amount of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) were measured, as well as the soluble protein concentration in flag leaves at ear emergence and 8–15 days after anthesis. A high nitrogen supply increased Vcmax, the Rubisco amount and activity and soluble protein contents, but did not significantly change the Rubisco kcat. Both elevated CO2 and above ambient temperatures had negative effects on Vcmax and Rubisco activity, but at elevated CO2, an increase in temperature did not decrease Vcmax or Rubisco activity in relation to ambient temperature. The amounts of Rubisco and soluble protein decreased with elevated CO2 and temperature. The negative impact of elevated CO2 on Rubisco properties was somewhat counteracted at elevated temperatures by an increase in kcat. This effect can diminish the detrimental effects on photosynthesis of combined increases of CO2 and temperature.  相似文献   

2.
Several studies have shown improved soil stability under elevated atmospheric CO2 caused by increased plant and microbial biomass. These studies have not quantified the mechanisms responsible for soil stabilisation or the effect on water relations. The objective of this study was to assess changes in water repellency under elevated CO2. We hypothesised that increased plant biomass will drive an increase in water repellency, either directly or through secondary microbial processes. Barley plants were grown at ambient (360 ppm) and elevated (720 ppm) CO2 concentrations in controlled chambers. Each plant was grown in a separate tube of 1.2 m length constructed from 22 mm depth × 47 mm width plastic conduit trunk and packed with sieved arable soil to 55% porosity. After 10 weeks growth the soil was dried at 40°C before measuring water sorptivity, ethanol sorptivity and repellency at many depths with a 0.14 mm radius microinfiltrometer. This provided a microscale measure of the capacity of soil to rewet after severe drying. At testing roots extended throughout the depth of the soil in the tube. The depth of the measurement had no effect on sorptivity or repellency. A rise in CO2 resulted in a decrease in water sorptivity from 1.13 ± 0.06 (s.e) mm s−1/2 to 1.00 ± 0.05 mm s−1/2 (P < 0.05) and an increase in water repellency from 1.80 ± 0.09 to 2.07 ± 0.08 (P < 0.05). Ethanol sorptivity was not affected by CO2 concentration, suggesting a similar pore structure. Repellency was therefore the primary cause of decreased water sorptivity. The implications will be both positive and negative, with repellency potentially increasing soil stability but also causing patchier wetting of the root-zone.  相似文献   

3.
4.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may cause changes in Chinese pine’s growth. An erratum to this article can be found at  相似文献   

5.
Using open top chambers, the effects of elevated O3 (80 nmol mol−1) and elevated CO2 (700 μmol mol−1), alone and in combination, were studied on young trees of Quercus mongolica. The results showed that elevated O3 increased malondialdehyde content and decreased photosynthetic rate after 45 days of exposure, and prolonged exposure (105 days) induced significant increase in electrolyte leakage and reduction of chlorophyll content. All these changes were alleviated by elevated CO2, indicating that oxidative stress on cell membrane and photosynthesis was ameliorated. After 45 days of exposure, elevated O3 stimulated activities of superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate peroxidase (APX, EC 1.11.1.11), but the stimulation was dampened under elevated CO2 exposure. Furthermore, ascorbate (AsA) and total phenolics contents were not higher in the combined gas treatment than those in elevated O3 treatment. It indicates that the protective effect of elevated CO2 against O3 stress was achieved hardly by enhancing ROS scavenging ability after 45 days of exposure. After 105 days of exposure, elevated O3 significantly decreased activities of SOD, catalase (CAT, EC 1.11.1.6) and APX and AsA content. Elevated CO2 suppressed the O3-induced decrease, which could ameliorate the oxidative stress in some extent. In addition, elevated CO2 increased total phenolics content in the leaves both under ambient O3 and elevated O3 exposure, which might contribute to the protection against O3-induced oxidative stress as well.  相似文献   

6.
Increased concentrations of atmospheric carbon dioxide (CO2) and drought stress have greatly influenced plant growth, the status of nitrogen (N) and phosphorus (P), and N:P ratios. We identified the plant biomass, N and P distributional patterns, and N:P stoichiometry of a grass species on the Loess Plateau in China under elevated CO2 concentration and drought stress conditions. Bothriochloa ischaemum, a C4 perennial herbaceous grass, was grown in pots at CO2 concentrations of 400 (ambient) and 800 (elevated) μmol mol?1 and at 60 ± 5 and 40 ± 5 % of field capacity. The elevated CO2 concentration significantly increased plant total biomass, N concentration, N and P content, allocation of biomass to roots, and allocation of N to shoots, and increased the N:P ratios of whole plants and the shoots, especially under well-watered conditions. Drought stress significantly decreased plant biomass and plant N and P content, especially under elevated CO2. Drought stress decreased the N:P ratios, but was only significant in the roots under ambient CO2. Drought stress may attenuate the stimulation of plant growth and N and P acquisition by CO2 enrichment, and projected elevated CO2 concentrations may partially offset the negative effects of increased drought by increasing the assimilation of N and P.  相似文献   

7.
Azolla filiculoides is a floating aquatic fern growing in tropical and temperate freshwater ecosystems. As A. filiculoides has symbiotic nitrogen-fixing cyanobacteria (Anabaena azollae) within its leaf cavities, it is cultivated in rice paddies to improve N availability and suppress other wetland weeds. To understand how C assimilation and N accumulation in A. filiculoides respond to elevated atmospheric carbon dioxide concentration (CO2) in combination with P addition and higher temperatures, we conducted pot experiments during the summer of 2007 and 2008. In 2007, we grew A. filiculoides in pots at two treatment levels of added P fertilizer and at two levels of [CO2] (380 ppm for ambient and 680 ppm for elevated [CO2]) in controlled-environment chambers. In 2008, we grew A. filiculoides in four controlled-environment chambers at two [CO2] levels and two temperature levels (34/26°C (day/night) and 29/21°C). We found that biomass and C assimilation by A. filiculoides were significantly increased by elevated [CO2], temperature, and P level (all P < 0.01), with a significant interaction between elevated [CO2] and added P (P < 0.01). Tissue N content was decreased by elevated [CO2] and increased by higher temperature and P level (all P < 0.01). The acetylene reduction assay showed that the N-fixation activity of A. filiculoides was not significantly different under ambient and elevated [CO2] but was significantly stimulated by P addition. N-fixation activity decreased at higher temperatures (34/26°C), indicating that 29/21°C was more suitable for A. azollae growth. Therefore, we conclude that the N accumulation potential of A. filiculoides under future climate warming depends primarily on the temperature change and P availability, and C assimilation should be increased by elevated [CO2].  相似文献   

8.
Nitrogen availability in terrestrial ecosystems strongly influences plant productivity and nutrient cycling in response to increasing atmospheric carbon dioxide (CO2). Elevated CO2 has consistently stimulated forest productivity at the Duke Forest free‐air CO2 enrichment experiment throughout the decade‐long experiment. It remains unclear how the N cycle has changed with elevated CO2 to support this increased productivity. Using natural‐abundance measures of N isotopes together with an ecosystem‐scale 15N tracer experiment, we quantified the cycling of 15N in plant and soil pools under ambient and elevated CO2 over three growing seasons to determine how elevated CO2 changed N cycling between plants, soil, and microorganisms. After measuring natural‐abundance 15N differences in ambient and CO2‐fumigated plots, we applied inorganic 15N tracers and quantified the redistribution of 15N for three subsequent growing seasons. The natural abundance of leaf litter was enriched under elevated compared to ambient CO2, consistent with deeper rooting and enhanced N mineralization. After tracer application, 15N was initially retained in the organic and mineral soil horizons. Recovery of 15N in plant biomass was 3.5 ± 0.5% in the canopy, 1.7 ± 0.2% in roots and 1.7 ± 0.2% in branches. After two growing seasons, 15N recoveries in biomass and soil pools were not significantly different between CO2 treatments, despite greater total N uptake under elevated CO2. After the third growing season, 15N recovery in trees was significantly higher in elevated compared to ambient CO2. Natural‐abundance 15N and tracer results, taken together, suggest that trees growing under elevated CO2 acquired additional soil N resources to support increased plant growth. Our study provides an integrated understanding of elevated CO2 effects on N cycling in the Duke Forest and provides a basis for inferring how C and N cycling in this forest may respond to elevated CO2 beyond the decadal time scale.  相似文献   

9.
Large‐scale, long‐term FACE (Free‐Air CO2 enrichment) experiments indicate that increases in atmospheric CO2 concentrations will influence forest C cycling in unpredictable ways. It has been recently suggested that responses of mycorrhizal fungi could determine whether forest net primary productivity (NPP) is increased by elevated CO2 over long time periods and if forests soils will function as sources or sinks of C in the future. We studied the dynamic responses of ectomycorrhizae to N fertilization and atmospheric CO2 enrichment at the Duke FACE experiment using minirhizotrons over a 6 year period (2005–2010). Stimulation of mycorrhizal production by elevated CO2 was observed during only 1 (2007) of 6 years. This increased the standing crop of mycorrhizal tips during 2007 and 2008; during 2008, significantly higher mortality returned standing crop to ambient levels for the remainder of the experiment. It is therefore unlikely that increased production of mycorrhizal tips can explain the lack of progressive nitrogen limitations and associated increases in N uptake observed in CO2‐enriched plots at this site. Fertilization generally decreased tree reliance on mycorrhizae as tip production declined with the addition of nitrogen as has been shown in many other studies. Annual NPP of mycorrhizal tips was greatest during years with warm January temperatures and during years with cool spring temperatures. A 2 °C increase in average late spring temperatures (May and June) decreased annual production of mycorrhizal root tip length by 50%. This has important implications for ecosystem function in a warmer world in addition to potential for forest soils to sequester atmospheric C.  相似文献   

10.
In recent decades, the frequency and intensity of harmful algal blooms (HABs), as well as a profusion of toxic phytoplankton species, have significantly increased in coastal regions of China. Researchers attribute this to environmental changes such as rising atmospheric CO2 levels. Such addition of carbon into the ocean ecosystem can lead to increased growth, enhanced metabolism, and altered toxicity of toxic phytoplankton communities resulting in serious human health concerns. In this study, the effects of elevated partial pressure of CO2 (pCO2) on the growth and toxicity of a strain of Alexandrium tamarense (ATDH) widespread in the East and South China Seas were investigated. Results of these studies showed a higher specific growth rate (0.31 ± 0.05 day−1) when exposed to 1000 μatm CO2, (experimental), with a corresponding density of (2.02 ± 0.19) × 107 cells L−1, that was significantly larger than cells under 395 μatm CO2(control). These data also revealed that elevated pCO2 primarily affected the photosynthetic properties of cells in the exponential growth phase. Interestingly, measurement of the total toxin content per cell was reduced by half under elevated CO2 conditions. The following individual toxins were measured in this study: C1, C2, GTX1, GTX2, GTX3, GTX4, GTX5, STX, dcGTX2, dcGTX3, and dcSTX. Cells grown in 1000 μatm CO2 showed an overall decrease in the cellular concentrations of C1, C2, GTX2, GTX3, GTX5, STX, dcGTX2, dcGTX3, and dcSTX, but an increase in GTX1 and GTX4. Total cellular toxicity per cell was measured revealing an increase of nearly 60% toxicity in the presence of elevated CO2 compared to controls. This unusual result was attributed to a significant increase in the cellular concentrations of the more toxic derivatives, GTX1 and GTX4.Taken together; these findings indicate that the A. tamarense strain ATDH isolated from the East China Sea significantly increased in growth and cellular toxicity under elevated pCO2 levels. These data may provide vital information regarding future HABs and the corresponding harmful effects as a result of increasing atmospheric CO2.  相似文献   

11.
To examine the role of sink size on photosynthetic acclimation under elevated atmospheric CO2 concentrations ([CO2]), we tested the effects of panicle-removal (PR) treatment on photosynthesis in rice (Oryza sativa L.). Rice was grown at two [CO2] levels (ambient and ambient + 200 μmol mol−1) throughout the growing season, and at full-heading stage, at half the plants, a sink-limitation treatment was imposed by the removal of the panicles. The PR treatment alleviated the reduction of green leaf area, the contents of chlorophyll (Chl) and Rubisco after the full-heading stage, suggesting delay of senescence. Nonetheless, elevated [CO2] decreased photosynthesis (measured at current [CO2]) of plants exposed to the PR treatment. No significant [CO2] × PR interaction on photosynthesis was observed. The decrease of photosynthesis by elevated [CO2] of plants was associated with decreased leaf Rubisco content and N content. Leaf glucose content was increased by the PR treatment and also by elevated [CO2]. In conclusion, a sink-limitation in rice improved N status in the leaves, but this did not prevent the photosynthetic down-regulation under elevated [CO2].  相似文献   

12.
The inverse relationship between the number of stomata on a leaf surface and the atmospheric carbon dioxide concentration ([CO2]) in which the leaf developed allows plants to optimise water-use efficiency (WUE), but it also permits the use of fossil plants as proxies of palaeoatmospheric [CO2]. The ancient conifer family Araucariaceae is often represented in fossil floras and may act as a suitable proxy of palaeo-[CO2], yet little is known regarding the stomatal index (SI) responses of extant Araucariaceae to [CO2]. Four Araucaria species (Araucaria columnaris, A. heterophylla, A. angustifolia and A. bidwillii) and Agathis australis displayed no significant relationship in SI to [CO2] below current ambient levels (~380 ppm). However, representatives of the three extant genera within the Araucariaceae (A. bidwillii, A. australis and Wollemia nobilis) all exhibited significant reductions in SI when grown in atmospheres of elevated [CO2] (1,500 ppm). Stomatal conductance was reduced and WUE increased when grown under elevated [CO2]. Stomatal pore length did not increase alongside reduced stomatal density (SD) and SI in the three araucariacean conifers when grown at elevated [CO2]. These pronounced SD and SI reductions occur at higher [CO2] levels than in other species with more recent evolutionary origins, and may reflect an evolutionary legacy of the Araucariaceae in the high [CO2] world of the Mesozoic Era. Araucariacean conifers may therefore be suitable stomatal proxies of palaeo-[CO2] during periods of “greenhouse” climates and high [CO2] in the Earth’s history.  相似文献   

13.
Diatoms are responsible for a large proportion of global carbon fixation, with the possibility that they may fix more carbon under future levels of high CO2. To determine how increased CO2 concentrations impact the physiology of the diatom Thalassiosira pseudonana Hasle et Heimdal, nitrate‐limited chemostats were used to acclimate cells to a recent past (333 ± 6 μatm) and two projected future concentrations (476 ± 18 μatm, 816 ± 35 μatm) of CO2. Samples were harvested under steady‐state growth conditions after either an abrupt (15–16 generations) or a longer acclimation process (33–57 generations) to increased CO2 concentrations. The use of un‐bubbled chemostat cultures allowed us to calculate the uptake ratio of dissolved inorganic carbon relative to dissolved inorganic nitrogen (DIC:DIN), which was strongly correlated with fCO2 in the shorter acclimations but not in the longer acclimations. Both CO2 treatment and acclimation time significantly affected the DIC:DIN uptake ratio. Chlorophyll a per cell decreased under elevated CO2 and the rates of photosynthesis and respiration decreased significantly under higher levels of CO2. These results suggest that T. pseudonana shifts carbon and energy fluxes in response to high CO2 and that acclimation time has a strong effect on the physiological response.  相似文献   

14.
Warming temperatures and increasing CO2 are likely to have large effects on the amount of carbon stored in soil, but predictions of these effects are poorly constrained. We elevated temperature (canopy: +2.8 °C; soil growing season: +1.8 °C; soil fallow: +2.3 °C) for 3 years within the 9th–11th years of an elevated CO2 (+200 ppm) experiment on a maize–soybean agroecosystem, measured respiration by roots and soil microbes, and then used a process‐based ecosystem model (DayCent) to simulate the decadal effects of warming and CO2 enrichment on soil C. Both heating and elevated CO2 increased respiration from soil microbes by ~20%, but heating reduced respiration from roots and rhizosphere by ~25%. The effects were additive, with no heat × CO2 interactions. Particulate organic matter and total soil C declined over time in all treatments and were lower in elevated CO2 plots than in ambient plots, but did not differ between heat treatments. We speculate that these declines indicate a priming effect, with increased C inputs under elevated CO2 fueling a loss of old soil carbon. Model simulations of heated plots agreed with our observations and predicted loss of ~15% of soil organic C after 100 years of heating, but simulations of elevated CO2 failed to predict the observed C losses and instead predicted a ~4% gain in soil organic C under any heating conditions. Despite model uncertainty, our empirical results suggest that combined, elevated CO2 and temperature will lead to long‐term declines in the amount of carbon stored in agricultural soils.  相似文献   

15.
The establishment of non-native species and the increase in atmospheric CO2, in combination, have the ability to alter current ecosystems. Previous studies have shown that invasive species tend to respond more strongly to CO2 than natives, but these comparisons have been of different and unrelated species. To assess how response to CO2 might be related to invasiveness per se, we compared a native (Typha latifolia) with a congeneric invasive (Typha angustifolia), as well as their hybrid (T. × glauca). All three taxa are common components of wetland vegetation, often occurring in near monocultures. An open-top chamber experiment was used to examine the effects of elevated and ambient CO2 concentrations on the three taxa. All three increased rhizome biomass by 40% in elevated CO2. Although the absolute increase did not differ among taxa, the invasive T. angustifolia had a much higher proportional response in biomass and photosynthetic rate (45 and 40% respectively). The weaker response of the two larger taxa native T. latifolia (16 and 2%) and hybrid T. × glauca (−4% and −1%) was possibly driven by soil nutrient deficiency, such that they were not able to benefit from increased CO2. However, under low nutrients the smaller species T. angustifolia may become more a problematic invader in the future.  相似文献   

16.
Few studies have evaluated elevated CO2 responses of trees in variable light despite its prevalence in forest understories and its potential importance for sapling survival. We studied two shade-tolerant species (Acer rubrum, Cornus florida) and two shade-intolerant species (Liquidambar styraciflua, Liriodendron tulipifera) growing in the understory of a Pinus taeda plantation under ambient and ambient+200 ppm CO2 in a free air carbon enrichment (FACE) experiment. Photosynthetic and stomatal responses to artificial changes in light intensity were measured on saplings to determine rates of induction gain under saturating light and induction loss under shade. We expected that growth in elevated CO2 would alter photosynthetic responses to variable light in these understory saplings. The results showed that elevated CO2 caused the expected enhancement in steady-state photosynthesis in both high and low light, but did not affect overall stomatal conductance or rates of induction gain in the four species. Induction loss after relatively short shade periods (<6 min) was slower in trees grown in elevated CO2 than in trees grown in ambient CO2 despite similar decreases in stomatal conductance. As a result leaves grown in elevated CO2 that maintained induction well in shade had higher carbon gain during subsequent light flecks than was expected from steady-state light response measurements. Thus, when frequent sunflecks maintain stomatal conductance and photosynthetic induction during the day, enhancements of long-term carbon gain by elevated CO2 could be underestimated by steady-state photosynthetic measures. With respect to species differences, both a tolerant, A. rubrum, and an intolerant species, L. tulipifera, showed rapid induction gain, but A. rubrum also lost induction rapidly (c. 12 min) in shade. These results, as well as those from independent studies in the literature, show that induction dynamics are not closely related to species shade tolerance. Therefore, it cannot be concluded that shade-tolerant species necessarily induce faster in the variable light conditions common in understories. Although our study is the first to examine dynamic photosynthetic responses to variable light in contrasting species in elevated CO2, studies on ecologically diverse species will be required to establish whether shade-tolerant and -intolerant species show different photosynthetic responses in elevated CO2 during sunflecks. We conclude that elevated CO2 affects dynamic gas exchange most strongly via photosynthetic enhancement during induction as well as in the steady state. Received: 1 April 1999 / Accepted: 16 August 1999  相似文献   

17.
We describe the long-term effects of a CO2 exhalation, created more than 70 years ago, on a natural C4 dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO2 enrichment changes the competitive balance between plants with C3 and C4 photosynthetic pathways and how CO2 enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO2 on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO2 alone. Species compositional data and soil δ13C isotopic evidence suggest no detectable effect of CO2 enrichment on C3:C4 plant mixtures and individual species dominance. Contrary to many general predictions C3 grasses did not become more abundant and C3 shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO2 concentrations averaging 610 μmol mol−1. Leaf properties such as total N decreased in the C3 but not C4 grass under elevated CO2 while total non-structural carbohydrate accumulation was not affected. Elevated CO2 possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO2 enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO2 source. The conservative response of this grassland suggests that many of the reported effects of elevated CO2 on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO2 conditions.  相似文献   

18.
We experimentally demonstrate that elevated CO2 can modify herbivory-induced plant chemical responses in terms of both total and individual glucosinolate concentrations. Overall, herbivory by larvae of diamondback moths (Plutella xylostella) resulted in no change in glucosinolate levels of the annual plant Arabidopsis thaliana under ambient CO2 conditions. However, herbivory induced a significant 28–62% increase in glucosinolate contents at elevated CO2. These inducible chemical responses were both genotype-specific and dependent on the individual glucosinolate considered. Elevated CO2 can also affect structural defenses such as trichomes and insect-glucosinolate interactions. Insect performance was significantly influenced by specific glucosinolates, although only under CO2 enrichment. This study can have implications for the evolution of inducible defenses and coevolutionary adaptations between plants and their associated herbivores in future changing environments.  相似文献   

19.
Predicted responses of transpiration to elevated atmospheric CO2 concentration (eCO2) are highly variable amongst process‐based models. To better understand and constrain this variability amongst models, we conducted an intercomparison of 11 ecosystem models applied to data from two forest free‐air CO2 enrichment (FACE) experiments at Duke University and Oak Ridge National Laboratory. We analysed model structures to identify the key underlying assumptions causing differences in model predictions of transpiration and canopy water use efficiency. We then compared the models against data to identify model assumptions that are incorrect or are large sources of uncertainty. We found that model‐to‐model and model‐to‐observations differences resulted from four key sets of assumptions, namely (i) the nature of the stomatal response to elevated CO2 (coupling between photosynthesis and stomata was supported by the data); (ii) the roles of the leaf and atmospheric boundary layer (models which assumed multiple conductance terms in series predicted more decoupled fluxes than observed at the broadleaf site); (iii) the treatment of canopy interception (large intermodel variability, 2–15%); and (iv) the impact of soil moisture stress (process uncertainty in how models limit carbon and water fluxes during moisture stress). Overall, model predictions of the CO2 effect on WUE were reasonable (intermodel μ = approximately 28% ± 10%) compared to the observations (μ = approximately 30% ± 13%) at the well‐coupled coniferous site (Duke), but poor (intermodel μ = approximately 24% ± 6%; observations μ = approximately 38% ± 7%) at the broadleaf site (Oak Ridge). The study yields a framework for analysing and interpreting model predictions of transpiration responses to eCO2, and highlights key improvements to these types of models.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号