Teis N. Mikkelsen

Technical University of Denmark, Lyngby, Capital Region, Denmark

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Publications (53)140.45 Total impact

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    ABSTRACT: The response in production parameters to projected future levels of temperature, atmospheric carbon dioxide ([CO2]), and ozone ([O3]) was investigated in 138 spring barley accessions. The comprehensive set of landraces, cultivars, and breeder-lines, were during their entire life cycle exposed to a two-factor treatment of combined elevated temperature (+5 °C day/night) and [CO2] (700 ppm), as well as single-factor treatments of elevated temperature (+5 °C day/night), [CO2] (700 ppm), and [O3] (100–150 ppb). The control treatment was equivalent to present average South Scandinavian climate (temperature: 19/12 °C (day/night), [CO2]: 385 ppm). Overall grain yield was found to decrease 29% in the two-factor treatment with concurrent elevation of [CO2] and temperature, and this response could not be predicted from the results of treatments with elevated [CO2] and temperature as single factors, where grain yield increased 16% and decreased 56%, respectively. Elevated [O3] was found to decrease grain yield by 15%. Substantial variation in response to the applied climate treatments was found between the accessions. The results revealed landraces, cultivars, and breeder-lines with phenotypes applicable for breeding towards stable and high yield under future climate conditions. Further, we suggest identifying resources for breeding under multifactor climate conditions, as single-factor treatments did not accurately forecast the response, when factors were combined.
    European Journal of Agronomy 02/2015; 63. DOI:10.1016/j.eja.2014.12.003 · 2.92 Impact Factor
  • Dan Bruhn, Kristian R. Albert, Teis N. Mikkelsen, Per Ambus
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    ABSTRACT: Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone-depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20–50 nmol m−2 h−1, mostly due to the UV component. The emission response to UV-A is of the same magnitude as that to UV-B. Therefore, UV-A is more important than UV-B given the natural UV-spectrum at Earth's surface. Plants also emitted N2O in darkness, although at reduced rates. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.
    Atmospheric Environment 12/2014; 99:206–214. DOI:10.1016/j.atmosenv.2014.09.077 · 3.06 Impact Factor
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    ABSTRACT: The projected future climate will affect the global agricultural production negatively, however, to keep abreast of the expected increase in global population, the agricultural production must increase. Therefore, to safeguard the future crop yield and quality, the adaptive potential of crops to environmental change needs to be explored in order to select the most productive genotypes. Presently, it is unknown whether cereal crops like spring barley can adapt to climate stressors over relatively few generations. To evaluate if strong selection pressures could change the performance of barley to environmental stress, we conducted a selection experiment over five plant generations (G0–G4) in three scenarios, where atmospheric [CO2] and temperature were increased as single factors and in combination. The treatments represented the expected environmental characteristics in Northern Europe around year 2075 [700 ppm CO2, 22/17 °C (day/night)] as well as a control mimicking present day conditions (390 ppm CO2, 19/12 °C). Two different barley accessions, a modern cultivar and an old landrace, were evaluated in terms of yield and biomass production. In all treatments representing future environmental scenarios, the G4-generation of selected plants did not improve its reproductive output compared to the G0-generation, as G4 produced less seeds and had a lower yield than unselected plants. These results indicate that barley might not respond positively to rapid and strong selection by elevated [CO2] and temperature, contrary to previous results from oilseed rape. The two barley accessions analyzed presented almost the same response pattern in a given treatment, though the modern cultivar had the highest yield in the climate scenarios, while the landrace was superior in yield under present day climate conditions.
    Genetic Resources and Crop Evolution 01/2014; 61(1). DOI:10.1007/s10722-013-0021-1 · 1.48 Impact Factor
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    ABSTRACT: Plant responses to warming, elevated CO2, and changes in summer precipitation patterns involve complex interactions. In this study we aim to reveal the single factor responses and their interactive effects on photosystem II (PSII) performance during an autumn-to-winter period. The study was carried out in the CLIMAITE multifactor experiment, which includes the combined impact of elevated CO2 (free air carbon enrichment; CO2), warming (passive nighttime warming; T) and summer drought (rain-excluding curtains; D) in a temperate heath ecosystem. PSII performance was probed by the effective quantum yield in light, Fv′/Fm′, using the pulse amplitude methodology, and the total performance index, PItotal, which integrate changes of the chlorophyll-a fluorescence transient including the maximal quantum yield in darkness, Fv/Fm.
    Environmental and Experimental Botany 09/2013; 93:1-12. DOI:10.1016/j.envexpbot.2013.03.008 · 3.00 Impact Factor
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    ABSTRACT: The impact of climate change on herbivorous insects can have far-reaching consequences for ecosystem processes. However, experiments investigating the combined effects of multiple climate change drivers on herbivorous insects are scarce. We independently manipulated three climate change drivers (CO2, warming, drought) in a Danish heathland ecosystem. The experiment was established in 2005 as a full factorial split-plot with 6 blocks 9 2 levels of CO2 9 2 levels of warming 9 2 levels of drought = 48 plots. In 2008, we exposed 432 larvae (n = 9 per plot) of the heather beetle (Lochmaea suturalis THOMSON), an important herbivore on heather, to ambient versus elevated drought, temperature, and CO2 (plus all combinations) for 5 weeks. Larval weight and survival were highest under ambient conditions and decreased significantly with the number of climate change drivers. Weight was lowest under the drought treatment, and there was a three-way interaction between time, CO2, and drought. Survival was lowest when drought, warming, and elevated CO2 were combined. Effects of climate change drivers depended on other co-acting factors and were mediated by changes in plant secondary compounds, nitrogen, and water content. Overall, drought was the most important factor for this insect herbivore. Our study shows that weight and survival of insect herbivores may decline under future climate. The complexity of insect herbivore responses increases with the number of combined climate change drivers.
    Ecology and Evolution 06/2013; 3(6):1149-1160. DOI:10.1002/ece3.564 · 1.66 Impact Factor
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    ABSTRACT: Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO2] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO2] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur.
    Ecology and Evolution 05/2013; 3(5):1163-72. DOI:10.1002/ece3.523 · 1.66 Impact Factor
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    ABSTRACT: High air concentrations of ammonium were detected at low and high altitude sites in Sweden, Finland and Norway during the spring 2006, coinciding with polluted air from biomass burning in eastern Europe passing over central and northern Fennoscandia. Unusually high values for throughfall deposition of ammonium were detected at one low altitude site and several high altitude sites in north Sweden. The occurrence of the high ammonium in throughfall differed between the summer months 2006, most likely related to the timing of precipitation events. The ammonia dry deposition may have contributed to unusual visible injuries on the tree vegetation in northern Fennoscandia that occurred during 2006, in combination with high ozone concentrations. It is concluded that long-range transport of ammonium from large-scale biomass burning may contribute substantially to the nitrogen load at northern latitudes.
    Environmental Pollution 02/2013; 176C:71-79. DOI:10.1016/j.envpol.2012.12.006 · 3.90 Impact Factor
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    ABSTRACT: There is an ongoing debate on how to correct leaf gas-exchange measurements for the unavoidable diffusion leakage that occurs when measurements are done in non-ambient CO(2) -concentrations. In this study we present a theory on how the CO(2) diffusion gradient over the gasket is affected by leaf mediated pores (LMP) and how LMP reduce diffusive exchange across the gaskets. Recent discussions have so far neglected the processes in the quasi-laminar boundary layer around the gasket. Counter intuitively, LMP reduce the leakage through gaskets, which can be explained by assuming that the boundary layer at the exterior of the cuvette is enriched with air from the inside of the cuvette. The effect can thus be reduced by reducing the boundary layer thickness. The theory clarifies conflicting results from earlier studies. We developed leaf adaptor frames that eliminate LMP during measurements on delicate plant material such as grass leaves with circular cross section, and the effectiveness is shown with respiration measurements on a harp of Deschampsia flexuosa leaves. We conclude that the best solution for measurements with portable photosynthesis systems is to avoid LMP rather than trying to correct for the effects.
    Plant Cell and Environment 01/2013; DOI:10.1111/pce.12064 · 5.91 Impact Factor
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    ABSTRACT: Climate change has been shown to affect ecosystem process rates 1 and community composition 2 , with direct and indirect effects on belowground food webs 3 . In particular, altered rates of herbivory under future climate 4 can be expected to influence above–belowground interactions 5 . Here, we use a multifactor, field-scale climate change experiment and inde-pendently manipulate atmospheric CO 2 concentration, air and soil temperature and drought in all combinations since 2005. We show that changes in these factors modify the interaction between above-and belowground organisms. We use an insect herbivore to experimentally increase aboveground herbivory in grass phytometers exposed to all eight combinations of climate change factors for three years. Aboveground herbivory increased the abundance of belowground protozoans, micro-bial growth and microbial nitrogen availability. Increased CO 2 modified these links through a reduction in herbivory and cas-cading effects through the soil food web. Interactions between CO 2 , drought and warming can affect belowground protozoan abundance. Our findings imply that climate change affects aboveground–belowground interactions through changes in nutrient availability. Plant species composition and community structure in terres-trial environments have been predicted to shift in response to climate change 6 . Recent climate change experiments have shown the effects of drought, warming and increased CO 2 on plant productivity 7 , nitrogen cycling 8 and species interactions 4 . However, multifactor experiments on climate change are scarce 9 and climate change effects on interactions between the above-and the below-ground subsystem 5,10,11 are rarely considered. Most terrestrial plant species control or mediate the interaction between above-and belowground subsystems, for example through altered litter quality 5 or root exudates 12 , suggesting that changes in the aboveground compartment will cascade between the aboveground-and the belowground compartment 13 . For example, herbivores feeding on aboveground plant parts have been shown to induce changes in a wide range of processes in the root zone, affecting rhizodeposition 12 and soil decomposer organisms 14 . Furthermore, indirect pathways from herbivores through greenfall, frass or litter input to the belowground subsystem have been reported 5 . Increased CO 2 (ref. 15), increased temperature 16 or drought 17 have been shown to affect aboveground herbivory. Owing to the strong link between aboveground herbivory and belowground processes, it is likely that such climatic or atmospheric changes will lead to herbivory-induced changes in belowground processes
    Nature Climate Change 05/2012; DOI:10.1038/nclimate1544 · 15.30 Impact Factor
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    ABSTRACT: The long-term and diurnal responses of photosystem II (PSII) performance to near-ambient UV-B radiation were investigated in High Arctic Betula nana. We conducted an UV exclusion experiment with five replicated blocks consisting of open control (no filter), photosynthetic active radiation and UV-B transparent filter control (Teflon), UV-B-absorbing filter (Mylar) and UV-AB-absorbing filter (Lexan). Ethylenediurea (EDU), a chemical normally used to protect plants against ozone injury, was sprayed on the leaves both in the field and in an additional laboratory study to investigate if EDU mitigated the effects of UV-B. Chlorophyll-a fluorescence induction curves were used for analysis of OJIP test parameters. Near-ambient UV-B radiation reduced across season maximum quantum yield (TR(o) /ABS = F(v) /F(m)), approximated number of active PSII reaction center (RC/ABS) and the performance index (PI(ABS)), despite improved leaf screening against UV-B with higher content of UV-B-absorbing compounds and a lower specific leaf area. EDU application counteracted the negative impact of UV-B on TR(o) /ABS, RC/ABS and PI(ABS) . This indicates that the mechanisms behind UV-B and ozone damage share some common features. The midday depression was present in all treatments, but TR(o) /ABS and PI(ABS) were persistently lower in near-ambient UV-B compared to UV-B reduction. The recovery phase was particularly impaired in near-ambient UV-B and interactive effects between treatment × hour raised TR(o) /ABS, RC/ABS and PI(ABS) higher in reduced UV-B compared to near-ambient UV-B. This demonstrates current solar UV-B to reduce the PSII performance both on a daily as well as a seasonal basis in this High Arctic species.
    Physiologia Plantarum 02/2012; 145(3):485-500. DOI:10.1111/j.1399-3054.2012.01596.x · 3.26 Impact Factor
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    ABSTRACT: The evidence that is currently available demonstrates that future changes in precipitation patterns will affect plant carbon uptake. However, the outcome in terms of success, productivity and fecundity depends upon individual species and different responses of various growth forms. Examination of these differences in response in dry versus rewetting conditions can be used to highlight the limitations coherent in different strategies adopted by, for example, evergreen shrubs and grasses. We investigated the leaf-level photosynthetic performance, leaf C, N and δ13C along with vegetation cover and biomass in the evergreen dwarf shrub Calluna vulgaris and the grass species Deschampsia flexuosa in a temperate heath during seasonal changes in soil moisture. Higher photosynthetic capacity compensated for lower stomatal conductance and sustained higher rates of photosynthesis in the grass compared to the dwarf shrub. In combination with dieback of aboveground biomass and reduction of stomatal conductance reduction during dry conditions, the grass continued to have high carbon uptake in the remaining leaves. The dwarf shrub endured the dry conditions by preserving shoot biomass and reducing stomatal conductance. Soil rewetting increased leaf nitrogen and photosynthesis in the grass much more than for the dwarf shrub. These different strategies may have a considerable impact on carbon uptake and on the ability of a species to compete, as future climatic changes are likely to extend the summer drought period together with the more frequent and extensive precipitation events outside the summer season. --------------------------------------------------------------------------------
    Acta Oecologica 01/2012; 45:79-85. · 1.84 Impact Factor
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    ABSTRACT: Climate change scenarios predict simultaneously increase in temperature, altered precipitation patterns and elevated atmospheric CO2 concentration, which will affect key ecosystem processes and plant growth and species interactions. In a large-scale experiment, we investigated the effects of in situ exposure to elevated atmospheric CO2 concentration, increased temperature and prolonged drought periods on the plant biomass in a dry heathland (Brandbjerg, Denmark). Results after 3 years showed that drought reduced the growth of the two dominant species Deschampsia flexuosa and Calluna vulgaris. However, both species recovered quickly after rewetting and the drought had no significant effect on annual aboveground biomass production. We did not observe any effects of increased temperature. Elevated CO2 stimulated the biomass production for D. flexuosa in one out of three years but did not influence the standing biomass for either D. flexuosa or the ecosystem as more litter was produced. Treatment combinations showed little interactions on the measured parameters and in particular elevated CO2 did not counterbalance the drought effect on plant growth, as we had anticipated. The plant community did not show any significant responses to the imposed climate changes and we conclude that the two heathland species, on a short time scale, will be relatively resistant to the changes in climatic conditions.
    Ecosystems 01/2012; 15(2). DOI:10.1007/s10021-011-9508-9 · 3.53 Impact Factor
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    ABSTRACT: Full recovery of the ozone layer is not expected for several decades and consequently, the incoming level of solar ultraviolet-B (UV-B) will only slowly be reduced. Therefore to investigate the structural and photosynthetic responses to changes in solar UV-B we conducted a 5-year UV-B exclusion study in high arctic Greenland. During the growing season, the gas exchange (H₂O and CO₂) and chlorophyll-a fluorescence were measured in Vaccinium uliginosum. The leaf dry weight, carbon, nitrogen, stable carbon isotope ratio, chlorophyll and carotenoid content were determined from a late season harvest. The net photosynthesis per leaf area was on average 22% higher in 61% reduced UV-B treatment across the season, but per ground area photosynthesis was unchanged. The leaf level increase in photosynthesis was accompanied by increased leaf nitrogen, higher stomatal conductance and F(v)/F(m). There was no change in total leaf biomass, but reduction in total leaf area caused a pronounced reduction of specific leaf area and leaf area index in reduced UV-B. This demonstrates the structural changes to counterbalance the reduced plant carbon uptake seen per leaf area in ambient UV-B as the resulting plant carbon uptake per ground area was not affected. Thus, our understanding of long-term responses to UV-B reduction must take into account both leaf level processes as well as structural changes to understand the apparent robustness of plant carbon uptake per ground area. In this perspective, V. uliginosum seems able to adjust plant carbon uptake to the present amount of solar UV-B radiation in the High Arctic.
    Physiologia Plantarum 12/2011; 145(4):540-50. DOI:10.1111/j.1399-3054.2011.01564.x · 3.26 Impact Factor
  • Dan Bruhn, Ian M Møller, Teis N Mikkelsen, Per Ambus
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    ABSTRACT: In this minireview, we evaluate all experimental work published on the phenomenon of aerobic methane (CH(4) ) generation in terrestrial plants and plant. Clearly, despite much uncertainty and skepticism, we conclude that the phenomenon is true. Four stimulating factors have been observed to induce aerobic plant CH(4) production, i.e. cutting injuries, increasing temperature, ultraviolet radiation and reactive oxygen species. Further, we analyze rates of measured emission of aerobically produced CH(4) in pectin and in plant tissues from different studies and argue that pectin is very far from the sole contributing precursor. In consequence, scaling up of aerobic CH(4) emission needs to take into consideration other potential sources than pectin. Due to the large uncertainties related to effects of stimulating factors, genotypic responses and type of precursors, we conclude that current attempts for upscaling aerobic CH(4) into a global budget is inadequate. Thus it is too early to draw the line under the aerobic methane emission in plants. Future work is needed for establishing the relative contribution of several proven potential CH(4) precursors in plant material.
    Physiologia Plantarum 12/2011; 144(3):201-9. DOI:10.1111/j.1399-3054.2011.01551.x · 3.26 Impact Factor
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    ABSTRACT: Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination with leaf angle control. Two sites with natural leaf positions had ground angles of 0° (‘level site’) and 45° (‘sloping site’), while at a third site the leaves were fixed in an angle of 45° to homogenize the irradiance dose (‘fixed leaf angle site’). The photosynthetic performance of the leaves was characterized by simultaneous gas exchange and chlorophyll fluorescence measurements and the PSII performance through the growing season was investigated with fluorescence measurements. Leaf harvest towards the end of the growing season was done to determine the specific leaf area and the content of carbon, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate of electron transport (Jmax) and the maximum carboxylation rate of Rubisco (Vcmax), and the PSII performance showed a decreased quantum yield and increased energy dissipation. A parallel response pattern and reduced PSII performance at all three sites indicate that these responses take place in all leaves across position in the vegetation. These findings add to the evidence that the ambient solar UV-B currently is a significant stress factor for plants in high Arctic Greenland.
    Environmental and Experimental Botany 11/2011; 72(3):439-447. DOI:10.1016/j.envexpbot.2010.07.001 · 3.00 Impact Factor
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    ABSTRACT: The projected changes of atmospheric composition and associated climatic parameters will challenge the agricultural production in ways, which existing crop populations have not previously experienced. Therefore, understanding the responsiveness to changes of multiple environmental parameters in existing genotypes is vital. In this study, the responses in yield and biomass production of four different cultivars of oilseed rape (Brassica naps L.) were tested under five different combinations of increased [CO2] (700 ppm), temperature (+5 degrees C) and [O-3] (+40 ppb). Especially the multifactor treatments are relevant for predictions of the future production, as they mimic the multidimensional environmental changes that are expected within this century. All treatments were given the same amount of water, which mimicked future limited water availability e.g. in treatments with elevated temperature. The biomass and yield parameters were found to be significantly cultivar dependent. However, in all cultivars elevated temperature caused a significant reduction in yield parameters, while biomass was not affected significantly. Elevated [CO2] increased the vegetative biomass significantly, but seed yield was only significantly enhanced in one of the four cultivars studied. Increased [O-3] did not have significant effects on any of the cultivars. In general, the negative effects of a 5 degrees C temperature elevation on yield could not be compensated by elevated [CO2], when simultaneously applied in multifactor treatments. The evaluation of cultivar differences in productivity under elevated [CO2] in combination with increased temperatures and [O-3] is necessary to derive at a realistic prediction for the future food and biomass production and for the selection of cultivars providing an adaptation potential to environmental change. Our results suggest that future breeding of B. napus should be based on old cultivars, since more modern varieties seem to have lower potentials to respond to CO2 and thus counteract the detrimental effects of yield reducing environmental factors such as temperature and O-3. (C) 2011 Elsevier B.V. All rights reserved.
    European Journal of Agronomy 10/2011; 35(3-3):127-134. DOI:10.1016/j.eja.2011.05.004 · 2.92 Impact Factor
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    ABSTRACT: We exposed a semi-natural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO2), warming, and extended summer drought in all combinations to simulate a realistic climate scenario in Denmark in 2075. Here, we report on the short-term responses of the nitrogen (N) cycle after two years of treatments. In response to single treatments (i.e. CO2, warming or drought treatments alone) we saw effects, which in general could be expected based on previous studies. More interestingly, the treatments often interacted in an antagonistic way, i.e. responses were smaller in combinations than in single treatments. Overall, the simulated future climate scenario led to reduced N turnover, which could act to limit the potential growth response of plants to elevated atmospheric CO2 concentration and thereby the expected negative feedback to climate change.
    ClimMani-Interface workshop, Iceland; 06/2011