| 1. |
- Karlsson, Per Erik, 1957, et al.
(författare)
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Evidence for Impacts of Near-ambient Ozone Concentrations on Vegetation in Southern Sweden
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. ; 38:8, s. 425-431
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Tidskriftsartikel (refereegranskat)abstract
- Substantial impacts of near-ambient ozone concentrations on agricultural crops, trees, and seminatural vegetation are demonstrated for southern Sweden. Impacts of ambient ozone levels (2–15 μL L-¹ hr annual accumulated ozone exposure over a threshold of 40 nL L-¹ [AOT40]) range from a 2%–10% reduction for trees (e.g., leaf chlorophyll, tree growth) up to a 15% reduction for crops (e.g., yield, wheat/potato). Visible leaf injury on bioindicator plants caused by ambient ozone levels has been clearly demonstrated. The humid climatic conditions in Sweden promote high rates of leaf ozone uptake at a certain ozone concentration. This likely explains the comparatively large ozone impacts found for vegetation in southern Sweden at relatively low ozone concentrations in the air. It is important that the future methods used for the representation of ozone impacts on vegetation across Europe are based on the leaf ozone uptake concept and not on concentration-based exposure indices, such as AOT40.
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| 2. |
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| 3. |
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| 4. |
- Piikki, Kristin, et al.
(författare)
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Estimates of AOT ozone indices from time-integrated ozone data and hourly air temperature measurements in southwest Sweden
- 2009
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 157:11, s. 3051-3058
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Tidskriftsartikel (refereegranskat)abstract
- Surface ozone concentration and surface air temperature was measured hourly at three coastal sites, four low elevation inland sites and two high elevation inland sites in southwestern Sweden. Diurnal ozone concentration range (DOR) and diurnal temperature range (DTR) were strongly correlated, both spatially and temporally, most likely because both depended on atmospheric stability. Accumulated ozone exposure above a threshold concentration of x nmol mol(-1) (AOTx) was estimated from time-integrated ozone concentration (as from diffusive sampling) and measures of ozone concentration variability. Two methods both estimated 24-h AOTx with high accuracy (modelling efficiencies >90% for x <= 40 nmol mol(-1)). Daytime (08:00-20:00) AOTx could not be equally well estimated. Estimates were better for lower AOT thresholds. Diffusive ozone concentration sampling, combined with hourly temperature monitoring, could be a valuable complement to ozone concentration monitoring with continuous instruments. (C) 2009 Elsevier Ltd. All rights reserved.
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| 5. |
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| 6. |
- Piikki, Kristin, 1975, et al.
(författare)
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Impact of elevated O3 and CO2 exposure on potato (Solanum tuberosum L. cv. Bintje) tuber macronutrients (N, P, K, Mg, Ca)
- 2007
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809. ; 118:1-4, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- It was investigated whether exposure of elevated ozone (O3) and carbon dioxide (CO2) concentrations affected the macronutrient (N, P, K, Mg, Ca) concentrations in potato (Solanum tuberosum L.) tubers in three open-top chamber experiments from Sweden and Finland. The tuber concentrations of N, P, K and Mg correlated positively with O3 exposure (although not significantly in the case of N and P) but the O3 exposure had no effect on the tuber concentration of Ca. A likely mechanism behind the observed O3 effects was suggested to be that the more progressed senescence of O3 exposed plants was associated with a larger extent of reallocation of mobile nutrients from the haulm to the tubers. In addition, the uptake of macronutrients may have been less negatively affected by O3 exposure than the assimilation of carbon. O3 tended to reduce the total tuber contents of all investigated nutrients, which imply a reduced fertilizer need per unit field area. This was not associated with a decreased fertilizer need per tonnage of yield, as the tuber nutrient concentrations were increased by O3 exposure. The increased CO2 concentration did not significantly affect any of the investigated macronutrients in the present dataset but did generally prevent the O3 induced increases in nutrient concentrations to be expressed (only significant in the case of N and Mg). The O3 induced increase in tuber K concentration, may mediate earlier observed O3 effects on potato tuber concentrations of citric and malic acids. To conclude, anticipated future (and even presently occurring) O3 exposure has a negative impact on the total tuber contents of K and Ca and probably also on the total tuber contents of N, P and Mg. O3 exposure causes increased tuber concentrations of N, P, K and Mg at an early harvest. The O3 induced increase in tuber concentration tended to diminish by a CO2 elevation.
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| 7. |
- Piikki, Kristin, 1975, et al.
(författare)
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Mätningar av marknära ozon och meteorologi vid kustnära och urbana miljöer i Halland, Skåne och Västra Götalands län
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Under sommaren 2007 mättes ozon- (O3) halter samt meteorologi kontinuerligt under ca en månads tid vardera, på en ö i havet (Nidingen, N län), vid en kustnära plats med förväntat höga ozonhalter (Backåkra, M län) samt i en urban parkmiljö (Göteborg, O län). På dessa platser samt på ytterligare fyra olika platser i Göteborg mättes även O3- och kväveoxid- (NOx = NO2 + NO) halter med diffusionsprovtagare på vecko-basis. Mätningarna vid Nidingen, Backåkra samt parkmiljön i Göteborg gjordes inte samtidigt utan under olika perioder under olika delar av sommarhalvåret. Jämförelser med andra kustnära platser (Råö, som ligger strax söder om Göteborg, och Malmö), där ozonhalten mättes under hela sommaren, visade att den kustnära ozondynamiken med hög medelhalt och liten dygnsvariation fanns vid båda mätplatserna, men var mer utpräglad på Nidingen än i Backåkra. Värdena för några olika ozonindex, bland annat 8-timmars-medelvärde, som används i miljömålet Frisk Luft samt inom Miljökvalitetsnormerna, var högre på Nidingen, trots att landets högsta ozonbelastning, enligt vissa modellberäkningar, kan förväntas i Skåne. En slutsats blir att små öar i havet kan vara mycket utsatta för ozon. Mätningarna i Göteborg visade att ozonförekomsten kan skilja sig väsentligt mellan olika urbana platser beroende på vindförhållanden och närhet till NOx-utsläpp, och att det bara är på platser med mycket hög trafiktäthet som titrering med NO har stor betydelse för den lokala ozonhalten. Ozonförekomsten i urban parkmiljö (Slottsskogen) kan vara relativt hög. Diffusionsprovtagarna fungerade bra för ozon och NO2.. I rapporten utvärderas olika enkla matematiska modeller för att uppskatta olika ozonindex utifrån mätningar med diffusionsprovtagare i kombination med temperaturmätningar eller genom att ta hänsyn till lokalens topografiska läge. Flera olika metoder fungerade väl och rekommendationer ges för hur de bör tillämpas i olika situationer.
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| 8. |
- Piikki, Kristin, 1975, et al.
(författare)
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The grain quality of spring wheat (Triticum aestivum L.) in relation to elevated ozone uptake and carbon dioxide exposure
- 2008
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Ingår i: European Journal of Agronomy. - : Elsevier BV. - 1161-0301. ; 28:3, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- Ozone (O-3) and carbon dioxide (CO2) effects on the quality of spring wheat (Triticum aestivum L.) were evaluated. The dataset originated from 13 European open-top chamber experiments, including three countries, 10 years and four cultivars. The O-3 exposure significantly reduced the protein yield, even though the grain protein concentration (GPC) was increased and tended to increase the Zeleny value and the Hagberg falling number. These variables reached values representing enhanced grain maturity after elevated 03 exposure, possibly explained by O-3 induced early senescence. The CO2 elevation was demonstrated to increase the protein yield but reduce the GPC and the Zeleny value. Both O-3 and CO2 were demonstrated to affect wheat grain yield (GY) but by different means; O-3 reduced GY (P<0.001) mainly by limiting the 1000-grain weight, while CO2 enhanced GY (P < 0.01) mainly by increasing the number of grains produced per unit ground area. Two earlier used O-3 indices, the accumulated stomatal uptake of O-3 above a flux threshold of 6 nmol m(-2), s(-1) (AF(st)6), and the accumulated O-3 dose above a concentration threshold of 40 nmol mol(-1) (AOT40), were employed in parallel in the derivation of dose-response relationships with all investigated variables (GY, number of grains per unit area, 1000-grain weight, protein yield, GPC, Zeleny value, wet gluten, dry gluten, starch concentration, Hagberg falling number, specific weight and water quotient). The uptake-based index (AF(st)6) tended to better explain variation in the response variables and yielded dose-response regressions of a higher statistical quality than did the external-dose index (AOT40). Based on an independent subset of the present data, the validities of (1) a negative linear relationship between GPC and GY and (2) a positive but decelerating relationship between protein yield and GY including both O-3 and CO2 treatments were tested and confirmed. (c) 2007 Elsevier B.V. All rights reserved.
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| 9. |
- Piikki, Kristin, 1975, et al.
(författare)
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The open-top chamber impact on vapour pressure deficit and its consequences for stomatal ozone uptake
- 2008
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 42:26, s. 6513-6522
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Tidskriftsartikel (refereegranskat)abstract
- The vapour pressure deficit (VPD) in open-top chambers (OTCs) was analysed in relation to time of day and ambient meteorology. Effects of observed VPD differences (ΔVPD) between OTCs and the ambient air (AA) on stomatal conductance (gs) were simulated using 10 model functions from the literature. The dataset originated from 17 OTC crop experiments performed in Belgium, Germany and Sweden. ΔVPD is the resulting difference between the OTC effect on es(T), which is the temperature-dependent saturation pressure of water vapour and the OTC effect on ea, which is the prevailing partial pressure of water vapour in the air (ΔVPD = Δes(T) − Δea). Both Δes(T) and Δea were positive during daylight hours. ΔVPD was small in comparison and sensitive to changes in Δes(T) or Δea. ΔVPD was negative between 07:30 and 10:30 and positive thereafter with a maximum at 20:30 (local time). The positive afternoon ΔVPD was due to an early decrease in Δea, probably caused by ceased transpiration, while the positive Δes(T) persisted throughout the evening, most likely because of restrained cooling in the OTCs. Both the negative morning ΔVPD and the positive evening ΔVPD were more pronounced during clear, warm and dry weather. Circumstances when VPD had a stronger limiting effect on gs inside the OTCs compared to in the ambient air coincided with high ambient ozone concentrations ([O3]). Calculated wheat O3 uptake over an [O3] threshold of 40 nmol mol−1 was reduced by 8.7% in OTCs, assuming that VPD was the only factor limiting gs and that gs was the only resistance for O3 uptake. VPD is one factor of considerable importance for gs and the OTC impact on VPD may contribute to an underestimation of O3 effects expressed in relation to the external O3 exposure.
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| 10. |
- Uddling, Johan, 1972, et al.
(författare)
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Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings
- 2007
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Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 91:3, s. 37-46
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Tidskriftsartikel (refereegranskat)abstract
- Relationships between chlorophyll concentration ([chl]) and SPAD values were determined for birch, wheat, and potato. For all three species, the relationships were non-linear with an increasing slope with increasing SPAD. The relationships for birch and wheat were strong (r(2) similar to 0.9), while the potato relationship was comparatively weak (r(2) similar to 0.5). Birch and wheat had very similar relationships when the chlorophyll concentration was expressed per unit leaf area, but diverged when it was expressed per unit fresh weight. Furthermore, wheat showed similar SPAD-[chl] relationships for two different cultivars and during two different growing seasons. The curvilinear shape of the SPAD-[chl] relationships agreed well with the simulated effects of non-uniform chlorophyll distribution across the leaf surface and multiple scattering, causing deviations from linearity in the high and low SPAD range, respectively. The effect of non-uniformly distributed chlorophyll is likely to be more important in explaining the non-linearity in the empirical relationships, since the effect of scattering was predicted to be comparatively weak. The simulations were based on the algorithm for the calculation of SPAD-502 output values. We suggest that SPAD calibration curves should generally be parameterised as non-linear equations, and we hope that the relationships between [chl] and SPAD and the simulations of the present study can facilitate the interpretation of chlorophyll meter calibrations in relation to optical properties of leaves in future studies.
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