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| 2. |
- Hall, Marianne, 1976, et al.
(författare)
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Carbon dioxide exchange of buds and developing shoots of boreal Norway spruce exposed to elevated or ambient CO2 concentration and temperature in whole-tree chambers
- 2009
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 29:4
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Tidskriftsartikel (refereegranskat)abstract
- Effects of ambient and elevated temperature and atmospheric carbon dioxide concentration ([CO2]) on CO2 assimilation rate and the structural and phenological development of shoots during their first growing season were studied in 45-year-old Norway spruce trees (Picea abies (L.) Karst.) enclosed in whole-tree chambers. Continuous measurements of net assimilation rate (NAR) in individual buds and shoots were made from early bud development to late August in two consecutive years. The largest effect of elevated temperature (TE) was manifest early in the season as an earlier start and completion of shoot length development, and a 1–3-week earlier shift from negative to positive NAR compared with the ambient temperature (TA) treatments. The largest effect of elevated [CO2] (CE) was found later in the season, with a 30% increase in maximum NAR compared with trees in the ambient [CO2] treatments (CA), and shoots assimilating their own mass in terms of carbon earlier in the CE treatments than in the CA treatments. Once the net carbon assimilation compensation point (NACP) had been reached, TE had little or no effect on the development of NAR performance, whereas CE had little effect before the NACP. No interactive effects of TE and CE on NAR were found. We conclude that in a climate predicted for northern Sweden in 2100, current-year shoots of P. abies will assimilate their own mass in terms of carbon 20–30 days earlier compared with the current climate, and thereby significantly contribute to canopy assimilation during their first year.
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- Wallin, Göran, 1955, et al.
(författare)
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Impacts of elevated [CO2] and temperature on photosynthetic capacity in boreal Norway spruce during spring
- 2010
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Ingår i: The IUFRO conference: Canopy processes in a changing climate, 7-15 Oct 2007 in South East Australia. Oral presentation.
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Konferensbidrag (refereegranskat)abstract
- Apparent quantum yield (AQY) and light saturated net CO2 assimilation (Asat) were used to assess the responses of photosynthetic capacity to changing environmental conditions during spring for three consecutive years. Whole-tree chambers (WTC) were used to expose 40-year-old field-grown Norway spruce trees in northern Sweden to elevated [CO2], 700 mol CO2 mol-1, and elevated air temperature (T), between 2.8 and 5.6 ºC above ambient T, during summer and winter, respectively. Net shoot CO2 exchange was measured continuously on 1-year-old shoots and was used to calculate the Asat and AQY on a daily basis. Elevated air T had a prominent influence on the timing and extent of photosynthetic recovery expressed as AQY and Asat during the spring. The recovery of AQY and Asat commenced ~10 days earlier and the activity of these parameters were significantly higher through-out the recovery period. Under favourable conditions full recovery of the photosynthetic capacity could be reached within a week, but as the capacity was delayed or set back each time a frost event occurred full recovery sometimes took up to 60 days to be reached. Elevated [CO2] had little or no effect on the recovery rate, but Asat was stimulated on average by ~50% through-out the recovery period. The [CO2] had no effect on the AQY. With the combination of elevated T and [CO2], the Asat was decreased during the last year. This may be a sign of down-regulation caused by a decrease in the needle N content.
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| 4. |
- Wallin, Göran, 1955, et al.
(författare)
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Spring photosynthetic recovery of boreal Norway spruce under conditions of elevated [CO2] and air temperature
- 2013
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 33:11, s. 1177-1191
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Tidskriftsartikel (refereegranskat)abstract
- Accumulated carbon uptake, apparent quantum yield (AQY) and light-saturated net CO2 assimilation (Asat) were used to assess the responses of photosynthesis to environmental conditions during spring for three consecutive years. Whole-tree chambers were used to expose 40-year-old field-grown Norway spruce trees in northern Sweden to an elevated atmospheric CO2 concentration, [CO2], of 700μmolCO2mol−1 (CE) and an air temperature (T) between 2.8 and 5.6°C above ambient T (TE), during summer and winter. Net shoot CO2 exchange (Anet) was measured continuously on 1-year-old shoots and was used to calculate the accumulated carbon uptake and daily Asat and AQY. The accumulated carbon uptake, from 1 March to 30 June, was stimulated by 33, 44 and 61% when trees were exposed to CE, TE, and CE and TE combined, respectively. Air temperature strongly influenced the timing and extent of photosynthetic recovery expressed as AQY and Asat during the spring. Under elevated T (TE), the recovery of AQY and Asat commenced ∼10days earlier and the activity of these parameters was significantly higher throughout the recovery period. In the absence of frost events, the photosynthetic recovery period was less than a week. However, frost events during spring slowed recovery so that full recovery could take up to 60days to complete. Elevated [CO2] stimulated AQY and Asat on average by ∼10 and ∼50%, respectively, throughout the recovery period, but had minimal or no effect on the onset and length of the photosynthetic recovery period during the spring. However, AQY, Asat and Anet all recovered at significantly higher T (average +2.2°C) in TE than in TA, possibly caused by acclimation or by shorter days and lower light levels during the early part of the recovery in TE compared with TA. The results suggest that predicted future climate changes will cause prominent stimulation of photosynthetic CO2 uptake in boreal Norway spruce forest during spring, mainly caused by elevated T, but also elevated [CO2]. However, the effects of elevated T may not be linearly extrapolated to future warmer climates.
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