Spectral Distribution of Solar Radiation in the Nordic Countries

Kvifte, G.; Hegg, K.; Hansen, V.

doi:10.1175/1520-0450(1983)022<0143:sdosri>2.0.co;2

Cited by 33 publications

(13 citation statements)

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“…However, a significant delay was observed, with larger delay in more southern than more northern populations, indicating some role or other of blue light in control of shoot elongation and growth cessation. The ecological implication of this is unclear since blue light easily dissipates in the atmosphere and no clear latitudinal pattern is observed (Kvifte et al 1983). …”

Section: Relative Importance Of Photoperiod and Light Quality Differsmentioning

confidence: 99%

Light and temperature sensing and signaling in induction of bud dormancy in woody plants

2010

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In woody species cycling between growth and dormancy must be precisely synchronized with the seasonal climatic variations. Cessation of apical growth, resulting from exposure to short photoperiod (SD) and altered light quality, is gating the chain of events resulting in bud dormancy and cold hardiness. The relative importance of these light parameters, sensed by phytochromes and possibly a blue light receptor, varies with latitude. Early in SD, changes in expression of light signaling components dominate. In Populus active shoot elongation is linked to high expression of FLOWERING LOCUS T (FT) resulting from coincidence of high levels of CONSTANS and light at the end of days longer than a critical one. In Picea, PaFT4 expression increases substantially in response to SD. Thus, in contrast to Populus-FT, PaFT4 appears to function in inhibition of shoot elongation or promotion of growth cessation. Accordingly, different FT-genes appear to have opposite effects in photoperiodic control of shoot elongation. Reduction in gibberellin under SD is involved in control of growth cessation and bud formation, but not further dormancy development. Coinciding with formation of a closed bud, abscisic acid activity increases and cell-proliferation genes are down-regulated. When dormancy is established very few changes in gene expression occur. Thus, maintenance of dormancy is not dependent on comprehensive transcriptional regulation. In some species low temperature induces growth cessation and dormancy, in others temperature affects photoperiod requirement. The temperature under SD affects both the rate of growth cessation, bud formation and depth of dormancy. As yet, information on the molecular basis of these responses to temperature is scarce.

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Section: Relative Importance Of Photoperiod and Light Quality Differsmentioning

confidence: 99%

Light and temperature sensing and signaling in induction of bud dormancy in woody plants

2010

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“…The ratio of PAR to SR for certain areas has been reported in many studies. For example, the ratio ranges from 0.47 to 0.51 for Cambridge, U.K. (Szeicz 1974), and from 0.47 to 0.5 for Copenhagen, Denmark (Kvifte et al 1983). For our simulations we have tested different ratios of SR to PAR, and a ratio of 0.47 shows best agreement between simulated PAR and measurements performed in the investigation area (not shown).…”

Section: The Coupled Foot3dk/gas Exchange Modelmentioning

confidence: 99%

The Simulation of the Opposing Fluxes of Latent Heat and CO2 over Various Land-Use Types: Coupling a Gas Exchange Model to a Mesoscale Atmospheric Model

Reyers

Krüger

Werner³

et al. 2010

Boundary-Layer Meteorol

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A mesoscale meteorological model (FOOT3DK) is coupled with a gas exchange model to simulate surface fluxes of CO 2 and H 2 O under field conditions. The gas exchange model consists of a C3 single leaf photosynthesis sub-model and an extended big leaf (sun/shade) sub-model that divides the canopy into sunlit and shaded fractions. Simulated CO 2 fluxes of the stand-alone version of the gas exchange model correspond well to eddycovariance measurements at a test site in a rural area in the west of Germany. The coupled FOOT3DK/gas exchange model is validated for the diurnal cycle at singular grid points, and delivers realistic fluxes with respect to their order of magnitude and to the general daily course. Compared to the Jarvis-based big leaf scheme, simulations of latent heat fluxes with a photosynthesis-based scheme for stomatal conductance are more realistic. As expected, flux averages are strongly influenced by the underlying land cover. While the simulated net ecosystem exchange is highly correlated with leaf area index, this correlation is much weaker for the latent heat flux. Photosynthetic CO 2 uptake is associated with transpirational water loss via the stomata, and the resulting opposing surface fluxes of CO 2 and H 2 O are reproduced with the model approach. Over vegetated surfaces it is shown that the coupling of a photosynthesis-based gas exchange model with the land-surface scheme of a mesoscale model results in more realistic simulated latent heat fluxes.

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“…The data from Visby were available as hourly integrated continuous measurements of total irradiation (290 to 4000 nm) on a horizontal surface. PAR was estimated as 50% of total irradiation (Kvifte et al 1983). …”

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Blooms of Baltic Sea Aphanizomenon sp. (Cyanobacteria) collapse after internal phosphorus depletion

Walve¹,

Larsson²

2007

Aquat. Microb. Ecol.

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We studied C:N:P stoichiometry, heterocyst frequency, and biomass of the N 2 -fixing cyanobacteria Aphanizomenon sp. and Nodularia spumigena from May to September 1999 and 2000 at an offshore station in the NW Baltic Proper. In 2000, we included iron (Fe) and molybdenum (Mo) contents and biomass-specific 14 C uptake. We also complemented published C:N:P stoichiometry data from 1998 with heterocyst frequency. We found a drastic increase in C:P and N:P ratios in Aphanizomenon sp., indicating severe P deficiency at the biomass maximum. N. spumigena also had high C:P and N:P ratios at high abundances. In 2000, and 1998, the total amount of P stored in Aphanizomenon sp. biomass in early summer equalled that at the bloom peak. Only a small part of the DIP surplus remaining after the spring bloom of diatoms and dinoflagellates ended up in the peak biomass of the subsequent cyanobacterial bloom. Aphanizomenon sp. heterocyst frequency peaked in early summer when the C:P ratio was near the Redfield value, and then decreased with increasing C:P ratio, initially perhaps due to increased temperature, and later to P limitation. This decrease occurred parallel to a decrease in Aphanizomenon sp. Mo content. We found no indication of Fe limitation since there was no clear decrease in Aphanizomenon sp. Fe content as the bloom progressed. N. spumigena had considerably higher Fe content, but a high Fe:Mo ratio suggests that Fe adsorbed to cell surfaces biased the measurements. An expected reduction in growth rate due to the high C:P ratio was not mirrored in a decreased specific C uptake of Aphanizomenon sp. as measured in short-term 14 C incubations. This may indicate short-term C storage with subsequent respiration or excretion of excess carbon when growth is P limited.KEY WORDS: Cyanobacteria · Stoichiometry · Cell quota · Nitrogen · Phosphorus · Iron · Molybdenum · Heterocysts · Baltic Sea Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 49: [57][58][59][60][61][62][63][64][65][66][67][68][69] 2007 in estuaries. The Baltic Proper, the main basin of the Baltic Sea, commonly has high abundances of the heterocystous N 2 -fixing species Nodularia spumigena and Aphanizomenon sp. (hereafter referred to by their genus names) in the stratified summer period (Granéli et al. 1990, Larsson et al. 2001). New estimates indicate N 2 fixation in the Baltic Proper to be a larger source of nitrogen than previously thought, almost as large as that from river discharges or up to twice that from atmospheric inputs (Larsson et al. 2001, Wasmund et al. 2005. Thus, N 2 fixation may contribute 30 to 90% of the nitrogen needed to sustain the phytoplankton net community production during the summer (Larsson et al. 2001).The severely N-limited spring bloom of diatoms and dinoflagellates in the Baltic Proper leaves a substantial pool of dissolved inorganic P (DIP) (Larsson et al. 2001), which is generally assumed to support the succeeding large N 2 -fixing cyanobacterial blooms (e.g. Rahm et al. ...

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Spectral Distribution of Solar Radiation in the Nordic Countries

Cited by 33 publications

References 2 publications

Light and temperature sensing and signaling in induction of bud dormancy in woody plants

Light and temperature sensing and signaling in induction of bud dormancy in woody plants

The Simulation of the Opposing Fluxes of Latent Heat and CO2 over Various Land-Use Types: Coupling a Gas Exchange Model to a Mesoscale Atmospheric Model

Blooms of Baltic Sea Aphanizomenon sp. (Cyanobacteria) collapse after internal phosphorus depletion

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