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  • 1
    Electronic Resource
    Electronic Resource
    The human footprint in the carbon cycle of temperate and boreal forests (2007)
    [s.l.] : Nature Publishing Group
    Nature 447 (2007), S. 849-851 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Temperate and boreal forests in the Northern Hemisphere cover an area of about 2 × 107 square kilometres and act as a substantial carbon sink (0.6–0.7 petagrams of carbon per year). Although forest expansion following agricultural abandonment is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05847
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  • 2
    Electronic Resource
    Electronic Resource
    Atmospheric science Ultraviolet light and leaf emission of NO x (2003)
    [s.l.] : Nature Publishing Group
    Nature 422 (2003), S. 134-134 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Nitrogen oxides are trace gases that critically affect atmospheric chemistry and aerosol formation. Vegetation is usually regarded as a sink for these gases, although nitric oxide and nitrogen dioxide have been detected as natural emissions from plants. Here we use in situ measurements to show ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/422134a
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonal patterns of soil CO2 efflux and soil air CO2 concentration in a Scots pine forest: comparison of two chamber techniques (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: A non-vented non-steady state flow-through chamber and a non-vented non-steady state non-flow-through chamber technique were used to measure CO2 efflux of a young Scots pine forest on a fertile till soil in southern Finland. Soil temperature, soil moisture and soil CO2 concentration were measured concurrently with CO2 efflux for two and a half successive years. The CO2 efflux showed a seasonal pattern, effluxes ranging from low 0.0–0.1 g CO2 m−2 h−1 in winter to peak values of 2.3 g CO2 m−2 h−1 occurring in late June and in July. The daily average effluxes in July measured by flow through chambers were 1.23 and 0.98 g CO2 m−2 h−1 in 1998 and 1999, respectively. The annual accumulated CO2 efflux was 3117 and 3326 g CO2 m−2 in 1998 and 1999, respectively. The spatial variation in CO2 efflux was high (CV 0.18–0.45) and increased with increasing efflux. Soil air CO2 concentration showed similar seasonal pattern the peak concentrations occurring in July–August. The CO2 concentrations ranged from 580 to 780 µmol mol−1 in the humus layer to 13 620–14 470 µmol mol−1 in the C-horizon. In winter the soil air CO2 concentrations were lower, especially in deeper soil layers. Drought decreased CO2 efflux and soil air CO2 concentration. The in situ comparison on forest soil between the chamber methods showed the non-flow-through chamber to give ∼∼50% lower efflux values than that of the flow-through chamber. When calibrated against known CO2 efflux ranging from 0.4 to 0.8 g CO2 m−2 h−1 generated with a diffusion box method developed by Widén and Lindroth [Acta Universitatis Agriculturae Suecia Silvestria, 2001], the flow-through chamber gave equal effluxes at the lower end of the calibration range, but overestimated high effluxes by 20%. Non-flow-through chamber underestimated the CO2 efflux by 30%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00588.x
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  • 4
    Electronic Resource
    Electronic Resource
    Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The timing of the commencement of photosynthesis (P*) in spring is an important determinant of growing-season length and thus of the productivity of boreal forests. Although controlled experiments have shed light on environmental mechanisms triggering release from photoinhibition after winter, quantitative research for trees growing naturally in the field is scarce. In this study, we investigated the environmental cues initiating the spring recovery of boreal coniferous forest ecosystems under field conditions. We used meteorological data and above-canopy eddy covariance measurements of the net ecosystem CO2 exchange (NEE) from five field stations located in northern and southern Finland, northern and southern Sweden, and central Siberia. The within- and intersite variability for P* was large, 30–60 days. Of the different climate variables examined, air temperature emerged as the best predictor for P* in spring. We also found that ‘soil thaw’, defined as the time when near-surface soil temperature rapidly increases above 0°C, is not a useful criterion for P*. In one case, photosynthesis commenced 1.5 months before soil temperatures increased significantly above 0°C. At most sites, we were able to determine a threshold for air-temperature-related variables, the exceeding of which was required for P*. A 5-day running-average temperature (T5) produced the best predictions, but a developmental-stage model (S) utilizing a modified temperature sum concept also worked well. But for both T5 and S, the threshold values varied from site to site, perhaps reflecting genetic differences among the stands or climate-induced differences in the physiological state of trees in late winter/early spring. Only at the warmest site, in southern Sweden, could we obtain no threshold values for T5 or S that could predict P* reliably. This suggests that although air temperature appears to be a good predictor for P* at high latitudes, there may be no unifying ecophysiological relationship applicable across the entire boreal zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00597.x
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon balance of different aged Scots pine forests in Southern Finland (2004)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 10 (2004), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We estimated annual net ecosystem exchange (NEE) of a chronosequence of four Scots pine stands in southern Finland during years 2000–2002 using eddy covariance (EC). Net ecosystem productivity (NEP) was estimated using growth measurements and modelled mass losses of woody debris. The stands were 4, 12, 40 and 75 years old. The 4-year-old clearcut was a source of carbon throughout the year combining a low gross primary productivity (GPP) with a total ecosystem respiration (TER) similar to the forest stands. The annual NEE of the clearcut, measured by EC, was 386 g C m−2. Tree growth was negligible and the estimated NEP was −262 g C m−2 a−1. The annual GPPs at the other sites were close to each other (928−1072 g C m−2 a−1), but TER differed markedly, being greatest at the 12-year-old site (905 g C m−2 a−1) and smallest in the 75-year-old stand (616 g C m−2 a−1). Measurements of soil CO2 efflux showed that different rates of soil respiration largely explained the differences in TER. The NEE and NEP of the 12-year-old stand were close to zero. The forested stands were sinks of carbon. They had similar annual patterns of carbon exchange and half-hourly eddy fluxes were highly correlated, indicating similar responses to the environment. The NEE in the 40-year-old stand varied between −179 and –192 g C m−2 a−1, while NEP was between 214 and 242 g C m−2 a−1. The annual NEE of the 75-year-old stand was 323 g C m−2 and NEP was 252 g C m−2. This indicates that there was no reduction in carbon sink strength with stand age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1529-8817.2003.00797.x
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  • 6
    Electronic Resource
    Electronic Resource
    Paired comparisons of carbon exchange between undisturbed and regenerating stands in four managed forests in Europe (2004)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 10 (2004), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The effects of harvest on European forest net ecosystem exchange (NEE) of carbon and its photosynthetic and respiratory components (GPP (gross primary production) and TER (total ecosystem respiration)) were examined by comparing four pairs of mature/harvested sites in Europe via a combination of eddy covariance measurements and empirical modeling. Three of the comparisons represented high coniferous forestry (spruce in Britain, and pines in Finland and France), while a coppice-with-standard oak plantation was examined in Italy.While every comparison revealed that harvesting converted a mature forest carbon sink into a carbon source of similar magnitude, the mechanisms by which this occurred were very different according to species or management practice. In Britain, Finland, and France the annual sink (source) strength for mature (clear-cut) stands was estimated at 496 (112), 138 (239), and 222 (225) g C m−2, respectively, with 381 (427) g C m−2 for the mature (coppiced) stand in Italy. In all three cases of high forestry in Britain, Finland, and France, clear-cutting crippled the photosynthetic capacity of the ecosystem – with mature (clear-cut) GPP of 1970 (988), 1010 (363), and 1600 (602) g C m−2– and also reduced ecosystem respiration to a lesser degree – TER of 1385 (1100), 839 (603), and 1415 (878) g C m−2, respectively. By contrast, harvesting of the coppice oak system provoked a burst in respiration – with mature (clear-cut) TER estimated at 1160 (2220) gC m−2– which endured for the 3 years sampled postharvest. The harvest disturbance also reduced GPP in the coppice system – with mature (clear-cut) GPP of 1600 (1420) g C m−2– but to a lesser extent than in the coniferous forests, and with near-complete recovery within a few years. Understanding the effects of harvest on the carbon balance of European forest systems is a necessary step towards characterizing carbon exchange for timberlands on large scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2004.00846.x
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  • 7
    Electronic Resource
    Electronic Resource
    Comparisons between Photosynthesis and Transpiration in Birch (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 33 (1975), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in photosynthesis and transpiration of a potted birch seedling were simultaneously followed in the field using two infrared gas analyzers. Wet and dry temperature measurements alone explained 81% of the variation in the transpiration rate when the plant was not suffering from water deficit. During drought and the period after the water balance had been restored, net photosynthesis decreased more distinctly than transpiration. This result was in accordance with our previous results on the after-effects of water deficit on photosynthesis, and it was also interpreted as evidence for at least partly separate control mechanisms for photosynthesis and transpiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1975.tb03756.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Water Stress on Transpiration in Birch Seedlings (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 35 (1975), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Transpiration of birch seedlings in the field is largely controlled by the amount of available water in the soil. This is in contrast with the situation found in CO2 exchange, where distinct interaction between temperature and drought was observed in our previous studies. The present study indicates that no similar relationships exist as far as transpiration is concerned, and in agreement with our previous preliminary studies, separate control mechanisms thus seem to affect transpiration on the one hand and photosynthesis on the other under natural conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1975.tb03877.x
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  • 9
    Electronic Resource
    Electronic Resource
    Field Studies of Photosynthesis as Affected by Water Stress, Temperature, and Light in Birch (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 32 (1974), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This study continues the investigations previously conducted as laboratory experiments. The results from the present study confirm our earlier observations made on alder seedlings concerning the effect of water stress, temperature and light on the net uptake of CO2.A variable that we could call the physiological water stress is proposed as a measure of the intrinsic factor of photosynthesis during and after drought. A physiological water stress builds up and discharges slowly and interacts strongly with temperature. Our model for the effects of physiological water stress, temperature, and light intensity explains satisfactorily the net uptake of CO2 in birch in the field. Thus, our earlier results concerning the effects of physiological water stress on photosynthesis are not artifacts generated by the unnatural laboratory environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1974.tb03734.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Water Stress, Temperature, and Light on Photosynthesis in Alder Seedlings (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 29 (1973), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seedlings of Alnus incana (L.) Moench were studied in controlled environmental conditions. Net photosynthetic capacity of four plants simultaneously as well as light, temperature, and atmospheric water pressure deficit were continuously recorded during approximately two months. The potted plants were continuously given known quantities of water.Two different effects of water stress were found in the experimental plants. When sufficient amounts of water had been available to them, photosynthetic CO2 fixation rates largely followed the variation in temperature and light. On the other hand, after prolonged water stress, higher temperatures caused a large decrease in net CO2 uptake even if the plant apparently had sufficient water during the actual measurements. Possible mechanisms for this effect are discussed.Effects of water stress on photosynthesis were studied at a constant temperature as well as in conditions where temperature, light, soil water content, and atmospheric water vapor pressure were allowed to vary in a complex pattern. Mathematical models for expressing net CO2 uptake as a function of environmental variables were constructed for both of these experimental situations. However, only the latter approach clearly demonstrated the fundamental role of temperature in controlling the photosynthesis of plants under water stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1973.tb04808.x
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