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  • Articles  (4)
  • Articles: DFG German National Licenses  (4)
  • 1975-1979  (4)
  • 1905-1909
  • 1977  (4)
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  • Articles  (4)
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  • 1975-1979  (4)
  • 1905-1909
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  • 1
    Electronic Resource
    Electronic Resource
    Ecophysiological investigations on lichens of the Negev desert (1977)
    Springer
    Oecologia 28 (1977), S. 247-259 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous publications have reported on investigations of CO2 exchange in the desert lichenRamalina maciformis both in its natural habitat in the Negev and in the laboratory. Utilizing laboratory data, net photosynthesis and dark respiration were expressed as mathematical functions of the most important environmental factors. Based on these relationships, a model is developed that allows one to predict CO2 exchange of the plant. Input data are light intensity, temperature, and water content of the thallus, together with a measure of the rate of the seasonal change of photosynthetic and respiratory activity. The validity of the model is tested by comparing simulated daily courses of CO2 uptake and release of the lichen with independent results of CO2 exchange measurements conducted in the field during and after the condensation of dew. The sensitivity of the model is shown by simulating changes in the input data of temperature and water content of the lichen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751603
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  • 2
    Electronic Resource
    Electronic Resource
    Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of Northern Germany (1977)
    Springer
    Oecologia 29 (1977), S. 43-61 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Biomass distribution and diurnal CO2 uptake under natural conditions were investigated on Picea abies in a mountainous climate (Solling, Northwest Germany). Spruce has a remarkable variability in leaf characteristics. Even on a single branch in the lower sun crown, needle dry weight and surface area change considerably from the branch base to the tip and accoring to exposure. Only about 18% of the total biomass of the tree was current year's growth, about 40% of the needles were 4 years and older reaching a maximal age of 12 years. The main growing zone was at the border of upper shade and lower sun crown and the main accumulation of dry weight was at a greater tree height than was observed for maximal growth of needle numbers or surface area. The annual, new growth shifted toward the upper sun crown. Maximal daily CO2 uptake was highest in the lower sun crown on days with variable cloud cover when temperatures were moderate and water vapor pressure deficits were low. Also the annual CO2 uptake was highest in the lower sun crown, where 4-year-old and older needles contributed about 35% to the annual CO2 uptake of the tree. Current year growth contributed about 15% of the total CO2 gain. The upper and lower sun crowns produce about 70% of the total carbon gain. The carbon balance of spruce and the distribution of the production process in relation to needle age and crown level are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345361
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  • 3
    Electronic Resource
    Electronic Resource
    Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of northern Germany (1977)
    Springer
    Oecologia 29 (1977), S. 329-340 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Net photosynthesis of Picea abies was measured in a spruce forest in northern Germany with temperature- and humidity-controlled cuvettes in 4 different crown layers on shoots of different ages. These measurments were performed such that temperature and humidity either followed ambient conditions or were kept constant. Annual courses of light-, temperature-, and humidity-related net photosynthesis were determined. Spruce had a remarkably constant rate of CO2 uptake from April to September for 1-year and older needles. Light saturation was achieved at 25 klx. Current year needles had the highest rates of CO2 uptake in early summer, but these rates decreased by autumn. Photosynthetic capacity decreased with needle age and, on a dry weight basis, it was higher in the shade than in the sun crown. The temperature optimum was between 13 and 23° C. Photosynthesis in spruce decreased when air humidity was low. The effect of the natural weather conditions on photosynthetic capacity was determined. The habitat is characterized by a high frequency of low light intensities (75% of total daytime below 20 klx) and cool temperatures (80% of daytime between 9 and 21° C). Low air humidity was only present when light intensities were high. The major limiting factor for production was low light intensities, which reduced photosynthetic capacity in the sun crown to 42% below maximum possible rates. Adverse temperatures reduced CO2 uptake by 28% and large water vapor pressure deficits reduced rates by only 2% compared with maximum possible rates. The limited adaptation to light is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345806
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  • 4
    Electronic Resource
    Electronic Resource
    Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of Northern Germany (1977)
    Springer
    Oecologia 30 (1977), S. 239-248 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Growth and CO2 uptake in the crown of a spruce tree is described and the production processes of this evergreen conifer are compared with those of a deciduous beech. Spruce had 60% lower rates of net photosynthesis per dry weight than beech. But, beech had a 30% shorter growing season and a 84% smaller biomass than spruce. The annual CO2 gain was 40% lower in beech than it was in spruce. An analysis shows the following conclusions for this habitat. (1) The effect of a prolonged growing season is small. The annual CO2 gain of spruce would be reduced only by 9% if the growing season was the same length as for beech. (2) The annual CO2 gain would increase 14% if all needles in spruce were deciduous, because the current year needles have a higher average rate of CO2 uptake than 3-year old and older needles, but a lower average rate than 1- and 2-year old ones. However, the carbon balance of the tree shows that spruce could not afford to produce the existing needle biomass (14 t ha-1) each year. (3) If spruce were to produce the same deciduous foliage biomass during the same growing season as beech then total production by spruce would be reduced 67%. (4) The annual CO2 uptake by evergreen spruce was higher than deciduous beech not because of a long growing season, but because of the longevity of its needles, which during their total life time (an average of 5 years) have a two to three times greater CO2 uptake than a deciduous leaf in one summer season. The relatively small investment in current year needles produces an annually low, but long lasting assimilation of CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01833630
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