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  • Articles  (117)
  • 2000-2004  (63)
  • 1975-1979  (30)
  • 1905-1909  (24)
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  • 1
    Electronic Resource
    Electronic Resource
    Forest and agricultural land-use-dependent CO2 exchange in Thuringia, Germany (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: Eddy covariance was used to measure the net CO2 exchange (NEE) over ecosystems differing in land use (forest and agriculture) in Thuringia, Germany. Measurements were carried out at a managed, even-aged European beech stand (Fagus sylvatica, 70–150 years old), an unmanaged, uneven-aged mixed beech stand in a late stage of development (F. sylvatica, Fraxinus excelsior, Acer pseudoplantanus, and other hardwood trees, 0–250 years old), a managed young Norway spruce stand (Picea abies, 50 years old), and an agricultural field growing winter wheat in 2001, and potato in 2002. Large contrasts were found in NEE rates between the land uses of the ecosystems. The managed and unmanaged beech sites had very similar net CO2 uptake rates (∼−480 to −500 g C m−2 yr−1). Main differences in seasonal NEE patterns between the beech sites were because of a later leaf emergence and higher maximum leaf area index at the unmanaged beech site, probably as a result of the species mix at the site. In contrast, the spruce stand had a higher CO2 uptake in spring but substantially lower net CO2 uptake in summer than the beech stands. This resulted in a near neutral annual NEE (−4 g C m−2 yr−1), mainly attributable to an ecosystem respiration rate almost twice as high as that of the beech stands, despite slightly lower temperatures, because of the higher elevation. Crops in the agricultural field had high CO2 uptake rates, but growing season length was short compared with the forest ecosystems. Therefore, the agricultural land had low-to-moderate annual net CO2 uptake (−34 to −193 g C m−2), but with annual harvest taken into account it will be a source of CO2 (+97 to +386 g C m−2). The annually changing patchwork of crops will have strong consequences on the regions' seasonal and annual carbon exchange. Thus, not only land use, but also land-use history and site-specific management decisions affect the large-scale carbon balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2004.00863.x
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  • 2
    Electronic Resource
    Electronic Resource
    The long way from Kyoto to Marrakesh: Implications of the Kyoto Protocol negotiations for global ecology (2002)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 8 (2002), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The Sixth and Seventh Conference of the Parties (COP 6 and 7) at The Hague, Bonn and Marrakesh came to a final Agreement on the Kyoto Protocol, which is thus ready for ratification by the individual nations. The Agreement was only achieved by allowing countries to offset their fossil fuel emission targets (on average 95% of the 1990 emissions) by increasing biological carbon sequestration, and by trading carbon credits. Activities that would count as increasing biological carbon sequestration include afforestation and reforestation, and changes in management of agriculture and forestry. According to the Agreement reached in Marrakesh, biological carbon sequestration may reach an offset of up to 80% of the required reduction in fossil fuel emissions (4% of the 5% reduction commitment). We explain why the allowable offset rose as high during the course of the negotiations. It is highlighted that major unintended consequences may be a result of the policy as it stands in the Marrakesh Accord. Major losses of biodiversity and primary forest are expected. We present scientific concerns regarding verification, which lead to scientific doubts that the practices encouraged by the Agreement can actually increase sequestration under a full carbon accounting scheme. We explain that there is a ‘win-win’ option that would protect high carbon pools and biodiversity in an economically efficient way. But, this is not supported by the Agreement. Despite the very positive signal that most nations of the United Nations will devote major efforts towards climate protection, there remains a most urgent need to develop additional rules to avoid unintended outcomes, and to promote the ‘win-win’ options that we explain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2002.00523.x
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  • 3
    Electronic Resource
    Electronic Resource
    Respiration as the main determinant of carbon balance in European forests (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 404 (2000), S. 861-865 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Carbon exchange between the terrestrial biosphere and the atmosphere is one of the key processes that need to be assessed in the context of the Kyoto Protocol. Several studies suggest that the terrestrial biosphere is gaining carbon, but these estimates are obtained primarily by indirect ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35009084
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of caveolins from human knee joint cartilage: expression of caveolin-1, -2, and -3 in chondrocytes and association with integrin β1 (2000)
    Springer
    Histochemistry and cell biology 113 (2000), S. 221-225 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Interactions between the extracellular matrix (ECM) and chondrocytes are of great importance for structure and function of cartilage. The present study was undertaken to answer the question whether caveolins take part in integrin-mediated cell–ECM interactions in the human cartilage. In samples of human knee joint cartilage, we detected the caveolin subtypes -1, -2, and -3 by immunohistochemical methods. Double-label experiments revealed a colocalization of caveolin with β1-integrin. Results of immunoprecipitation and immunoblotting assays show that β1-integrins associate with all three caveolin subtypes in human chondrocytes and indicate that they are part of the same complexes. Furthermore, immunoelectron microscopy shows the localization of β1-integrin in caveolae-like structures of the cell membrane. The data stimulate further investigations on the role of the caveolin–integrin complex for integrin-mediated signaling pathways in chondrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180050441
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  • 5
    Electronic Resource
    Electronic Resource
    The temperature-related photosynthetic capacity of plants under desert conditions (1975)
    Springer
    Oecologia 18 (1975), S. 45-53 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a previous paper seasonal shifts of the temperature optimum (OP) and of the upper temperature compensation point (CP) of net photosynthesis were described for Hammada scoparia growing wild, and for Prunus armeniaca cultivated in the Negev Desert (Israel). In this paper the relationships between these shifts and the microclimatic conditions, plant-water relations, and plant development are studied. The energy budged of the thin, round photosynthesizing stems of H. scoparia growing in an open desert habitat differes from that of the broad leaves of P. armeniaca within the orchard. This explains the fact that daily maximum temperatures of the apricot increased until August and September, whereas maximum temperatures of H. scoparia reached a peak in May and June and decreased thereafter during the second half of the growing season. For H. scoparia a correspondence was found between the daily maximum tissue temperatures (and also the average temperatures of the warmest periods of the day) and the seasonal changes of the OP and CP values. This may indicate that the shifts in the temperature sensitivity of net photosynthesis of this plant are adaptations to the temperature conditions of the plant. This, however, cannot be the case for P. armeniaca, where during the second part of the growing season a period of rising leaf temperatures coincides with a period of decreasing OP and CP values. Therefore, the seasonal changes of the temperature dependence of net photosynthesis of P. armeniaca could not always be considered an adaptation to the prevailing temperature conditions of the plant. In this case, the changes in temperature sensitivity of photosynthesis could be due to developmental processes such as aging. In both lants the seasonal changes of the OP and CP values correspond to changes of the daily photoperiod and to changes of the daily average light intensity. It appears possible that this correlation indicates a causal relationship.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350634
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  • 6
    Electronic Resource
    Electronic Resource
    The role of air humidity and leaf temperature in controlling stomatal resistance of Prunus armeniaca L. under desert conditions (1975)
    Springer
    Oecologia 18 (1975), S. 219-233 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gas exchange of the apricot (Prunus armeniaca L.) growing in the runoff farm at Avdat (Negev, Israel) was measured during its growing period using temperature- and humidity-controlled chambers. Water potentials of the xylem were measured with a pressure bomb, and the mesophyll internal CO2 concentration was calculated from simultaneous measurements of net photosynthesis and transpiration. The daily changes in water potential Ψ had only little effect on the daily course of stomatal resistance. The early morning peak of CO2 uptake was reached when Ψ had already dropped to very low values. On dry days, Ψ and the relative water content of the leaf were improved at noon during the time of stomatal closure. On humid days, Ψ dropped to very low values (43.5 bar) at a high transpiration rate without causing stomatal closure, as much as on the dry days when stomata where more closed at less water stress. The observed changing sensitivity of the stomata to changes in air humidity during the season is related to the water status in the plant. This change is possibly caused by a long-term effect of stress in this habitat. The daily changes in stomatal diffusion resistance did not consistently correlate with changes of the CO2 concentration in the intercellular air spaces. In the morning a decreasing internal CO2 concentration was even inversely correlated to the stomatal response. In the afternoon the effect of an increasing internal CO2 concentration and the effect of external climate on stomatal response could be additive. However, at the time, when CO2 uptake reached a second peak in the afternoon the same value of diffusion resistance is reached at very different levels of internal CO2 concentration as compared to the morning. For the regulation of the diffusion resistance in apricot under the natural conditions, the effects of plant internal control mechanisms are overruled and/or modified by the external climatic factors of air humidity and temperature. The significance of the climate-controlled stomatal response for the existence and cultivation of this plant species in an arid habitat is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345424
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  • 7
    Electronic Resource
    Electronic Resource
    The role of air humidity and temperature in controlling stomatal resistance of Prunus armeniaca L. under desert conditions (1975)
    Springer
    Oecologia 19 (1975), S. 303-314 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Measurements of CO2 and water vapor exchange were performed on Prunus armeniaca L. with humidity- and temperature-controlled chambers under the climatic conditions of a desert habitat. In apricot, the stomatal response to changes in temperature and water-vapor concentration difference between leaf and air (WD) significantly determined the rates of gas exchange during the day (parts I and II). The effect of climate-controlled stomatal response on the transpiration/net photosynthesis (T/P)-ratio was analyzed and simulated using experiments conducted at constant temperature and/or humidity conditions for input parameters. The measured values of the T/P-ratio at naturally varying conditions of humidity and temperature were compared with calculated results of a model in which it was assumed, (1) that stomata and photosynthetic activity are not affected by air humidity and temperature, (2) that the stomata only respond with a constant photosynthetic activity to changes in WD, and (3) that the stomata respond to both, leaf temperature and air humidity with a constant photosynthetic activity. These simulations facilitated an analysis of the naturally observed changes in the T/P-ratio. The calculated T/P-ratios were very small if the simulation assumed that stomata only respond to WD at a constant photosynthetic activity. These low predicted values of the T/P-ratio were not obtained under natural conditions, since an increase in WD during the day was correlated with a temperature rise which tended to open stomata and change the photosynthetic activity. Humidity induced stomatal closure did appear to substantially reduce T/P-ratios. The measured T/P-ratio changed considerably during the year. The lowest T/P-ratios were obtained in the middle of the dry season at a time when stomata responded strongly to air humidity and when optimum of photosynthesis was reached at high temperatures. The daily average T/P-ratio calculated from the daily sum of P and T showed little change during the seasons. A high T/P-ratio was also observed at reduced rates of gas exchange. The T/P-ratios of apricot were compared with different species in different environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348106
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  • 8
    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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  • 9
    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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  • 10
    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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