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  • Articles  (24)
  • 2005-2009  (13)
  • 1990-1994  (11)
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  • 1
    Publication Date: 2008-05-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Field, Christopher B -- England -- Nature. 2008 May 8;453(7192):154-5. doi: 10.1038/453154b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18464715" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2008-06-20
    Description: Dinitrogen (N(2)) fixation is widely recognized as an important process in controlling ecosystem responses to global environmental change, both today and in the past; however, significant discrepancies exist between theory and observations of patterns of N(2) fixation across major sectors of the land biosphere. A question remains as to why symbiotic N(2)-fixing plants are more abundant in vast areas of the tropics than in many of the mature forests that seem to be nitrogen-limited in the temperate and boreal zones. Here we present a unifying framework for terrestrial N(2) fixation that can explain the geographic occurrence of N(2) fixers across diverse biomes and at the global scale. By examining trade-offs inherent in plant carbon, nitrogen and phosphorus capture, we find a clear advantage to symbiotic N(2) fixers in phosphorus-limited tropical savannas and lowland tropical forests. The ability of N(2) fixers to invest nitrogen into phosphorus acquisition seems vital to sustained N(2) fixation in phosphorus-limited tropical ecosystems. In contrast, modern-day temperatures seem to constrain N(2) fixation rates and N(2)-fixing species from mature forests in the high latitudes. We propose that an analysis that couples biogeochemical cycling and biophysical mechanisms is sufficient to explain the principal geographical patterns of symbiotic N(2) fixation on land, thus providing a basis for predicting the response of nutrient-limited ecosystems to climate change and increasing atmospheric CO(2).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Houlton, Benjamin Z -- Wang, Ying-Ping -- Vitousek, Peter M -- Field, Christopher B -- England -- Nature. 2008 Jul 17;454(7202):327-30. doi: 10.1038/nature07028. Epub 2008 Jun 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biological Sciences, Stanford University, Stanford, California 94305, USA. bzhoulton@ucdavis.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18563086" target="_blank"〉PubMed〈/a〉
    Keywords: *Ecosystem ; Models, Biological ; *Nitrogen Fixation ; Nitrogenase/metabolism ; Phosphates/metabolism ; Phosphoric Monoester Hydrolases/metabolism ; Plants/enzymology/*metabolism ; Soil/analysis ; Symbiosis ; Temperature ; Tropical Climate
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2009-12-25
    Description: The ranges of plants and animals are moving in response to recent changes in climate. As temperatures rise, ecosystems with 'nowhere to go', such as mountains, are considered to be more threatened. However, species survival may depend as much on keeping pace with moving climates as the climate's ultimate persistence. Here we present a new index of the velocity of temperature change (km yr(-1)), derived from spatial gradients ( degrees C km(-1)) and multimodel ensemble forecasts of rates of temperature increase ( degrees C yr(-1)) in the twenty-first century. This index represents the instantaneous local velocity along Earth's surface needed to maintain constant temperatures, and has a global mean of 0.42 km yr(-1) (A1B emission scenario). Owing to topographic effects, the velocity of temperature change is lowest in mountainous biomes such as tropical and subtropical coniferous forests (0.08 km yr(-1)), temperate coniferous forest, and montane grasslands. Velocities are highest in flooded grasslands (1.26 km yr(-1)), mangroves and deserts. High velocities suggest that the climates of only 8% of global protected areas have residence times exceeding 100 years. Small protected areas exacerbate the problem in Mediterranean-type and temperate coniferous forest biomes. Large protected areas may mitigate the problem in desert biomes. These results indicate management strategies for minimizing biodiversity loss from climate change. Montane landscapes may effectively shelter many species into the next century. Elsewhere, reduced emissions, a much expanded network of protected areas, or efforts to increase species movement may be necessary.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Loarie, Scott R -- Duffy, Philip B -- Hamilton, Healy -- Asner, Gregory P -- Field, Christopher B -- Ackerly, David D -- England -- Nature. 2009 Dec 24;462(7276):1052-5. doi: 10.1038/nature08649.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Carnegie Institution for Science, Department of Global Ecology, Stanford, California 94305, USA. loarie@stanford.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20033047" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biodiversity ; Conservation of Natural Resources ; Ecosystem ; *Global Warming ; *Models, Biological ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2009-05-09
    Description: The quantity of land available to grow biofuel crops without affecting food prices or greenhouse gas (GHG) emissions from land conversion is limited. Therefore, bioenergy should maximize land-use efficiency when addressing transportation and climate change goals. Biomass could power either internal combustion or electric vehicles, but the relative land-use efficiency of these two energy pathways is not well quantified. Here, we show that bioelectricity outperforms ethanol across a range of feedstocks, conversion technologies, and vehicle classes. Bioelectricity produces an average of 81% more transportation kilometers and 108% more emissions offsets per unit area of cropland than does cellulosic ethanol. These results suggest that alternative bioenergy pathways have large differences in how efficiently they use the available land to achieve transportation and climate goals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Campbell, J E -- Lobell, D B -- Field, C B -- New York, N.Y. -- Science. 2009 May 22;324(5930):1055-7. doi: 10.1126/science.1168885. Epub 2009 May 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉College of Engineering, University of California, Merced, CA 95344, USA. ecampbell3@ucmerced.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19423776" target="_blank"〉PubMed〈/a〉
    Keywords: Agriculture ; Air Pollutants ; Automobile Driving ; *Bioelectric Energy Sources ; *Biomass ; *Energy-Generating Resources ; *Ethanol ; Greenhouse Effect ; *Motor Vehicles ; Zea mays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2007-05-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gullison, Raymond E -- Frumhoff, Peter C -- Canadell, Josep G -- Field, Christopher B -- Nepstad, Daniel C -- Hayhoe, Katharine -- Avissar, Roni -- Curran, Lisa M -- Friedlingstein, Pierre -- Jones, Chris D -- Nobre, Carlos -- New York, N.Y. -- Science. 2007 May 18;316(5827):985-6. Epub 2007 May 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17495140" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Carbon ; *Climate ; *Conservation of Natural Resources ; Developing Countries ; Forestry ; Greenhouse Effect ; International Cooperation ; *Public Policy ; *Trees ; *Tropical Climate
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 23 (1992), S. 201-235 
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: At elevated atmospheric CO2 concentrations ([CO2]a), photosynthetic capacity (Amax) and root fraction (ηR, the ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible causes of this, focusing on the relative magnitudes of the effects of elevated [CO2]a on specific leaf (nm) and plant (np) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (α). In our survey of 39 studies with 35 species, we found that elevated [CO2]a led to decreased nm and np in all the studies and to increased h and α in most of the studies. The magnitudes of these changes varied with species and with experimental conditions.Based on a model that integrated [CO2]a-induced changes in leaf nitrogen into a biochemically based model of leaf photosynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (Amax will increase) when growth at increased [CO2]a leads to increases in h that are larger than decreases in nm. Photosynthesis will be downregulated (Amax will decrease) when increases in h are smaller than decreases in nm. The model suggests that photosynthetic capacity increases at elevated [CO2]a only when additional leaf mesophyll more than compensates the effects of nitrogen dilution.We considered two kinds of regulatory paradigms that could lead to varying responses of ηR to elevated [CO2]a, and compared the predictions of each with the data. A simple static model based on the functional balance concept predicts that ηR should increase when neither np nor h is very responsive to elevated [CO2]a. The quantitative and qualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts ηR from the relative sensitivities of photosynthesis and relative growth rate to elevated [CO2]a corresponds much more closely to the observations. In general, root fraction increases if the response of photosynthesis to [CO2]a is greater than that of relative growth rate.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 14 (1991), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Sunflower plants (Helianthus annuus L., cv. CGL 208) were field-grown in adjacent plots of varying resource availability. Control plants received irrigation (on a 4–5 d interval) and high levels of fertilizer nitrogen. Nutrient-stress (N-stress) plants received control levels of irrigation but no nutrient amendments and were determined to be nitrogen-limited. Water-stress (H2O-stress) plants received control levels of fertilizer nitrogen, but no irrigation after approximately 6 weeks of plant growth. Both stress treatments reduced maximum and diurnal net photosynthesis (A) but resulted in different physiological or biochemical adjustments that tended to maintain or increase A per unit of resource (nitrogen or water) in shortest supply while decreasing the ratio of A per unit of abundant resource. Nutrient-stress reduced total foliar nitrogen, foliar chlorophyll, and initial and total RuBPCase activities, thereby enhancing or preserving photosynthetic nitrogen-use efficiency (NUE), defined as the maximum A observed per unit of leaf nitrogen, relative to the control and H2O-stress treatments. In addition, N-stress reduced photosynthetic water-use efficiency (WUE), defined as the ratio of A to stomatal conductance to water vapour (g). The slope of A versus g increased with H2O-stress. In addition, sunflower plants responded to H2O-stress by accumulating foliar glucose and sucrose and by exhibiting diurnal leaf wilting, which presumably provided additional improvements in photosynthetic WUE through osmoregulation and reduction of midday radiation interception respectively. Photosynthetic NUE was decreased by H2O-stress in that control levels of total nitrogen, foliar chlorophyll, and RuBPCase activities were maintained even after mean diurnal levels of A had fallen to less than 50% of the control level. We conclude that field-grown sunflower manages a trade-off between photosynthetic WUE and NUE, increasing use efficiency of the scarce resource while decreasing use efficiency of the abundant resource.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1939
    Keywords: Chlorophyll fluorescence ; Photosynthesis ; Remote sensing ; Sunflower (Helianthus annuus) ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sudden illumination of sunflower (Helianthus annuus L. cv. CGL 208) leaves and canopies led to excess absorbed PFD and induced apparent reflectance changes in the green, red and near-infrared detectable with a remote spectroradiometer. The green shift, centered near 531 nm, was caused by reflectance changes associated with the de-epoxidation of violaxanthin to zeaxanthin via antheraxanthin and with the chloroplast thylakoid pH gradient. The red (685 nm) and near-infrared (738 nm) signals were due to quenching of chlorophyll fluorescence. Remote sensing of shifts in these spectral regions provides non-destructive information on in situ photosynthetic performance and could lead to improved techniques for remote sensing of canopy photosynthesis.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1939
    Keywords: Annual grassland ; Avena barbata CO2 ; Reproduction ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Global atmospheric CO2 is increasing at a rate of 1.5–2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO2 in a California annual grassland. Elevated CO2 led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30–35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO2 concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO2 on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discrimination. Increases in CO2 and photosynthesis resulted in more seeds per plant (30%) and taller and heavier plants (27% and 41%, respectively). Elevated CO2 also reduced seed N concentrations (9%).
    Type of Medium: Electronic Resource
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