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  • 1
    Electronic Resource
    Electronic Resource
    Effects of elevated CO2 and increased nitrogen deposition on photosynthesis and growth of understory plants in spruce model ecosystems (1996)
    Springer
    Oecologia 106 (1996), S. 172-180 
    Details
    ISSN: 1432-1939
    Keywords: Carbon dioxide enrichment ; Forest ecology ; Light climate ; Nitrogen deposition ; Shade tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the effects of atmospheric CO2 enrichment (280, 420 and 560 μl CO2 l−1) and increased N deposition (0,30 and 90 kg ha−1 year−1) on the spruce-forest understory species Oxalis acetosella, Homogyne alpina and Rubus hirtus. Clones of these species formed the ground cover in nine 0.7 m2 model ecosystems with 5-year-old Picea abies trees (leaf area index of approx 2.2). Communities grew on natural forest soil in a simulated montane climate. Independently of N deposition, the rate of light-saturated net photosynthesis of leaves grown and measured at 420 μl CO2 l−1 was higher in Oxalis and in Homogyne, but was not significantly different in Rubus compared to leaves grown and measured at the pre-industrial CO2 concentration of 280 μl l−1. Remarkably, further CO2 enrichment to 560 μl l−1 caused no additional increase of CO2 uptake. With increasing CO2 supply concentrations of non-structural carbohydrates in leaves increased and N concentrations decreased in all species, whereas N deposition had no significant effect on these traits. Above-ground biomass and leaf area production were not significantly affected by elevated CO2 in the more vigorously growing species O. acetosella and R. hirtus, but the “slow growing” H. alpina produced almost twice as much biomass and 50% more leaf area per plant under 420 μl CO2 l−1 compared to 280 μl l−1 (again no further stimulation at 560 μl l−1). In contrast, increased N addition stimulated growth in Oxalis and Rubus but had no effect on Homogyne. In Oxalis (only) biomass per plant was positively correlated with microhabitat quantum flux density at low CO2, but not at high CO2 indicating carbon saturation. On the other hand, the less shade-tolerant Homogyne profited from CO2 enrichment at all understory light levels facilitating its spread into more shady micro-habitats under elevated CO2. These species-specific responses to CO2 and N deposition will affect community structure. The non-linear responses to elevated CO2 of several of the traits studied here suggest that the largest responses to rising atmospheric CO2 are under way now or have already occurred and possible future responses to further increases in CO2 concentration are likely to be much smaller in these understory species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328596
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf carbohydrate responses to CO2 enrichment at the top of a tropical forest (1998)
    Springer
    Oecologia 116 (1998), S. 18-25 
    Details
    ISSN: 1432-1939
    Keywords: Key words: Anacardium ; Cecropia ; Ficus ; Elevated CO2 ; Light climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The accumulation of non-structural leaf carbohydrates is one of the most consistent plant responses to elevated CO2. It has been found in both fast-and slow-growing plants and is largely independent of the duration of exposure. Changes in leaf quality are thus to be expected, irrespective of other plant responses to atmospheric CO2 enrichment. However, there is no experimental evidence from tropical forests, the biome with the largest biomass carbon pool. Here we report in situ mesophyll responses of mature tropical trees to a doubling of CO2. Individually CO2-enriched leaves on 25 to 35-m-tall forest trees living at 26–35°C can be assumed to experience little sink limitation, and so, may be expected to exhibit no or very little carbohydrate accumulation. We tested this hypothesis using the leaf cup method on leaves accessible via the canopy crane of the Smithsonian Tropical Research Institute in a semi-deciduous tropical forest in Panamá. We also investigated the influence of the leaf-specific light regime, another possible environmental determinant of leaf carbon gain and mobile leaf carbohydrates. Total non-structural carbohydrates (TNC) reached a new steady state concentration after less than 4 days of exposure to twice ambient CO2 concentration. Against expectation, all four tree species investigated (Anacardium excelsum, Cecropia longipes, C. peltata, Ficus insipida) accumulated significant amounts of TNC (+41 to +61%) under elevated CO2. The effect was stronger at the end of the daylight period (except for Ficus), but was still significant in all four species at the end of the dark period. In contrast, neither artificial nor natural shading affected leaf TNC. Taken together, these observations suggest that TNC accumulation reflects a mesophyll-bound tissue response specific to elevated CO2, presumably unrelated to sink limitations. Thus, leaves of tropical forests seem not to be an exception, and will most likely contain more non-structural carbohydrates in a CO2-rich world.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013821
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of elevated CO2 on canopy development and red:far-red ratios in two-storied stands ofRicinus communis (1993)
    Springer
    Oecologia 94 (1993), S. 510-515 
    Details
    ISSN: 1432-1939
    Keywords: CO2 enrichment ; Light climate ; Leaf area index ; R:FR ratio ; Radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to differential responses of overstory and understory plants or plant parts. In the long term, seedling recruitment, competition, and thus population or community structure may be affected. Aside from the possible differential direct effects of elevated CO2 on photosynthesis and growth, both the quantity and quality of the light below the overstory canopy could be indirectly affected by CO2-induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order to explore such possible interactions, we compared canopy leaf area development, canopy light extinction and the quality of light beneath overstory leaves of two-storied monospecific stands ofRicinus communis exposed to ambient (340 μl l−1) and elevated (610 μl l−1) CO2. Plants in each stand were grown in a common soil as closed “artificial ecosystems” with a ground area of 6.7 m2. LAI of overstory plants in all ecosystems more than doubled during the experiment but was not different between CO2 treatments at the end. As a consequence, extinction of photosynthetically active radiation (PAR) was also not altered. However, under elevated CO2 the red to far-red ratio (R:FR) measured beneath overstory leaves was 10% lower than in ecosystems treated with ambient CO2. This reduction was associated with increased thickness of palisade layers of overstory leaves and appears to be a plausible explanation for the specific enhancement of stem elongation of understory plants (without a corresponding biomass response) under elevated CO2. CO2 enrichment led to increased biomass of overstory plants (mainly stem biomass) but had no effect on understory biomass. The results of this study raise the possibility of an important indirect effect of elevated CO2 at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio beneath overstory canopies may affect understory plant development independently of the effects of PAR extinction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566966
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    Paper (German National Licenses)
    Fulltext
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