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  • 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry  (2)
  • Evaporation  (2)
  • Heterosis  (2)
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 95 (1993), S. 153-163 
    ISSN: 1432-1939
    Keywords: Evaporation ; Aerodynamic conductance ; Canopy conductance ; Humidity response ; Soil water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Canopy-scale evaporation rate (E) and derived surface and aerodynamic conductances for the transfer of water vapour (gs and ga, respectively) are reviewed for coniferous forests and grasslands. Despite the extremes of canopy structure, the two vegetation types have similar maximum hourly evaporation rates (E max) and maximum surface conductances (gsmax) (medians = 0.46 mm h-1 and 22 mm s-1). However, on a daily basis, median E max of coniferous forest (4.0 mm d-1) is significantly lower than that of grassland (4.6 mm d-1). Additionally, a representative value of ga for coniferous forest (200 mm s-1) is an order of magnitude more than the corresponding value for grassland (25 mm s-1). The proportional sensitivity of E, calculated by the Penman-Monteith equation, to changes in gs is 〉0.7 for coniferous forest, but as low as 0.3 for grassland. The proportional sensitivity of E to changes in ga is generally ±0.15 or less. Boundary-line relationships between gs and light and air saturation deficit (D) vary considerably. Attainment of gsmax occurs at a much lower irradiance for coniferous forest than for grassland (15 versus about 45% of full sunlight). Relationships between gs and D measured above the canopy appear to be fairly uniform for coniferous forest, but are variable for grassland. More uniform relationships may be found for surfaces with relatively small ga, like grassland, by using D at the evaporating surface (D0) as the independent variable rather than D at a reference point above the surface. An analytical expression is given for determining D0 from measurable quantities. Evaporation rate also depends on the availability of water in the root zone. Below a critical value of soil water storage, the ratio of evaporation rate to the available energy tends to decrease sharply and linearly with decreasing soil water content. At the lowest value of soil water content, this ratio declines by up to a factor of 4 from the non-soil-water-limiting plateau. Knowledge about functional rooting depth of different plant species remains rather limited. Ignorance of this important variable makes it generally difficult to obtain accurate estimates of seasonal evaporation from terrestrial ecosystems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Trees 1 (1987), S. 219-224 
    ISSN: 1432-2285
    Keywords: Larix ; Heterosis ; Photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Individual 33-year-old forest trees of the deciduous conifer speciesLarix decidua, Larix leptolepis andLarix decidua x leptolepis were investigated with respect to the phenomenon of stem heterosis in hybrid larch; the first part of this study compares the gas exchange responses of leaves. CO2 assimilation per leaf area was similar in the three larch species, but on a dry weight basis the nitrogen content of the needles and maximum CO2 assimilation rate (Amax) were slightly higher in the hybrid. This increase was accompanied by a higher protein content than in the Japanese and a lower specific leaf weight than in the European larch. All three species were similar in terms of the photosynthetic “nitrogen use” and stomatal conductance atA max. The similar slopes of the area-related steady-state responses of gas exchange against irradiance, evaporative demand and internal CO2 concentration led to similar rates of CO2 uptake under ambient conditions. The natural combinations and variability of the environmental factors also reduced the small dry weight-related difference inA max between hybrid larch and the parent species, such that all trees achieved similar daily carbon gains. Thus, the ecological significance of small interspecific differences in the metabolism of leaves has very little effect under the natural habitat conditions of a temperate climate. The second part of the study will investigate the effect of growth characteristics on the heterosis of hybrid larch.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Trees 1 (1987), S. 225-231 
    ISSN: 1432-2285
    Keywords: Larix ; Heterosis ; Growth ; Branching pattern ; Needle density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Among 33-year-old forest trees ofLarix decidua, L. leptolepis andL. decidua x leptolepis, the hybrid possessed an above-ground biomass which was three times greater, although all larches displayed similar relative distributions of biomass. At a “relative growth rate” slightly lower than in the parent species, hybrid larch achieved twice the annual carbon gain, increment in stem length and above-ground production, and its foliage-related stem growth was higher than in European (L. decidua) but similar to Japanese (L. leptolepis) larch. A similar “relative growth efficiency” and foliage-related total above-ground production in all trees did reflect the similarity of photosynthetic capacity of the hybrid found at the leaf level. While the lengths of lateral twigs on hybrid branches were intermediate between the European larch with short, and the Japanese larch with large, twigs the hybrid possessed the longest branches with the highest needle biomass. This resulted in a crown structure of the hybrid crown similar to the Japanese larch together with a high needle density on branches as in the European larch. In total, the foliage biomass per crown length was about 30% higher in hybrid larch than in both of the parent species. Thus, the high carbon input for the stem heterosis was based on a “complementation principle” of advantageous parent features at the crown level. Similar slopes of foliage against sapwood area of stem and branches did not indicate a special need for a thick hybrid stem with respect to water transport.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 121 (1995), S. 79-87 
    ISSN: 1573-5052
    Keywords: Canopy ; Evaporation ; Leaf area index ; Scaling ; Surface conductance ; Stomata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examine conductances for evaporation from both vegetation and soil in response to environmental variables. Data from a vertically-structured pristine forest of Nothofagus are presented as an example of the effects of biodiversity on the scaling of conductances between tiers of plant organisation. Available data sets of maximum leaf stomatal conductances (g lmax ) and bulk vegetation surface conductances (G smax ) are compared. Overall, the ratio G smax /g lmax is consistently close to 3 for seven major vegetation types of diverse structure. An analytical model accounts for this close relationship, and in particular how G smax is conservative against changes in leaf area index because of the compensating decrease in plant canopy transpiration and increase in soil evaporation as leaf area index diminishes. The model is also successfully tested by comparison with canopy conductances of emergent trees measured in the Nothofagus forest. The constraint of vegetation surface conductance and evaporation via environmental regulation by irradiance, air saturation deficit and root zone water supply are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2020-12-09
    Description: Climate change negotiations aim to reduce net greenhouse-gas emissions by encouraging direct reductions of emissions and crediting countries for their terrestrial greenhouse-gas sinks. Ecosystem carbon dioxide uptake has offset nearly 10% of Europe’s fossil fuel emissions, but not all of this may be creditable under the rules of the Kyoto Protocol. Although this treaty recognizes the importance of methane and nitrous oxide emissions, scientific research has largely focused on carbon dioxide. Here we review recent estimates of European carbon dioxide, methane and nitrous oxide fluxes between 2000 and 2005, using both top-down estimates based on atmospheric observations and bottom-up estimates derived from ground-based measurements. Both methods yield similar fluxes of greenhouse gases, suggesting that methane emissions from feedstock and nitrous oxide emissions from arable agriculture are fully compensated for by the carbon dioxide sink provided by forests and grasslands. As a result, the balance for all greenhouse gases across Europe’s terrestrial biosphere is near neutral, despite carbon sequestration in forests and grasslands. The trend towards more intensive agriculture and logging is likely to make Europe’s land surface a significant source of greenhouse gases. The development of land management policies which aim to reduce greenhouse-gas emissions should be a priority.
    Description: Published
    Description: 842-850
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: carbon budget ; carbon dioxide ; methane ; greenhouse gas emission ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2021-01-11
    Description: Globally, terrestrial ecosystems have absorbed about 30% of anthropogenic greenhouse gas emissions over the period 2000–2007 and inter-hemispheric gradients indicate that a significant fraction of terrestrial carbon sequestration must be north of the Equator. We present a compilation of the CO2, CO, CH4 and N2O balances of Europe following a dual constraint approach in which (1) a landbased balance derived mainly from ecosystem carbon inventories and (2) a land-based balance derived from flux measurements are compared to (3) the atmospheric data-based balance derived from inversions constrained by measurements of atmospheric GHG (greenhouse gas) concentrations. Good agreement between the GHG balances based on fluxes (1294±545 Tg C in CO2-eq yr−1), inventories (1299±200 Tg C in CO2-eq yr−1) and inversions (1210±405 Tg C in CO2-eq yr−1) increases our confidence that the processes underlying the European GHG budget are well understood and reasonably sampled. However, the uncertainty remains large and largely lacks formal estimates. Given that European net land to atmosphere exchanges are determined by a few dominant fluxes, the uncertainty of these key components needs to be formally estimated before efforts could be made to reduce the overall uncertainty. The net land-to-atmosphere flux is a net source for CO2, CO, CH4 and N2O, because the anthropogenic emissions by far exceed the biogenic sink strength. The dual-constraint approach confirmed that the European biogenic sink removes as much as 205±72 Tg C yr−1 from fossil fuel burning from the atmosphere. However, This C is being sequestered in both terrestrial and inland aquatic ecosystems. If the C-cost for ecosystem management is taken into account, the net uptake of ecosystems is estimated to decrease by 45% but still indicates substantial C-sequestration. However, when the balance is extended from CO2 towards the main GHGs, C-uptake by terrestrial and aquatic ecosystems is offset by emissions of non-CO2 GHGs. As such, the European ecosystems are unlikely to contribute to mitigating the effects of climate change.
    Description: Published
    Description: 3357–3380
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: restricted
    Keywords: carbon dioxide ; methane ; soil ; ecosystems ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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