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  • 1
    Electronic Resource
    Electronic Resource
    Assessing forest growth across southwestern Oregon under a range of current and future global change scenarios using a process model, 3-PG (2001)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 7 (2001), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: With improvements in mapping regional distributions of vegetation using satellite-derived information, there is an increasing interest in the assessment of current limitations on forest growth and in making projections of how productivity may be altered in response to changing climatic conditions and management policies. We utilised a simplified physiologically based process model (3-PG) across a 54 000 km2 mountainous region of southwestern Oregon, USA, to evaluate the degree to which maximum periodic mean annual increment (PAI) of forests could be predicted at a set of 448 forest inventory plots. The survey data were pooled into six broad forest types (coastal rain forest, interior coast range forest, mixed conifer, dry-site Douglas-fir, subalpine forest, and pine forest) and compared to the 3-PG predictions at a spatial resolution of 1 km2. We found good agreement (r2 = 0.84) between mean PAI values of forest productivity for the six forest types with those obtained from field surveys. With confidence at this broader level of integration, we then ran model simulations to evaluate the constraints imposed by (i) soil fertility under current climatic conditions, (ii) the effect of doubling monthly precipitation across the region, and (iii) a widely used climatic change scenario that involves modifications in monthly mean temperatures and precipitation, as well as a doubling in atmospheric CO2 concentrations. These analyses showed that optimum soil fertility would more than double growth, with the greatest response in the subalpine type and the least increase in the coastal rain forests. Doubling the precipitation increased productivity in the pine type (〉 50%) with reduced responses elsewhere. The climate change scenario with doubled atmospheric CO2 increased growth by 50% on average across all forest types, primarily as a result of a projected 33% increase in photosynthetic capacity. This modelling exercise indicates that, at a regional scale, a general relationship exists between simulated maximum leaf area index and maximum aboveground growth, supporting the contention that satellite-derived estimates of leaf area index may be good measures of the potential productivity of temperate evergreen forests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2001.00385.x
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  • 2
    Electronic Resource
    Electronic Resource
    Measurements of gross and net ecosystem productivity and water vapour exchange of a Pinus ponderosa ecosystem, and an evaluation of two generalized models (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 6 (2000), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Net ecosystem productivity (NEP), net primary productivity (NPP), and water vapour exchange of a mature Pinus ponderosa forest (44°30′ N, 121°37′ W) growing in a region subject to summer drought were investigated along with canopy assimilation and respiratory fluxes. This paper describes seasonal and annual variation in these factors, and the evaluation of two generalized models of carbon and water balance (PnET-II and 3-PG) with a combination of traditional measurements of NPP, respiration and water stress, and eddy covariance measurements of above-and below-canopy CO2 and water vapour exchange. The objective was to evaluate the models using two years of traditional and eddy covariance measurements, and to use the models to help interpret the relative importance of processes controlling carbon and water vapour exchange in a water-limited pine ecosystem throughout the year. PnET-II is a monthly time-step model that is driven by nitrogen availability through foliar N concentration, and 3-PG is a monthly time-step quantum-efficiency model constrained by extreme temperatures, drought, and vapour pressure deficits. Both models require few parameters and have the potential to be applied at the watershed to regional scale. There was 2/3 less rainfall in 1997 than in 1996, providing a challenge to modelling the water balance, and consequently the carbon balance, when driving the models with the two years of climate data, sequentially. Soil fertility was not a key factor in modelling processes at this site because other environmental factors limited photosynthesis and restricted projected leaf area index to ∼1.6. Seasonally, GEP and LE were overestimated in early summer and underestimated through the rest of the year. The model predictions of annual GEP, NEP and water vapour exchange were within 1–39% of flux measurements, with greater disparity in 1997 because soil water never fully recharged. The results suggest that generalized models can provide insights to constraints on productivity on an annual basis, using a minimum of site data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2000.00291.x
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  • 3
    Electronic Resource
    Electronic Resource
    The contribution of stored water to transpiration in Scots pine (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 2 (1979), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The amount of water available diurnally and annually from the storage tissues was measured in plots of Scots pine trees with four different population densities (608–3281 trees per ha) in a 40-year-old plantation in north eastern Scotland. The water storage capacity of stems, branches, and foliage was estimated from equations derived from harvested trees and measurements of relative water content. On average 64% of the water considered to be available for transpiration was in the stem sapwood and less than 5% in the phloem, cambium and foliage. Trees on the plot with the highest population density had a water storage capacity of 212 m3 ha−1 (21.2 mm), whereas those on the plot with the lowest population density had a water storage capacity of 124 m3 ha−1 (12.4 mm). The utilization of stored water in transpiration was estimated from seasonal and diurnal measurements of the relative water content of foliage and stem sapwood. The largest change in sapwood relative water content over a 2-week period was a reduction of 27% corresponding to extraction from the sapwood of 2.5 and 5.1 mm of water on the plots with the lowest and highest population densities, respectively. In rapidly changing weather conditions 1–1.5 mm day−1 could be removed from the stem sapwood alone. Since transpiration rarely exceeded 3 mm day−1, 30–50% of the transpired water was extracted from water stored in the stem sapwood over short periods. Trees on the plot with the lowest population density occasionally had slightly higher relative water contents and exhibited larger diurnal fluctuations than those on the plot with the highest population density, possibly because of differences in wood density. Sapwood water content was generally lower at times of high transpiration rate and in winter during freezing conditions. Resaturation took several months to complete during the winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1979.tb00085.x
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  • 4
    Electronic Resource
    Electronic Resource
    Sapwood water storage: its contribution to transpiration and effect upon water conductance through the stems of old-growth Douglas-fir (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 1 (1978), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Enough water is stored in the sapwood of large Douglas-fir to significantly contribute to transpiration. Sapwood water content falls through the season, causing the wood's conductivity to fall. This leads to low leafwater potentials, stomatal closure, and reduced photosynthesis by the trees.The amount of water stored in the sapwood of Douglasfir 50-60 m tall, growing in the Cascade Mountains of Oregon, was estimated periodically over two seasons from measurements of sapwood relative water content (Rs). The relationship between Rs and volume of water contained in the sapwood was determined in the laboratory, and an equation describing the variation of relative conductivity (K) with Rs was derived from the literature. Stomatal conductance (ks) and leaf water potentials were measured in the field.The relative conductivity of the sapwood was calculated from estimates of the flow rate through the tree and differences in water potential between dawn and the time of comparison. Flow rate was assumed to equal transpiration rate, calculated from the Penman-Monteith equation using measured ks values. A sixfold decrease in K during the summer was attributed to changes in Rs. The maximum observed diurnal variation in K would require a change in RS estimated at 25%.About 270 m3 ha−1 (27 mm) of water were stored in sapwood, and 75% of that was in the stemwood. Withdrawal from this store reached 1.7 mm day−1 on clear days after cloudy or rainy weather. Recharge could be almost as fast (up to 1.6 mm day−1) after rain, but was very slow if the foliage remained wet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1978.tb00754.x
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  • 5
    Electronic Resource
    Electronic Resource
    Physiological control of water flux in conifers (1975)
    Springer
    Oecologia 18 (1975), S. 1-16 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A water flux model with daily resolution is described which permits one to assess how changes in the rooting volume, amount of sapwood, leaf area and conductance properties interact to affect water uptake, internal storage, and transpiration. A root zone water compartment is defined for a particular tree on the basis of root depth, lateral extension and moisture holding characteristics of the soil. Water is taken up from different subcompartments of the root zone as a function of vertical position, soil water content, and water deficit within the sapwood. Excess water entering the root zone is channeled into runoff or seepage. The sapwood compartment of the model is restricted to the main stem of the tree and does not include sapwood in the branches or roots. The model assumes whatever water deficit is built up in the sapwood during the day will be replenished at night if the root zone water supply/capacity ratio exceeds 20%. A complex exponential equation describes the amount of water extractable from 20% to 0 capacity when no uptake is possible. The maximum change in volume of water in the sapwood of a large Douglas-fir is estimated to represent more than a 10 day supply for transpiration. Water loss through transpiration is predicted as a function of the mean daily absolute humidity deficit, leaf area, leaf conductance and daylength. Leaf conductance is controlled by predawn plant moisture stress which in turn is a function of the rooting zone water supply. The model incorporates two special constraints upon water uptake and transpiration. The first accounts for the effect of cold soil temperatures reducing the possible uptake by Douglas-fir to half at 2°C and to 0 at-2°C. The second represents a critical absolute humidity deficit sufficient to cause stomatal closure which results in leaf conductance being reduced to a minimum. The model is employed to compare trees of different sizes and those with different stomatal behavior. From this experience, it is suggested that future studies include, at a minimum, simultaneous measurements of: absolute humidity deficit, leaf area, sapwood volume and change in water content, predawn stress and leaf conductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350630
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  • 6
    Electronic Resource
    Electronic Resource
    Differences in chemical composition of plants grown at constant relative growth rates with stable mineral nutrition (1985)
    Springer
    Oecologia 66 (1985), S. 157-160 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf chemistry of a willow clone (Salix aquatica Smith) differed significantly when grown at constant relative growth rates depending upon the relative availability of nutrients and light. Concentration of amino acids and nitrate were high in plants grown with a relative surplus of nutrients. Concentrations of starch, tannin, and lignin, on the other hand, were high in plants grown with a relative surplus of carbon. Photosynthetic rates, expressed per unit leaf area, were similar when plants were grown under high light conditions, regardless of nutrient availability. Dark respiration was much higher in plants supplied with abundant nutrients than in those with a more limited supply, reflecting differences in nitrogen concentration of the tissue. The experimental approach allows plants to be grown to a standard size with differing, but highly uniform chemistry. Plants grown in such a manner may provide good experimental material to evaluate interactions between herbivores or pathogens and their hosts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379849
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  • 7
    Electronic Resource
    Electronic Resource
    Odorous urine following asparagus ingestion in man (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 382-383 
    Details
    ISSN: 1420-9071
    Keywords: Asparagus ; genetic polymorphism ; urinary odour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The production of odorous urine after the ingestion of asparagus has been shown to occur in 43% of 800 volunteers investigated. This characteristics is reproducible over a 12-month-period and has been shown to remain with individuals for virtually a lifetime. Family studies suggest that the ability to produce the odorous urine is inherited as an autosomal dominant trait.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01940418
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  • 8
    Electronic Resource
    Electronic Resource
    Estimating mean monthly incident solar radiation on horizontal and inclined slopes from mean monthly temperatures extremes (2000)
    Springer
    International journal of biometeorology 44 (2000), S. 204-211 
    Details
    ISSN: 1432-1254
    Keywords: Keywords Radiation ; Prediction ; Minimum and maximum temperature ; Slope correction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  Although satellite-borne sensors are now available to estimate cloud cover and incoming short-wave radiation across the Earth’s surface, the study of climatic variation and its impact on terrestrial and marine ecosystems involves historical analyses of data from networks of weather stations that only record extremes in temperatures and precipitation on a daily basis. Similarly, when projections are made with global atmospheric circulation models, the spatial resolution of predicted radiation is too coarse to incorporate the effects of heterogeneous topography. In this paper, we review the development and set forth a set of general equations that allow both diffuse and direct solar radiation to be estimated for each month on the basis of mean daily maximum and minimum temperatures, latitude, elevation, slope, and aspect. Adjustments for differences in slope, aspect, and elevation are made by varying the fraction of diffuse and direct solar beam radiation. To test the equations on various slopes and under different climatic conditions, we drew on high-quality radiation data recorded at a number of sites on three continents. On horizontal surfaces the set of equations predicted both direct and diffuse components of solar radiation within 1%–7% of recorded values. On slopes, estimates of monthly mean solar radiation were with 13% of observed values with a mean error of less than 2 MJ m–2day–1 over any given month.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840000073
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  • 9
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    Application of the pipe model theory to predict canopy leaf area (1982)
    Canadian Science Publishing
    Details
    Publication Date: 1982-09-01
    Description: The pipe model theory presents the idea that a unit weight of tree foliage is serviced by a specific cross-sectional area of conducting sapwood in the crown. Below the crown, a large fraction of the tree bole may be nonconducting tissue, so the sapwood area would have to be known to estimate foliage. We applied the pipe model theory to the analysis of several western coniferous species to learn whether the distribution of canopy leaf area could be accurately estimated from knowledge of the sapwood cross-sectional area at various heights, including breast height (1.37 m). Results are excellent, but taper in the conducting area must be considered when sapwood area is measured below the crown.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 10
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    Stomatal conductance, transpiration, and resistance to water uptake in a Pinussylvestris spacing experiment (1984)
    Canadian Science Publishing
    Details
    Publication Date: 1984-10-01
    Description: Stomatal conductance was measured with porometers in two plots of Pinussylvestris L. with markedly different tree spacings (plot 1, 608 stems ha−1; plot 2, 3281 stems ha−1), and hourly rates of transpiration were calculated using the Penman–Monteith equation at intervals throughout one growing season. Stomatal conductance varied little in relation to height or age of foliage. There was a linear decrease in canopy conductance with increasing water vapour pressure deficit of the air. Transpiration rates on both plots increased during the summer (maximum 0.3 mm h−1); rates on plot 1 were always lower (ca. 0.7 times) than on plot 2. Needle water potentials were similar throughout the season and only slightly lower on plot 1 than on plot 2. The mean hydraulic resistance of the trees on plot 1 was 2.4 times that on plot 2. The results support a hypothesis that considers the changes in transpiration rate, conducting cross-sectional area, canopy leaf area, water potential, and hydraulic resistance following thinning as a set of homeostatic relationships.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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