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  • 1
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Estimates of hourly transpiration from a 16–17 yr old Sitka spruce forest were calculated from the Penman-Monteith combination equation and compared with estimates from an eddy correlation/energy balance method. Canopy conductances were estimated from stomatal conductances measured using null balance diffusion porometers and took account of canopy variations of stomatal conductance and needle area index. Vertical heat fluxes were measured by the eddy correlation method; transpiration fluxes were then estimated from an energy balance of the forest. There was not a 1:1 relationship between the estimates of transpiration from the two methods. The major sources of error were concluded to be (i) difficulties of estimating the variation in stomatal conductance and leaf area through the canopy, (ii) errors in the value of total leaf area index, and (iii) errors in stomatal conductance measurements. The eddy correlation method was suggested as the more useful for future studies of the variation of forest transpiration in time or space, because the Penman-Monteith equation requires extensive biological measurements.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary As part of an investigation into the primary production of a forest the activity of fine roots was estimated by taking weekly soil cores from 24 May to 27 September in the 11 year of growth of a plantation of Picea sitchensis. Distinct maxima were found in 1) starch and soluble carbohydrate concentration in the root, mid-June, 2) root weight/soil volume, early July, and 3) root length/soil volume, late July with a second maximum in early September. However, root concentrations in the soil were the same at the end as at the start of the period and it is suggested that the fine root system of the forest had reached a dynamic equilibrium. The growth of the fine root system, from mid-May to late July is described as a continuous process; there is no indication that root activity ceases during the period of shoot elongation. Two populations of fine roots were found in the forest. In the surface horizons of the soil roots classified with a diameter 〈 0.5 mm have a greater mean diameter, more root tips per unit length and are present in greater concentrations than in the peat and mineral soil below. Higher concentrations of root were found both in regions of soil which had been disturbed by preplanting cultivation and in regions close to the tree trunk. re]19760304
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 71 (1983), S. 189-195 
    ISSN: 1573-5036
    Keywords: Roots ; Root system modelling ; Sitka spruce ; Windthrow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seven fully excavated 16 year-old root systems of Sitka spruce were analysed. All roots in excess of 1 cm diameter at their origin on the stumps were analysed, data being collected until root diameter declined to less than 0.5 cm. Root morphology and distribution was identified as a balance between systematic biological mechanisms and their disruption by environmental factors, particularly changes of soil density and soil surface contours. The biological mechanisms have been modelled and the model is capable of simulating root systems in response to a few simple input variablese.g. the number of roots originating at stumps, stem ratius, total number of roots of all ordersetc. Additionally equations have been developed to estimate the distribution of root diameter, and root weight at all distances from tree stems and a similar equation permits the estimation of tree diameter at chosen heights. These latter estimates being utilized to calculate the turning moment of stems when blown by the wind. The influence of the wind on turning moment is explored for simulated root systems of differing strength and gross morphology.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 56 (1984), S. 75-85 
    ISSN: 1573-5052
    Keywords: Inhibition ; Invasion ; Pattern ; Simulation ; Spectral analysis ; Vegetation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two-dimensional spectral analysis is a general interrogative technique for describing spatial patterns. Not only is it able to detect all possible scales of pattern which can be present in the data but it is also sensitive to directional components. Four functions are described: the autocorrelation function; the periodogram; and, the R- and Θ-spectra which respectively summarize the periodogram in terms of scale and directional components of pattern. The use of these functions is illustrated by their application to a simple wave pattern, a wave pattern with added noise, and patterns simulating competition and invasion processes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5052
    Keywords: Calluna vulgaris ; Competition ; Invasion ; Pattern ; Pteridium aquilinum ; Spectral analysis ; Vegetation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two-dimensional spectral analyses of spatial patterns are made using (i) the autocorrelation function, (ii) the periodogram, and its polar summary (iii) the R-spectrum and (iv) the Θ-spectrum. Together these give a sensitive analysis of both the complete range of scales of pattern and directional components which exist in data sets and we illustrate how the significance of observed spectral features can be assessed. We investigate the spatial pattern of Calluna vulgaris in a regenerating woodland and of Epilobium angustifolium spreading in a woodland following the thinning of trees. Evidence in the spectra is found for directional, clumping and inhibition patterns, and is discussed in relation to spectra obtained from simulations of known pattern generating processes. Hypotheses about the important biological, environmental and management influences on the structure of the communities are examined.
    Type of Medium: Electronic Resource
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