The relation between fine root density and proximity of stems in closed Douglas-fir plantations on homogenous sandy soils: implications for sampling design |
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Authors: | Olsthoorn AFM Klap JM Oude Voshaar JH |
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Institution: | (1) IBN-DLO, Institute for Forestry and Nature Research, P.O. Box 23, NL-6700 AA Wageningen, Netherlands;(2) SC-DLO, Winand Staring Centre, P.O. Box 125, NL-6700 AC Wageningen, Netherlands;(3) CPRO-DLO, Centre for Biometry Wageningen, P.O. Box 16, NL-6700 AA Wageningen, Netherlands |
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Abstract: | Studies have been carried out in two fully stocked, fast growing Douglas-fir plantations of the Dutch ACIFORN project in three
consecutive years, to obtain information on fine root densities (Olsthoorn 1991). For the present paper, data collected in
early summer 1987 were used to study the relation of fine root density and proximity to the nearest tree or the dominant tree.
A large number of samples (37 in one site and 55 in another) was collected in a small plot (10 × 11 m). Two distances were
measured at each sampling point: the distance to the nearest tree and the distance to the tree with a dominant crown above
that point. There was large variability in fine root density in the samples. Tests with different regression models showed
a distinct rooting pattern for one of the two locations. It is concluded that systematic errors in the assessment of fine
root density can arise when sampling points are chosen at a constant distance from trees. For Douglas-fir, this systematic
error could have been an overestimation of the fine root density by up to 10%. These systematic errors can be avoided easily,
using a stratified random design or a random sampling design. When trees are spaced irregularly, a grid sampling design is
also appropriate.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | fine root distribution methods Pseudotsuga menziesii sampling design spatial variability |
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