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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 64 (1985), S. 29-36 
    ISSN: 1573-5052
    Keywords: Coniferous forest ; Multi-scaled pattern ; Nearest neighbor distance ; Pattern ; Quadrat variance analysis ; Spectral analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An investigation of spatial pattern in relatively sparse Pinus ponderosa-P. Jeffreyi stands showed that a simple Poisson model of random distribution described the pattern at 5 to 50 m scales in the denser stands examined when allowance is made for inhibition between nearest neighbors. There is evidence for a clumped distribution in large quadrats for the sparsest stands, which concurs with prior work where a mixed Poisson model was fit to the data. The technique used was innovative in that it involved digitally recording tree locations from high resolution aerial photos, which allowed for the automatic application of several statistical techniques in order to determine how pattern varies with plot density and scale. Point locations were recorded for six 11.3 ha plots in three density regions of a 340 ha study area in northeastern California, USA. The inter-event distance distribution, and one- and two-dimensional power spectra were calculated, and variable quadrat analysis was performed for the data sets. The second order and spectral analyses showed no evidence of a distinctive clumped pattern at any scale, and all analyses showed that the pattern was regular at the scale of the average inter-plant distance in the denser stands. For the sparser stands, the counts in large quadrats did not fit a Poisson distribution, but were better fit by a mixed Poisson model describing aggregated pattern.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5052
    Keywords: Maryland vegetation ; Site factors ; Vegetation measurement ; Vegetation sampling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A detailed analysis of sample plots quantifying woody vegetation and environment in the Piedmont and Coastal Plain of Maryland, USA, shows (1) that sample sites must be selected according to some formal design, and (2) that binary (presence or absence) measurement of species serves equally well as continuous measurements of importance value or percent cover in identifying significant species-environment relationships. A comparison of data from a set of samples located at the discretion of the investigators with a set chosen according to a predetermined stratified random sampling plan shows that each set produces different results. The samples located at the investigators' discretion show a larger number of significant species-environment relationships, and in addition, the outcomes of many individual species-environment tests differ between the two sets of samples. Binary and continuous measurements were compared within the random stratified samples, and nearly all species showed similar environmental trends whether analyzed by continuous or binary techniques. The differences between outcomes of binary and continuous techniques are of the magnitude which can be expected from random variation. These results suggest that where an area containing great floristic variation is to be sampled to identify species-environment relationships, the best sample plan would involve many species taken according to a carefully divised random sampling plan.
    Type of Medium: Electronic Resource
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