Vegetation Report - California Native Plant Society

Dataset – 165 surveys/6 variables
A significant Mantel Test statistic (p=0.007) for all the combined surveys (165 surveys) with one
quantitative variable and five categorical variables indicates a correspondence between the
species patterns and environmental variables (r=0.11). A significant (randomization test
p=0.04), three-dimensional NMS solution was interpreted with a final stress of 25.68, after
verifying consistency among several NMS solutions. The proportion of variance explained along
axis 1 of the NMS ordination was 28%, while axis 2 represented an additional 26%. Three axes
cumulatively represented 74% of the variance within the dataset. Though categorical variables
are useful as overlays on the ordination diagram, Species richness was the only quantitatively
interpretable variable for this full set of plots.
Species richness had a significant correlation along axis 3 (r = 0.463), (Figure 10). This pattern
of species richness was similar to those obtained using other PC-ORD analysis tools, including
Principal Component Analysis (PCA) and Detrended Correspondence Analysis (DCA), and was
consistently significant throughout the different data sets analyzed. Acacia greggii / Eriogonum
davidsonii, Lepidospartum / mixed ephemeral annuals, Lepidospartum squamatum–Eriodictyon
trichocalyx–Hesperoyucca whipplei and Encelia actoni Associations were among the most
species-rich habitats while Lepidospartum squamatum–Artemisia californica and Lepidospartum
squamatum–Eriogonum fasciculatum were less species-rich.
Other visual interpretations of the ordination diagram include clustering of stands within certain
associations. For example, see the Lepidospartum squamatum–Eriogonum fasciculatum
association in the lower central area, Encelia actoni in the upper right, Acacia greggii /
Eriogonum davidsonii along the upper edge, Lepidospartum squamatum / desert ephemeral
annuals along the right edge, and the Lepidospartum squamatum / Baccharis salicifolius
association along the left edge of the diagram.
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