Indirect gradient analysis - Alaska Geobotany Center

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Relating the ordination to environmental factors: Combining classified units with biplot diagram and correlated axes • Plots are grouped into vegetation classes (colored ellipses). • X an Y axes have been correlated with environmental data. X axis is most strongly correlated with a suite of variables related to soil moisture. The Y axis is correlated with a suite of variables most strongly related to soil pH. Walker et al. 1994 • The arrows in the center of the diagram form a biplot diagram, that shows the strength and direction of correlation of the three environmental variables most strongly correlated with the species data. • This ordination uses detrended correspondence analysis (DCA).
Other ordination methods • Principal components analysis (PCA) (Orloci 1966) • Detrended correspondence analysis (DCA) (Hill 1979) • Canonical correspondence analysis (CCA) (ter Braak 1986) • Nonmetric multidimensional scaling (NMDS) (Minchin 1987) NMDS appears to the current method in vogue, but software packages allow user to test a variety of methods fairly easily. All these are highly mathematical. Users should be aware of the assumptions inherent in each method and use with caution.
Page 1 and 2: Lesson 18 Ordination II: Indirect g
Page 3 and 4: Vegetation Ecosystem Environmental
Page 5 and 6: Indirect gradient analysis • “I
Page 7 and 8: Plot ordinations vs. species ordina
Page 9 and 10: 1-, 2-, and 3-dimensional plot ordi
Page 11 and 12: Species ordination Species ordinati
Page 13 and 14: Relating the plot ordination to env
Page 15 and 16: Polar ordination • Developed by B
Page 17 and 18: Steps in calculation of the ordinat
Page 19 and 20: Jaccard s and Sorenson s similarity
Page 21 and 22: Similarity and dissimilarity for pl
Page 23 and 24: Step 2. Matrices of similarities an
Page 25 and 26: Calculation of x values along the 1
Page 27 and 28: Geometric determination of plots al
Page 29 and 30: Step 4. Define the second axis and
Page 31 and 32: Plotting the ordination Bray and Cu
Page 33 and 34: Polar ordination weaknesses and adv
Page 35 and 36: Example of isoline diagrams from Ba
Page 37 and 38: Example of Biplot Diagram from Anja
Page 39: Relating the ordination to environm
Page 43 and 44: Summary • Oridination is based on

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