Indirect gradient analysis - Alaska Geobotany Center

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PC-Ord • PC-Ord is a relatively simple-to-use vegetation <strong>analysis</strong> package that contains several ordination methods including polar ordination, DCA, PCA, and CCA. It also contains programs for numerical classification, including dendrograms and TWINSPAN.
Summary • Oridination is based on ordering vegetation types according to their floristic similarity. It can also be used to examine the similarity of speicies distribution within samples. • The Bray and Curtis (polar ordination) method was the first indirect ordination method. It was based on simple geometric principals that showed plots in relation to each other based on their floristic similarity. • There are several ways to relate ordinations to environmental <strong>gradient</strong>s, including isoline diagrams, biplot diagrams, and correlation of the axes with environmental variables. • Numerous more modern methods of ordination have been developed in response to perceived weaknesses of the Bray and Curtis method. All of these have specific assumptions and their own weaknesses that must be recognized, and users of these methods should make sure they understand these aspects before using the methods. • PC-Ord is a good PC-based program that permits easy application of a variety of ordination methods.
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 and 40: Relating the ordination to environm
Page 41: Other ordination methods • Princi

Indirect gradient analysis - Alaska Geobotany Center

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