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Community Measurements

Community Measurements. Indirect Gradient Analysis. Use Importance Values (Sum of Relative Frequency, Rel. Dominance, Rel. Density). Indirect Gradient Analysis. Develop Climax adaptation number for each species (By comparing the stands with different leading dominants).

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Community Measurements

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  1. Community Measurements

  2. Indirect Gradient Analysis • Use Importance Values (Sum of Relative Frequency, Rel. Dominance, Rel. Density)

  3. Indirect Gradient Analysis • Develop Climax adaptation number for each species (By comparing the stands with different leading dominants)

  4. Indirect Gradient Analysis • Those stands the most different are placed at either end • Those most like the extremes are placed close to them • #’s are assigned based on similarity

  5. Indirect Gradient Analysis • Use Importance Values (Sum of Relative Frequency, Rel. Dominance, Rel. Density) • Develop Climax adaptation number for each species (By comparing the stands with different leading dominants) • Continuum Index for stand = ∑Imp. Val. x Climax Adaptation # for each species found in stand • Plot the dominant species with point for each stand (Imp. Value on Y axis; Cont. Index on X)

  6. Distribution & Abundance

  7. Direct Gradient Analysis • Some figure (usually density) plotted against an environmental gradient (such as elevation)

  8. Direct Gradient Analysis • If difficulty in measuring environmental factor: • Classify species into ecological amplitude • Trees: a)mesic b)submesic c)subxeric d)xeric • Values assigned (a=0, d=3) • For each stand count individuals in each group • Then multiply value X # of individuals in that group. Sum products and divide by total # of individuals • One value for trees & tall shrubs, one for herbaceous plants, then plot values

  9. Continuum classes

  10. Possible outcomes

  11. Gradual vs. Steep (Whittaker) Great Smoky Mtns. Siskyou Mtns.

  12. Ordination • Similar to Gradient Analysis • Stands ordered according to composition and abundance, often with cluster analysis • Stands are plotted on a 2-dimensional grid • Values for each stand assigned to environmental factors are then plotted • Look to see trends of factors that correlate with the spread of the stands studied. • Stands may also be plotted geographically

  13. Similarity Index • Coefficient of Community • CC = 2Sab/(Sa+Sb) Where: Sa = # of species in sample A only Sb = # of species in sample B only Sab = # found in both samples • Same formulation as the Bray and Curtis Similarity Index (simply different terms used)

  14. Old Growth Forests - LS Index • 200m X 10m plots (or transect taken) • Count trees over 16”dbh and trees with lichen (Collema or Leptogium) Northern Hardwood Index

  15. LS index then places the stand in one of the categories seen here

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