Download presentation

Presentation is loading. Please wait.

Published byPatrick Armstrong Modified over 3 years ago

1
**Managing Dimensionality (but not acronyms) PCA, CA, RDA, CCA, MDS, NMDS, DCA, DCCA, pRDA, pCCA**

2
Type of Data Matrix

3
**Ordination Techniques**

Linear methods Weighted averaging unconstrained Principal Components Analysis (PCA) Correspondence Analysis (CA) constrained Redundancy Analysis (RDA) Canonical Correspondence Analysis (CCA)

4
**Models of Species Response**

There are (at least) two models:- Linear - species increase or decrease along the environmental gradient Unimodal - species rise to a peak somewhere along the environmental gradient and then fall again

5
A Theoretical Model

6
Linear

7
Unimodal

8
**Alpha and Beta Diversity**

alpha diversity is the diversity of a community (either measured in terms of a diversity index or species richness) beta diversity (also known as ‘species turnover’ or ‘differentiation diversity’) is the rate of change in species composition from one community to another along gradients; gamma diversity is the diversity of a region or a landscape.

9
A Short Coenocline

10
A Long Coenocline

11
**Inferring Gradients from Species (or Attribute) Data**

12
**Indirect Gradient Analysis**

Environmental gradients are inferred from species data alone Three methods: Principal Component Analysis - linear model Correspondence Analysis - unimodal model Detrended CA - modified unimodal model

13
PCA - linear model

14
PCA - linear model

15
**Terschelling Dune Data**

16
**PCA gradient - site plot**

17
**PCA gradient - site/species biplot**

standard biodynamic & hobby nature

18
Reciprocal Averaging Site A B C D E F Species Prunus serotina Tilia americana Acer saccharum Quercus velutina Juglans nigra

19
Reciprocal Averaging Site A B C D E F Species Score Species Iteration Prunus serotina Tilia americana Acer saccharum Quercus velutina Juglans nigra Iteration Site Score

20
Reciprocal Averaging Site A B C D E F Species Score Species Iteration Prunus serotina Tilia americana Acer saccharum Quercus velutina Juglans nigra Iteration Site Score

21
Reciprocal Averaging Site A B C D E F Species Score Species Iteration Prunus serotina Tilia americana Acer saccharum Quercus velutina Juglans nigra Iteration Site Score

22
Reciprocal Averaging Site A B C D E F Species Score Species Iteration Prunus serotina Tilia americana Acer saccharum Quercus velutina Juglans nigra Iteration Site Score

23
**Reordered Sites and Species**

Site A C E B D F Species Species Score Quercus velutina Prunus serotina Juglans nigra Tilia americana Acer saccharum Site Score

24
**Arches - Artifact or Feature?**

25
**The Arch Effect What is it? Why does it happen?**

What should we do about it?

26
**From Alexandria to Suez**

27
**CA - with arch effect (sites)**

28
**CA - with arch effect (species)**

29
Long Gradients A B C D

30
**Gradient End Compression**

31
**CA - with arch effect (species)**

32
**CA - with arch effect (sites)**

33
**Detrending by Segments**

34
**DCA - modified unimodal**

35
**Making Effective Use of Environmental Variables**

36
**Direct Gradient Analysis**

Environmental gradients are constructed from the relationship between species environmental variables Three methods: Redundancy Analysis - linear model Canonical (or Constrained) Correspondence Analysis - unimodal model Detrended CCA - modified unimodal model

37
**CCA - site/species joint plot**

38
**CCA - species/environment biplot**

39
**Removing the Effect of Nuisance Variables**

40
**Partial Analyses Remove the effect of covariates**

variables that we can measure but which are of no interest e.g. block effects, start values, etc. Carry out the gradient analysis on what is left of the variation after removing the effect of the covariates.

Similar presentations

Presentation is loading. Please wait....

OK

The basics for simulations

The basics for simulations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on single phase and three phase dual converter kit Ppt on pierre de fermat Ppt on structure of chromosomes in eukaryotes Ppt on fdi retail in india Ppt on water scarcity solutions Decoding in reading ppt on ipad Ppt on indian culture vs western culture Ppt on power quality problems Ppt on conceptual art photography Ppt on asian continent pictures