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CADDIS Volume 4: Data Analysis

Predicting Environmental Conditions from Biological Observations (PECBO) Appendix

Overview

Taxon-environment relationships estimated from local data can potentially provide more accurate environmental inferences than the regional-scale relationships provided in the CADDIS database. In this section, different statistical methods for estimating taxon-environment relationships are presented. More extensive details on each of these methods can be found in Yuan (2006).

Before computing taxon-environment relationships, it is important to consider whether you have sufficient data.

The simplest approaches for estimating taxon-environment relationships represent the entire relationship using a single value. This single value can quantify the average conditions that are preferred by a taxon (i.e., the taxon's central tendencies), or it can quantify the limiting environment conditions under which a taxon can persist.

Methods that estimate the entire taxon-environment relationship (rather than a single value) are somewhat more involved, requiring that one solve a regression equation that relates taxon occurrences or abundances to different values of one or more environmental variables. However, once taxon-environment relationships are estimated, one can usually develop more accurate biological inferences.

Two regression approaches are common:

When applying any regression approach, one must consider the following questions:

When entire taxon-environment relationships are available, they can be used to classify taxa into broad categories (e.g., tolerant or intolerant to elevated fine sediments); these classifications can be useful for building biological metrics. Placing taxa into tolerance categories provides guidance on classification of taxa tolerances.

Once taxon-environment relationships have been estimated, different inference methods can be applied to estimate environmental conditions at sites using biological observations.

References

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