Detrended Correspondence Analysis

method
Detrended Correspondence Analysis (DCA) is an extension of CA that aims to avoid the arch effect in the resulting ordination.
Published

January 26, 2024

Modified

January 26, 2024

Description

Detrended Correspondence Analysis (DCA) is an extension of CA designed to reduce the arch-artefact. DCA detrends the data by removing the long gradients present in the data, allowing for more accurate representation of ecological patterns.

The length of the first DCA axis (in SD units) is related to the heterogeneity/homogeneity of the dataset, and can be used to decide whether data should be analysed by linear (axis shorter than 3 SD) or unimodal (axis longer than 4 SD) ordination methods.

Example

wetlands <- readRDS("wetlands.rds")
library(vegan)
library(vegtable)

# Reclasify abundance
wetlands$obs$abund <- cut(wetlands$obs$cover_perc,
        breaks = c(0, 25, 50, 100), labels = FALSE)
wetlands$cross2 <- crosstable(abund ~ taxon_code + plot_id,
        FUN = max, data = wetlands$obs,
        na_to_zero = TRUE,
        as_matrix = TRUE)

dca_ord <- decorana(wetlands$cross2)
plot(dca_ord)

Alternative functions

  • vegan::decorana()

Further References