Select this option to undertake a Detrended Correspondence Analysis using the vegan package in R.
The data set used will be your working data.
Detrended Correspondence Analysis was devised by Hill (1979) as an attempt to improve upon reciprocal averaging (RA). Two problems that occur with reciprocal averaging are termed the 'arch effect' and 'end point compression'. When the first and second axes produced by RA are plotted, it is often observed that the points are arranged in an arch, because of the quadratic relationship between the axes, rather than because of any relationship between the samples. DECORANA removes this arch by a technique termed detrending. The tendency for points at each end of the first axis to be closer together than those in the middle is removed by segmenting the axis and expanding the terminal segments and compressing those towards the centre. Whereas RA scales the axes between 0 and 100 in relation to the magnitude of the eigenvalue, DECORANA scales in units of average standard deviation of species turnover. Therefore a change of 50% in species composition occurs in about 1 standard deviation.
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