Can naturalness indicator values reveal habitat degradation? A test of four methodological approaches

摘要

Assessing habitat naturalness belongs to the most current issues in conservation biology. It has been recognized that plants are able to indicate the naturalness of their habitat. Thus, species may be given relative naturalness indicator values (i.e. scores on an ordinal scale), reflecting their different tolerances against habitat degradation. In the present study, our first goal was to test whether relative naturalness indicator values are able to reveal known differences in naturalness levels. Our second purpose was to compare four different methodological approaches in order to identify which is the most reliable when analyzing habitat naturalness. We compared near-natural and degraded plots on the bases of (1) unweighted plot means, (2) plot medians, (3) unweighted naturalness indicator value populations, and (4) frequency-weighted naturalness indicator value populations. We found that relative naturalness indicator values performed well in differentiating among near-natural and degraded vegetation. Unweighted mean indicator values were the most reliable, but frequency-weighted indicator value populations were nearly as efficient as unweighted means. We conclude that relative naturalness indicator values provide a simple but reliable tool for estimating habitat deterioration.