Conservation monitoring, assessment of responses to environmental impacts, as well as elucidation of many natural ecological phenomena, requires ways of reliably assessing changes in population size over time.

Plant populations may alter in two main ways, density and areal extent, or a combination of both. Assessment of these requires ways of comparing abundance and distributional survey data from different periods.

The unbiased sampling methods used by CS are designed to allow such statistically valid comparisons to be made. Use of GIS tools for examining interpolated abundance surfaces for change also makes a quick, valid and easier to interpret procedure.

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Assessing changes in abundance by simple comparison of means between sample periods can be used, although it must be considered that the methods of estimating abundance may be influenced by phenology. Range changes can be estimated simply by comparison of frequency of occurrence of each species recorded in samples for the two time periods, and this is mostly unaffected by phenology.

Although both these methods have a role and are deployed for confirmation purposes, they cannot, of themselves, identify areas where change is occuring, especially valuable information for assessing consequences of management or development.

The interpolation vegetation mapping procedures used during survey allow the use of GIS raster tools however, and these provide readily interpretable visual outputs.

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