It is often impractical to describe the species composition (or
floristics) of a site. Hence a sample is collected to obtain
a subset of data that is assumed to represent the entire site or
population.
Sampling gives estimates of true population values and each
independent sample will give a different estimate. Variation among
estimates is a result of the following:
 The heterogeneity of the population being sampled or arrangement
of individuals within it.
Vegetation is rarely homogeneous. Usually there is a diversity
of species  some may be abundant, some rare. Also, the plants
may be distributed in a variety of spatial patterns (e.g. clumped)
due to random historical events or smallscale landscape features.
In addition, there may be considerable variation over time in
the distribution and abundance of some species.
 Sample design (i.e. number of plots, size, shape and
placement of sampling plots).
Sampling design is essential in determining the efficiency of
sampling, the value of the data and which statistical models may
be applied during data analysis.
 The interaction between these two factors.
Sampling methods and Sampling
criteria will provide you with further information.
