This leads on to the issue of scale which is well
documented by Anderson (1995) who considers
why soil macrofauna, although important in plant
growth, cannot be linked reliably to plant productivity
as defined by yield. His four main reasons
were: (1) that agricultural management practices
such as tillage, fertiliser usage and irrigation transcend
the effects of the biological processes on
plant growth; (2) unless soil properties affected by
soil macrofauna are limiting plant growth, their
effects may not be quantified by yield measurements
(Clements et al., 1991); (3) the effects of soil
macrofauna, which are active for short periods of
time, are often obliterated by processes operating
over longer time scales; and (4) finally, yield is
measured at a spatial and temporal scale (over 1
ha and yearly) inappropriate to the activity of soil
macrofauna which operate over several metres
and in short-term events (weeks to months) (Anderson,
1995). To reliably link soil macrofauna
with soil processes it requires researchers to define
the temporal and spatial scales at which soil
macrofauna operate.