64 Pedodiversity
irregularity over time, high levels of spatial variability uncorrelated to
observable environmental controls, and divergent evolution have long been
well known in pedology and geomorphology. Earlier work (Phillips 1999,
2006a) explicitly and formally made those connections, as well as suggesting
analytical methods appropriate for fi eld-based sciences.
As an example, consider small local variations (i.e., small joints) in
the bedrock forming the parent material for a forest soil. Plant roots enter
these joints and enlarge them by focusing water fl ow and biological activity,
facilitating weathering. These become locally deeper pockets of soil, which
are preferentially exploited by tree roots, further deepening the soil and ...