ABSTRACT
The causes for forest soil variability are many. Spatial variability is a function of bedrock
type and parent material, climate, tree species composition and understory vegetation,
disturbances (e.g., harvesting, fire, windthrow), and forest management activities (e.g., site
preparation, thinning, pruning, fertilization, vegetation management). For example, a second
generation 50-year-old Radiata pine plantation grown on plowed alluvial sands in Australia
would have lower spatial variability compared to mixed hardwoods developed from a
shallow rocky till of the Precambrian (Canadian) Shield after harvest. The mixed hardwoods
would likely show high variability in forest floor properties such as forest floor thickness due
to tree fall (Beatty and Stone 1986; Clinton and Baker 2000) and the influence of different
tree species (Finzi et al. 1998; Dijkstra and Smits 2002). Moreover, the fact that the soil is
plowed in the pine plantation would likely reduce some of the soil variability that could have
been created by the previous plantation (e.g., changes in soil properties when sampling away
from the stem). In the mineral soil, it would be more difficult to assess nutrient pools
compared to the pine plantation because of the problem of measuring bulk density and
percentage of coarse fragments in the rocky till (Kulmatiski et al. 2003). It would also be
more problematic to develop a replicated sampling scheme by depth in the natural forest
because horizon thickness across the landscape evolves as a continuum with complex spatial
patterns (e.g., Ae pockets along old root channels and thick FH material in pits).
