subgrids, duplicate area integrated samples were
the uncertainty due to the fact that only about 10%
prepared in a manner identical to that described
of a subgrid was included in any one area inte-
above, except that the sampled area was offset
grated sample. All samples were returned to the
from the initial one as shown for each of the se-
processing area in plastic Ziploc bags in a cooler.
lected subgrids in Figure 4. This was done to assess
Sample storage and processing
Soil samples were kept cold and in the dark
until processed. Processing was conducted
either the same day soils were collected or the
20 cm
Sampling Path for
morning following collection the previous
Sub-grid Sample
afternoon. Soil samples varied somewhat in
moisture content and texture from location to
location. Some soils were quite dry and con-
sisted mainly of sands and gravels, while
others had a much greater level of moisture
67 cm
and had a much greater organic content.
Individual soil samples in Ziploc bags were
shaken and kneaded and then emptied into
aluminum pans. Soils were further homog-
enized by breaking up clumps with gloved
hands and stirring. Small stones and any other
debris were removed, samples were coned
and quartered, and 20-g subsamples were
weighed into 125-mL plastic wide-mouth
bottles for extraction with acetone. For the
wheel samples, used to assess short-range
3 meters
heterogeneity, samples were processed in an
identical manner to that described elsewhere
Figure 6. Sampling path for obtaining "area-integrated"
samples.
(Jenkins et al. 1996) and duplicate subsamples
Figure 7. Subgrid sampling path and sample collection.
5
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