properties were tested with ANCOVA. Data were
log (x + 1) transformed prior to regression analysis
where necessary to linearize the relationships.
The total amounts of soil nutrients excavated,
deposited, and net transported to the surface for
each day were calculated by multiplying soil
nutrient concentrations by their corresponding soil
amounts. The amounts of soil and nutrients transported
per unit area were obtained by multiplying
the mean amount of transported nutrients per
burrow or burrow mimic by burrow density. Soil
turnover rates through crab burrowing were also
calculated, which are here defined as the total
amount of soil transported, that is, excavation plus
deposition, by crabs per unit area per day (compare
Gutierrez and others 2006).
Within the top 30 cm of soil, soil mass per m2
was determined by multiplying mean bulk density
(for a depth of 0–30 cm) by volume (that is,
0.3 m3). The soil C stock was calculated by multiplying
soil C concentration by soil mass of 0.3 m3.
The calculation methods for TN and TOC stocks
were similar to those for TC stocks. The turnover
times of soil and nutrients, defined as the time required
for crabs to complete a turnover of all the
soil or nutrients for the top 30 cm soil, were calculated
by dividing the total soil mass, TC, TN, or
TOC stocks by corresponding turnover rates. All
analyses were performed using a statistical package
of Statistica (Version 6.0, StatSoft). All the results of
statistic analyses are given in the supplemental
Appendices (Tables A2–A7) for this manuscript