1 research outputs found
Impact of Forestry on Total and Methyl-Mercury in Surface Waters: Distinguishing Effects of Logging and Site Preparation
Forestry operations can increase
the export of mercury (both total
and methyl) to surface waters. However, little is known about the
relative contribution of different forestry practices. We address
this question using a paired-catchment study that distinguishes the
effects of site preparation from the antecedent logging. Runoff water
from three catchments, two harvested and one untreated control, was
sampled biweekly during one year prior to logging, two years after
logging, and three years after site preparation. The logging alone
did not significantly increase the concentrations of either total
or methyl-mercury in runoff, but export increased by 50–70%
in one of the harvested catchments as a consequence of increased runoff
volume. The combined effects of logging and site preparation increased
total and methyl-mercury concentrations by 30–50% relative
to preharvest conditions in both treated catchments. The more pronounced
concentration effect after site preparation compared to logging could
be related to site preparation being conducted during summer. This
caused more soil disturbance than logging, which was done during winter
with snow covering the ground. The results suggest that the cumulative
impact of forest harvest on catchment mercury outputs depends on when
and how forestry operations are implemented