The influence of charcoal on biotic processes in soils remains poorly
understood. Charcoal is a natural product of wildfires that burned
on a historic return interval of not, vert, similar100 years in Scots
pine (Pinus sylvestris L.) forests of northern Sweden. Fire suppression
and changes in forest stand management have resulted in a lack of
charcoal production in these ecosystems. It is thought that charcoal
may alter N mineralization and nitrification rates, however, previous
studies have not been conclusive. Replicated field studies were conducted
at three late-succession field sites in northern Sweden and supporting
laboratory incubations were conducted using soil humus collected
from these sites. We used activated carbon (AC), as a surrogate for
natural-occurring fire-produced charcoal. Two rates of AC (0 and
2000 kg ha?1), and glycine (0 and 100 kg N as glycine ha?1) were
applied in factorial combination to field microplots in a randomized
complete block pattern. Net nitrification, N mineralization, and
free phenol concentrations were measured using ionic and non-ionic
resin capsules, respectively. These same treatments and also two
rates of birch leaf litter (0 and 1000 kg ha?1) were applied in a
laboratory incubation and soils from this incubation were extracted
with KCl and analyzed for NH4+ and NO3?. Nitrification rates increased
with AC amendments in laboratory incubations, but this was not supported
by field studies. Ammonification rates, as measured by NH4+ accumulation
on ionic resins, were increased considerably by glycine applications,
but some NH4+ was apparently lost to surface sorption to the AC.
Phenolic accumulation on non-ionic resin capsules was significantly
reduced by AC amendments. We conclude that charcoal exhibits important
characteristics that affect regulating steps in the transformation
and cycling of N.
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