Data from: High-severity wildfire leads to multi-decadal impacts on soil biogeochemistry in mixed-conifer forests

During the past century, systematic wildfire suppression has decreased
fire frequency and increased fire severity in the western United States of
America. While this has resulted in large ecological changes aboveground
such as altered tree species composition and increased forest density,
little is known about the long-term, belowground implications of altered,
ecologically novel fire regimes, especially on soil biological processes.
To better understand the long-term implications of ecologically novel,
high-severity fire, we used a 44-y high-severity fire chronosequence in
the Sierra Nevada where forests were historically adapted to frequent,
low-severity fire, but were fire suppressed for at least 70 years.
High-severity fire in the Sierra Nevada resulted in a long-term (44+ y)
decrease (>50%, p < 0.05) in soil extracellular enzyme
activities, basal microbial respiration (56-72%, p < 0.05), and
organic carbon (>50%, p < 0.05) in the upper 5 cm compared
to sites that had not been burned for at least 115 y. However, nitrogen
(N) processes were only affected in the most-recent fire site (4 y
post-fire). Net nitrification increased by over 600% in the most recent
fire site (p < 0.001), but returned to similar levels as the
unburned control in the 13-y site. Contrary to previous studies, we did
not find a consistent effect of plant cover type on soil biogeochemical
processes in mid-successional (10-50 y) forest soils. Rather, the 44-y
reduction in soil organic carbon (C) quantity correlated positively with
dampened C cycling processes. Our results show the drastic and long-term
implication of ecologically novel, high-severity fire on soil
biogeochemistry and underscore the need for long-term fire ecological
experiments.