Data from: Fall prescribed burns deplete surface soil C pools more than spring burns in a young mixed-conifer forest

Wildfires burn as much as 3% of Earth’s surface annually and remove carbon
(C) stored in surface soils. Prescribed burns may offer an opportunity to
preserve soil C stocks by limiting the extent and severity of wildfires.
However, there is a limited number of days that are dry enough to conduct
prescribed burns but wet enough to prevent the unintentional spread of
fire. While prescribed burns mostly occur during the historical fire
season—late summer and fall—burning during other favorable seasons, like
spring, would facilitate forest management. Yet, it is not clear how
burning in the spring versus the fall affects soil C stocks. To assess how
burn season affects soil C dynamics, we measured bulk soil C,
mineral-associated organic C (MAOC), particulate organic C (POC),
pyrogenic organic matter (PyOM), microbial respiration, and extracellular
enzyme activity in surface soils for two years after burning young
mixed-conifer forest stands in either the fall or spring. We found that
fall burning, which tended to consume more surface fuels, immediately
combusted soil organic matter, lowering POC from 37 ± 14 to 14 ± 8.3 g C
kg-1 three days after burning. Furthermore, fall burning stimulated
microbial respiration, preventing bulk C from increasing above 43 ± 14 g C
kg-1 for two years. Spring burning did not decrease soil C, and MAOC
increased by 36%. Taken together, our results suggest that spring
prescribed burns preserved soil C stocks relative to fall burns in young
mixed-conifer forest stands.