Data from: Wildfire-induced losses of soil particulate and mineral-associated organic carbon persist for over four years in a chaparral ecosystem

<p>Wildfires are increasing in frequency and severity with changes in the climate. Increases in fire activity may lower soil carbon (C) stocks if photosynthetic C inputs are outpaced by microbial decomposition in burned ecosystems. However, fires may preferentially deplete particulate organic carbon (POC, which is more susceptible to microbial decomposition) over mineral-associated organic carbon (MAOC, which is protected from decomposers), potentially slowing microbial C losses after wildfires. Yet it remains unclear how plants, microorganisms, and soil organic matter pools interact to control the fate of C after wildfires. To assess how wildfires affect the persistence of soil C, we measured POC, MAOC, pyrogenic organic C, plant cover, extracellular enzyme activity (EEA), soil microbial abundance, and microbial community composition 17 days, 1, 3, and 4 years after the Holy Fire burned 94 km2 of a fire-adapted chaparral. We found that the fire immediately decreased POC by 50% (from 50.9 ± 20.5 to 25.5 ± 5.67 µg C g-1) and MAOC by 33% (from 9.25 ± 0.87 to 6.31 ± 0.92 µg C g-1), consistent with our hypothesis that MAOC would be less vulnerable to loss than POC. POC further decreased by another 38% by 1 year post-fire, likely as a result of increased microbial access to this C given increases in microbial abundance and EEA. Between one and four years after the fire, the percent cover of the dominant shrub (Arctostaphylos glandulosa) increased from 3.9 ± 1.6 % to 16 ± 5.4 % (compared to 58 ± 4.6 % in unburned control plots), marking the end of the decreasing trend in soil C. However, soil C stocks did not increase during this time, likely because plant C inputs did not meet microbial demand for C, a finding consistent with the enrichment in soil δ13C as microbes would have preferentially metabolized δ12C. As global change increases wildfire frequency and severity, C volatilization and decomposition may outpace the recovery of plant C inputs during the first four years after fire, slowing the recovery of soil C.</p>