Fire decreases soil respiration and its components in terrestrial ecosystems

The impact of fire on aboveground biomass has significant consequences on
soil carbon (C) dynamics, which is essential in predicting the global C
budget during the Anthropocene. However, there is considerable
spatiotemporal variability in the directions and magnitudes of fire
effects on soil respiration, and the drivers associated with these effects
are not well understood. Here, we conducted a global meta-analysis of 1327
individual observations from 170 studies to determine the extent to which
fire influenced soil total respiration (Rs), heterotrophic respiration
(Rh), and autotrophic respiration (Ra). We found fires reduced Rs, Rh, and
Ra, with an average effect of -11.0%, -17.5%, and -40.6%, compared to
unburnt sites. Specifically, wildfires significantly
reduced Rsand Rh (-20.4% and -25.0%,
respectively), and prescribed fire significantly decreased Ra (-74.8%).
The influences of fire on Rs and its components were moderated by
fire severity, season, type, climate zones, and biomes. After several
years from the time of the fire, the negative effects of fire
on Rs diminished and then recovered to a state not
significantly different from unburnt sites; Rh exhibited a similar but
decayed temporal response. Similarly, the negative effects on Ra
disappeared after 3 years following the latest fire. The magnitude of the
effect on Rs was strongly associated with soil
temperature, cation exchange capacity, total nitrogen (N) content, and
N-acquiring enzyme activity. In contrast, the magnitude of the effect
on Rh significantly changed with pH, bulk density,
texture, soil C and nutrient contents, and C- acquiring enzyme activity.
Our findings advance the understanding of the inhibition and associated
mechanisms of fire on Rs and its components, highlighting the
need for new research efforts to predict the spatial-temporal shifts in
underground C cycling induced by fire.