Soil carbon dioxide response to meteorology in a Neotropical wet forest

Repository for Precipitation‐drainage cycles lead to hot moments in soil carbon dioxide dynamics in a Neotropical wet forest, in Global Change Biology, by Fernandez-Bou et al., 2020. https://doi.org/10.1111/gcb.15194

Soil
CO2 concentrations and emissions from tropical forests are modulated
seasonally by precipitation. However, sub-seasonal responses to meteorological events
(for example, storms, drought) are less well-known. Here we present the effects
of meteorological variability on short-term (hours to months) dynamics of soil
CO2 concentrations and emissions in a Neotropical wet forest. We continuously
monitored soil temperature, moisture, and CO2 for a three-year
period (2015 to 2017), encompassing normal conditions, floods, a dry El Niño period,
and a hurricane. We used a coupled model (Hydrus-1D) for soil water
propagation, heat transfer, and diffusive-gas transport to explain observed soil
moisture, soil temperature, and soil CO2 concentration responses to
meteorology, and we estimated soil CO2 efflux with a gradient-flux
model. Then, we predicted changes in soil CO2 concentrations and
emissions under different warming climate change scenarios. Observed short-term
(hourly to daily) soil CO2 concentration responded more to
precipitation than to other meteorological variables (including lower pressure during
the hurricane). Observed soil CO2 failed to exhibit diel patterns (associated
with diel temperature fluctuations in drier climates), except during the drier El
Niño period. Climate change scenarios showed enhanced soil CO2 due
to warmer conditions, while precipitation played a critical role in moderating the
balance between concentrations and emissions. The scenario with increased
precipitation (based on a regional model projection) led to increases of +11 %
in soil CO2 concentrations and +4 % in soil CO2 emissions.
The scenario with decreased precipitation (based on global circulation model
projections) resulted in increases of +4 % in soil CO2
concentrations and +18 % in soil CO2 emissions, and presented more
prominent hot moments in soil CO2 outgassing. These findings suggest
that soil CO2 will increase under warmer climate in tropical wet
forests, and precipitation patterns will define the intensity of CO2
outgassing hot moments.