Modeling the short-term fire effects on vegetation dynamics and surface energy in southern Africa using the improved SSiB4/TRIFFID-Fire model
<p>Fire causes abrupt changes in vegetation properties and modifies flux exchanges between land and atmosphere at subseasonal to seasonal scales. Yet these short-term fire effects on vegetation dynamics and surface energy balance have not been comprehensively investigated in the fire-coupled v...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-12-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/14/7639/2021/gmd-14-7639-2021.pdf |
| Summary: | <p>Fire causes abrupt changes in vegetation properties and modifies flux
exchanges between land and atmosphere at subseasonal to seasonal scales. Yet
these short-term fire effects on vegetation dynamics and surface energy
balance have not been comprehensively investigated in the fire-coupled
vegetation model. This study applies the SSiB4/TRIFFID-Fire (the Simplified
Simple Biosphere Model coupled with the Top-down Representation of Interactive
Foliage and Flora Including Dynamics with fire) model to study
the short-term fire impact in southern Africa. Specifically, we aim to
quantify how large impacts fire exerts on surface energy through
disturbances on vegetation dynamics, how fire effects evolve during the fire
season and the subsequent rainy season, and how surface-darkening effects
play a role besides the vegetation change effects.</p>
<p>We find fire causes an annual average reduction in grass cover by 4 %–8 %
for widespread areas between 5–20<span class="inline-formula"><sup>∘</sup></span> S and a tree cover reduction
by 1 % at the southern periphery of tropical rainforests. The regional
fire effects accumulate during June–October and peak in November, the
beginning of the rainy season. After the fire season ends, the grass cover
quickly returns to unburned conditions, while the tree fraction hardly
recovers in one rainy season. The vegetation removal by fire has reduced the
leaf area index (LAI) and gross primary productivity (GPP) by 3 %–5 % and
5 %–7 % annually. The exposure of bare soil enhances surface albedo and
therefore decreases the absorption of shortwave radiation. Annual mean
sensible heat has dropped by 1.4 W m<span class="inline-formula"><sup>−2</sup></span>, while the latent heat reduction
is small (0.1 W m<span class="inline-formula"><sup>−2</sup>)</span> due to the compensating effects between canopy
transpiration and soil evaporation. Surface temperature is increased by as
much as 0.33 K due to the decrease of sensible heat fluxes, and the warming
would be enhanced when the surface-darkening effect is incorporated. Our
results suggest that fire effects in grass-dominant areas diminish within
1 year due to the high resilience of grasses after fire. Yet fire effects
in the periphery of tropical forests are irreversible within one growing
season and can cause large-scale deforestation if accumulated for hundreds
of years.</p> |
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| ISSN: | 1991-959X 1991-9603 |