Vegetation fires influen
ce the properties and turnover of soil organi
c matter in numerous e
cosystems. Thermal alteration tends to in
crease the stability of soil organi
c matter. Fire indu
ces the destru
ction of above©\ground biomass, whi
ch is asso
ciated with a large produ
ction of new partially-
charred litter. Plant regeneration is dire
ctly affe
cted by the fire itself, and by the ensuing modifi
cations to the C, N and nutrient
cy
cles asso
ciated with soil organi
c matter transformations. The obje
ctives of the present study were to determine 1)
changes in soil organi
c matter
composition indu
ced by fire, and 2) the dynami
cs of soil organi
c matter re
covery in the first two de
cades following a fire event.. In a Florida s
crub oak e
cosystem, a
chronosequen
ce of soils prote
cted from vegetation fire for 1 to 20 years was studied. The bulk organi
c matter and oxidation resistant elemental
carbon were quantified in depths 0-5
cm, 5-15
cm, and 15-25
cm. The soil organi
c matter was
chara
cterized by solid-state
13C NMR spe
ctros
copy and Curie point pyrolysis.
The combination of these techniques allowed us to identify three steps in soil organic matter evolution: first the un-charred litter brought by the fire degraded between 1 and 4 years after fire; second the contribution of aryl carbon, and most probably the pyrogenic carbon, significantly decreased between 4 and 11 years after fire; Thirdly, after 11 years, the soil organic matter quality appeared driven again by the fresh litter input from regenerating plant ecosystem. In this study, the soil organic matter did not appear strongly modified by the fire. The pyrogenic carbon did not dominate the soil organic matter composition and underwent significant degradation at the decadal timescale. Our results also highlight a potential underestimated effect of dead root input to soil organic matter after the fire.