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Universidad de Santiago de Compostela (1997)

Influencia de los incendios forestales sobre la materia orgánica edáfica

Fernández Piñeiro, Irene

Titre : Influencia de los incendios forestales sobre la materia orgánica edáfica

Effects of forest wildfires on soil organic matter

Auteur : Fernández Piñeiro, Irene

Université de soutenance : Universidad de Santiago de Compostela

Grade : Doctora en Química 1997

Résumé
Immediate, short, middle and long term effects of the forest wildfires on content, composition and mineralization activity of the soil organic matter were studied. The results obtained in field experiences were compared with the effects produced by laboratory soil heating at different temperatures (150º C, 220º C, 350º C y 490º C), under controlled conditions. Surface (0-5 cm) and subsurface (5-10 cm) soil layers lost about 50% of their total C content during wildfire ; however at short or medium term the normal levels of soil organic matter were recovered. The fire also altered the composition of the organic matter, producing a relative increase of lipids and lignin and a decrease of the cellulosic fraction. The unhumified organic matter disappeared in greater proportion than the humified fractions, this causing an increase of the percentage of humification of the remaining organic matter. Furthermore, the humus composition resulted strongly modified after a wildfire. Both, fulvic and humic acids decreased while there was a net increase of the humin fraction exclusively due to the formation of insoluble humin. The percentages of polymerization and complexation with Fe and Al increased notably The organic matter mineralization activity was also altered by burning. Immediately after fire, the C mineralized decreased in the surface layer ; however, the percentage of total C mineralized significantly increased in both layers. The cumulative CO2-C mineralized fitted a double exponential first order kinetic model but the fire affected the kinetic parameters increasing both the labile pool of the potentially mineralizable C and the mineralization rate constants of the recalcitrant and labile pools. After 10 years from the fire many of the studied parameters showed similar values to those of the corresponding unburned soil ; however, the recovery rate differed for each parameter. Thus, the total organic matter content, particularly the unhumified fraction, and the parameters related to the C mineralization activity showed a rapid recovery, while the carbon-bearing compounds and the humus composition, showed a relatively slow recovery. Soil recovery was highly dependent on the reestablishment of a vegetable cover of similar characteristics to those of the unburned forests.

Mots clés  : Incendios forestales Materia orgánica Humus Mineralización del carbono Suelo Forest wildfires Organic matter Humus Carbon mineralization Soil

Présentation (DIALNET)

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