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Conference papers

Effets de la récurrence des incendies et des sècheresses en région méditerranéenne sur la matière organique et la diversité microbienne des sols

Abstract : Climate change marked by an increased frequency and duration of severe droughts favours the recurrence of wildfires. These repeated disturbances, considered as a deciding factor in the processes of ecosystem degradation, were little studied. Our general hypothesis is that the Mediterranean ecosystems are balanced with fire regime in a limit which depends on fire frequency. High frequencies would lead to an impoverishment of the environment, an erosion of biodiversity and a decrease of its resistance to droughts. To test this hypothesis, we selected in the Maure massif (Var - south-eastern France) 17 plots characterized by different fire regimes(variable in number of fires, at time since the last fire and in interval of time between fires). In the laboratory, these soils were subjected either to only one, or to 4 successive water stresses to assess the resistance of microbial diversity, studied by the technique of micropatches Biolog ®. The quality of the organic matter of 17 samples of soils was studied by MNR of C13. Our results show that 4 fires in 40 years, compared with unburnt control soils, decrease soil organic matter quantity by 42 %, while increasing by 70 % its degree of aromaticity. The modifications of the quality of the organic matter are correlated to a decrease of microbial diversity (r 0,86, p < 0,001). Soils with the highest level of OM aromaticity (high fire frequency) also possess the strongest resistance of microbial diversity for many water stresses. NIRS analyses were used to build predictive PLS models for microbial diversity and its resistance to water stress which are controlled by fire frequency. This frequency was also modelled by NIRS. This work suggests that microbial diversity and its stability are strongly controlled by organic matter quality, itself strongly modified beyond 3 successive fires.
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Submitted on : Friday, May 15, 2020 - 3:21:52 PM
Last modification on : Monday, May 18, 2020 - 2:41:36 PM

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  • HAL Id : hal-02591693, version 1
  • IRSTEA : PUB00025968

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René Guénon, N. Dupuy, M. Vennetier, F. Ziarelli, Raphaël Gros. Effets de la récurrence des incendies et des sècheresses en région méditerranéenne sur la matière organique et la diversité microbienne des sols. Séminaire Matière organique et environnement, Jan 2009, Sainte Maxime, France. ⟨hal-02591693⟩

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