Direct and combined impacts of fire and drought stresses on earthworm community in a mediterranean ecosystem | Effets directs et combinés des stress liés aux sécheresses et incendies sur les communautés de vers de terre dans un écosystème méditerranéen
2011
Vennetier, M. | Brun, J.J. | Cecillon, L. | Cassagne, Nathalie | Juvy, B.
We studied the dynamics of earthworm populations in a fire prone forest environment in Mediterranean France from 2005 to 2011. Species diversity, worm number, size and biomass and worm casts size, number and spatial distribution were measured in an experimental design including 33 plots, with various fire regimes combining 2 fire frequencies (few fires vs many fires in 50 years) and 3 dates for the last fire (1, 4 and 15 years ago) and unburnt control plots. The follow up included a period of repeated drought (2003-2007) followed by a period of normal climate (2008-spring 2011). The two last fires (2003 and 2007 occurred respectively at the beginning and at the end of the dry period, which allowed assessing the drought-fire stress interaction. Worm populations, diversity and activity were reduced by fire as well by repeated drought. The reduction was higher in case of repeated fires. Fire and drought mutually increased their respective impact, showing a strong interaction. Worm activity, size and spatial distribution gradually recovered in 4 years after the end of drought but remained lower than normal in recently or frequently burned plots. Population spreading from refugees was studied too and proved to be slow (2-3 m/year).
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