Soil fauna as bioindicators of organic matter export in temperate forests

Numerous studies predict a short-term important decrease in fossil resources and stress the need to develop alternative renewable energies, thus European countries aim at increasing biomass production for energetic purposes. One such source of bioenergy could be obtained from forest biomass pools by exporting logging residues, yet this practice would have strong impacts on forest ecosystems (e.g. disturbance of soil biodiversity and chemical properties). Most studies on biomass removal effects focused on boreal forests but responses in temperate forests are still scarcely studied. Soil macrofauna is involved in forest ecosystem functioning through numerous chemical, physical and biological processes and multiple interactions with other organisms. A disturbance of the soil macrofauna community can thus lead to a response of the forest ecosystem as a whole. Experimental plots were set up in 6 northern France forests (either dominated by oak or beech), with a treatment corresponding to Whole Tree Harvesting (WTH) practices compared to control, in order to characterize the response of soil macrofaunal communities to organic matter (OM) export. Our study showed that OM export leads to a short-term loss of abundance in macrofaunal communities in temperate deciduous forest soils that can also lead to an alteration of soil OM cycle, and revealed that the breadth of this negative impact is modulated by tree species and faunal trophic groups. Furthermore, some results of community responses were directly applicable to forest management as marked responses of several taxa revealed four bioindicators of OM disturbance. Therefore, the level of disturbance related to new forest management practices, such as WTH to increase forest biofuel yields, (i) could be characterized by surveying either total soil macrofauna or using tools such as bioindicator taxa and (ii) should be assessed regarding tree stand identity.