Sustainable fuel wood production and wood ash recycling on acidic forest soils

Fuel wood is a critical component of the sustainable French energy development plan. To anticipatethe demand, foresters have to consider innovative silvicultures that ensure an increased andsustainable biomass supply. On fertile agricultural soils, biomass-dedicated plantations provedefficient. Their transposition on more acidic forest soils requires studies targeting soil chemical andphysical fertility management, adapted tree species selection, silvicultural developments adaptationalong with assessments of both technical feasibility, economic efficiency and short- to long-termecosystem impacts. These developments suppose focused experiments on planting techniques (soilpreparation and liming), a prerequisite for enhancing productivity.An 11 ha experiment was initiated in the French Ardennes by a partnership between FCBA, INRAand ONF. It compares the effects of various soil mechanical preparation and fertility managementtechniques on the productivity of biomass-dedicated (hardwood) and semi-dedicated (coniferous)silvicultures. More specifically, we tested the use of wood ash from heating plants for soil protectiveliming, one option for a closed-loop and sustainable forest soil fertility management.In order to establish a baseline for long-term ecosystem monitoring, just after tree plantation (in2013) soil from the 48 experimental plots was sampled and measured for chemical properties, andground flora was surveyed on a subset of 30 experimental plots, crossing soil-preparation technique(deep or superficial soil decompaction), liming type (none, commercial or wood ash/dolomitemixture) and two tree species (1 coniferous, 1 hardwood).A few months after soil liming, wood ash/dolomite mixture supply increased soil exchangeablecations contents similarly to commercial liming and soil preparation technique interacted with limingtype. Both liming types impacted similarly plant community composition, but the type of soilpreparation technique had no effect.