Contexte

The generalization of mechanization of forest operation increases the risk of physical soil degradation, which impacts all the functions of the ecosystem: wood production, biodiversity, environmental functions like maintaining surface water quality, or limiting GHG emission.
Heavy machinery driven on wet soils, compacts the whole profile, producing ruts, sometimes mixing the layers. Compaction increases both soil bulk density and physical resistance, by decreasing the macro-porosity. The consequence is a strong decrease in fluid transfer, gas and water, leading to anoxy and hydromorphy driven processes. In steep soils, erosion can be induced by compaction, at least during the time when vegetation disappears.
The highest impacts would occur in so-called sensitive soils, which are non-degraded soils, but which are supposed to be quickly degraded when inappropriate management is practiced. These soils are silt textured, poorly structured. Soil acidity is an additional parameter to take into account, because the cation saturation the CEC is not the same in acidic and neutral soils, biological activity decreases with acidity, and consequently soil structure is less developed and stable in acidic conditions. Its means that the soil restoration capacity would be lower in acidic soils than in richer ones.

Objectives

• characterize the current changes in soil after the compaction was applied;
• characterize the dynamics of restoration of soil porosity and its consequences on soil functioning, in the short and medium terms;
• study the effects of chemical remediation (liming) and physical remediation (tillage, local de-compaction around young trees) on tree growth and soil processes;
• identify the indicators of restoration in order to sustain manager decisions.

Site description

Two sites were selected in the plateau lorrain, where very sensitive soils to compaction dominated, respectively at Azerailles, estate forest of les Hauts-Bois  (54), and Clermont-en Argonne estate forest of Grand-Pays (55). In both cases soils were polycyclic (continental deposit of silty material about 50 cm thick) lying on clayey material (>40% clay).
The experimental sites were installed on previous high forest broadleaved stands dominated by beech (Fagus sylvatica L.) and oak (Quercus petraea Liebl.). Stands were clearcut, and trees were harvested using cable crane system, in order to avoid uncontrolled soil degradation.

Experimental design and monitoring

Each site about 6 ha, was divided into three blocks, where three or four treatments were replicated in plots 50 x 50 m each: control (C), compaction (T), de-compaction on the whole area (D), de-compaction around the trees (D) (Azerailles), and specifically on the acidic soil at Clermont-en-Argonne [Liming (A), compacted and limed (TA)]. A rather limited compaction was applied using a Valmet forwarder 20 t in charge, driven on soils at about 40% volumic moisture.
The Azerailles site was installed in May 2007 and the Clermont en Argonne site in March 2008. Since that time investigations were made on meso-climate (hourly), soil climate, moisture and temperature (hourly), perched water table level (hourly), soil solid-phase (annually), soil gas (monthly), soil solutions, both water table and solutions of non-saturated soil (monthly), vegetation (annually). All the information on methods & results is stored in a database managed by Pascal BONNAUD.

Running multidisciplinary projects on the network

ADEME GHG emission, project headed by Pr D EPRON UL ; Région Lorraine, earthworms, project headed by Frédéric DARBOUX (BEF)

Project investigators

Jacques RANGER, Frédéric DARBOUX, Gregory Van den HEIJDEN, Arnaud LEGOUT, Laurent SAINT-ANDRE, Bernd ZELLER (INRA- BEF); Engineer in charge of the sites Pascal BONNAUD (INRA-BEF) Technical staff : Pascal BONNAUD, Jérôme DEMAISON, Gilles NOURRISSON

Publications

SELADJI et al. 2010 European Journal of Soil Science, 61, 1043 – 1055 ;  GOUTAL et al.. 2011. European Journal of Soil Science. Doi: 10.1111/j.1365-2389.2011.01423.x ; GOUTAL et al. 2011. Soil Sci. Soc. Am. J. doi:10.2136/sssaj2011.0402 ; GOUTAL et al. 2013. Geoderma 193-194 : 29-40. ; GOUTAL et al. 2013- Ann. For. Sci. 70: 545-556 ; GOUTAL-POUSSE et al. 2016. EJSS (in press) ; BOTTINELLI et al.. 2014 Geoderma 217-218 : 10,47 ; BOTTINELLI et al.2013. Soil Applied Soil Ecology. vol 70 : 57 – 61 ; BOTTINELLI et al. 2014. Soil Ecology. vol 73 : 130-133 ; BEDEL, L., et al.  2016 -. Geoderma 264: 103-116 ; NAWAZ et al. 2016. J. of Soils & Sediments (in press) ; BEDEL, L et al. Biogeochemistry (submitted) ; EPRON et al. 2016. Forest Ecology and management (in press)

Funding

ANR, Région Lorraine, ONF, LHOIST Society, Allenvi and GIP Ecofor - Soere F-Ore-T, Ademe, Ministries in charge of Research, Agriculture, Environment.