Growth and root architecture of several species, provenances and varieties grown in a sandy spodosol in an Atlantic mild climate, after two years in the field

The Landes forest is located South-West France and produces 20% of french wood, it ismainly composed of intensively managed even-aged stands of Pinus pinaster (Ait). Thisone million hectare forest was hit by two major storms in 1999 and 2009, destroying halfof the standing volume. Most of the reafforestation are made with genetically improvedvarieties originating from a population breeding program with a selection at 10 years onheight and butt stem lean. In the coming years, other species, provenances or varieties ofP. pinaster will certainly be used for reafforestation to improve biodiversity, to specialiseproduction e.g. biomass, or resistance to biotic or abiotic stresses, e.g. drought. Rootsystem architecture is a key component in mechanical stability of trees. Therefore species,provenances and varieties which could be potentially used in the Landes forest wereplanted for 10 years in three locations to gain information about the dynamics of rootarchitecture in young trees. Each year ca. 150 trees are uprooted and the root system ismeasured using 3D digitizing. An in-depth phenotyping of root architecture is made by“architectural analysis”.Robinia Pseudoacacia and Quercus Rubra showed an overall small growth in the threeexperimental plots after two years in the field. Conversely, the two Eucalyptus clones weretwo and three times higher than the P. pinaster in the medium-wet location, but did notgrow well in the most humid locations with Molinia Caerulea understory. Pinus taeda wasslightly higher than P. pinaster in the best location. The 12 P. pinaster provenances, orvarieties did not differ for stem dimensions, except the Moroccan provenance which hassignificantly lower height, but a similar collar diameter than the other P. pinaster.Root architecture and biomass measurements are just finished, and will be analysed in thecomming weeks