Structural root architecture of 5-year-old Pinus pinaster measured by 3D digitising and analysed with AMAPmod

Pinus pinaster (Ait.) is a high yielding forest tree, producing nearly a fo urth of French marketed timber essentially from intensively managed stands located in southwestern France, in the Landes Forest. This species has gene rally a poor stem straightness, especially when it grows in poor sandy podz ol of the Landes Forest, affected by summer droughts and winter floods. Abo ve- and below-ground architecture and biomass as well as stem straightness were measured on twenty-nine 5-year-old planted trees uprooted by pulling w ith a lumbering crane. A very precise numeric representation of the geometr y and topology of structural root architecture was gained using a low-magne tic-field digitising device (Danjon et al., 1998; Sinoquet and Rivet, 1997) . Data were analysed with AMAPmod, a database software designed to analyse plant topological structures (Godin et al., 1997). Several characteristics of root architecture were extracted by queries including root number, lengt h, diameter, volume, spatial position, ramification order, branching angle and inter-laterals length. Differences between root systems originated from their dimensions, but also from the proportion of deep roots and the tapro ot size, which represented 8% of the total root volume. The proportion of r oot volume in the zone of rapid taper was negatively correlated with the pr oportion of root volume in the taproot indicating a compensation between ta proot and main lateral root volume. Among all studied root characteristics the maximal rooting depth, the proportion of deep roots and the root partit ioning coefficient were correlated with stem straightness.