The ORPHEE experiment is located 40km south of Bordeaux (44°440 N, 00° 460 W) and belongs to the worldwide Tree Diversity Network (TreeDivNet). The experimental plantation was established in January 2008 on a clear cut of former maritime pine stands on a sandy podzol. Eight blocks were established, with 32 plots in every block. Each plot contained 10 rows of 10 trees planted 2 m apart, resulting in 100 trees within a plot of 400 m². The total initial stand density was therefore 2500 trees per hectare in each plot. Each plot was planted with one to five species. Only maritime pine (Pinus pinaster/Ppin) and silver birch (Betula pendula/Bpen) were considered in this data set.

For this study, we have selected 14 plots per blocks. The present data set is composed by data collected in 2014 (7 years-old) on the target trees at the center of the plots in order to avoid edge effects (measured planting locations = 36). The total height was measured on living trees using a graduate pole. We also measured circumferences at 1.30m height on 7 randomly chosen pines and 7 randomly chosen birches per plot. We estimated missing tree heights and circumferences and tree volumes by:

• Using height-circumference relationships to estimate the circumferences of trees that have not been measured in 2014 by mean of separate generalized additive models for each stand composition and tree density.

• Using the generic model developed by Deleuze et al. (2014) to aboveground tree volumes. We assigned a minimum volume of 0.01m3/ha to the few trees below 1.30m in height (corresponding to the minimum volume found in the data set).

• Eventually we estimated dimensions of dead trees by averaging diameter, height and volume of living trees in the plot.