In mixed forests, complementarity can be expressed by a differentiate use of space between species so that each species makes the best use of the light resource according to its photosynthetic capacities. This spatial differentiation between species is possible thanks to plasticity in crown architecture. Thus many articles report an increase in the extent and the volume of the crowns in the mixtures compared to the monospecific stands, but with a significant tree species and size tree effects. We wanted to know if the effect of the mixture on tree crown architecture was also observed on the OPTMix plots between sessile oak and Scots pine and to see if there was a relationship with the amount of litter and the nutritional status of the trees.
We therefore carried out measurements of the height of the first living branch and the radius of the crowns according to the “vertical sighting method” (Preuhsler, 1979), to calculate the projection surface and the volume of the crowns of 75 pines and 75 oaks. Several Master trainees did this measurement campaign. The operator effect on the crown measurements will also be studied. A comparison with previous crown data collected in 2017 will be made if possible.