Communitree, established in 2009, is a small common garden experiment with 90 synthetic mixtures of oak saplings composed of one to four half-sib families. The goal of the experiment is to investigate the effects of genetic diversity in plant populations on ecosystem functioning (productivity, stability, resistance to herbivores). The experiment is located in southwestern France, close to the ORPHEE experiment.
Acorns were selected from the canopy of four mature pedunculate oaks (Quercus robur) growing within 10 km of the planting site in autumn 2007. The acorns were sown in the INRA nursery in March 2008; seedlings were grown in individual pots. The seedlings were transplanted in the field in March 2009.
Six blocks were established, with 15 plots per block. The plots were separated by a distance of 3 m and were randomly distributed within the blocks. Blocks were 14 m x 6 m in size and were located 4 m apart.
Plots were planted with seedlings of 1 to 4 mother trees. In each block, all possible mother tree combinations were represented: one mother tree (n = 4 plots), 2 mother trees (n = 6), 3 mother trees (n = 4) and 4 mother trees (n = 1) per plot. Each plot contains 4 rows of 3 seedlings; the seedlings were planted 0.2 m apart; and the plot area was 0.24 m2 (0.6 m x 0.4 m). Within each plot, the seedlings from the different mother trees were planted at equal density in a regular alternate pattern, such that seedlings from the same mother tree were never adjacent in mixed plots.
Experimental design: each coloured square represents an individual oak sapling.
|former land use||pine plantation|
|soil type||sandy podzol|
|no of plots||90|
|plot size||0.6 m x 0.4 m|
|no of trees planted||1080|
|planting date||March 2009|
|diversity variables||genetic diversity
|diversity gradient||1, 2, 3, 4 half-sib families|
|size species pool||1 (4 mother trees)|
|species pool||Quercus robur|
|contact person||Hervé Jactel|
All saplings were genotyped and the level of genetic diversity was assessed in each mixture. Monitoring includes damage caused by generalist and specialist insect herbivores and above- and belowground biomass production in order to study relations between genetic diversity, primary production, food availability, herbivory damage, and host specialization of herbivores.
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|1 month after planting (April 2009)||2nd growing season (July 2010)|