botanyone
There is considerable evidence for the presence of positive species diversity–productivity relationships in plant populations, but the parameters determining the type and strength of the relationship are poorly defined. Collet et al. study a tree plantation that mixes beech (Fagus sylvatica) and sycamore (Acer pseudoplatanus) according to a double gradient of density and species’ proportion, and find that density and tree size are the primary factors determining individual growth and stand productivity. Mixtures of these two functionally similar species have highest production at maximum evenness, indicating a complementary effect between them. The presence of a mixture combines both stabilizing mechanisms (individuals from both species show higher growth when surrounded by individuals from the other species) and equalizing mechanisms (the two species have very similar growth curves) that, in turn, determine the species’ relative dominance.
