Productivity is great in forests with a capacity to intercept incoming radiation and harness its energy efficiently. Thus, understanding the relationships between forest diversity, tree canopy biomass and photosynthetic parameters is central to predicting how diversity will affect a key ecosystem function (i.e., productivity). Specific hypotheses to be tested: I) higher tree species diversity enables greater exploitation of light within forest canopies due to niche partitioning, increasing photosynthesis and primary production (NPP); II) photosynthetic acclimation (ecological resilience to changing environmental factors) on singular species may vary according to the varying ecological conditions, but is supposed to be maintained at plot level in mixed population (interaction of different species-specific behaviors). Photosynthetic acclimation was measured with chlorophyll fluorescence (ChlF), by applying fast and reliable techniques based on the fast kinetics of the chlorophyll fluorescence induction in dark adapted leaves. This method is called JIP-test and is based on the measure of the variable fluorescence at different steps of the fluorescence induction. The measurements were carried out in 36 plots (30mx30m) of Spain Exploratory Region.

Chlorophyll fluorescence measurements were replicated on 8 randomly chosen leaves per tree per two level of crown (top and bottom). The measurements were done on the twigs after the dark adaptation (at minumum four hours in black plastic bag, at ambient temperature). In all evergreen species chlorophyll fluorescence measurements took in current year leaves and needles (i.e., needles sprouted in 2013, 1-year leaves/needles)

Alto Tajo, Spain

4 tree species (total number sampled tree/specie): Pinus nigra (69), Pinus sylvestris (54), Quercus ilex (50), Quercus faginea (67)

Data are treated at tree level (for each tree the data are treated for crown level)