Work package 3

In WP3, the orthogonality and experimental control of canopy disturbance and drought is elevated even more to increase the mechanistic understanding on the relative importance of canopy opening vs drought on below-canopy biodiversity. There is a need to better understand species-specific responses and assess, for instance, why particular species decline. The major objective of WP3 is to create artificially disturbed canopies and no-analog light regimes brought about by experimental clipping of tree branches and foliage – in hitherto undisturbed forest – that reflect the actual disturbance regimes occurring across temperate European forests, in interaction with a drought treatment in fully hydrologically isolated mesocosms. Indeed, although 300 plots are being in WP1 and 50 plots (150 subplots) in WP2 across Europe, there might be undetected co-variation of other environmental drivers with drought and light (e.g. due to soil nutrient co-variation). To increase orthogonality, but at the expense of spatiotemporal representativeness and comprehensiveness, a highly controlled full-factorial mesocosm experiment is needed. At the WP3 experimental forest site, clipping treatments are conducted in 15 circular plots that will each contain 8 mesocosms (120 mesocosms in total). The question here is again how biodiversity at different levels of biological organisation responds to different forms of novel light regimes in interaction with drought.