P3G: Spatio-temporal complementarity (TreeDì_P3G Spatio-temporal complementarity)

Water use Theory predicts that diverse communities use resources more efficiently than monocultures. Under water shortage resource complementarity of water use may buffer growth decline. Carbon isotopes (d13C) in tree rings are used to infer diversity effects during drought. Temporal complementarity Variation in growth phenology – expected to occur in diverse mixtures – is predicted to exploit the resource ‘time’ more efficiently – as first results suggest. Using dendrometers we will test the hypothesis that diverse mixtures have an extended growth period. Asymmetry Size dependency of relative growth rates of two interacting individuals can be used to infer competitive asymmetry. Low asymmetry promotes coexistence and complementarity. We hypothesize that asymmetry is minimal in a diverse neighborhood and at intermediate levels of trait dissimilarity. Objectives: Assess how neighborhood diversity affects water use efficiency (~stomatal closure) and growth during an extreme drought year (2016) for tree species with contrasting stomatal control (water savers vs. spenders) Test how competitive asymmetry is controlled by diversity at the level of TSPs and their neighborhood based on biometric measurements