Leaf traits explaining the growth of tree species planted in a Central Amazonian disturbed area

Tree species selected for planting should exhibit both high survival and fast growth. The growth of a tree or forest plantation is affected by the resource supply (light, water and nutrients), the fraction of resources acquired and resource use efficiency. Leaf traits related to the last two processes have the potential to explain the growth rates. In this study, we evaluated 24 leaf traits (morphological and physiological) at the individual level to investigate whether simple leaf traits can be used to predict the variation in relative growth rates of eight native tree species in a mixed plantation in disturbed areas in Central Amazonia 15 months after planting. Tachigali vulgaris and Trattinnickia rhoifolia exhibited the highest growth rates in both height and diameter, which were approximately three and two times higher than those of Bombacopsis macrocalyx, respectively. Species exhibited different establishment strategies as indicated by the functional leaf trait performance. Tachigali vulgaris, Ochroma pyramidale, Trattinnickia rhoifolia and Ceiba pentandra are efficient resource use species, have high light-saturated photosynthetic rates and are tolerant to high irradiance stress. Endlicheria anomala exhibited the worst performance based on functional traits, with the lowest light-saturated photosynthetic rate (Amax) and maximum quantum yield of photosystem II (FV/FM). Of all traits analyzed, 12 leaf traits were correlated with the relative growth rate (RGR). Leaf traits related to resource acquisition, such as individual leaf area, chlorophyll content, leaf water potential and leaf nutrient concentration, were not good predictors of growth. Only stomatal conductance (gs) was related to the RGR. Leaf traits related to photosynthetic use efficiency (carbon use efficiency and photosynthetic nitrogen and phosphorus use efficiency) explained, on average, 20% and 30% of tree growth in height and diameter, respectively. Resource use efficiency traits were better predictors of growth than the individual physiological traits gs and Amax, which explained, on average, 12% and 19% of the growth in height and diameter, respectively. Photosynthetic efficiency-related traits are good predictors of tree growth, and species with high efficiency - such as T. vulgaris, O. pyramidale, T. rhoifolia and C. pentandra - can achieve high growth in Amazonian disturbed areas. The identification of species with better performance during initial establishment can improve the design of mixture plantations in disturbed areas. Additionally, the selection of traits most correlated with growth performance can be more informative for reforestation monitoring; consequently, previous silvicultural interventions can be adopted prior to the reduction in both growth and survival rates.