Carbon partitioning as a drought-tolerance strategy in clonal eucalyptus under thermal and water stress

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• We provided amplitudes for C balance parameters for eco-physiological models. • We elucidated the C allocation strategies for adaptation and acclimation in Eucalyptus plantations. • Temperature is the most important variable that drives the carbon fluxes and partitioning. • Fast-growing clones show 3 times higher loss in productivity with temperature rise. • Drought-tolerant clones have conservative behavior in changing C partitioning. The increase in the frequency, duration, and intensity of drought associated with climate change may alter the current productivity rates of planted forests and the risk of tree mortality associated with physiological stress. In this context, we aim to understand carbon allocation strategies in fast-growing (FG) and drought-tolerant (DT) clonal Eucalyptus plantations under different water and thermal stress. We used carbon balance data from two DT and three FG clones at four climatically contrasting sites, covering an area of 3185 km in Brazil. With the aid of a generalized linear mixed model (GLMM), we observed that under extreme conditions of water and thermal stress, the clones tended to reduce gross primary production (GPP) and the partitioning of aboveground carbon, in detriment in increase in root growth. FG clones showed more significant reductions in GPP and carbon fluxes compared to DT clones, which demonstrates that FG clones are more sensitive to climate change. Our work contributes to elucidating carbon allocation strategies for the main groups of clones planted in Brazil, producing reference values that can be used in sustainable management projects and ecophysiological modeling aimed at more productive plantations that are tolerant to climatic adversity.