Adaptation of eucalypt trees to water and nutrient deficiencies: Insights from Brazilian experiments question conventional recommendations

Drought is a major abiotic stress that will be exacerbated by climate changes in many forest ecosystems. A scarcity of fertilizers for the management of tropical plantations is also predicted due to finite reserves of phosphorus and potassium (K) worldwide. Identifying management practices enhancing tree tolerance to drought and nutrient deficiencies is, therefore, of primary interest. Carbon, water, and nutrient fluxes have been monitored intensively over entire rotations in experiments manipulating rainfall and nutrition in Eucalyptus grandis plantations in southern Brazil. These studies question the relevance of some silvicultural practices well established in regions with relatively high annual rainfall. The early tree growth does not always need to be maximized; weeding can also be important after canopy closure; K fertilization is not always beneficial to face drought; it is not always necessary to split the applications of N and K fertilizers to prevent losses by leaching; and sodium application can enhance tree growth in K-deficient soils. We show that studies carried out at a single site can have broad applications for the management of tropical plantations, provided that they improve our comprehension of the mechanisms driving tree growth. In addition to multilocal trials, multidisciplinary research at a few sites associated to modelling and remote sensing is needed to adapt silvicultural practices to global changes.