Biomass production and nutritional efficiency in short rotation eucalypt clone plantations for energy in north-east Brazil

Abstract

Selecting adapted hybrids with greater efficiency in the use and return of nutrients is essential to ensure the success of forestry activities.  Although topics on the nutritional sustainability of eucalypt biomass harvesting have frequently been discussed, few studies  have focused on short rotation eucalypt clonal plantations (aimed at energy production), especially in conditions of nutrient scarcity and  water limitations in Brazil. Therefore, our objective was to evaluate the nutritional efficiency and sustainability (for nitrogen (N),  phosphorus (P) and potassium (K)) of six eucalypt clones in short rotation cultivation in the north-east of Brazil, considering different  harvesting scenarios and using the Eucalyptus urophylla species as a reference, which is traditionally planted in the study region. Direct  quantification of the biomass of 21 trees of each clone was carried out at 5 years of age. The clones did not affect the accumulation of  total biomass (on average, 199.9 Mg ha⁻¹). The 1296 and 1355 clones provided lower biomass export and greater  nutritional efficiency,  favouring an increase in the potential number of rotations (PNR) for P and a reduction in the N removal rate (RR). However, the VM58  clone showed higher biomass export and lower PNR. Thus, clones 1296 and 1355 are more favourable, while clone VM58 is less  favourable to nutritional sustainability under the studied conditions. Nitrogen and K may cause productivity limitations in future rotations  in whole-tree harvesting systems. Adopting more conservationist harvesting systems with removing only the stemwood or  stemwood with bark can optimise the potential of clones, minimise the need to add fertilisers and ensure maintenance of the site’s  productivity.