Biomass Production and Quality of Twelve Fast-Growing Tree Taxa in Short Rotation under Mediterranean Climate

Sustainable production of lignocellulosic biomass for energy use can contribute to climate change mitigation. This work aims to compare the biomass production of twelve fast-growing woody taxa belonging to the Eucalyptus, Casuarina, Populus and Paulownia genera, the quality of their biomass for energy use and its valorizing through transformation into pellets, as well as the effect of the crop on the soil. Over the course of two rotations, plant growth and biomass production were assessed. The yield of aboveground dry biomass ranged from 9 to 61 Mg ha(-1) year(-1) (equivalent to 137-867 GJ ha(-1) year(-1)). The highest yields were obtained for Eucalyptus clones (51-61 Mg ha(-1) year(-1)). The N-fixing species Casuarina equisetifolia and two Populus x euramericana clones ('Adige' and 'AF2') also achieved high yields (28-33 Mg ha(-1) year(-1)), though significantly smaller than those of the eucalypts. Due to its low wood density, Paulownia fortunei was not very productive in terms of biomass (18 Mg ha(-1) year(-1)), despite its good growth in diameter and height. However, some management practices, such as not removing nutrient-rich and poor-quality biomass fractions for energy use (leaves and thin branches) from the harvested crop, as well as the use of N-fixing species and by taking into account all nutrient inputs and outputs, can ensure the sustainability of the cultivation systems and improve degraded soils.