Eucalyptus globulus Labill is the main exotic broadleaf species planted and managed for pulp and energy production in Spain, where it covers an area of more than 0.6 million ha. The climatic and soil conditions of the planting areas range from the predominantly acidic or fertile soils developed over limestone in Atlantic areas of the north and northwest of the Iberian Peninsula to the less weathered soils developed from slates, sandy deposits or limestone in the drier southwest. The widely varying conditions explain the large differences in proposed fertilizer prescriptions. This review paper provides an analysis of the proposed practices and prescriptions by considering trial results and the need to develop site specific prescriptions for seedling standards and fertilization at planting establishment. Analysis of nutritional studies and of nutrient balances over a whole rotation is presented in order to provide basic information for defining maintenance fertilization, identified as the main bottleneck for sustainable wood production in these stands. Different fertilization practices are used by non industrial owners and Spanish pulp companies, with the last one applying a more intense management relying in more fertilization. A complete consideration of nutrition-related operation and decisions is shown to be essential for maintaining potential productivity, reduce biotic and abiotic damages and reduce mineral fertilization needs.

Background and Objectives. Water stress is a major constraining factor of Eucalyptus plantations’ growth. Within a genetic improvement program, the selection of genotypes that improve drought resistance would help to improve productivity and to expand plantations. Leaf characteristics, among others, are important factors to consider when evaluating drought resistance evaluation, as well as the clone’s ability to modify leaf properties (e.g., stomatal density (d) and size, relative water content at the time of stomatal closure (RWC_c), cuticular transpiration (E_c), specific leaf area (SLA)) according to growing conditions. Therefore, this study aimed at analyzing these properties in nursery plants of nine high-productivity Eucalyptus clones. Material and Methods: Five Eucalyptus globulus Labill. clones and four hybrids clones (Eucalyptus urophylla S.T. Blake × Eucalyptus grandis W. Hill ex Maiden, 12€; Eucalyptus urograndis × E. globulus, HE; Eucalyptus dunnii Maiden–E. grandis × E. globulus, HG; Eucalyptus saligna Sm. × Eucalyptus maidenii F. Muell., HI) were studied. Several parameters relating to the aforementioned leaf traits were evaluated for 2.5 years. Results: Significant differences in stomatal d and size, RWC_c, E_c, and SLA among clones (p < 0.001) and according to the dates (p < 0.001) were obtained. Each clone varied seasonally the characteristics of its new developing leaves to acclimatize to the growth conditions. The pore opening surface potential (i.e., the stomatal d × size) did not affect transpiration rates with full open stomata, so the water transpired under these conditions might depend on other leaf factors. The clones HE, HG, and 12€ were the ones that differed the most from the drought resistant E. globulus control clone (C14). Those three clones showed lower leaf epidermis impermeability (HE, HG, 12€), higher SLA (12€, HG), and lower stomatal control under moderate water stress (HE, HG) not being, therefore, good candidates to be selected for drought resistance, at least for these measured traits. Conclusions: These parameters can be incorporated into genetic selection and breeding programs, especially E_c, SLA, RWC_c, and stomatal control under moderate water stress.

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 × 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.