RESUMO Em um plantio de salgueiro manejado em um sistema de curta rotação estudou o efeito da composição clonal, densidade de plantação e irrigação suplementar sobre anatomia da madeira, densidade, teor de umidade, poder calorífico inferior, teor de cinzas e a energia acumulada na biomassa lenhosa, e também estabeleceu as associações entre características anatômicas e físicas da madeira e os parâmetros que determinam a sua qualidade como combustível. Um experimento fatorial completo com três fatores foi estabelecido: irrigação, densidade de plantação e clone, cada um com dois níveis. Os clones foram: Salix matsudana Koidz. x Salix alba L. ‘Barrett 13-44 INTA´ (B), e Salix alba L. ‘Yaguareté INTA - CIEF´ (Y). Foram amostrados 46 varas de 1 m de comprimento para determinações anatomia (diâmetro e frequência do vasos, a espessura da parede da fibra e a área ocupada de parede), densidade da madeira, teor de umidade, cinza e variáveis energéticas. O clone B foi ligeiramente mais elevado do que o clone de Y, tendo maior densidade da madeira (0,406 vs. 0,395 g/cm3), e teor de umidade inferior (47,11 vs 50,53 %). A densidade de plantio não afetou nenhuma das variáveis analisadas, mas a irrigação suplementar teve influência sobre a eficiência energética (393,2 vs. 309,15 Gj/ha sem irrigação). Um sistema de produção implementado com o clone B, com menor densidade de plantio (13.000 plantas / ha) e cultivada com irrigação apresenta vantagens energéticas em relação a outras combinações avaliadas.

ABSTRACT A short rotation intensive system with willows was analyzed with the following aims: a - to determine the effects of irrigation, genotype and plantation density on wood anatomy, wood density, moisture content, lower heating value, total ash content and energy accumulated in the woody biomass; b - to explore the relationships between anatomical and physical wood properties and the parameters determining their quality as a biofuel. A complete factorial experiment was set up, with three factors and two levels for each factor. The factors were: irrigation, plantation density and clone (genotype). The clones were Salix matsudana Koidz. x Salix alba L. ‘Barrett 13-44 INTA´ (B) and Salix alba L. ‘Yaguareté INTA - CIEF´ (Y). 46 stools of 1 m long were sampled, on which the following determinations were carried out: vessel diameter and frequency, fiber wall thickness and area, wood density, moisture content, ash content and heating values. Clone B had higher wood density than clone Y (0.406 vs. 0.395 g/cm3) and lower moisture content (47.11 vs. 50.53 %). The plantation density did not affect any of the variables analyzed. Irrigation increased the energy yield to 393.2 Gj/ha, compared to 309.15 Gj/ha without irrigation. A system with clone B planted at a lower density (13,000 plants/ha) and under irrigation has the best advantage as an energetic crop over the other alternatives evaluated in this work.

In Argentina, energy production depends mostly on fossil fuels; hence it is desirable to diversify the energy sources including renewable fuels such as forest biomass. A drawback for this development is the lack of information about the productivity of short rotation coppice systems (SRC) under local conditions. Willows are used in several countries as a source of biomass for energy, although in Argentina the information about yield at local level is scarce. An SRC system was established in agricultural soil in Buenos Aires Province, Argentina. The aim of this work was to estimate the effects of irrigation, plantation density and genotype on biomass production. The clones used were the hybrid Salix matsudana x Salix alba `Barrett 13-44 INTA´ and the open pollinated Salix alba `Yaguareté INTA - CIEF´. There were no statistically significant effects of clone and plantation density on biomass productivity. The only significant factor was irrigation, which explained 83 to 92 % of yield variability. The dry biomass yields are similar to those reported elsewhere for rainfed SRC willows, ranging between 11.1 and 22.6 Mg ha-1 year-1.

La matriz energética de Argentina depende principalmente de los combustibles fósiles, por lo que resulta deseable diversificarla, incluyendo fuentes renovables como la biomasa forestal. Una limitación para este desarrollo es la falta de información sobre la productividad de sistemas de rotación corta de alta densidad (SRC) destinados a la producción de biomasa en condiciones locales. El objetivo de este trabajo fue evaluar el efecto del genotipo, la densidad de plantación y la disponibilidad hídrica sobre la productividad de un sistema SRC con sauces en un suelo agrícola en la provincia de Buenos Aires. La principal limitación para la productividad es la disponibilidad de agua, que explica entre el 83 y el 92 % de la variabilidad en la biomasa seca, mientras que no hubo efectos significativos del genotipo y la densidad de plantación. Los rendimientos de biomasa seca obtenidos en este ensayo son comparables a los reportados para sistemas SRC en otros países, variando entre 11,1 y 22,6 Mg ha-1 año-1.

Flooding tolerance should be included as a trait in breeding programs in forested areas where extreme flooding events lasting several months can occur. In this context, it is difficult to carry out controlled, long-term flooding experiments with big trees due to the large number of specimens to screen. The hypothesis in this work was that a relatively short-term flooding experiment in a greenhouse would be useful to select clones capable of enduring long term flooding events in the field. The survival of 4 willow clones in a long term, 12 years field trial that was subjected twice to long term flooding events, was compared with the survival, growth and gas exchange of those same clones subjected to flooding in the greenhouse for three months. There were differences in flooding survival in the field: clone AN4 showed a 100 % survival, followed by clone 395 (43 %), clone 131-27 (18 %) and clone 13-44 (14 %). In the greenhouse, all plants survived and only flooded plants of clone 13-44 experienced a statistically significant growth and stomatal conductance reduction. The food tolerance ranking in the field and in the greenhouse only partially overlapped; the worst clone in the field could be identified in the short-term greenhouse experiment, though the best one could not. It was not possible to identify clones with tolerance to long-term flooding episodes in the field. Nevertheless, the greenhouse results were useful to identify clones showing flooding sensitivity and tolerance to short term flooding episodes.

Es necesario incluir la tolerancia a la inundación como un carácter en programas de mejoramiento para zonas forestadas donde eventos extremos de inundación que pueden durar meses son comunes. En este contexto, es difícil llevar a cabo experimentos controlados de larga duración con árboles de gran tamaño, debido al elevado número de ejemplares que es necesario evaluar. La hipótesis de este trabajo fue que un experimento relativamente corto de inundación en el invernáculo sería útil para seleccionar clones capaces de soportar eventos de inundación de varios meses en el campo. Se comparó la supervivencia de cuatro clones de sauces en un ensayo a campo que experimentó dos episodios largos de inundación a lo largo de 12 años, y la supervivencia, crecimiento e intercambio gaseoso de los mismos clones inundados por tres meses en invernáculo. Se encontraron diferencias en la supervivencia en el ensayo a campo, del clon AN4 sobrevivieron el 100 % de las plantas, seguido por el clon 395 (43 %), clon 131-27 (18 %) y clon 13-44 (14 %). En el invernáculo, todas las plantas sobrevivieron y sólo las plantas inundadas de 13-44 experimentaron una reducción significativa del crecimiento y la conductancia estomática. El ranking de tolerancia en el campo y en invernáculo sólo coincidió parcialmente, el clon menos tolerante en el campo pudo ser identificado en el invernáculo, pero no el clon más tolerante. Si bien no fue posible identificar clones con tolerancia a episodios largos de inundación, los datos del ensayo en invernáculo permitieron identificar clones con sensibilidad a la inundación, y con tolerancia a episodios cortos de anegamiento.