Rómulo Santelices

Efecto de la cobertura y de la fertilización en el desarrollo de plantas de Nothofagus alessandrii cultivadas en contenedor

Nothofagus alessandrii es una especie en peligro de extincion, de la cual aun no hay informacion suficiente sobre el cultivo de plantas en vivero. Por ello, el objetivo de este estudio fue analizar el efecto de la cobertura y de la fertilizacion en el desarrollo inicial de las plantas durante una temporada. Utilizando un diseno en parcelas divididas en bloques al azar, se ensayaron tres niveles de sombra (malla Raschel® de 35, 50, y 80 %) y tres dosis de fertilizante de entrega lenta (4, 6, y 10 g de Osmocote® por litro de sustrato). Los resultados muestran que hubo un efecto significativo de la sombra en el desarrollo de las plantas, observandose mejores atributos en plantas con 35-50 % de sombra, respecto de las cultivadas con 80 %. En general, la fertilizacion no afecto el desarrollo de las plantas. Se puede concluir que es mas eficiente cultivar plantas de N. alessandrii en vivero bajo una cobertura de 35 % de sombra y fertilizando con 4 g L-1. Asi, es posible producir, en promedio, plantas de 28 cm de longitud de tallo, 4 mm de diametro de cuello de la raiz, 3,2 g planta-1 de biomasa total e indices de calidad de 6,9 para el de esbeltez, 2,2 para el de tallo-raiz y 2,1 para el de Dickson.

Establishment of a Nothofagus alessandrii plantation using different levels of shade and weed control methods in Talca province, central Chile

There is a lack of information regarding the establishment of Nothofagus alessandrii plantations, including any impacts that shading and weed control may have on early survival and growth. A trial was therefore initiated where four shade levels (0% and Rachel® plastic net of 50%, 65%, and 80%) and two weed control methods (chemical and mulching) were tested. Three years after establishment, significant differences in survival were found in response to shading with 0% survival of seedlings planted with no shade protection. At the end of the three-year study period, there were no differences in height and diameter growth in response to weed control and shade protection. However, there were significant differences in carbohydrate concentration and plant biomass in response to level of shading, with differences in the morphological attributes of leaves also apparent. In general, as the shade level increased, the carbohydrate concentration and the biomass decreased and the leaves showed a greater specific leaf area. The method of weed control did not significantly affect any of the variables studied. The results indicate that shading is necessary for establishing young N. alessandrii plants.

Effect of shading and fertilisation on the development of container-grown Nothofagus glauca seedlings, a threatened species from central Chile

Nothofagus glauca is an endemic tree of the Mediterranean zone of Chile and is a threatened species. Currently, available information for the propagation and nursery cultivation of this species is conspicuously lacking. This study examined the effect of four levels of shade (18%, 35%, 65% and 80% with Raschel® plastic net) and four rates of slow-release fertiliser (2.5, 5, 7.5, and 10 g l−1 of Basacote® Plus 9M) on container-grown seedlings after one growing season. Growth was significantly affected by shade and fertilisation. Seedlings grown under 18% or 35% shade were larger in diameter and had more roots than those grown under 80% shade and fertilisation with 2.5–5 g l−1 of media were smaller than those fertilised with 7.5–10 g l−1.

The physiological and growth response of Acacia caven under water stress and the application of different levels of biosolids

Acacia caven (Mol.) Mol. (Leguminosae), generally known as “espino,” is one of the most common tree species in the Mediterranean region of Chile. This species grows in nutritionally poor soils with low water availability during the summer, so it is very difficult for new seedlings to become established. To investigate the effects of water restriction and the potential benefit of the application of biosolids (sludge bio-dried to 25% moisture) on the growth of the plant, a completely random, two x three factorial design was carried out in controlled nursery conditions under two irrigation regimes (well-watered plants and controlled water restriction) and three biosolid application rates (0:100, 10:90 and 20:80) in a clay substrate. Physiological evaluations (predawn water potential, photosynthesis and gas exchange) were performed at representative times along the water restriction gradients and supplemented with measurements of growth and biomass distribution. Once plants entered the water restriction phase, those in the biosolid-treated substrate exhibited better hydration compared to plants in the untreated substrate. This was attributed to the increased organic matter content as well as to changes in the textural characteristics of the original substrate that increased its capacity to deliver water to the plants. Additionally, the application of biosolids promoted shoot and leaf growth in well-watered plants, increasing the shoot:root ratio, which could be a disadvantage under water stress. Acacia c aven (Mol.) Mol. (Leguminosae), generalmente conocido como “espino”, es una de las especies arboreas mas comunes en la region mediterranea de Chile. Esta especie crece en suelos nutricionalmente pobres y con una baja disponibilidad hidrica estival, que dificulta el proceso de establecimiento de nuevas plantulas. Para investigar los efectos de la restriccion hidrica y el potencial benefico de la aplicacion de biosolidos (biosolido-seco a 25% de humedad) en el crecimiento de la planta, se establecio un ensayo con un diseno bifactorial completamente al azar en vivero bajo condiciones controladas. Se aplicaron dos tipos de riego (plantas bien regadas y restriccion hidrica controlada) y tres dosis de aplicacion de biosolidos en un sustrato arcilloso (0:100, 10:90 y 20:80). La evaluacion fisiologica (potencial hidrico a pre-alba, fotosintesis e intercambio gaseoso) fue realizada en momentos representativos del gradiente de restriccion hidrica, y fue complementada con mediciones de crecimiento y distribucion de biomasa. Cuando las plantas entraron en la fase de restriccion hidrica, aquellas que se crecieron en un sustrato con biosolido, presentaron una mejor condicion hidrica en comparacion con las plantas sin biosolido. Esto se debe a un aumento en el contenido de materia organica y a un cambio en las caracteristicas texturales del sustrato original, incrementando la capacidad para suministrar agua a las plantas. Adicionalmente, la aplicacion de biosolidos promovio el crecimiento de hojas y tallos en plantas bien regadas, e incremento la relacion tallo: raiz, que es una desventaja para la tolerancia al estres hidrico.

MORPHOANATOMY OF NOTHOFAGUS ALESSANDRII SEEDS AND ITS USE IN THE VARIABILITY OF POPULATIONS

Nothofagus alessandrii es una especie endemica del area Mediterranea de Chile, de la cual no se cuenta con informacion sobre la estructura anatomica de sus semillas. Existen muy pocos estudios sobre la variabilidad morfologica y de germinacion entre sus poblaciones. El objetivo de este estudio fue describir la estructura morfoanatomica de semillas de N. alessandrii con el fin de comparar la morfologia y la germinacion entre cuatro poblaciones geograficamente separadas. Se seleccionaron semillas de cuatro origenes geograficos a lo largo de la distribucion latitudinal de la especie, y se midieron el tamano, la forma, el peso seco, y la germinacion. Los resultados mostraron que las semillas de N. alessandrii tienen una estructura anatomica similar a la de otras especies de la familia Fagaceae como Fagus sylvatica. No se encontraron diferencias significativas en las caracteristicas morfologicas de los lotes estudiados, ni tampoco en el poder germinativo, por lo que no se ha observado una variacion clinal entre poblaciones, aunque la poblacion localizada mas al sur presento variaciones en longitud y peso, sugiriendo la posibilidad de ecotipo diferenciado.

Efectos combinados de la restricción hídrica, el tamaño de contenedor y la dosis de fertilizante en la supervivencia, intercambio gaseoso y atributos morfológicos en plantas de Quillaja saponaria

Quillaja saponaria is a valuable commercial and ecological Chilean native species that has suffered considerably degradation countrywide; however, the determination of the optimum characteristics of the planting stock, an important aspect in restoration projects, has receive little attention. The aim of this study was to evaluate the effect of container size and dose of fertilizer on morphological and physiological responses of Q. saponaria seedlings cultivated in a nursery under well-watered and water restricted conditions. After 27 days growing under contrasting watering regimes, growth, biomass allocation, and gas exchange were measured in 6-month-old seedlings. We found that survival, height and diameter increment, and root dry weight were higher in the water stressed seedlings cultivated in large containers. The water stressed seedlings cultivated in large containers also had superior stomatal conductance, however when the fertilizer dose was decreased, this trait decreased considerably. Thus, a superior performance in a water-restricted environment could be expected in those seedlings cultivated in larger containers with low fertilizer.

Biomass production and carbon balance of a short rotation forestry of Populus deltoides (clone Lux) under two different cutting cycles

The emissions of green house gases contribute to global warming. Consequently, renewable energies such as solar, wind power, hydropower and bio energy appear as alternatives for reducing these emissions. One promising source of renewable energy is forest biomass, for it is considered to have neutral CO2 balance. The problem is to quantify the amount of CO2 that is emitted for a certain amount of energy generated, compared to the CO2 emitted to generate the same amount of energy from a non-renewable source. In this paper we calculate biomass production and carbon dioxide balance of an eight-year-old Populus deltoides short rotation forestry (SRF) under two cutting cycles (harvesting every two years, biennial and every three years, triennial). We also compare the amount of energy generated per kg of CO2 emitted in the use of fossil fuels versus the amount of energy generated per kilogram of CO2 emitted. On the one hand, total biomass yield was 12.6 ± 0.9 Mg ha-1 year-1 and 15.1 ± 1.5 Mg ha-1 year-1 for biennial and triennial cutting cycles respectively. On the other hand, total emissions of CO2 for growing a poplar SRF with a cycle of eight year and biennial cutting sequence reached a value of 738.8 kg ha-1 year-1; however, triennial short total emissions are equivalent to 695.5 kg ha-1 year-1. We concluded that the use of biomass makes a positive contribution to the reduction of greenhouse gases, in particular CO2, reducing emissions almost five times compared with fossil fuels.

Energy balance in a bioenergy plantation of Populus deltoides clone Lux in a site with Mediterranean environment.

Ante el desafio energetico al cual se enfrenta el mundo en general, y Chile no es una excepcion, los cultivos forestales con destinacion energetica se han ido posicionando como una alternativa viable para la diversificacion de la matriz energetica del pais. Este tipo de cultivos, aun en fase de desarrollo, se basan en turnos cortos de rotacion con altas producciones de biomasa. El problema surge a la hora de evaluar la sostenibilidad de dichos cultivos. El calculo del balance energetico es clave para valorar dicha sostenibilidad, es decir, no se puede gastar mas energia en producir biomasa que la que esta otorga con la combustion. En este trabajo se calcula el balance energetico, considerando los productos de la cosecha puestos a orilla de camino, de un cultivo de Populus deltoides clon Lux con fines energeticos durante un periodo de ocho anos (2000-2008), comparando un turno de rotacion bienal (T2) con uno trienal (T3) en un sitio con ambiente mediterraneo. Para ello se ha calculado el costo energetico de la produccion y cosecha, y la cantidad de energia liberada en la combustion de la biomasa generada. En ambos turnos de rotacion se obtienen resultados positivos, siendo mas conveniente energeticamente el turno trienal respecto al bienal (34,7 T2 vs 25 T3).