Memoria para optar al Título Profesional de Ingeniero Forestal

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Memoria para optar al Título Profesional de Ingeniero Forestal / El estudio tuvo como propósito evaluar el ensayo clonal de Sequoia sempervirens, ubicado en Forestal Voipir, región de la Araucanía, a siete años de su establecimiento. El ensayo diseñado en bloques completos al azar, compuesto por 34 tratamientos (clones) de la colección de clones de Kuser, provenientes del condado de Humboldt, Estado de California, Estados Unidos. Para realizar la evaluación se midió Diámetro a la Altura del Pecho (DAP), Diámetro a la Altura de la Base (DAB), Altura (H) y se calculó el Índice de Biomasa (DAP2H). Adicionalmente se realizó calificación basada en apreciación visual de la presencia de daño, excentricidad de fuste, grosor de ramas, presencia de bifurcaciones y rectitud fustal. En esta última, además, se empleó una escala de puntuación, la cual estuvo basada en la magnitud de la desviación más cercana al DAP y al número de curvaturas por cada metro de fuste. Todas estas mediciones se realizaron en el mes de Abril en el año 2009.

Memoria para optar al Título Profesional de Ingeniero Forestal

The 3-PG physiological/mensurational hybrid model is a useful forest management tool capable of producing accurate growth results across a number of parameterised species. The temperature data used in the model are the average maximum and minimum values for photosynthesis above the compensation point (Landsberg and Sands 2011). There is a minimum temperature below which positive net CO₂ exchange will not occur, a maximum temperature above which it will not occur and an optimum temperature at which it is maximised. These parameters are used in the 3-PG physiological model of forest production. However, a species’ photosynthetic response to short-term variation may differ from one season to another as species acclimate to temperatures over periods of a few weeks. In this study, acclimation responses of four species of eucalypt and Sequoia sempervirens to long-term temperatures were studied over a wide range of short-term temperature changes in order to identify the minimum, optimum and maximum temperatures of CO₂ assimilation for physiological/mensurational hybrid modelling, and also to identify the sites for which the species would be best suited. In order to achieve the aims of this study, a growth chamber experiment was established. Seedlings of four eucalypt species and Sequoia sempervirens were grown at base-line day/night temperatures of 30/16, 22/12 and 10/5ºC in controlled environment chambers for three months and leaf gas exchange measurements were made of the species at seven short-term temperature levels (5, 10, 15, 20, 25, 30 and 35ºC). The optimum and the maximum temperatures for net photosynthesis increased with an increase in base-line temperature for all species. The highest optimum temperature and net photosynthetic rates recorded were in plants grown at 30/16ºC and the lowest were in those grown at 10/5ºC. The maximum rate of net CO₂ assimilation increased with the temperature at which plants were grown partly because of acclimation in key photosynthetic processes in the Calvin cycle. Responses of maximal carboxylation rate (Vcmax) and also the maximal light-driven electron flux (Jmax) to short-term temperature change varied with base-line temperature for all species studied. Net photosynthesis and photosynthetic parameters measured did not vary significantly with effects of nitrogen, phosphorus and their interaction (p = 0.1468). The ratio of Jmax to Vcmax decreased with increasing leaf temperatures for all species (p < 0.001). These results indicate that the species studied will adapt to long-run changes in temperature, and the parameters obtained from these studies can be used for models that simulate the physiology and growth of the species.

Memoria para optar al Título Profesional de Ingeniero de la Madera

Memoria para optar al Título Profesional de Ingeniero Forestal

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Disturbance is fundamental to forest ecosystem function and overall health, but climate change is likely to increase both disturbance frequency and intensity in the future. Forests subject to increasingly frequent and intense disturbances are more likely to experience compounding disturbance effects. Compounding disturbances may exert unpredicted, non-additive stresses on ecosystems, leading to novel conditions that may exceed the capacity for local species to survive and regenerate. I further hypothesize that compounding disturbances could create conditions misaligned with species’ adaptations by altering physical and chemical growing conditions in forest soils, affecting forest composition, structure, and, subsequently, function for many years following disturbance. A better understanding of these remnant effects will be essential to managing and conserving coast redwood forests, which are projected to see increased frequency of fire under future climate scenarios. My objectives in this study were to quantify the effects of time-since-fire and single vs. compounding disturbances on coast redwood forest structure, composition, and regeneration dynamics and to evaluate the effects of abiotic soil qualities on post-fire regeneration. I mapped and sampled coast redwood forests burned in 1985, both 1985 and 1999, 2008, and 2013; modeled regeneration as a function of burn history, understory light, and post-fire nutrient levels; and tested redwood seed regeneration in post-fire soils in a greenhouse experiment. Forest structure, composition, and regeneration following compounding disturbance were most similar to the homogenous, redwood-dominated forest of the recent 2013 burn. There were no unique effects of compounding disturbance on soil nutrient levels, although variations in nutrient levels generally followed patterns seen in previous studies. Soil nitrate was positively associated with coast redwood regeneration levels, showing that soil nutrients may be influential in regeneration processes following disturbance. Time since burn and single burn histories were negatively associated with regeneration levels in the field, and there were no differences in seed germination in the greenhouse between soils from different fire histories. Increases in coast redwood forest dominance accompanied declines in bay laurel and tanoak presence, indicating a shift in post-fire forest structure and composition resulting from compounding disturbance. These results illustrate a complex relationship between regeneration dynamics, post-fire soil quality, and disturbance histories. Forest homogenization from compounding disturbances may have negative implications for ecosystem services and overall function if compounding disturbances are more frequent as predicted under future climate conditions.