La acción de los cerambícidos xilófagos, principalmente los géneros Cerambyx y Prinobius, se ha c... more La acción de los cerambícidos xilófagos, principalmente los géneros Cerambyx y Prinobius, se ha considerado un factor desencadenante y/o agravante en el problema de la «seca» del género Quercus en nuestro país (Montoya, 1992; Muñoz et al., 1996; Navarro et al., 2004). A pesar de ello, se desconoce la importancia real del papel que desempeñan en el decaimiento de las formaciones forestales donde la encina y el alcornoque son especies arbóreas dominantes, en especial las dehesas y los alcornocales. A este desconocimiento contribuyen los hábitos de comportamiento de
La brea, Cercidium praecox (Ruiz y Pav.) Burkart y Carter, es un árbol con amplia distribución en... more La brea, Cercidium praecox (Ruiz y Pav.) Burkart y Carter, es un árbol con amplia distribución en el Noroeste argentino, donde forma parte de las grandes unidades de vegetación del Parque Chaqueño o bien rodales puros (breales) en ambientes degradados. Esta especie tiene un escaso valor económico para la actividad de extracción maderera, pero su exudado vascular (goma) ha sido aprovechado tradicio- nalmente por las comunidades campesinas de las zonas más áridas como medicina, curación de artículos de cerámicas, como pegamento casero. Sus propiedades químicas son similares a las de la goma arábiga.
Eucalyptus globulus Labill. es una especie ampliamente utilizada en plantaciones comerciales y ad... more Eucalyptus globulus Labill. es una especie ampliamente utilizada en plantaciones comerciales y adaptada a vivir sobre suelos pobres y bajo clima mediterráneo. Durante 32 meses se estudió la evolución del crecimiento diametral diario de cuatro clones de la especie, tres de ellos de la generación de mejora F1 (C, O, T) y un clon de referencia de la F0 (A), en una parcela de secano de la provincia de Huelva, realizando lecturas cada 30 min. El crecimiento diametral medio de todo el período estudiado rondó los 4 cm, con diferencias entre clones A<T<C=O. Durante el verano se ralentizó bruscamente el crecimiento pero se mantuvo activo durante las otras tres estaciones, en concordancia con la humedad edáfica y la temperatura ambiente. Los árboles alcanzaban la máxima dilatación diaria del diámetro justo antes del amanecer y el valor mínimo sobre las 16 horas solares, pero dependía de las condiciones ambientales. Los clones más productivos, bien adelantaban dicho máximo (C), bien retr...
El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de... more El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de combustibles fósiles, el abandono de terrenos agrícolas marginales y el despoblamiento rural pueden dar un nuevo impulso al cultivo de biomasa lignocelulósica para su uso como fuente de energía renovable. No obstante, las particularidades edafoclimáticas de los suelos cultivados del ambiente mediterráneo pueden limitar la producción y conducir a procesos de degradación irreversibles en dichos ecosistemas. Se hace, por tanto, necesaria la realización de estudios conducentes a establecer qué especies son las más apropiadas en diferentes condiciones edafo-climáticas, con el fin de optimizar los costes económicos y medioambientales, atendiendo a la eficiencia del proceso productivo. Por ello se ha realizado un ensayo donde 15 genotipos (especies, variedades, clones) de especies leñosas se plantaron en dos lugares de condicones edafo-climáticas contrastadas (provincias de Huelva y Granada). ...
Leucaena leucocephala and L. diversifolia produced high biomass with regrowths of a year, 30-35 (... more Leucaena leucocephala and L. diversifolia produced high biomass with regrowths of a year, 30-35 (max. 50) TDM ha-1 yr-1. After 10 years of study and up to 6 short ,in some cases, the plants continue to show vigorous regrowth and soil have evolved favourably in N, OM and enzymatic activities. However, it would be necessary phosphorus fertilization to assure sustainability.
El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de... more El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de combustibles fósiles, el abandono de terrenos agrícolas marginales y el despoblamiento rural pueden dar un nuevo impulso al cultivo de biomasa lignocelulósica para su uso como fuente de energía renovable. No obstante, las limitaciones hídricas del ambiente mediterráneo y la pobreza y vulnerabilidad de los suelos cultivados pueden dar lugar a procesos de degradación irreversibles en dichos ecosistemas. Se hace, por tanto, necesaria la realización de estudios conducentes a establecer qué especies y con qué costes medioambientales se pueden implantar en diferentes condiciones edafo-climáticas. Por ello se ha estudiado el consumo de agua de nueve genotipos (Populus x canadensis “AF2”, Eucalyptus globulus, Eucalyptus dunnii, Eucalyptus camaldulensis, Paulownia x “UHU”, Leucaena diversifolia, Ulmus pumila, Casuarina equisetifolia y Robinia pseudoacacia), cultivados en vivero, en contenedores ...
ABSTRACT Phytophthora cinnamomi Rands is the main pathogen behind for holm and cork oak decline i... more ABSTRACT Phytophthora cinnamomi Rands is the main pathogen behind for holm and cork oak decline in the southwest of the Iberian Peninsula and poses one of the most severe environmental problems currently threatening the ecological and economic sustainability of Quercus forests in this region. In this work, we examined variability in the tolerance/resistance of cork oak saplings to this pathogen. To this end, seeds from 20 individuals in each of 8 different Spanish and Portuguese regions were studied. Following pregermination in sterile substrate in the laboratory, seedlings were grown in a greenhouse, using 300 ml pots that were filled with substrate infested with the pathogen at three different levels, namely: N (naturally infested, natural soil containing vermiculite), P (as N, but subjected to partial pasteurization) and A (artificially infested soil obtained by adding a fixed amount of fungal mycelium). The trial was conducted by using na identical experimental design in two dif...
Gestión adaptativa al cambio Global en masas de Quercus mediterráneos pau vericat Grau 1 (ed.) mí... more Gestión adaptativa al cambio Global en masas de Quercus mediterráneos pau vericat Grau 1 (ed.) míriam piqué nicolau 1 (ed.) rafael serrada Hierro 2 (ed.
Investigación Agraria: Sistemas y Recursos Forestales, 2005
The mediterranean-climate regions are linked to the presence of the unusual global conditions of ... more The mediterranean-climate regions are linked to the presence of the unusual global conditions of cool rainy winters and warm dry summers. Thus, the common drought periods, frost nights, summer heat and fires and soil erosion disturb plants life. These regions have a global significance by their floristic richness. Nevertheless, these areas have been more heavily impacted by human activities than almost any other ecosystem. The foreseeable global change will most likely influence plant life, and the Mediterranean Basin will be specially affected (e.g. a decrease in spring and winter rainfalls, an increase in mean annual temperature), affecting the delicate equilibrium of these ecosystems. Ecophysiology is a powerful tool to examine the controlling mechanisms behind the functioning, distribution, abundance, and productivity of forest tree species and their response to a changing environment. This science discipline can help to the forest management by physiological approaches of the response of plant processes to the biotic and abiotic constraints imposed by the environment.
In order to identify fast growing species utilizable for olygomer and monomer production, five fa... more In order to identify fast growing species utilizable for olygomer and monomer production, five fast growing species (Paulownia fortunei, Chamaecytisus proliferus, Arundo donax, Leucaena.diversifolia and Sesbania grandiflora) were tested. Concurrently, the biomass productivity of these species was also tested on a field scale. The biomass productivity of the selected species studied ranges from 0.36 to 21.30 t ha-1 (o.d.b.) under Mediterranean conditions for the year 1 sprouts. In addition, the hydrothermal treatment results show that the selected species could be employed as alternative raw material for the production of oligomers, leading to a high concentration of oligomers (9.4-23.4 g/L-1 at 190ºC).
Se describió la evolución anual del estado hídrico y la producción de bellota de Quercus ilex ssp... more Se describió la evolución anual del estado hídrico y la producción de bellota de Quercus ilex ssp. ballota en una parcela de la provincia de Huelva, suroeste de España, en relación a distintos tratamientos de suelo. Para ello se obtuvieron parámetros hídricos derivados de curvas presión-volumen y transpiración cuticular. Junto a ello se describió la producción de bellotas del período 2006-2007. Los parámetros hídricos analizados no presentaron diferencias significativas entre tratamientos, pero sí entre fechas, estando comprendidos los valores de potenciales hídricos xilemáticos entre -2,7 MPa y -0,7 MPa. La transpiración cuticular presentó valores de oscilación entre 70,3 y 192,9 mmol.kg-1.s-1. La producción de bellota no presentó diferencias entre tratamientos de suelo, y se caracterizó por la amplia variabilidad entre individuos con valores entre 0 y 1258 g.m-2. Los resultados reflejaron características propias de esta especie para lograr su adaptación al clima mediterráneo, logr...
Forest restoration programs using Holm oak have enjoyed only limited success. The vulnerability t... more Forest restoration programs using Holm oak have enjoyed only limited success. The vulnerability to stress and the low plant quality seem to be the main factors that limit plantation success. In addition the effect of using inappropriate provenances in plantation success is still unknown and previous studies about phenotypic plasticity in this specie are in disagreement about in what extent tolerance to stress may be due to acclimatization to environmental conditions or to genetic adaptation to individual provenances. Our objective was to test the hypothesis that seedlings from different provenances have different response to stress factors, such as frosts and drought, in nursery and after field plantation. Healthy acorns of Quercus ilex ssp. ballota (Desf.) Samp. from two Spanish provenances (Sierra de Segura (GR) and Sierra Morena Occidental (HU)) were randomly sown in 300 cm3 containers (215 per provenance). They were watered as needed and a constant fertilization regimen was appl...
Silvopastoralism and sustainable land management. Proceedings of an international congress on silvopastoralism and sustainable management held in Lugo, Spain, April 2004, 2005
This study evaluates the use possibilities of a fastgrowing leguminous woody plants like alternat... more This study evaluates the use possibilities of a fastgrowing leguminous woody plants like alternative crops dedicated to biomass production for energy source. We cultivate 14 species / provenances of genera Leucaena (L. leucocephala, L. salvadorensis, L. diversifolia, L. collinsi), Prosopis (P. alba and P. julyflora), Sesbania (S. sesban), Chamaecytisus (C. proliferus var palmensis) and Retama (R. monosperma). The plants were produced from seeds and inoculated with specific bacteria of the genus Rhizobium. After a nursery phase, seedling were planted in two experimental plots subjected to two water regimes. Annual biomass production was evaluated under three management systems: annual biannual and three annual clear-cutting All the species and varieties except Leucaena salvadorensis and Sesbania sesban showed a good edafo-climatic adaptation to the characteristics of the study area (Huelva). Variation in growth rates among species was high, from the 0.3 t of woody dry matter per hectare and year (Retama monosperma, Prosopis juliflora) until 25-35 t ha-1 year-1 (Leucaena leucocephala). All the species supported annual cutting with a vigorous re-sprouts except Chamaecytisus proliferus that was very susceptible especially in the most irrigated plots.
This work presents the first results about the aptitude for electroantennography (EAG) of olfacto... more This work presents the first results about the aptitude for electroantennography (EAG) of olfactory stimuli of Cerambyx welensii Kuster (Coleoptera, Cerambycidae), the main woodborer of holm oak (Quercus ilex L.) and cork oak (Quercus suber L.) in Western Andalusia (Spain). Due to the importance of the damages caused by this species, the characteristics and complexity of the ecosystems where he
A wide set of phenotypic characteristics related to life history were studied in mature stands of... more A wide set of phenotypic characteristics related to life history were studied in mature stands of Pinus canariensis throughout its natural range of distribution in the Canary archipelago. Natural forests ranging from those located in xeric areas through to the subtropical cloud forests and high mountain stands were classified into eight ecological regions according to their main climatic features. The recent history of forest fires (covering the last 30 years) was taken into account using a categorical factor with three levels. The phenotypic variables studied included those related to seed dispersal (cone size, number of seed scales, seed and wing size and percentage of serotinous trees) and stem growth both on the breast height section (bark thickness, radial growth at various ages and sapwood and heartwood sizes) and on the entire stem (height growth related to age). The average percentage of serotinous trees present in the ecological regions studied varied from 3 to 35%. Average bark thickness in adult trees ranged from 22 to 49 mm and was found to be unrelated to age or diameter. Growth both in height and diameter was found to decline after an average of 25 years, although clear trends in relation to this could not be established across the ecological regions. A high correlation was found to exist between annual rainfall, fire frequency, serotiny and bark thickness at a regional level. Sapwood area per hectare proved to be a valuable indirect site-quality index for the objectives of this paper. Favourable sites (characterised by a high sapwood area per hectare) displayed the highest levels of both bark thickness and serotiny. These particular areas are those, which have suffered more frequent and intense fires over the last decades. The evolutionary implications of this trend and of other general traits of the species, such as vegetative resprouting, are discussed here in relation to the role of understorey vegetation in fire regimes, competition and volcanic history of the islands.
La acción de los cerambícidos xilófagos, principalmente los géneros Cerambyx y Prinobius, se ha c... more La acción de los cerambícidos xilófagos, principalmente los géneros Cerambyx y Prinobius, se ha considerado un factor desencadenante y/o agravante en el problema de la «seca» del género Quercus en nuestro país (Montoya, 1992; Muñoz et al., 1996; Navarro et al., 2004). A pesar de ello, se desconoce la importancia real del papel que desempeñan en el decaimiento de las formaciones forestales donde la encina y el alcornoque son especies arbóreas dominantes, en especial las dehesas y los alcornocales. A este desconocimiento contribuyen los hábitos de comportamiento de
La brea, Cercidium praecox (Ruiz y Pav.) Burkart y Carter, es un árbol con amplia distribución en... more La brea, Cercidium praecox (Ruiz y Pav.) Burkart y Carter, es un árbol con amplia distribución en el Noroeste argentino, donde forma parte de las grandes unidades de vegetación del Parque Chaqueño o bien rodales puros (breales) en ambientes degradados. Esta especie tiene un escaso valor económico para la actividad de extracción maderera, pero su exudado vascular (goma) ha sido aprovechado tradicio- nalmente por las comunidades campesinas de las zonas más áridas como medicina, curación de artículos de cerámicas, como pegamento casero. Sus propiedades químicas son similares a las de la goma arábiga.
Eucalyptus globulus Labill. es una especie ampliamente utilizada en plantaciones comerciales y ad... more Eucalyptus globulus Labill. es una especie ampliamente utilizada en plantaciones comerciales y adaptada a vivir sobre suelos pobres y bajo clima mediterráneo. Durante 32 meses se estudió la evolución del crecimiento diametral diario de cuatro clones de la especie, tres de ellos de la generación de mejora F1 (C, O, T) y un clon de referencia de la F0 (A), en una parcela de secano de la provincia de Huelva, realizando lecturas cada 30 min. El crecimiento diametral medio de todo el período estudiado rondó los 4 cm, con diferencias entre clones A<T<C=O. Durante el verano se ralentizó bruscamente el crecimiento pero se mantuvo activo durante las otras tres estaciones, en concordancia con la humedad edáfica y la temperatura ambiente. Los árboles alcanzaban la máxima dilatación diaria del diámetro justo antes del amanecer y el valor mínimo sobre las 16 horas solares, pero dependía de las condiciones ambientales. Los clones más productivos, bien adelantaban dicho máximo (C), bien retr...
El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de... more El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de combustibles fósiles, el abandono de terrenos agrícolas marginales y el despoblamiento rural pueden dar un nuevo impulso al cultivo de biomasa lignocelulósica para su uso como fuente de energía renovable. No obstante, las particularidades edafoclimáticas de los suelos cultivados del ambiente mediterráneo pueden limitar la producción y conducir a procesos de degradación irreversibles en dichos ecosistemas. Se hace, por tanto, necesaria la realización de estudios conducentes a establecer qué especies son las más apropiadas en diferentes condiciones edafo-climáticas, con el fin de optimizar los costes económicos y medioambientales, atendiendo a la eficiencia del proceso productivo. Por ello se ha realizado un ensayo donde 15 genotipos (especies, variedades, clones) de especies leñosas se plantaron en dos lugares de condicones edafo-climáticas contrastadas (provincias de Huelva y Granada). ...
Leucaena leucocephala and L. diversifolia produced high biomass with regrowths of a year, 30-35 (... more Leucaena leucocephala and L. diversifolia produced high biomass with regrowths of a year, 30-35 (max. 50) TDM ha-1 yr-1. After 10 years of study and up to 6 short ,in some cases, the plants continue to show vigorous regrowth and soil have evolved favourably in N, OM and enzymatic activities. However, it would be necessary phosphorus fertilization to assure sustainability.
El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de... more El déficit energético en la Unión Europea, las emisiones de contaminantes y CO2 por el consumo de combustibles fósiles, el abandono de terrenos agrícolas marginales y el despoblamiento rural pueden dar un nuevo impulso al cultivo de biomasa lignocelulósica para su uso como fuente de energía renovable. No obstante, las limitaciones hídricas del ambiente mediterráneo y la pobreza y vulnerabilidad de los suelos cultivados pueden dar lugar a procesos de degradación irreversibles en dichos ecosistemas. Se hace, por tanto, necesaria la realización de estudios conducentes a establecer qué especies y con qué costes medioambientales se pueden implantar en diferentes condiciones edafo-climáticas. Por ello se ha estudiado el consumo de agua de nueve genotipos (Populus x canadensis “AF2”, Eucalyptus globulus, Eucalyptus dunnii, Eucalyptus camaldulensis, Paulownia x “UHU”, Leucaena diversifolia, Ulmus pumila, Casuarina equisetifolia y Robinia pseudoacacia), cultivados en vivero, en contenedores ...
ABSTRACT Phytophthora cinnamomi Rands is the main pathogen behind for holm and cork oak decline i... more ABSTRACT Phytophthora cinnamomi Rands is the main pathogen behind for holm and cork oak decline in the southwest of the Iberian Peninsula and poses one of the most severe environmental problems currently threatening the ecological and economic sustainability of Quercus forests in this region. In this work, we examined variability in the tolerance/resistance of cork oak saplings to this pathogen. To this end, seeds from 20 individuals in each of 8 different Spanish and Portuguese regions were studied. Following pregermination in sterile substrate in the laboratory, seedlings were grown in a greenhouse, using 300 ml pots that were filled with substrate infested with the pathogen at three different levels, namely: N (naturally infested, natural soil containing vermiculite), P (as N, but subjected to partial pasteurization) and A (artificially infested soil obtained by adding a fixed amount of fungal mycelium). The trial was conducted by using na identical experimental design in two dif...
Gestión adaptativa al cambio Global en masas de Quercus mediterráneos pau vericat Grau 1 (ed.) mí... more Gestión adaptativa al cambio Global en masas de Quercus mediterráneos pau vericat Grau 1 (ed.) míriam piqué nicolau 1 (ed.) rafael serrada Hierro 2 (ed.
Investigación Agraria: Sistemas y Recursos Forestales, 2005
The mediterranean-climate regions are linked to the presence of the unusual global conditions of ... more The mediterranean-climate regions are linked to the presence of the unusual global conditions of cool rainy winters and warm dry summers. Thus, the common drought periods, frost nights, summer heat and fires and soil erosion disturb plants life. These regions have a global significance by their floristic richness. Nevertheless, these areas have been more heavily impacted by human activities than almost any other ecosystem. The foreseeable global change will most likely influence plant life, and the Mediterranean Basin will be specially affected (e.g. a decrease in spring and winter rainfalls, an increase in mean annual temperature), affecting the delicate equilibrium of these ecosystems. Ecophysiology is a powerful tool to examine the controlling mechanisms behind the functioning, distribution, abundance, and productivity of forest tree species and their response to a changing environment. This science discipline can help to the forest management by physiological approaches of the response of plant processes to the biotic and abiotic constraints imposed by the environment.
In order to identify fast growing species utilizable for olygomer and monomer production, five fa... more In order to identify fast growing species utilizable for olygomer and monomer production, five fast growing species (Paulownia fortunei, Chamaecytisus proliferus, Arundo donax, Leucaena.diversifolia and Sesbania grandiflora) were tested. Concurrently, the biomass productivity of these species was also tested on a field scale. The biomass productivity of the selected species studied ranges from 0.36 to 21.30 t ha-1 (o.d.b.) under Mediterranean conditions for the year 1 sprouts. In addition, the hydrothermal treatment results show that the selected species could be employed as alternative raw material for the production of oligomers, leading to a high concentration of oligomers (9.4-23.4 g/L-1 at 190ºC).
Se describió la evolución anual del estado hídrico y la producción de bellota de Quercus ilex ssp... more Se describió la evolución anual del estado hídrico y la producción de bellota de Quercus ilex ssp. ballota en una parcela de la provincia de Huelva, suroeste de España, en relación a distintos tratamientos de suelo. Para ello se obtuvieron parámetros hídricos derivados de curvas presión-volumen y transpiración cuticular. Junto a ello se describió la producción de bellotas del período 2006-2007. Los parámetros hídricos analizados no presentaron diferencias significativas entre tratamientos, pero sí entre fechas, estando comprendidos los valores de potenciales hídricos xilemáticos entre -2,7 MPa y -0,7 MPa. La transpiración cuticular presentó valores de oscilación entre 70,3 y 192,9 mmol.kg-1.s-1. La producción de bellota no presentó diferencias entre tratamientos de suelo, y se caracterizó por la amplia variabilidad entre individuos con valores entre 0 y 1258 g.m-2. Los resultados reflejaron características propias de esta especie para lograr su adaptación al clima mediterráneo, logr...
Forest restoration programs using Holm oak have enjoyed only limited success. The vulnerability t... more Forest restoration programs using Holm oak have enjoyed only limited success. The vulnerability to stress and the low plant quality seem to be the main factors that limit plantation success. In addition the effect of using inappropriate provenances in plantation success is still unknown and previous studies about phenotypic plasticity in this specie are in disagreement about in what extent tolerance to stress may be due to acclimatization to environmental conditions or to genetic adaptation to individual provenances. Our objective was to test the hypothesis that seedlings from different provenances have different response to stress factors, such as frosts and drought, in nursery and after field plantation. Healthy acorns of Quercus ilex ssp. ballota (Desf.) Samp. from two Spanish provenances (Sierra de Segura (GR) and Sierra Morena Occidental (HU)) were randomly sown in 300 cm3 containers (215 per provenance). They were watered as needed and a constant fertilization regimen was appl...
Silvopastoralism and sustainable land management. Proceedings of an international congress on silvopastoralism and sustainable management held in Lugo, Spain, April 2004, 2005
This study evaluates the use possibilities of a fastgrowing leguminous woody plants like alternat... more This study evaluates the use possibilities of a fastgrowing leguminous woody plants like alternative crops dedicated to biomass production for energy source. We cultivate 14 species / provenances of genera Leucaena (L. leucocephala, L. salvadorensis, L. diversifolia, L. collinsi), Prosopis (P. alba and P. julyflora), Sesbania (S. sesban), Chamaecytisus (C. proliferus var palmensis) and Retama (R. monosperma). The plants were produced from seeds and inoculated with specific bacteria of the genus Rhizobium. After a nursery phase, seedling were planted in two experimental plots subjected to two water regimes. Annual biomass production was evaluated under three management systems: annual biannual and three annual clear-cutting All the species and varieties except Leucaena salvadorensis and Sesbania sesban showed a good edafo-climatic adaptation to the characteristics of the study area (Huelva). Variation in growth rates among species was high, from the 0.3 t of woody dry matter per hectare and year (Retama monosperma, Prosopis juliflora) until 25-35 t ha-1 year-1 (Leucaena leucocephala). All the species supported annual cutting with a vigorous re-sprouts except Chamaecytisus proliferus that was very susceptible especially in the most irrigated plots.
This work presents the first results about the aptitude for electroantennography (EAG) of olfacto... more This work presents the first results about the aptitude for electroantennography (EAG) of olfactory stimuli of Cerambyx welensii Kuster (Coleoptera, Cerambycidae), the main woodborer of holm oak (Quercus ilex L.) and cork oak (Quercus suber L.) in Western Andalusia (Spain). Due to the importance of the damages caused by this species, the characteristics and complexity of the ecosystems where he
A wide set of phenotypic characteristics related to life history were studied in mature stands of... more A wide set of phenotypic characteristics related to life history were studied in mature stands of Pinus canariensis throughout its natural range of distribution in the Canary archipelago. Natural forests ranging from those located in xeric areas through to the subtropical cloud forests and high mountain stands were classified into eight ecological regions according to their main climatic features. The recent history of forest fires (covering the last 30 years) was taken into account using a categorical factor with three levels. The phenotypic variables studied included those related to seed dispersal (cone size, number of seed scales, seed and wing size and percentage of serotinous trees) and stem growth both on the breast height section (bark thickness, radial growth at various ages and sapwood and heartwood sizes) and on the entire stem (height growth related to age). The average percentage of serotinous trees present in the ecological regions studied varied from 3 to 35%. Average bark thickness in adult trees ranged from 22 to 49 mm and was found to be unrelated to age or diameter. Growth both in height and diameter was found to decline after an average of 25 years, although clear trends in relation to this could not be established across the ecological regions. A high correlation was found to exist between annual rainfall, fire frequency, serotiny and bark thickness at a regional level. Sapwood area per hectare proved to be a valuable indirect site-quality index for the objectives of this paper. Favourable sites (characterised by a high sapwood area per hectare) displayed the highest levels of both bark thickness and serotiny. These particular areas are those, which have suffered more frequent and intense fires over the last decades. The evolutionary implications of this trend and of other general traits of the species, such as vegetative resprouting, are discussed here in relation to the role of understorey vegetation in fire regimes, competition and volcanic history of the islands.
Uploads
Papers by R. Tapias