Linking Dendrometry and Dendrochronology in the Dominant Azorean Tree Laurus azorica (Seub.) Franco

As in many archipelagos, the Azorean primary forest was largely cleared and replaced by secondary forest and grassland, the Azorean tree Laurus azorica (Seub.) Franco being one of the dominant trees in the remaining natural forests. Dendrochronological and dendrometric studies in the Azores mainly focused on non-indigenous trees, either used for timber (e.g., Cryptomeria japonica D. Don) or considered as invasive (Pittosporum undulatum Vent.). Therefore, this study aims to describe the growth ring anatomy of L. azorica, and to understand the relationship between dendrometric traits (e.g., trunk diameter at breast height; tree height), and the number of growth rings. Growth ring anatomy was accessed by wood anatomical preparation of microcore samples while tree age estimation was based on growth ring counts in wood cores taken at breast height and at base. A total of 145 trees were sampled, resulting in 262 increment cores, at six representative stands of laurel forest in São Miguel Island (Azores). The wood anatomical analysis confirmed the presence of clear annual ring boundaries, and a high structural similarity towards Laurus novocanariensis Rivas Mart., Lousã, Fern.Prieto, E.Días, J.C.Costa & C.Aguiar. Age at tree base averaged 33 years, with 60% of the trees between 25 and 50 years old, and only about 15% above 50 years old. This suggests the existence of a secondary forest that is more recent than expected, probably due to human disturbance. The allometric models showed best fit when calculated by stand, suggesting the effect of local environmental conditions on growth rate. Radial growth rate was estimated at 0.68 cm.year−1. Given the known dominance of this species and the threats affecting natural forests, this baseline study will allow a better understanding of forest distribution and dynamics, and support a more effective forest management approach.

Diet of the Endemic Madeira Laurel Pigeon and Fruit Resource Availability: A Study Using Microhistological Analyses

We studied the temporal diet variation of the endemic Madeira Laurel Pigeon (Columba trocaz) and fruit resource availability in the laurel forests of northwestern Madeira Island, during 1996 and 1997. We studied a total of 224 fecal samples using microhistological methods and conducted surveys of fruiting phenology throughout a year. Fruits (pulp and seeds) represented 57% of the optical fields analyzed. Leaves and flowers constituted 38% and <1% respectively. Over 33 plant species were identified in the fecal samples. Fruits of Ocotea foetens, Laurus azorica, Persea indica, and Ilex canariensis (fruits and leaves) were the most frequently detected food items. Most seeds were defecated intact (Ilex canariensis, Myrica faya, Visnea mocanera, Ocotea foetens, and Apollonias barbujana), except in the case of Laurus azorica where most were damaged. The diet showed a marked seasonal variation. Fruits constituted the major component of the diet in winter and autumn, whereas leaves were frequent in spring and summer. The presence of fruits in the diet was concordant with their availability, and leaves and flowers became important when fruits were scarce. This fact suggests that the Madeira Laurel Pigeon is capable of dietary switching, corresponding to temporal variations in food resource availability. This microhistological technique shows promise for study of the diets of pigeons and other herbivorous bird species. Dieta de Columba trocaz y Su Relación con la Disponibilidad de Frutos: Un Estudio Realizado Mediante Análisis Microhistológicos Resumen. Se estudió la dieta estacional de Columba trocaz y la disponibilidad de frutos en los bosques de laurisilva de la zona noroeste de la Isla Madeira, durante 1996 y 1997. Se analizó un total de 224 excrementos mediante métodos microhistológicos, y se realizó un seguimiento estacional de la disponibilidad de frutos, por medio de transectos, a lo largo de un año. Los frutos (pulpa y semillas) representaron un 57% de los campos ópticos analizados; las hojas y las flores constituyeron un 38% y <1%, respectivamente. Más de 33 especies fueron identificadas en los excrementos; restos de frutos de Ocotea foetens, Laurus azorica, Persea indica e Ilex canariensis (tanto frutos como hojas) resultaron ser los más frecuentemente detectados. La mayoría de las semillas fueron defecadas intactas (Ilex canariensis, Myrica faya, Visnea mocanera, Ocotea foetens y Apollonias barbujana), excepto en el caso de Laurus azorica, donde la mayoría de ellas aparecieron dañadas. La dieta mostró un marcado carácter estacional, constituyendo los frutos el componente más importante en invierno y otoño, mientras que las hojas fueron más abundantes en primavera y verano. La presencia de frutos en los excrementos fue concordante con su disponibilidad, adquiriendo una mayor relevancia las hojas y las flores cuando la producción de los frutos fue escasa. Este hecho sugiere que C. trocaz exhibe una alta flexibilidad en la dieta, aprovechando aquellos recursos que son estacionalmente abundantes. Los resultados obtenidos en estos análisis microhistológicos ofrecen un aceptable nivel de fiabilidad para ser utilizados en estudios sobre dieta de palomas y, probablemente, extensibles a otras aves herbívoras.

Two New Sesquiterpenes from Laurus azorica

The structures of a new eudesmane sesquiterpene, lauradiol, and a new secoeudesmane, azoridione, have been determined by spectroscopic methods. These compounds and the known sesquiterpenic alcohols, clovanediol and caryophyllenol II, have been isolated from the aerial parts of Laurus azorica