Minimal Ten-parameter Hermitian Texture Zeroes Mass Matrices and the CKM Matrix

Hermitian mass matrices for the up and down quarks with texture zeroes but with the minimum number of parameters, ten, are investigated. We show how these {\em minimum parameter} forms can be obtained from a general set of hermitian matrices through weak basis transformations. For the most simple forms we show that one can derive exact and compact parametrizations of the CKM mixing matrix in terms of the elements of these mass matrices (and the quark masses).Comment: 14 pages.Talk given by M.B. at the MRST 98, ``Towards the Theory of Everything", Montr\'eal, 13-15 May 199

The role of forest genetic resources in responding to biotic and abiotic factors in the context of anthropogenic climate change

The current distribution of forest genetic resources on Earth is the result of a combination of natural processes and human actions. Over time, tree populations have become adapted to their habitats including the local ecological disturbances they face. As the planet enters a phase of human-induced climate change of unprecedented speed and magnitude, however, previously locally-adapted populations are rendered less suitable for new conditions, and ‘natural’ biotic and abiotic disturbances are taken outside their historic distribution, frequency and intensity ranges. Tree populations rely on phenotypic plasticity to survive in extant locations, on genetic adaptation to modify their local phenotypic optimum or on migration to new suitable environmental conditions. The rate of required change, however, may outpace the ability to respond, and tree species and populations may become locally extinct after specific, but as yet unknown and unquantified, tipping points are reached. Here, we review the importance of forest genetic resources as a source of evolutionary potential for adaptation to changes in climate and other ecological factors. We particularly consider climate-related responses in the context of linkages to disturbances such as pests, diseases and fire, and associated feedback loops. The importance of management strategies to conserve evolutionary potential is emphasised and recommendations for policy-makers are provided

Hacia la restauración con Annona glabra (Annonaceae) de una selva inundable: establecimiento y crecimiento de plántulas, y cambio en la vegetación acompañante

Background and Aims: Currently, freshwater swamps are deteriorating and their cover is decreasing, mainly due to deforestation for livestock and the introduction of exotic grasses. The objectives of this study were to evaluate the survival and the growth of Annona glabra seedlings, monitor changes in the accompanying vegetation, and estimate the cost of our experimental ecological restoration treatments in a freshwater swamp transformed into a flooded pasture and invaded by the exotic grass Echinochloa pyramidalis.Methods: The study was carried out on a floodplain surrounding a mangrove on the coast of central Veracruz, Mexico. It consisted of sowing four A. glabra seedlings in experimental quadrats exposed to different restoration techniques. Fifteen experimental restoration treatments were tested consisting of five restoration techniques (no modification, covering with plastic, planting Pontederia sagittata, soil removal, and raising the soil level), and three pretreatments applied to the seedlings planted (nursery seedlings with and without fertilizer, seedlings collected from the wetlands) in a random block design.Key results: Low seedling survival was recorded (30.7%), but this was higher for the seedlings from freshwater wetlands (41.1%). The highest percent survival was recorded where the soil was raised, followed by the soil removal technique. Regarding the vegetation, 40 species were recorded and the highest species richness was observed where the soil had been raised and where it had been removed. The Relative Importance Value was highest for Echinochloa pyramidalis, Mimosa pigra, and Annona glabra. The pretreatment of obtaining seedlings directly from the wetland was the cheapest one.Conclusions: Action is required to increase reforestation success. For future restoration projects, we recommend that the soil in the transplanting area be raised and covered with plastic before planting, to increase the probability of seedling survival and reduce grass cover. Moreover, seedlings collected from a swamp fragment should be used for reforestation.Antecedentes y Objetivos: Actualmente existe deterioro y disminución de selvas inundables debido a la deforestación para ganadería e introducción de pastos exóticos. Los objetivos del presente estudio fueron evaluar el porcentaje de supervivencia de plántulas de Annona glabra, el cambio en la vegetación acompañante, y estimar los costos de los tratamientos experimentales de restauración ecológica de una selva inundable de A. glabra transformada en pastizal e invadida por el pasto exótico Echinochloa pyramidalis. Métodos: El estudio se realizó en un pastizal inundable en la costa central de Veracruz, México. Consistió en sembrar cuatro plántulas de A. glabra en cuadros experimentales expuestos a distintas técnicas de restauración. Se probaron 15 tratamientos experimentales que consistieron en cinco técnicas de restauración (sin modificación, cubierta plástica, plantación de Pontederia sagittata, remoción de suelo, y elevación del suelo) y tres pretratamientos aplicados a las plántulas sembradas (plántulas de vivero con y sin fertilizante, plántulas de selva) en un diseño de bloques al azar.Resultados clave: Se registró baja supervivencia de plántulas (30.7%), siendo mayor en plántulas de selva (41.1%). El mayor porcentaje de supervivencia se registró con la técnica de elevación del suelo, seguido de la de remoción. Se registraron 40 especies en la vegetación; la mayor riqueza específica se observó en las técnicas de elevación del nivel del suelo y remoción. Las especies con mayor Valor de Importancia Relativa fueron Echinochloa pyramidalis, Mimosa pigra y Annona glabra. El pretratamiento en el cual se obtuvieron las plántulas directamente de la selva fue el más económico.Conclusiones: Se requieren acciones para incrementar el éxito de la reforestación. Para futuros proyectos de restauración, recomendamos la elevación del suelo en áreas de transplante y cubierta de plástico previo a la plantación, para incrementar la probabilidad de supervivencia, y reducir la cobertura del pasto; además de la reforestación con plántulas colectadas de un fragmento de selva