Radiocarbon dating of peat profiles from the subarctic ecoclimatic region, west-central Canada

Long-term vegetation succession and permafrost dynamics in subarctic peat plateaus of west-central Canada have been studied through detailed plant macrofossil analysis and extensive AMS radiocarbon dating of two peat profiles. Peatland inception at these sites occurred around 5800-5100 yr BP (6600-5900 cal. BP) as a result of paludification of upland forests. At the northern peat plateau site, located in the continuous permafrost zone, palaeobotanical evidence suggests that permafrost was already present under the forested upland prior to peatland development. Paludification was initiated by permafrost collapse, but re-aggradation of permafrost occurred soon after peatland inception. At the southern site, located in the discontinuous permafrost zone, the aggradation of permafrost occurred soon after peatland inception. In the peat plateaus, permafrost conditions have remained very stable until present. Sphagnum fuscum-dominated stages have alternated with more xerophytic communities characterized by ericaceous shrubs. Local peat fires have occurred, but most of these did not cause degradation of the permafrost. Starting from 2800-1100 yr BP (2900-1000 cal. BP) consistently dry surface conditions have prevailed, possibly related to continued frost heave or nearby polygon crack formation.

Farming strategy of African smallholder farmers in transition from traditional to alternative agriculture : the case of the Nupe in central Nigeria

It is worthwhile to understand farming strategies of smallholder farmers in sub-Saharan Africa, especially those of farmers who are in transition from traditional to alternative agriculture in terms of adoption of innovative technologies. In a case study of inland valleys in central Nigeria, we investigated the farming strategy of Nupe farmers who have a long-term tradition of wet rice cultivation and indigenous methods of land preparation for soil, water and weed management. In this region, a new method of land preparation has recently been introduced along with a recommendation to use improved seeds and chemical fertilizers. Our findings reveal that Nupe farmers directly sow traditional seeds and apply a marginal amount of fertilizer to paddy plots prepared by labor-saving methods on drought-prone hydromorphic valley fringes and flood-susceptible valley bottoms, whereas they preferentially transplanted improved seedlings and applied a relatively large quantity of fertilizer to paddy fields prepared by a labor-intensive and mechanized method on a valley position where they can access to optimum water condition (less risky against the drought and flood).

Gold Ores Related to Shear Zones, West Santa Comba Fervenza Area (Galicia, NW Spain): A Mineralogical Study

Recent research has discovered high-grade Au ores in NNE-SSW trending shear zones in metamorphic proterozoic and palaeozoic terranes, some 40 km NW of Santiago de Compostela (NW Spain). The orebodies are bound to late-stage Hercynian structures, mainly due to brittle deformation, which are superimposed on earlier ductile shear zones, cutting through various catazonal lithologies, including ortho- and paragneisses, amphibolites, eclogites, and granites. Ore mineralogy, alteration, and ore textures define a frame whose main features are common to all prospects in the area. Main minerals are arsenopyrite and pyrite - accompanied by quartz, adularia, sericite, + (tourmaline, chlorite, carbonates, graphite), as main gangue minerals - with subordinate amounts of boulangerite, bismuthinite, kobellite, jamesonite, chalcopyrite, marcasite, galena, sphalerite, rutile, titanite, scheelite, beryl, fluorite, and minor native gold, electrum, native bismuth, fahlore, pyrrhotite, mackinawite, etc., defining a meso-catathermal paragenesis. Detailed microscopic study allows the author to propose a general descriptive scheme of textural classification for this type of ore. Most of the ores fill open spaces or veins, seal cracks or cement breccias; disseminated ores with replacement features related to alteration (mainly silicification, sericitization, and adularization) are also observed. Intensive and repeated cataclasis is a common feature of many ores, suggesting successive events of brittle deformation, hydrothermal flow, and ore precipitation. Gold may be transported and accumulated in any of these events, but tends to be concentrated in later ones. The origin of the gold ores is explained in terms of hydrotherreal discharge, associated with mainly brittle deformation and possibly related to granitic magmas, in the global tectonic frame of crustal evolution of West Galicia. The mineralogical and textural study suggests some criteria which will be of practical value for exploration and for ore processing. Ore grades can be improved by flotation of arsenopyrite. Non-conventional methods, such as pressure or bacterial leaching, may subsequently obtain a residue enriched in gold.

Thresholding Soil Surface Images

Soil erosion is a complex phenomenon involving the detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude and importance of these processes depends on several factors being one of them surface micro-topography, usually quanti[U+FB01]ed trough soil surface roughness (SSR). SSR greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. The methods commonly used to measure SSR involve measuring point elevation using a pin roughness meter or laser, both of which are labor intensive and expensive. Lately a simple and inexpensive technique based on percentage of shadow in soil surface image has been developed to determine SSR in the field in order to obtain measurement for wide spread application. One of the first steps in this technique is image de-noising and thresholding to estimate the percentage of black pixels in the studied area. In this work, a series of soil surface images have been analyzed applying several de-noising wavelet analysis and thresholding algorithms to study the variation in percentage of shadows and the shadows size distribution

Valorización de subproductos agrícolas y forestales como sustratos de cultivo en el estado de Oaxaca (México)

El presente trabajo aborda el aprovechamiento de algunos subproductos agrícolas (bagazo de maguey y fibra de coco) y forestales (corteza de pino) en el Estado de Oaxaca (Sur de México). El objetivo principal se centra en localizar, cuantificar y caracterizar estos con vistas a su aplicación como sustratos o componentes de sustratos en cultivos ornamentales, forestales y hortícolas, y a su uso como enmiendas en cultivos tipo. Así mismo se persigue reducir el uso de la turba y la tierra de monte como sustratos mayoritarios en la actualidad. Para la localización de los subproductos se utilizaron los datos de los registros parcelarios de los productores de coco para la obtención de copra (generadores de fibra de coco) de la región costa y de los productores de mezcal (generadores del residuo de bagazo de maguey) de la región valles centrales, así como las ubicaciones de los aserraderos forestales en el Estado de Oaxaca. Se emplea un Sistema de Información Geográfica (SIG) con una cartografía digitalizada de los elementos del medio (clima, geología y suelo), de los cultivos generadores (bagazo de maguey, fibra de coco y corteza de pino), de la agricultura protegida como receptora (tomate) y de la agricultura extensiva con cultivos receptores de enmienda (café, hule, limón, mango, palma de coco y maguey). La producción anual de los residuos se cartografía y cuantifica con los siguientes resultados: bagazo de maguey 624.000 t, fibra de coco 86.000 m3 y 72.000 t de corteza de pino. Mediante el estudio de las características de los suelos de los cultivos receptores y de los requerimientos de materia orgánica de cada cultivo se calcularon las necesidades totales de materia orgánica para cada suelo. Los resultados de las cantidades globales para cada cultivo en todo el Estado muestran una necesidad total de 3.112.000 t de materia orgánica como enmienda. Con los datos obtenidos y a través de un algoritmo matemático se realiza una propuesta de localización de dos plantas de compostaje (de bagazo de maguey y fibra de coco) y cuatro plantas de compostaje de corteza de pino. Con el fin de conocer los subproductos a valorizar como sustrato o componente de sustrato se caracteriza su composición física‐química, siguiendo Normas UNE‐EN, y se analizan mediante Resonancia Magnética Nuclear (RMN). Para el acondicionamiento de bagazo de maguey y la corteza de pino se realizaron ensayos de compostaje. Al final de 241 días la temperatura y la humedad de ambos procesos se encontraban en los rangos recomendados, indicando que los materiales estaban estabilizados y con calidad para ser utilizados como sustrato o componente de sustrato. Para la fibra de coco se realizó el proceso de molienda en seco de conchas de coco provenientes de la comunidad de Río Grande Oaxaca (Principal zona productora de copra en Oaxaca). Posteriormente se emplean los materiales obtenidos como componentes para sustratos de cultivo. Se estudia el compost de bagazo de maguey y siete mezclas; el compost de corteza de pino y ocho mezclas y la fibra de coco con tres mezclas. Estos sustratos alternativos permiten obtener mezclas y reducir el uso de la tierra de monte, turba, arcilla expandida y vermiculita, siendo por tanto una alternativa sostenible para la producción en invernadero. Se elaboraron mezclas especificas para el cultivo de Lilium hibrido asiático y oriental (siete mezclas), sustratos eco‐compatibles para cultivo de tomate (nueve mezclas), para la producción de planta forestal (siete mezclas) y para la producción de plántula hortícola (ocho mezclas). Como resultados más destacados del bagazo de maguey, corteza de pino y las mezclas obtenidas se resume lo siguiente: el bagazo de maguey, con volúmenes crecientes de turba (20, 30, 50 y 60 %) y la corteza de pino, con volúmenes de turba 40 y 60%, presentan valores muy recomendados de porosidad, capacidad de aireación, capacidad de retención de humedad y equilibrio agua‐aire. Para la fibra de coco, la procedente de Río Grande presenta mejor valoración que la muestra comercial de fibra de coco de Morelos. Por último se llevó a cabo la evaluación agronómica de los sustratos‐mezclas, realizando cinco experimentos por separado, estudiando el desarrollo vegetal de cultivos tipo, que se concretan en los siguientes ensayos: 1. Producción de Lilium asiático y oriental en cama para flor de corte; 2. Producción de Lilium oriental en contenedor para flor de corte; 3. Producción de plántula forestal (Pinus greggii E y Pinus oaxacana M); 4. Producción de tomate (Solanum lycopersicum L) y 5. Producción de plántula de tomate en semillero (Solanum lycopersicum L). En relación a la producción de Lilium hibrido asiático en cama los sustratos corteza de pino (CPTU 80:20 v/v), corteza de pino + sustrato comercial (CPSC 80:20 v/v) y corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) presentan los mejores resultados. Dichos sustratos también presentan adecuados resultados para Lilium hibrido oriental con excepción de la corteza de pino + turba (CPTU 80:20 v/v). En la producción de Lilium hibrido oriental en contenedor para flor de corte, además de los sustratos de CPSC y CPTAEV2, la mezcla de corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV 70:20:5:5 v/v) manifestó una respuesta favorable. En el ensayo de producción de plántulas de Pinus greggii E y Pinus oaxacana Mirov, las mezclas con corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) y bagazo de maguey turba+arcilla expandida+vermiculita (BMTAEV2 30:60:5:5 v/v) son una alternativa que permite disminuir el empleo de turba, arcilla expandida y vermiculita, en comparación con el sustrato testigo de turba+arcilla expandida+vermiculita (TAEV 60:30:10 v/v). En la producción de tomate (Solanum lycopersicum L) frente a la utilización actual del serrín sin compostar (SSC), las mezclas alternativas de bagazo de maguey+turba (BMT 70:30 v/v), fibra de coco de Río Grande (FCRG 100v/v) y corteza de pino+turba (CPT 70:30 v/v), presentaron los mejores resultados en rendimientos. Así mismo, en la producción de plántulas de tomate las dos mezclas alternativas de bagazo de maguey+turba+ arcilla expandida+vermiculita (BMTAEV5 50:30:10:10 v/v) y (BMTAEV6 40:40:10:10 v/v) presentaron mejores resultados que los obtenidos en la mezcla comercial (Sunshine 3), mayoritariamente utilizada en México en la producción de plántula de tomate y hortícola. ABSTRACT This paper addresses the use of some agricultural products (maguey bagasse and coconut fiber) and forestry (pine bark) in the State of Oaxaca (southern Mexico). The principal purpose is to locate, quantify and characterize these with the idea of applying them as substrates or substrate components in ornamental crops, forestry, horticultural, and their use as crop amendments. On the other hand, the reduction of peat and forest soil as main substrates is pursued. For the location of the products, registry parcel data from copra producers (coconut fiber generators) of the coastal region and mescal producers (maguey bagasse residue generators) of the central valleys region, as well as the locations of forest mills in the State of Oaxaca. A Geographic Information System (GIS) with digital mapping of environmental factors (climate, geology and soil), crop generators of residues (maguey bagasse, coconut and pine bark) receptors of amendments such as protected agriculture (tomato) and extensive agriculture crops (coffee, rubber, lemon, mango, coconut and agave). The annual production of waste is mapped and quantified with the following results: 624,000t maguey bagasse, coconut fiber 72,000 m3 and 86,000 t of pine bark. Through the study of receiving crops soils properties of and organic matter requirements of each crop, total needs of organic matter for each soil were estimated. The results of the total quantities for each crop across the state show a total of 3,112,000 t of organic matter needed as amendment. Using that data and a mathematical algorithm, the location of two composting plants (agave bagasse and coconut fiber) and four composting plants pine bark was proposed. In order to know the by‐products that were going to be used as substrates or substrate components, their physical‐chemical composition was analyzed following UNE‐EN technics. Furthermore they were analyzed by Nuclear Magnetic Resonance (NMR). For conditioning of maguey bagasse and pine bark, composting essays were conducted. At the end of 241 days the temperature and humidity of both processes were at the recommended ranges, indicating that the materials were stabilized and had reached the quality to be used as a substrate or substrate component. Coconut shells from the community of Rio Grande Oaxaca (Main copra producing area in Oaxaca) were put through a process of dry milling. Subsequently, the obtained materials were used as components for growing media. We studied the maguey bagasse compost and seven mixtures; the pine bark compost and eight blends and coconut fiber with three mixtures. These alternative substrates allow obtaining mixtures and reduce the use of forest soil, peat, vermiculite and expanded clay, making it a sustainable alternative for greenhouse production. Specific mixtures were prepared for growing Lillium, Asian and eastern hybrids (seven blends), eco‐compatible substrates for tomato (nine mixtures), for producing forest plant (seven mixtures) and for the production of horticultural seedlings (eight mixtures). Results from maguey bagasse, pine bark and mixtures obtained are summarized as follows: the maguey bagasse, with increasing volumes of peat (20, 30, 50 and 60%) and pine bark mixed with 40 and 60% peat by volume, have very recommended values of porosity, aeration capacity, water retention capacity and water‐air balance. Coconut fiber from Rio Grande had better quality than commercial coconut fiber from Morelos. Finally the agronomic evaluation of substrates‐mixtures was carried out conducting five experiments separately: 1. Production of Asiatic and Eastern Lilium in bed for cut flower, 2. Production of oriental Lillium in container for cut flower, 3.Production of forest seedlings (Pinus greggii E and Pinus oaxacana M), 4. Production of tomato (Solanum lycopersicum L) and 5. Tomato seedling production in seedbed (Solanum lycopersicum L). In relation to the production of hybrid Asian Lilium in bed, pine bark substrates (CPTU 80:20 v/v), pine bark + commercial substrate (CPSC 80:20 v/v) and pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) showed the best results. Such substrates also have adequate results for Lilium Oriental hybrid except pine bark + peat (CPTU 80:20 v / v). In the production of Lilium oriental hybrid container for cut flower, besides the CPSC and CPTAEV2 substrates, the mixture of pine bark + peat + vermiculite expanded clay (CPTAEV 70:20:5:5 v / v) showed a favorable response. In the production of Pinus greggii E and Pinus oaxacana Mirov seedlings trial, mixtures with pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) and maguey bagasse+ peat+ expanded clay + vermiculite (BMTAEV2 30:60:5:5 v / v) are an alternative which allows reducing the use of peat, vermiculite and expanded clay in comparison with the control substrate made of peat + expanded clay+ vermiculite (60:30 TAEV: 10 v/v). In the production of tomato (Solanum lycopersicum L), alternative mixes of maguey bagasse + peat (BMT 70:30 v/v), coconut fiber from Rio Grande (FCRG 100 v / v) and pine bark + peat (CPT 70:30 v / v) showed the best results in yields versus the current use of sawdust without compost (SSC). Likewise, in the production of tomato seedlings of the two alternative mixtures maguey bagasse + peat expanded clay + vermiculite (BMTAEV5 50:30:10:10 v/v) and (BMTAEV6 40:40:10:10 v/v) had better results than those obtained in the commercial mixture (Sunshine 3), mainly used in Mexico in tomato seedling production and horticulture.

A distributed end-to-end overload control mechanism for networks of SIP servers.

The Session Initiation Protocol (SIP) is an application-layer control protocol standardized by the IETF for creating, modifying and terminating multimedia sessions. With the increasing use of SIP in large deployments, the current SIP design cannot handle overload effectively, which may cause SIP networks to suffer from congestion collapse under heavy offered load. This paper introduces a distributed end-to-end overload control (DEOC) mechanism, which is deployed at the edge servers of SIP networks and is easy to implement. By applying overload control closest to the source of traf?c, DEOC can keep high throughput for SIP networks even when the offered load exceeds the capacity of the network. Besides, it responds quickly to the sudden variations of the offered load and achieves good fairness. Theoretic analysis and extensive simulations verify that DEOC is effective in controlling overload of SIP networks.

Analog mitigation of out of band strong interferers in wide band acquisition for multiband HF transmissions

It is clear that in the near future much broader transmissions in the HF band will replace part of the current narrow band links. Our personal view is that a real wide band signal is infeasible in this environment because the usage is typically very intensive and may suffer interferences from all over the world. Therefore, we envision that dynamic multiband transmissions may provide better satisfactory performance. From the very beginning, we observed that real links with our broadband transceiver suffered interferences out of our multiband but within the acquisition bandwidth that degrade the expected performance. Therefore, we concluded that a mitigation structure is required that operates on severely saturated signals as the interference may be of much higher power. In this paper we address a procedure based on Higher Order Crossings (HOC) statistics that are able to extract most of the signal structure in the case where the amplitude is severely distorted and allows the estimation of the interference carrier frequency to command a variable notch filter that mitigates its effect in the analog domain.

Simplifying data acquisition in plant canopies- Measurements of leaf angles with a cell phone

1. Canopies are complex multilayered structures comprising individual plant crowns exposing a multifaceted surface area to sunlight. Foliage arrangement and properties are the main mediators of canopy functions. The leaves act as light traps whose exposure to sunlight varies with time of the day, date and latitude in a trade-off between photosynthetic light harvesting and excessive or photoinhibitory light avoidance. To date, ecological research based upon leaf sampling has been limited by the available echnology, with which data acquisition becomes labour intensive and time-consuming, given the verwhelming number of leaves involved. 2. In the present study, our goal involved developing a tool capable of easuring a sufficient number of leaves to enable analysis of leaf populations, tree crowns and canopies.We specifically tested whether a cell phone working as a 3Dpointer could yield reliable, repeatable and valid leaf anglemeasurements with a simple gesture. We evaluated the accuracy of this method under controlled conditions, using a 3D digitizer, and we compared performance in the field with the methods commonly used. We presented an equation to estimate the potential proportion of the leaf exposed to direct sunlight (SAL) at any given time and compared the results with those obtained bymeans of a graphicalmethod. 3. We found a strong and highly significant correlation between the graphical methods and the equation presented. The calibration process showed a strong correlation between the results derived from the two methods with amean relative difference below 10%. Themean relative difference in calculation of instantaneous exposure was below 5%. Our device performed equally well in diverse locations, in which we characterized over 700 leaves in a single day. 4. The newmethod, involving the use of a cell phone, ismuchmore effective than the traditionalmethods or digitizers when the goal is to scale up from leaf position to performance of leaf populations, tree crowns or canopies. Our methodology constitutes an affordable and valuable tool within which to frame a wide range of ecological hypotheses and to support canopy modelling approaches.

Validación del método de predicción de direcciones principales de drenaje subterráneo en macizos anisótropos, en los terrenos volcánicos del macizo de Anaga, Tenerife

Actualmente y desde hace ya más de 25 años, el Método de “Predicción de las Direcciones Principales de Drenaje Subterráneo en Macizos Anisótropos”, ha sido utilizado con éxito en diferentes terrenos Kársticos como: calizas, yesos, cuarcitas, pizarras, granitos y criokarst (karst en el hielo glaciar). Sin embargo hasta ahora, nunca se había validado en terrenos volcánicos donde está focalizada esta tesis que lleva por título, Validación de dicho Método en los Terrenos Volcánicos del Macizo de Anaga en Tenerife. Este Método matemático consiste esencialmente en “Predecir y Cuantificar” las direcciones principales de drenaje turbulento subterráneo en macizos anisótropos. Para ello se basa en el estudio realizado en campo de los tectoglifos o deformaciones permanentes del macizo, impresas éstas en la roca, como consecuencia de los esfuerzos tectónicos a los que ha estado sometido dicho macizo. Se consigue de esta manera cubrir el vacío para macizos anisótropos que existe con el modelo matemático de flujo subterráneo laminar (macizos isótropos) definido por Darcy (1856). Para validar el Método se ha elegido el macizo de Anaga, pues es la zona de mayor anisotropía existente en la isla de Tenerife, conformada por una gran y extensa red de diques de diversas formas y tamaños que pertenecen a la familia de diques del eje estructural NE de la isla. En dicho macizo se realizó un exhaustivo trabajo de campo con la toma 331 datos (diques basálticos) y se aplicó el Método, consiguiendo definir las direcciones preferentes de drenaje subterráneo en el macizo de Anaga. Esta predicción obtenida se contrastó con la realidad del drenaje en la zona, conocida gracias a la existencia de cinco galerías ubicadas en la zona trabajo, de las cuales se tiene información sobre sus alumbramientos. En todos los casos se demuestra la bondad de la predicción obtenida con el Método. Queda demostrado que a mayor caos geológico o geotectónico, se ha conseguido mejor predicción del Método, obteniéndose resultados muy satisfactorios para aquellas galerías de agua en las que su rumbo de avance fue coincidente con la dirección perpendicular a la obtenida con la predicción dada por el Método, como dirección preferente de drenaje en la zona en la que se encuentra ubicada cada galería. No cabe duda que la validación de Método en los terrenos volcánicos de Tenerife, supondrá un cambio considerable en el mundo de la hidrogeología en este tipo de terrenos. Es la única herramienta matemática que se dispone para predecir un rumbo acertado en el avance de la perforación de las galerías de aguas, lo que conlleva al mismo tiempo un ahorro importantísimo en la ejecución de las obras. Por otro lado, el Método deja un importante legado a la sociedad canaria, pues con él se abren numerosas vías de trabajo e investigación que generarán un importante desarrollo en el mundo de la hidrogeología volcánica. ABSTRACT Currently and for over 25 years now, the Method of "Prediction of Subsurface Drainage Main Directions in Anisotropic Massifs" has been successfully used in various karstic terrains such as: limestone, gypsum, quartzite, slate, granite and criokarst (karst in the glacier ice). However, until now, it had never been validated in volcanic terrains where is focused this thesis entitled Validation of such Method in the Anaga Massif Volcanic Terrains, in Tenerife. This mathematical method is essentially "predict and quantify" the main directions of groundwater turbulent drainage in anisotropic massifs. This is based on field study of tectoglifes or permanent deformation of the massif, printed on the rocks as a result of previous tectonic stresses. Therefore it is possible to use in anisotropic rock mathematical model instead of the isotropic laminar flow mathematical models defined by Darcy (1856). The Anaga Massif have been chosen to validate the method, because it presents the greatest anisotropy in Tenerife Island, shaped by a large and extensive network of dikes of various shapes and sizes that belong to the family of NE structural axis dikes of the island. An exhaustive field work was carried out in such massif, with 331 collected data (basaltic dikes) and the method was applied, in order to define the preferred direction of the underground drainage in the Anaga massif. This obtained prediction was contrasted to the reality of the drainage in the area, known thanks to the existence of five galleries located in the work area, from which information about their springs was available. In all cases it was possible to demonstrate the fitness of the prediction obtained by the method. It had been demonstrated that a greater geological or geotectonic chaos enhances a better prediction of the method, that predicted very satisfactory results for those water galleries which directions were perpendicular to that predicted by the Method as a drainage preferential direction, for the zone where was located each gallery. No doubt that the validation of the use of the Method in the volcanic terrain of Tenerife, means a considerable change in the world of hydrogeology in this type of terrain. It is the only mathematical tool available to predict a successful drilling direction in advancing water galleries, what also leads to major savings in execution of the drilling works. Furthermore, the method leaves an important legacy to the Canary Islands society, because it opens many lines of work and research to generate a significant development in the world of volcanic hydrogeology.