618 research outputs found

    Biomasa aérea en ecosistemas de Prosopis pallida (Humb. and Bonpl. ex Willd.) H. B. K. usando imágenes Landsat 7 ETM+

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    The significance of field work in remote sensing studies when applied to large areas has often been underestimated. The combination of specific forest inventories for the estimation of aboveground biomass in large dry tropical forest areas with remote sensor data has scarcely been explored to date. In this work, a systematic, stratified forest inventory involving 100 × 100 m square plots in an area of Peruvian Prosopis pallida dry forest, roughly one million hectares in size in the Piura province (Peru) has been compiled. The inventory encompassed the principal silvicultural variables defining the ecosystem studied, which were used in allometric equations for the different species, genera and plant associations in the area in order to estimate the amount of aboveground biomass present in each plot. Field data were related to a Landsat 7 ETM+ image by using six different vegetation indices derived from an image mosaic for the area. Two regression equations (relating the amount of aboveground phytomass to the different vegetation indices) provided reasonably acceptable phytomass predictions for the type of ecosystem concerned (R2 between 0.72 and 0.52).La importancia del trabajo de campo en estudios de teledetección radica en la necesidad de proveer una validación a los valores de reflectividad incluidos en los datos de los sensores remotos. La diversidad ecológica del medio forestal y la evaluación de grandes superficies de difícil acceso hacen de la combinación del inventario forestal y de la teledetección una herramienta compleja y útil en el análisis del medio terrestre. El presente trabajo muestra la aplicación de un inventario sistemático estratificado sobre un millón de hectáreas de bosque tropical seco de Prosopis pallida en el Departamento de Piura (Perú) en la validación de diferentes tipos de clasificación realizadas sobre dicho ecosistema mediante el uso de imágenes Landsat ETM+. El inventario recoge las principales variables del ecosistema y de los individuos, tomadas en parcelas de 1 hectárea, que posteriormente fueron relacionadas con los valores de reflectividad de las imágenes mediante el uso de índices de vegetación. Se hallaron ecuaciones de regresión entre valores de fracción de suelo cubierto y cinco índices de vegetación, obteniéndose resultados con R2 de hasta 72 %. Los niveles de significación hallados mediante el uso de los índices NDVI y EVI permiten una estimación razonable del estado del bosque seco de Prosopis pallida del Departamento de Piura de una forma económica, fácil de repetir en el tiempo y aplicable a zonas que difícilmente pueden ser evaluadas mediante inventarios convencionales

    Analysis of Site-dependent Pinus halepensis Mill. Defoliation Caused by ‘Candidatus Phytoplasma pini’ through Shape Selection in Landsat Time Series

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    High levels of ‘Candidatus Phytoplasma pini’ have produced extensive forest mortality on Pinus halepensis Mill forests in eastern Spain. This has led to the widespread levels of forest mortality. We used archival Landsat imagery and shapes algorithm implemented in the Google Earth Engine to explore the potential of the LandTrendr algorithm and its outputs, together with field observations, to analyze and predict the health status in P. halepensis stands affected by ‘Candidatus Phytoplasma pini’ in Andalusia (south-eastern Spain). We found that the Landsat time series algorithm (LandTrendr) has captured both long- and short-duration trends and changes in spectral reflectance related to phytoplasma disturbance in the Aleppo pine forest stands investigated. The normalized burn ratio (NBR) trends were positively associated with environmental variables: Annual precipitation, mean temperature, soil depth, percent base saturation and aspect. Environmental variables were tested for their contributions to the mapping of changes in Aleppo pine cover in the study area, as an empirical modeling approach to disturbance mapping in forests of south-eastern Spain. The methodology outlined in this paper has produced valuable results that indicate new possibilities for the use in forest management of remote-sensing technologies based on spectral trajectories associated with pest-diseases defoliation. Given the likely increase in pest risks in the forests of southern Europe, accurate assessment and map of pest outbreaks on forests will become increasingly important, both for research and for practical applications in forest management

    Contrasting Response to Drought and Climate of Planted and Natural Pinus pinaster Aiton Forests in Southern Spain

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    Extreme drought events and increasing aridity are leading to forest decline and tree mortality, particularly in populations near the limits of the species distribution. Therefore, a better understanding of the growth response to drought and climate change could show the vulnerability of forests and enable predictions of future dieback. In this study, we used a dendrochronological approach to assess the response to drought in natural and planted forests of the maritime pine (Pinus pinaster Aiton) located in its southernmost distribution (south of Spain). In addition, we investigated how environmental variables (climatic and site conditions) and structural factors drive radial growth along the biogeographic and ecological gradients. Our results showed contrasting growth responses to drought of natural and planted stands, but these differences were not significant after repeated drought periods. Additionally, we found differences in the climate–growth relationships when comparing more inland sites (wet previous winter and late spring precipitation) and sites located closer to the coast (early spring precipitation). Response functions emphasized the negative effect of defoliation and drought, expressed as the June standard precipitation-evapotranspiration index calculated for the 12-month temporal scale and the mean temperature in the current February, on growth. The strong relationship between climatic variables and growth enabled acceptable results to be obtained in a modeling approach. The study and characterization of this tree species’ response to drought will help to improve the adaptive management of forests under climate change

    Stand Delineation of Pinus sylvestris L. Plantations Suffering Decline Processes Based on Biophysical Tree Crown Variables: A Necessary Tool for Adaptive Silviculture

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    Many planted Pinus forests are severely affected by defoliation and mortality processes caused by pests and droughts. The mapping of forest tree crown variables (e.g., leaf area index and pigments) is particularly useful in stand delineation for the management of declining forests. This work explores the potential of integrating multispectral WorldView-2 (WV-2) and Airborne Laser Scanning (ALS) data for stand delineation based on selected tree crown variables in Pinus sylvestris plantations in southern Spain. Needle pigments (chlorophyll and carotenes) and leaf area index (LAI) were quantified. Eight vegetation indices and ALS-derived metrics were produced, and seven predictors were selected to estimate and map tree crown variables using a Random Forest method and Gini index. Chlorophylls a and b (Chla and Chlb) were significantly higher in the non-defoliated and moderately defoliated trees than in severely defoliated trees (F = 14.02, p < 0.001 for Chla; F = 13.09, p < 0.001 for Chlb). A similar response was observed for carotenoids (Car) (F = 14.13, p < 0.001). The LAI also showed significant differences among the defoliation levels (F = 26.5, p < 0.001). The model for the chlorophyll a pigment used two vegetation indices, Plant Senescence Reflectance Index (PSRI) and Carotenoid Reflectance Index (CRI); three WV-2 band metrics, and three ALS metrics. The model built to describe the tree Chlb content used similar variables. The defoliation classification model was established with a single vegetation index, Green Normalized Difference Vegetation Index (GNDVI); two metrics of the blue band, and two ALS metrics. The pigment contents models provided R2 values of 0.87 (Chla, RMSE = 12.98%), 0.74 (Chlb, RMSE = 10.39%), and 0.88 (Car, RMSE = 10.05%). The cross-validated confusion matrix achieved a high overall classification accuracy (84.05%) and Kappa index (0.76). Defoliation and Chla showed the validation values for segmentations and, therefore, in the generation of the stand delineation. A total of 104 stands were delineated, ranging from 6.96 to 54.62 ha (average stand area = 16.26 ha). The distribution map of the predicted severity values in the P. sylvestris plantations showed a mosaic of severity patterns at the stand and individual tree scales. Overall, the findings of this work underscore the potential of WV-2 and ALS data integration for the assessment of stand delineation based on tree health status. The derived cartography is a relevant tool for developing adaptive silvicultural practices to reduce Pinus sylvestris mortality in planted forests at risk due to climate change

    Caracterización del material forestal de reproducción de cinco procedencias de Nothofagus alessandrii Espinosa, una especie en peligro de extinción

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    Nothofagus alessandrii es una especie endémica de la zona mesomórfica de Chile que se encuentra en peligro de extinción y de la cual existe aún información insuficiente respecto de las diferencias entre sus poblaciones. Por ello, en este trabajo se analizan y caracterizan parámetros cualitativos y cuantitativos del material germinativo y el comportamiento en vivero de cinco procedencias representativas del área de distribución natural de la especie. Se colectaron semillas de estas procedencias en febrero 2000 y se determinó su tamaño, forma, peso y capacidad germinativa. En septiembre del mismo año se cultivaron plantas en vivero y se evaluó su crecimiento diametral y en altura. Los resultados indican que el tamaño de las semillas es, en general, homogéneo y solo se observan diferencias estadísticas en la longitud de las dímeras y ancho de las trímeras. El peso de 1000 semillas y la capacidad germinativa varió significativamente entre las procedencias. El desarrollo de las plantas en vivero fue homogéneo y no hubo diferencias en el diámetro de cuello de la raíz ni en la altura que alcanzaron las plantas después de una temporada de cultivo. N. alessandrii tiene un comportamiento diferente al de otras especies del mismo género, sin que se observe una variación de tipo clinal. Sin embargo, la procedencia más austral tiende a diferenciarse de las otras y, probablemente, corresponda a un ecotipo diferente.Nothofagus alessandrii is an endemic and endangered species from the mesomorphic zone of Chile. Currently, differences across populations are not well known. To this end, quantitative and qualitative parameters pertaining to germinative material and nursery performance of seedlings from five provenances representing the natural distribution of the species were analyzed and characterized. Seeds were collected in February 2000 and size, form, weight, and germination capacity were determined. Seedlings were then cultivated in nursery in September of the same year, and basal diameter and height growth were quantified. Results indicate that seed size is generally homogeneous across sites, and statistical differences were limited to length of dimerous seeds and width of trimerous seeds. Seed weight and germination capacity varied significantly among the provenances. After one cultivation season, the development of the nursery plants was homogenous across provenances, with no differences in basal diameter or height. N. alessandrii differs, in relation to the variation among the studied provenances, from that of other species of the same genus, with the exception of a pronounced clinal type. However, the southernmost provenance tended, in general, to differ from the other ones and likely represents a different ecotype.Nothofagus alessandrii é uma espécie endêmica da zona mesomórfica do Chile que se encontra em perigo de extinção e da qual existe ainda informação insuficiente em relação às diferenças entre suas populações. Por isto, neste trabalho se analisam e caracterizam parâmetros qualitativos e quantitativos do material germinativo e o comportamento em viveiro de cinco procedências representativas da área de distribuição natural da espécie. Recolheram-se sementes destas procedências em fevereiro de 2000 e se determinou seu tamanho, forma, peso e capacidade germinativa. Em setembro do mesmo ano se cultivaram plantas em viveiro e se avaliou seu crescimento diametral e em altura. Os resultados indicam que o tamanho das sementes é, em geral, homogêneo e somente se observam diferenças estatísticas no comprimento das dímeras e largura das trímeras. O peso de 1.000 sementes e a capacidade germinativa variou significativamente em relação às procedências. O desenvolvimento das plantas em viveiro foi homogêneo e não houve diferenças no diâmetro do colo da raíz nem na altura que alcançaram as plantas depois de uma temporada de cultivo. N. alessandrii tem um comportamento diferente ao de outras espécies do mesmo gênero, sem que se observe uma variação do tipo clinal. No entanto, a procedência mais austral tende a diferenciar-se das outras e, provavelmente, corresponda a um ecótipo diferent

    Evaluación de la cobertura de la vegetación después de un incendio mediante análisis de mezclas espectrales. Aplicación y comparación de diferentes métodos de caracterización de factores de referencia

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    The analysis of satellite images allows one to monitor the regeneration of vegetation after a fire. In this work, a methodology for quantifying post fire vegetation cover was developed. The proposed methodology is based on the examination of Landsat 7 ETM+ images by using Spectral Mixture Analysis (SMA) and involves the following steps: a) pre-processing, b) inherent dimensionality image determination c) endmember characterization following two methods that thus lead to different models: traditional method based on the knowledge of the area worked as well as Minimum Noise Fraction and Pixel Purity Index method, d) model inversion and combination, e) comparison between the vegetation cover estimated by each model and that measured in field, and f) selection of the most accurate model and mapping of the vegetation cover for the study area. The cover estimated provided by the different models exhibited a high correlation (Spearman’s correlation coefficient &gt;0.89). The average absolute difference between the estimated and field-measured vegetation cover obtained with the most accurate model for each fire never exceeded 6%.El an&aacute;lisis de im&aacute;genes de sat&eacute;lite permite el seguimiento y evaluaci&oacute;n de los procesos de restauraci&oacute;n post-incendio. En este trabajo se presentan parte de los resultados de una metodolog&iacute;a dirigida a la cuantificaci&oacute;n de la cobertura de la vegetaci&oacute;n despu&eacute;s de un incendio. La metodolog&iacute;a propuesta se basa en el empleo de im&aacute;genes Landsat 7 ETM+ mediante un An&aacute;lisis de Mezclas Espectrales (SMA) y supone los siguientes procesos: a) pre-procesado de la imagen, b) determinaci&oacute;n de la dimensi&oacute;n intr&iacute;nseca (inherent dimensionality) de la imagen c) selecci&oacute;n y caracterizaci&oacute;n de los factores de referencia (endmember) mediante dos m&eacute;todos propuestos en la literatura: estudio previo de la zona de trabajo, Minimum Noise Fraction y pixles puros (Pixel Purity Index), d) inversi&oacute;n del modelo y combinaci&oacute;n, e) comparaci&oacute;n entre la cobertura estimada por cada modelos y las medidas realizadas en el campo, y f) selecci&oacute;n del modelo de mayor precisi&oacute;n para la realizaci&oacute;n de una cartograf&iacute;a de la cobertura de la vegetaci&oacute;n en el &aacute;rea de estudio. La cobertura estimada por los diferentes modelos muestran una alta correlaci&oacute;n (Coeficiente de correlaci&oacute;n de Spearman &gt; 0.89), lo que ha permitido establecer una diferencia entre las medidas de cobertura a trav&eacute;s de la imagen y la estimaci&oacute;n de campo que en ning&uacute;n caso han superado el 6% de la cobertura post-inendio

    Buenas prácticas de innovación docente en la Universidad de Córdoba

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    El proyecto presenta la creación de la figura Bosque Universitario, que se incorpora al currículo docente de la titulación de Ingeniero de Montes para su uso didáctico en la Escuela Técnica Superior de Ingeniería Agronómica y de Montes de la Universidad de Córdoba (UCO). Gracias a esta herramienta –cuya gestión ha costado 1.200 euros–, el alumnado conoce la gestión forestal de un monte y las funciones que se llevan a cabo en beneficio de la sociedad

    Spin coherent manipulation in Josephson weak links

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    Novel designs of Josephson weak links based on semiconducting nanowires combined with circuit QED techniques have enabled the resolution of their fine structure due to spin-orbit interactions, opening a path towards Andreev spin qubits. Nevertheless, direct manipulation of the spin within a given Andreev state is in general suppressed compared to interdoublet manipulation in the absence of Zeeman effects. In addition, noisy spin-flip mechanisms limit any coherent manipulation protocol to spin postselection. We propose a combination of a spin polarization protocol analogous to sideband cooling with stimulated Raman adiabatic passage specifically tailored for these systems. We show this approach is robust for a large range of design parameters, including the currently rather stringent coherence time
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