Generación de un banco de áreas de reflectividad pseudoinvariante para la Península Ibérica mediante imágenes MODIS

La reflectividad derivada de imágenes satelitales sigue generalmente el ciclo fenológico de las cubiertas presentes en el territorio. A pesar de ello, es posible encontrar zonas donde la reflectividad es prácticamente invariante. Estas áreas definidas como pseudoinvariantes (API) permiten comparar y calibrar imágenes provenientes de distintos sensores y procesar series temporales con una elevada coherencia. Se presenta un nuevo método automático (especialmente útil en entornos Big Data) para seleccionar API a partir del producto diario MOD09GA derivado de imágenes Terra-MODIS, utilizando una serie temporal de 14 años y las bandas del espectro solar (visible, infrarrojo cercano y de onda corta) con una resolución espacial de 500 m. Dicha metodología consta de dos etapas de filtrado, una primera que evalúa la calidad de las imágenes de la serie mediante técnicas geoestadísticas, seleccionando las mejores, y una segunda que define umbrales específicos para cada banda espectral, en función de la dispersión que presentan los datos en la selección previa de imágenes. La aplicación de este método sobre ámbitos de características topográficas y estructura de paisaje diferenciados en la Península Ibérica ha permitido la obtención de más de 12 000 API en una superficie asimilable a 9 escenas Landsat (WRS-2). Los resultados muestran que la metodología aplicada contempla la adecuada distribución tanto interanual como intraanual de las imágenes, dando lugar a API que abarcan una amplia variedad de cubiertas con reflectividades diversas, ubicadas principalmente en zonas boscosas o seminaturales (77%),zonas agrícolas (21 %), así como en otros tipos de cubiertas no vegetales

Aligning citizen science and remote sensing phenology observations to characterize climate change impact on vegetation

Phenology observations are essential indicators to characterize the local effects of climate change. Citizen participation in the collection of phenological observations is a potential approach to provide data at both high temporal scale and fine grain resolution. Traditional observation practices of citizen science (CS), although precise at the species scale, are limited to few observations often closely located to an observer's residence. These limitations hinder coverage of the great variability of vegetation phenology across biomes and improvement of the knowledge of vegetation changes due to climate change impacts. This study presents a new approach to overcome these limitations by improving CS guidance and feedback as well as expanding phenology report sites and observations across different habitats and periods to contribute to monitoring climate change. This approach includes: (a) a new methodology focused on harmonizing remote sensing phenology products with traditional CS phenology observations to direct volunteers to active phenology regions and, (b) a new protocol for citizen scientists providing tools to guide them to specific regions to identify, collect and share species phenological observations and their phenophases. This approach was successfully tested, implemented and evaluated in Catalonia with more than 5000 new phenologically interesting regions identified and more than 200 observations collected and Sentinel-2 derived phenometrics were demonstrated as of good quality.info:eu-repo/semantics/publishedVersio

Factors affecting forest dynamics in the Iberian Peninsula from 1987 to 2012 : the role of topography and drought

In southern Europe, climate trends are expected to be characterized by an increase in temperatures and less water availability. Analyzing the role of structural factors and the influence of a changing climate provides insights into the evolution of forest ecosystems in regions with similar environmental conditions. The Mediterranean fringe of the Iberian Peninsula is of particular interest due to its diverse topo climatic conditions and the increase in drought episodes during the last decades. This work studies forest dynamics in large areas of this geographical region by analyzing nine forest transitions. Vegetation covers were classified from three Landsat scenes for the period 1987-2012, and sub-periods 1987-2002 and 2002-2012. Conditions were described by topography derived variables, human factors and drought-occurrence variables. Boosted regression trees were used to identify the most important variables and describe the relationships between the forest dynamics and key factors. Variables such as solar radiation, topographic wetness index and tolerance to drought have been shown to be key factors in forest succession and when comparisons are made between vegetation groups. Main findings: The transition rate to Mediterranean and sub-Mediterranean broadleaf forests has increased during the analyzed period, while the transition rate to coniferous forests has decreased; Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Transitions from shrublands to forest stages are more vulnerable to factors controlling water availability; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

Ten years of local water resource management : Integrating satellite remote sensing and geographical information systems

On 2002, a novel initiative was undertaken by the local water administration of Catalonia (the Agència Catalana de l'Aigua) and the Universitat Autònoma de Barcelona, leading to a ten-year project where a high number of medium resolution satellite images (MODIS and Landsat) were integrated to the daily water management to improve decision making effectiveness. This paper describes the methodology followed in the successful application of remote sensing, as well as the main problems that had to be overcome during its execution. It also presents the products that have been calculated. These are integrated into the Agency's corporate GIS and immediately available via the intranet for the staff, and a selection is available on the Internet