Evaluating the Consistency of the 1982–1999 NDVI Trends in the Iberian Peninsula across Four Time-series Derived from the AVHRR Sensor: LTDR, GIMMS, FASIR, and PAL-II

Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR) sensor archive to produce Normalized Difference Vegetation Index (NDVI) datasets (i.e., PAL, FASIR, GIMMS, and LTDR) under different corrections and processing schemes. Since NDVI datasets are used to evaluate carbon gains, differences among them may affect nations’ carbon budgets in meeting international targets (such as the Kyoto Protocol). This study addresses the consistency across AVHRR NDVI datasets in the Iberian Peninsula (Spain and Portugal) by evaluating whether their 1982–1999 NDVI trends show similar spatial patterns. Significant trends were calculated with the seasonal Mann-Kendall trend test and their spatial consistency with partial Mantel tests. Over 23% of the Peninsula (N, E, and central mountain ranges) showed positive and significant NDVI trends across the four datasets and an additional 18% across three datasets. In 20% of Iberia (SW quadrant), the four datasets exhibited an absence of significant trends and an additional 22% across three datasets. Significant NDVI decreases were scarce (croplands in the Guadalquivir and Segura basins, La Mancha plains, and Valencia). Spatial consistency of significant trends across at least three datasets was observed in 83% of the Peninsula, but it decreased to 47% when comparing across the four datasets. FASIR, PAL, and LTDR were the most spatially similar datasets, while GIMMS was the most different. The different performance of each AVHRR dataset to detect significant NDVI trends (e.g., LTDR detected greater significant trends (both positive and negative) and in 32% more pixels than GIMMS) has great implications to evaluate carbon budgets. The lack of spatial consistency across NDVI datasets derived from the same AVHRR sensor archive, makes it advisable to evaluate carbon gains trends using several satellite datasets and, whether possible, independent/additional data sources to contrast

Ecosystem functioning and geographic conservation priorities assessment

En este artículo mostramos el potencial de técnicas de teledetección, basadas en la descripción de atributos funcionales de los ecosistemas, para la resolución de cuestiones propias de la biología de la conservación. Para ello se presentan los análisis realizados para la evaluación de la representatividad de las redes de áreas protegidas de España y Uruguay. En dichos estudios se partió de la identificación del espacio funcional (aproximación en continuo) definido por los valores que la vegetación natural de cada país muestra para dos atributos derivados de índices de vegetación espectrales (IV). Dichos índices fueron, la media de IV (IV-I), un estimador de la fracción de radiación fotosintéticamente activa absorbida por el canopeo), y el RREL, un estimador de la estacionalidad en la intercepción de la radiación. El espacio funcional así identificado constituye una forma rápida de describir la variabilidad ecosistémica completa de la región de referencia frente a la cual evaluar la representatividad de las redes, ya que las variables empleadas para ello están relacionadas con la respuesta que los ecosistemas muestran frente al gradiente ambiental completo de una región,. De esta manera, mediante una metodología común, los análisis no sólo identifican los parques comunes o singulares protegidos de cada país, sino que también permiten obtener una visión rápida de los huecos existentes en ambas redes y qué tan redundantes o complementarios son en el contexto nacional del funcionamiento ecosistémico.This article shows the potential of remote sensing techniques, based on the descriptions of ecosystem functional attributes, to solve classical questions of conservation biology. We present an analysis aimed to evaluate how the protected area networks in two countries, Spain and Uruguay, represent the national ecosystems diversity. First, we identified the functional space (continuum approach) of natural vegetation in each country, using two functional attributes derived from vegetation indices (VI), mean VI (VI-I) and relative range (RREL). The VI-I is an estimator of the fraction of photosynthetic active radiation absorbed by the canopy, and the RREL is a surrogate of the seasonality of radiation interception. The functional space defined in this way constitutes a rapid way to describe the whole ecosystems variability within a region. Moreover, it allows the evaluation of the representation of the network, as the used variables are related to ecosystems’ response to the regional environmental gradient. Thus, this methodology identifies not only the common and singular protected areas in each country, but also the gaps in the network, and how redundant or complementary are the protected areas in the national context of ecosystem functioning.Junta de Andalucía (FPDI2000 -BOJA140/2000 y los proyectos RNM1280 y RNM1288), Secretaría de Estado de Universidades e Investigación del Ministerio de Educación y Ciencia, Organismo Autónomo de Parques Nacionales (Proyecto: Efectos del cambio global sobre el funcionamiento de los ecosistemas de la Red de Parques Nacionales Españoles: Impactos recientes y desarrollo de un sistema de seguimiento), Agencia Española de Cooperación Iberoamericana (Red temática para la evaluación del impacto de los cambios globales (vs locales) en el funcionamiento ecosistémico), Sistema Nacional de Áreas Protegidas, Dirección Nacional de Medio Ambiente, Ministerio de Vivienda, Ordenamiento Territorial y Medio Ambiente, Uruguay, Grupo de Investigación Ecología de Zonas Áridas de la Universidad de Almería

Linking biochemical and biophysical variables derived from imaging spectrometers to ecological models - The HyEco'04 Group Shoot

We report on the first results of the HyEco'04 campaign carried out in summer 2004 as a joint activity of a bi-national team of Belgian and Dutch researchers. This integrated approach of assessing the complexity of managed natural ecosystems is a demonstrator case for recent focus of airborne imaging spectroscopy activities on ecotones. The floodplain Millingerwaard located east to the city of Nijmegen along the river Rhine has been chosen to demonstrate the potential of imaging spectrometer data to support ecological modelling. Several ground support teams supported the data acquisition of the Hymap sensor during its overflight on two days in July and August 2004. Field measurements concentrated on two approaches: first, radiometric measurements supporting the linking between soil-vegetation-atmosphere transfer modelling (e.g., sunphotometer, leaf optical properties measurements, canopy reflectance, structural parameter measurements (gap fraction, leaf angle distribution, leaf area index) have been performed and secondly supporting additional measurements on vegetation (species mapping, destructive biomass sampling) and soil (moisture, temperature) have been performed. First, we will report on the data quality evaluation of the various data sources and their integration into an integrated system, dealing with various aspects of spatial sampling schemes and potential spatial discontinuities, as well as uncertainty measures. Secondly, we discuss two examples of spatially distributed products derived from either ground based measurements and inventory mapping, extrapolated to the full coverage of the test site or imaging spectrometer derived products. The resulting products are discussed in view of potential incorporation into land-biosphere models, where high or even unknown uncertainty in input data, and limited availability of geographically explicit input data are usually the limiting factors for the application of ecological models on a larger spatial extent (e.g. national).status: publishe

Linking biochemical and biophysical variables derived from imaging spectrometers to ecological models - The HyEco'04 Group Shoot.

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