Vegetation greenness in northeastern Brazil and its relation to ENSO warm events

The spatio-temporal variability of trends in vegetation greenness in dryland areas is a well-documented phenomenon in remote sensing studies at global to regional scales. The underlying causes differ, however, and are often not well understood. Here, we analyzed the trends in vegetation greenness for a semi-arid area in northeastern Brazil (NEB) and examined the relationships between those dynamics and climate anomalies, namely the El Nino Southern Oscillation (ENSO) for the period 1982 to 2010, based on annual Normalized Difference Vegetation Index (NDVI) values from the latest version of the Global Inventory Modeling and Mapping Studies (GIMMS) NDVI dataset (NDVI3g) dataset. Against the ample assumption of ecological and socio-economic research, the results of our inter-annual trend analysis of NDVI and precipitation indicate large areas of significant greening in the observation period. The spatial extent and strength of greening is a function of the prevalent land-cover type or biome in the study area. The regression analysis of ENSO indicators and NDVI anomalies reveals a close relation of ENSO warm events and periods of reduced vegetation greenness, with a temporal lag of 12 months. The spatial patterns of this relation vary in space and time. Thus, not every ENSO warm event is reflected in negative NDVI anomalies. Xeric shrublands (Caatinga) are more sensitive to ENSO teleconnections than other biomes in the study area.JRC.H.4-Monitoring Agricultural Resource

Global Ecosystem Response Types Derived from the Standardized Precipitation Evapotranspiration Index and FPAR3g Series

Observing trends in global ecosystem dynamics is an important first step, but attributing these trends to climate variability represents a further step in understanding Earth system changes. In the present study, we classified global Ecosystem Response Types (ERTs) based on common spatio-temporal patterns in time-series of Standardized Precipitation Evapotranspiration Index (SPEI) and FPAR3g anomalies (1982–2011) by using an extended Principal Component Analysis. The ERTs represent region specific spatio-temporal patterns of ecosystems responding to drought or ecosystems with decreasing severity in drought events as well as ecosystems where drought was not a dominant factor in a 30-year period. Highest explanatory values in the SPEI12-FPAR3g anomalies and strongest SPEI12-FPAR3g correlations were seen in the ERTs of Australia and South America whereas lowest explanatory value and lowest correlations were observed in Asia and North America. These ERTs complement traditional pixel based methods by enabling the combined assessment of the location, timing, duration, frequency and severity of climatic and vegetation anomalies with the joint assessment of wetting and drying climatic conditions. The ERTs produced here thus have potential in supporting global change studies by mapping reference conditions of long term ecosystem changes.JRC.H.5-Land Resources Managemen

Global Ecosystem Response Types Derived from the Standardized Precipitation Evapotranspiration Index and FPAR3g Series

Observing trends in global ecosystem dynamics is an important first step, but attributing these trends to climate variability represents a further step in understanding Earth system changes. In the present study, we classified global Ecosystem Response Types (ERTs) based on common spatio-temporal patterns in time-series of Standardized Precipitation Evapotranspiration Index (SPEI) and FPAR3g anomalies (1982–2011) by using an extended Principal Component Analysis. The ERTs represent region specific spatio-temporal patterns of ecosystems responding to drought or ecosystems with decreasing severity in drought events as well as ecosystems where drought was not a dominant factor in a 30-year period. Highest explanatory values in the SPEI12-FPAR3g anomalies and strongest SPEI12-FPAR3g correlations were seen in the ERTs of Australia and South America whereas lowest explanatory value and lowest correlations were observed in Asia and North America. These ERTs complement traditional pixel based methods by enabling the combined assessment of the location, timing, duration, frequency and severity of climatic and vegetation anomalies with the joint assessment of wetting and drying climatic conditions. The ERTs produced here thus have potential in supporting global change studies by mapping reference conditions of long term ecosystem changes

Multi-decadal trends in global terrestrial evapotranspiration and its components

Evapotranspiration (ET) is the process by which liquid water becomes water vapor and energetically this accounts for much of incoming solar radiation. If this ET did not occur temperatures would be higher, so understanding ET trends is crucial to predict future temperatures. Recent studies have reported prolonged declines in ET in recent decades, although these declines may relate to climate variability. Here, we used a well-validated diagnostic model to estimate daily ET during 1981–2012, and its three components: transpiration from vegetation (Et), direct evaporation from the soil (Es) and vaporization of intercepted rainfall from vegetation (Ei). During this period, ET over land has increased significantly (p < 0.01), caused by increases in Et and Ei, which are partially counteracted by Es decreasing. These contrasting trends are primarily driven by increases in vegetation leaf area index, dominated by greening. The overall increase in Et over land is about twofold of the decrease in Es. These opposing trends are not simulated by most Coupled Model Intercomparison Project phase 5 (CMIP5) models, and highlight the importance of realistically representing vegetation changes in earth system models for predicting future changes in the energy and water cycle

Assessing Vegetation Decline Due to Pollution from Solid Waste Management by a Multitemporal Remote Sensing Approach

Nowadays, the huge production of Municipal Solid Waste (MSW) is one of the most strongly felt environmental issues. Consequently, the European Union (EU) delivers laws and regulations for better waste management, identifying the essential requirements for waste disposal operations and the characteristics that make waste hazardous to human health and the envi-ronment. In Italy, environmental regulations define, among other things, the characteristics of sites to be classified as “potentially contaminated”. From this perspective, the Basilicata region is cur-rently one of the Italian regions with the highest number of potentially polluted sites in proportion to the number of inhabitants. This research aimed to identify the possible effects of potentially toxic element (PTE) pollution due to waste disposal activities in three “potentially contaminated” sites in southern Italy. The area was affected by a release of inorganic pollutants with values over the thresholds ruled by national/European legislation. Potential physiological efficiency variations of vegetation were analyzed through the multitemporal processing of satellite images. Landsat 5 Thematic Mapper (TM) and Landsat 8 Operational Land Imager (OLI) images were used to calcu-late the trend in the Normalized Difference Vegetation Index (NDVI) over the years. The mul-titemporal trends were analyzed using the median of the non-parametric Theil–Sen estimator. Fi-nally, the Mann–Kendall test was applied to evaluate trend significance featuring areas according to the contamination effects on investigated vegetation. The applied procedure led to the exclu-sion of significant effects on vegetation due to PTEs. Thus, waste disposal activities during previ-ous years do not seem to have significantly affected vegetation around targeted sites

The use of long-term high.spatial resolution Normalized Difference vegetation Index (NDVI) to determine different environmental processes in Spain

En esta tesis doctoral se han procesado imágenes de los satélites NOAA-AVHRR de 1,1 km de resolución espacial, disponibles durante tres décadas (1981 - 2015) para obtener una base de datos del índice de vegetación NDVI, para la España peninsular y las Islas Baleares, llamada Sp_1Km_NDVI. El método incluye la calibración de la información con los coeficientes de calibración posteriores al lanzamiento de cada satélite, correcciones geométricas y topográficas, la eliminación de nubes, el filtrado temporal de las series y la obtención de compuestos semi-mensales mediante el valor máximo NDVI de las imágenes. Además, la tesis compara la nueva base de datos Sp_1km_NDVI con otras tres bases de datos NDVI. Se ha comprobado si las tendencias anuales y estacionales de la base de datos Sp_1km_NDVI y las otras tres fuentes de información muestran patrones espaciales y tendencias temporales similares. Los resultados muestran que la nueva base de datos proporciona información sobre la actividad vegetal. Es útil para investigar procesos de cambio climático y procesos relacionados con las actividades humanas, en esta región mediterránea. Y permite identificar una tendencia positiva dominante del NDVI durante el periodo de estudio. En el presente trabajo también se han estudiado la relación entre la actividad vegetal y el crecimiento de los anillos de los árboles, en distintos tipos de bosques, bajo diferentes condiciones ambientales. Para ello, la base de datos de imágenes de satélite NDVI se ha combinado con registros dendrocronológicos y datos climáticos para analizar la variabilidad interanual del crecimiento de los anillos de los árboles y la actividad vegetal en distintos biomas forestales desde 1981 y hasta 2015. Los resultados revelan la existencia de una relación positiva y significativa entre la variabilidad interanual del NDVI y el crecimiento de los anillos de los árboles. Sin embargo, esta relación depende del tipo de bosque y de las condiciones ambientales. Finalmente, se han analizado los impactos de la sequía en el NDVI, ya que la sequía es uno de los principales riesgos naturales que afectan a la actividad de la vegetación en España. En esta parte de la tesis se determinan las posibles diferencias en la sensibilidad de la vegetación a la sequía, determinada por los distintos tipos de cubiertas vegetales y por las condiciones climáticas. Y analiza las escalas de tiempo en las que la actividad vegetal está respondiendo a la severidad de la sequía. Los resultados han demostrado que, en grandes áreas de la España peninsular, la actividad vegetal está fuertemente determinada por las variaciones interanuales de la sequía. Sin embargo, existen importantes diferencias estacionales y espaciales en las que el tipo de cubierta y las condiciones de aridez juegan un papel importante. En esta tesis también se ha mostrado que la escala temporal a la que se mide la sequía es muy relevante para entender los diferentes impactos estacionales, e informa sobre la sensibilidad del NDVI a la sequía a nivel estacional y en diferentes coberturas vegetales.<br /