Estimation of vineyard water requirements using satellite-based surface energy balance

115 p.Since the 90's as a consequence of the Global Warming and the “La Niña” (ENSO) phenomena, the Chilean wine industry has been forced to increase irrigation systems investments, adopting new strategies of irrigation scheduling to improve the vineyard water use efficiency without affecting the grapes yield and quality. To develop an adequate irrigation strategy, the first step has been to estimate the vineyard water uptake or actual evapotranspiration ETa).Traditionally, vineyard ETa has been estimated by multiplying the reference evapotranspiration (ETo) by a single crop coefficient (Kc). Unfortunately, a major uncertainty in this approach is that many Kc values reported in literature are empirically determined from point-based measurements, and they are unable to describe the spatial variability of vineyard Kc, for each phenological stage. Recent advancements in using satellite remote sensing to determine ETa over space and time have made it possible to assess the variation in crop ETa at low-cost. One of the most cited remote sensing-based algorithms is METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) which is a onedimensional surface energy based residual model that has been extensively customized for application in full covered crops. For sparse crops such vineyards, as far as we know the application of METRIC to estimate ETa and Kc is still unexplored. In this way, this thesis was developed with the aim of critically study the applicability of METRIC over a drip-irrigated Merlot vineyard. To meet this, a study was carried out during the 2006-2007, 2007-2008 and 2008-2009 growing seasons. METRIC-based estimations were compared against ground measurements of vegetation indexes, surface energy balance components and vineyard ETa. Results indicated that METRIC’s semi-empirical sub-models for estimate vegetation indexes should be calibrated before its direct application to vineyards (Chapter 2). On the other hand, in the evaluation of METRIC to estimate the different components of the vineyard surface energy balance, results indicated that the compensation between the instantaneous fluxes of net radiation, soil heat fluxes and latent heath fluxes produced acceptable estimations of latent heat luxes (error less than 10%) to extrapolate them to daily (24 h) evapotranspiration (ETa) (Chapter 3). Finally for the main phenological stages of the Merlot vineyard, METRIC overestimated the Kc by about 10% in relation to ground measurements. However, those errors did not significantly affect the overall performance of METRIC during the study period into the estimation of daily (24 h) ETa and Kc (Chapter 4). Results exposed from Chapters two to four suggest that it is possible to confirm that the METRIC model can be used for obtain relatively good estimations of the vineyard ETa during the complete growing season

Comparación del índice de vegetación de la diferencia normalizada (NDVI) obtenido desde imágenes satelitales y radiometría de campo en un huerto de olivos cv. arbequina

48 p.El presente trabajo consistió en la comparación entre valores del índice de vegetación de diferencia normalizada (NDVI) obtenidos a partir del satelite Landsat 7 (NDVISAT) y un radiómetro multiespectral portátil en terreno (NDVIPOND). Este estudio se realizó durante las temporadas 2008/2009, 2009/2010 y 2010/2011 en un huerto de Olivos (Olea europaea cv. Arbequina) ubicado en el valle de Pencahue, Región del Maule, Chile (35º23´ lat. Sur; 71º44´ long. Oeste; 90 m.s.n.m). Para realizar la comparación, los valores de NDVI obtenidos con radiometría de campo fueron ponderados de acuerdo a la fracción de cobertura vegetal (fc), la cual alcanzó aproximadamente un 30% de la superficie. Los resultados obtenidos indican que la relación entre los índices, presenta una pendiente significativamente igual a 1, con un nivel de confianza del 95% (α de 0,05). El análisis estadístico además indica que el error cuadrático medio (RMSE), el error absoluto medio (MAE) y el índice de acuerdo fueron 0,019, 0,014 y 0,98, respectivamente. La mejor comparación entre NDVIPOND y el NDVISAT presento una diferencia igual a cero (en 4 fechas de medidas) y en contraste la peor comparación presentó una diferencia de un 11,2%. Las diferencias observadas entre los NDVI obtenidos a ambas escalas pueden estar asociadas a que no se eliminaron los efectos atmosféricos (corrección atmosférica) en los valores de reflectancia a nivel de satélite o a errores inducidos por la dificultad en la obtención de valores puros de NDVI en la radiometría de campo sobre Olivos, dada la alta porosidad presente en el dosel del cultivo. Finalmente en cuanto a la relación entre el Kc y el NDVI está presento un R2 de 0,71 para valores correspondientes a la temporada 2009-2010 en donde estos coincidieron con lo reportado por la literatura. Palabras clave: Coeficiente de cultivo, METRIC, Landsat, Fracción de cobertura, Índice de vegetación./ ABSTRACT: A comparison between normalized difference vegetation index (NDVI) derived from satellite data (NDVIPOND) and a portable multispectral radiometer (NDVISAT) field was carried out. This study was performed in the 2008/2009, 2009/2010 and 2010/2011 seasons, in an olive trees orchard (Olea europaea cv. Arbequina) located in the valley of Pencahue, Maule Region, Chile (35 ° 23' Lat. South, 71; 44' Long W, 90 m.a.s.l.). Before making comparisons, the NDVI values from field radiometry were weighted according to the fraction of vegetation cover (fc), which reached about 30% of the surface. The results indicate that the linear fit between indices (NDVI weighted and NDVI satellite) have a significantly slope equal to 1, with a confidence level of 95% (α of 0.05). Statistical analysis also indicates that the mean square error (RMSE), mean absolute error (MAE) and the index of agreement were 0.019, 0.014 and 0.98, respectively. The best comparison between both NDVIs show differences equal to zero (in 4 dates) and the worst comparison showed a difference of 11,2%. The differences observed between NDVIs obtained in both scales can be associated with atmospheric effects (not atmospheric correction) in the reflectance values at satellite level or errors induced by the difficulty to obtain pure values of NDVI in olives plant using radiometry, given the high porosity present in the canopy. Finally regarding the relationship between Kc and NDVI is presented an R2 of 0.71 for values for the 2009-2010 agricultural season where these coincided with that reported in the literature. Keywords: Crop coefficient, METRIC, Landsat, Fractional cover, Vegetation inde

Análisis comparativo de estimación del NDVI mediante utilización de imágenes satelitales y espectroradiómetro portátil en un viñedo cv. merlot.

44 p.Esta investigación se desarrolló con el objetivo de analizar la variabilidad espacial del Índice de vegetación de la diferencia normalizada (NDVI) del viñedo, usando dos escalas de medición: satélite y mediciones de terreno, a lo largo de la temporada de crecimiento. Para ello se llevó a cabo un estudio en una parcela experimental de 4,25 ha de vid (Vitis vinífera L.) cv. Merlot, conducido en espaldera vertical simple y regada por goteo, para el período comprendido entre las temporadas 2007-2008 a la 2009-2010. Las mediciones en terreno se realizaron periódicamente usando un espectroradiómetro portátil, para una grilla de 64 puntos. Los datos obtenidos de NDVI para vid (NDVIp) y suelo (NDVIs) fueron escalados a nivel de viñedo usando la fracción de cobertura (Fc). Estos datos fueron comparados con los estimados a partir de imágenes satelitales del programa Landsat (NDVIsat), para los días donde hubo imágenes disponibles. Los resultados donde se obtuvieron valores del error absoluto medio (MAE) y cuadrado medio del error (RMSE) de 0,04 y 0,05, respectivamente. El análisis de regresión indica que el coeficiente de determinación (R2) y pendiente (b) presentaron valores de 98% y 0,98, respectivamente. El test-t indicó que la pendiente fue significativamente similar a la unidad, con un 95% de certeza. Estos resultados indican que el NDVI medido en terreno por un espectroradiómetro portátil y estimado por imágenes Landsat fueron similares para el período de estudio. Palabras claves: Viticultura de precisión, Teledetección, Reflectividad, Expresión vegetativa, Bandas espectrales./ABSTRACT:This research was developed with the aim of analyzing the spatial variability of the Normalized Difference Vegetation Index (NDVI) of the vineyard, using two measurement scales: satellite and field measurements throughout the growing season. For this purposes a study was carried out in an experimental plot (4.25 ha) of a drip-irrigated vineyard (Vitis vinifera L.) cv. Merlot, trained on a vertical shoot positioned system from 2007-2008 to 2009-2010 growing seasons. Ground measurements were regularly done using a hand-held multispectral radiometer for a grid of 64 points. Values of NDVI measured from vines (NDVIp) and soil (NDVIs) were scaled to vineyard using the fractional cover (Fc). These data were compared with NDVI-satellite based (NDVIsat) acquired from the Landsat program, for days when satellite images were available. The results indicate that the mean absolute error (MAE) and root mean square of error (RMSE) were 0.04 and 0.05, respectively. Regression analysis indicates that the coefficient of determination (R2) and slope (b) were 98% and 0.98, respectively. The t-test indicates that the slope was significantly similar to the unit, with a 95% of confidence. These results indicated that the NDVI measured from the hand-held multispectral radiometer and obtained from Landsat imagery were similar for the study periods Key words: Precision viticulture, Remote sensing, Reflectivity, Vegetative expression, Spectral bands

Estimación de la evapotranspiración de un huerto de manzanos cv. Pink Lady utilizando imágenes satelitales Landsat 7

47 p.Se realizó una investigación para validar el modelo METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) en la estimación del consumo de agua o evapotranspiración real (ETa) de un huerto de Manzanos (Malus domestica cv. Pink Lady) ubicado en el valle de Pelarco, Región del Maule, Chile (Lat. 35º25´ S; Long 71º23´ O; 189 m.s.n.m). Para estimar ETa usando el modelo METRIC se utilizaron seis imágenes satelitales (Landsat 7 ETM+) adquiridas durante días con cielo despejado en la temporada 2012-2013. El desempeño del modelo METRIC se evaluó usando mediciones de ETa desde un sistema de Flujos Turbulentos (EC) a la hora del paso del satélite (11:30 h). El análisis estadístico indicó que el modelo METRIC sobrestimó la ETa en alrededor de un 17 % con un error cuadrático medio (RMSE) de 1,03 mm d-1, un error absoluto (MAE) de 0,96 mm d-1 y una eficiencia del 0,48. Los mayores errores del modelo METRIC fueron asociados a la selección de pixeles fríos (sectores con menor temperatura en la imagen), los que fueron difíciles de obtener para algunas imágenes satelitales. Palabras clave: percepción remota, METRIC,evapotranspiración, Pink Lady, Eddy covariance, balance de energía./ABSTRACT: A study was carried out to validate the METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) model to estimate the water requirements or real evapotranspiration (ETa) for a drip-irrigated apple orchard which is located at Pelarco Valley, Maule Region, Chile (Lat. 35º25´ S; Long 71º23´ W; 189 m above mean sea level). For estimating ETa using the METRIC model, six satellite images (Landsat 7 ETM+) acquired during clear sky days were used for the 2012-2013 growing season. The performance of METRIC was evaluated using measurements of ETa from an eddy covariance system (EC) at the time of satellite overpass (11:30 h). The statistical analysis indicated that the METRIC model overestimated ETa values by about 17 % with a root mean square error (RMSE), mean absolute error (MAE) and index of agreement (d) of 1.03 mm d-1, 0.96 mm d-1 y 0.48, respectively. Main errors of the METRIC model were associated with the selection of the cold pixels (coldest spots in the image), which were difficult to obtain for some satellite images. Keywords: Remote sensing, METRIC, Evapotranspiration, Pink Lady, eddy covariance, energy balance

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

II. Evaluacion de la evapotranspiracion real de un viñedo cv Cabernet sauvignon utilizando el modelo de Shuttleworth & Wallace

41 p