The Threat of Multiâ Year Drought in Western Amazonia

Recent â onceâ inâ aâ centuryâ Amazonian droughts highlight the impacts of drought and climate change on this region’s vegetation, carbon storage, water cycling, biodiversity, land use, and economy. The latest climate model simulations suggest this region will experience worsening future drought. However, the instrumental record is too short to quantify the range of background drought variability, or to evaluate extended drought risk in climate models. To overcome these limitations, we generated a new, highly resolved lake record of hydroclimatic variability within the western Amazon Basin. We find that Amazonia has regularly experienced multiâ year droughts over the last millennium. Our results indicate that current climate model simulations likely underestimate the background risk of multiâ year Amazonian drought. These findings illustrate that the future sustainability of the Amazonian forest and its many services may require management strategies that consider the likelihood of multiâ year droughts superimposed on a continued warming trend.Plain Language SummaryThe Amazon basin recently experienced multiple â onceâ inâ aâ centuryâ droughts that impacted the region’s water cycle, economy, vegetation, and carbon storage. However, the instrumental record in this region tends to be too short to determine if these droughts are abnormal in a longâ term context. Paleoclimate data can extend drought records that help water and land managers plan for these events in the face of climate change. To provide additional information about preâ instrumental drought, here we present results from a new paleoclimate lake record based on sediments we recovered from Lake Limón in the Peruvian Amazon. We find that concentrations of elements in the Lake Limón sediment cores are likely recording past changes in rainfall variability. We use this elemental variability to generate a new, millennialâ length record of drought for the western Amazon. We show that this region has experienced multiâ year droughts at least twice a century over the last â ¼1,400 years. The frequency and severity of these paleoclimateâ inferred droughts may exceed most climate model and instrumentalâ era drought risk estimates. Our findings illustrate that the future sustainability of the Amazonian forest and its many ecosystem services may require management strategies that consider the likelihood of multiâ year droughts in addition to continued warming.Key PointsWe present results from a highâ resolution paleoclimate record of hydroclimatic variability in western AmazoniaOur paleoclimate record suggests western Amazonia has regularly experienced multiâ year drought over the last millenniumEarth system model simulations may underestimate the background risk of multiâ year western Amazonian droughtPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146272/1/wrcr23386_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146272/2/wrcr23386.pd

Curvas diferenciadas de índice de sitio para vochysia guatemalensis en la región Huetar norte y Huetar caribe de Costa Rica

The analysis of the dominant height growth for Vochysia guatemalensis, based on a sample of permanent plots located in the Northern Huetar and the Caribbean Huetar regions of Costa Rica, allowed to distinguish 2 dissimilar growth patterns and develop differentiated site index curves. In order to carry out this work, all the information available about the growth of this species from public and private organizations was used, giving rise to a sample of 43 permanent sampling plots; which produced 397 dominant height-age averages, with which all models were adjusted. The first step was to classify the dominant height growth and as a result 3 site quality classes were preliminarily created; it allowed proving the existence of 2 different growth patterns in the sample: one represented by classes I and II (sample 1), and the other by class III (sample 2). Levene test did not reject the hypothesis of equality of variances between the samples, which indicates there is a high probability that Samples 1 and 2 may come from the same population, while t test rejected the null hypothesis of equality of means, revealing there are significant differences in the average of the dominant heights of both samples. Because of this, it was decided to adjust 2 separated sets of site index curves, based on the observed discrepancies. To build the curves, a base age of 9 years were used. In both cases, eight linear and non-linear (but linearizable) functions and 12 non-linear models were tested. For sample 1 the selected function was that of Bailey and Clutter, and for sample 2 the selected function was that of Prodan; both equations showed a good statistical fit and a good performance when graphed against the observed values. The equation for sample 1, presented the following statistics: r = -0.94; R2adj = 0.89; MSE = 0.0565; SEE = 0.2378; and the second equation for sample 2, showed the following results: r = 0.93; R2adj = 0.87; MSE = 0.3886; SEE = 0.6234.El análisis del crecimiento en altura dominante para Vochysia guatemalensis, basado en una muestra de parcelas permanentes localizadas en las regiones Huetar Norte y Huetar Caribe, permitió distinguir 2 patrones de crecimiento disímiles y a la vez desarrollar curvas diferenciadas de índice de sitio. Para llevar a cabo este trabajo, se utilizó toda la información disponible sobre el crecimiento de esta especie, proveniente de organizaciones públicas y privadas, lo cual da origen a una muestra de 43 parcelas permanentes de muestreo; las mismas produjeron 397 promedios de altura dominante-edad con los que se ajustaron todos los modelos. El primer paso fue clasificar el crecimiento en altura dominante y como resultado se crearon, preliminarmente, 3 clases de calidad de sitio; esto permitió comprobar la existencia de 2 diferentes patrones de crecimiento en la muestra: uno representado por las clases I y II (Muestra 1) y el otro por la clase III (Muestra 2). La prueba de Levene no rechazó la hipótesis de igualdad de varianzas entre las muestras, lo cual indica que existe una alta probabilidad de que las muestras 1 y 2 provengan de la misma población, mientras que la prueba t rechazó la hipótesis nula de igualdad de medias, al revelar que existen diferencias significativas en el promedio de las alturas dominantes de ambas muestras. Debido a esto, se decidió ajustar 2 juegos de curvas separadas de índice de sitio, con base en las discrepancias observadas entre las muestras. Para construir las curvas se utilizó una edad base de 9 años. Para ambas muestras se probaron 8 funciones lineales y no lineales (pero linealizables) y 12 modelos no lineales. Para la Muestra 1 la función seleccionada fue la de Bailey y Clutter, y para la Muestra 2 se utilizó la función de Prodan; ambas ecuaciones presentaron un buen ajuste estadístico y mostraron un buen comportamiento cuando se graficaron contra los valores observados. La ecuación para la Muestra 1 presentó los siguientes estadísticos r = -0,94; R2adj = 0,89; MSE = 0,0565; SEE = 0,2378; y la ecuación para la Muestra 2 produjo los siguientes resultados: r = 0,93; R2adj = 0,87; MSE = 0,3886; SEE = 0,623

Homotypic cell cannibalism, a cell-death process regulated by the nuclear protein 1, opposes to metastasis in pancreatic cancer.

International audiencePancreatic adenocarcinoma (PDAC) is an extremely deadly disease for which all treatments available have failed to improve life expectancy significantly. This may be explained by the high metastatic potential of PDAC cells, which results from their dedifferentiation towards a mesenchymal phenotype. Some PDAC present cell-in-cell structures whose origin and significance are currently unknown. We show here that cell-in-cells form after homotypic cell cannibalism (HoCC). We found PDAC patients whose tumours display HoCC develop less metastasis than those without. In vitro, HoCC was promoted by inactivation of the nuclear protein 1 (Nupr1), and was enhanced by treatment with transforming growth factor β. HoCC ends with death of PDAC cells, consistent with a metastasis suppressor role for this phenomenon. Hence, our data indicates a protective role for HoCC in PDAC and identifies Nupr1 as a molecular regulator of this process