Sensitivity of the stress response function to packing preparation

A granular assembly composed of a collection of identical grains may pack under different microscopic configurations with microscopic features that are sensitive to the preparation history. A given configuration may also change in response to external actions such as compression, shearing etc. We show using a mechanical response function method developed experimentally and numerically, that the macroscopic stress profiles are strongly dependent on these preparation procedures. These results were obtained for both two and three dimensions. The method reveals that, under a given preparation history, the macroscopic symmetries of the granular material is affected and in most cases significant departures from isotropy should be observed. This suggests a new path toward a non-intrusive test of granular material constitutive properties.Comment: 15 pages, 11 figures, some numerical data corrected, to appear in J. Phys. Cond. Mat. special issue on Granular Materials (M. Nicodemi Editor

Bamboo phenology and life cycle drive seasonal and long‐term functioning of Amazonian bamboo‐dominated forests

Bamboo‐dominated forests (BDF) extend over large areas in the drought‐prone Southwestern Amazon, yet little is known about the dynamics of these ecosystems. Here, we investigate the hypothesis that bamboo modulates large‐scale ecosystem dynamics through competition with coexisting trees for water. We examined spatio‐temporal patterns of remotely sensed metrics (Enhanced Vegetation Index [EVI], Normalized Difference Moisture Index [NDMI]) in >300 Landsat images as proxies for canopy leaf phenology and water content at two time scales: (1) a complete bamboo life cycle (~28 years), and (2) the seasonal cycle; and at two spatial scales: (a) comparing adjacent areas of BDF vs. Terra‐firme forests (TFF) to investigate regional dynamics, and (b) comparing the vegetation classes of bamboo, trees in BDF, and trees in TFF to investigate the effects of bamboo on coexisting trees. At the regional scale, BDF showed higher EVI (leaf area density) and lower NDMI (water content) than nearby TFF but these differences disappeared as bamboo died, suggesting a strong influence of bamboo life stage in the functioning of these forests. BDF seasonal cycle showed a bimodal EVI pattern as trees and bamboos had asynchronized leaf production peaks. At the scale of vegetation classes, trees in BDF showed lower NDMI (i.e. water content) than trees in TFF except after bamboo mortality, indicating a release from competition with bamboo for water. Canopy water content of trees in BDF was also reduced during bamboo dry‐season greening (increased EVI ~ leaf production) due to increased water demands. Nevertheless, long‐term and seasonal phenology of trees in BDF did not differ from that of trees in TFF suggesting a potential selection for drought‐tolerant trees in BDF. Synthesis. Bamboo‐dominated forests have received less attention than other Amazonian forests and their functional dynamics are commonly ignored or misinterpreted. Using remote sensing to characterize forest phenology and water content, we show the distinctive seasonal and long‐term dynamics of BDF and coexisting trees and the importance of bamboo competition for water in shaping this ecosystem. Our results suggest a potential selection for drought‐tolerant trees in BDF since they maintain the same EVI as trees in bamboo‐free forests but with lower water content. A better characterization of BDF and their cyclical dynamics is crucial for accurately interpreting Amazonian forests' responses to extreme climatic events such as high temperatures and droughts. Resumen Los bosques dominados por bambú (BDB/BDF) se extienden a lo largo de grandes áreas del Suroeste Amazónico las cuales son propensas a la sequía; sin embargo, se conoce muy poco sobre la dinámica de estos ecosistemas. En este artículo investigamos la hipótesis de que el bambú moldea la dinámica a gran escala de este ecosistema mediante la competencia por agua con los árboles coexistentes. Examinamos patrones espacio‐temporales de índices obtenidos mediante el uso de sensores remotos (Enhanced Vegetation Index, [EVI], Normalized Difference Moisture Index [NDMI]) en >300 imágenes Landsat como aproximaciones a la fenología de las hojas del dosel y su contenido de agua a dos escalas temporales: (1) un ciclo de vida completo del bambú (~28 años), y (2) el ciclo estacional; y a dos escalas espaciales: (a) comparando áreas adyacentes de BDF vs bosques de Terra‐firme (BTF/TFF) para investigar dinámicas regionales, y (b) comparando las clases de vegetación de bambú, árboles en BDF y árboles en TFF independientemente, para investigar los efectos del bambú en los árboles con los que coexiste. A escala regional, los BDF mostraron EVI más alto (densidad de área foliar) y NDMI más bajo (contenido de agua) que los TFF cercanos pero estas diferencias desaparecieron cuando el bambú murió, sugiriendo una fuerte influencia del estadío de vida del bambú en el funcionamiento de estos bosques. Los BDF presentan un ciclo estacional con un patrón de EVI bimodal dado que árboles y bambús tienen picos de producción foliar asincrónicos. A escala de clases de vegetación, los árboles en BDF mostraron NDMI más bajo (contenido de agua) que los árboles en TFF excepto después de la mortalidad del bambú, indicando un alivio en la competencia por agua con el bambú. El contenido de agua en el dosel de los árboles en BDF también se redujo durante el reverdecimiento del bambú en la estación seca (incremento de EVI ~ producción de hojas) debido al incremento en la demanda de agua. No obstante, la fenología de los árboles en BDF no difiere de la de árboles en TFF ni a largo plazo, ni en el ciclo estacional sugiriendo una posible selección a favor de árboles tolerantes a la sequía en BDF. Síntesis. Los bosques dominados por bambú han recibido menos atención que otros bosques amazónicos y su funcionamiento y dinámica son comúnmente ignorados o malinterpretados. Usando sensores remotos para caracterizar la fenología de los bosques y su contenido de agua, mostramos la distintiva dinámica estacional y a largo plazo de los BDF y los árboles que coexisten en estos bosques. También demostramos la importancia de la competencia por agua entre bambú y árboles en el moldeamiento de este ecosistema. Nuestros resultados sugieren una posible selección a favor de especies tolerantes a la sequía en BDF ya que mantienen el mismo EVI que los árboles en bosques sin bambú, pero con menor contenido de agua. Una mejor caracterización de los bosques dominados por bambú y su dinámica cíclica es crucial para una correcta interpretación de la respuesta de los bosques amazónicos a los eventos climáticos extremos como los picos de temperatura y las sequías. Bamboo‐dominated forests have received less attention than other Amazonian forests and their functional dynamics are commonly ignored or misinterpreted. Using remote sensing to characterize forest phenology and water content, we show the distinctive seasonal and long‐term dynamics of BDF and coexisting trees and the importance of bamboo competition for water in shaping this ecosystem. Our results suggest a potential selection for drought‐tolerant trees in BDF since they maintain the same EVI as trees in bamboo‐free forests but with lower water content. A better characterization of BDF and their cyclical dynamics is crucial for accurately interpreting Amazonian forests' responses to extreme climatic events such as high temperatures and droughts

Prompt Release Cases of Vessels and Their Crew before ITLOS : How to Resolve Desputes in Appropriate Forums

We describe a new large-sized species of hypercarnivorous hyainailourine-Kerberos langebadreae gen. & sp. nov.-from the Bartonian (MP16) locality of Montespieu (Tarn, France). These specimens consist of a skull, two hemimandibles and several hind limb elements (fibula, astragalus, calcaneum, metatarsals, and phalanges). Size estimates suggest K. langebadreae may have weighed up to 140 kg, revealing this species as the largest carnivorous mammal in Europe at that time. Besides its very large size, K. langebadreae possesses an interesting combination of primitive and derived features. The distinctive skull morphology of K. langebadreae reflects a powerful bite force. The postcranial elements, which are rarely associated with hyainailourine specimens, indicate an animal capable of a plantigrade stance and adapted for terrestrial locomotion. We performed the first phylogenetic analysis of hyainailourines to determine the systematic position of K. langebadreae and to understand the evolution of the group that includes other massive carnivores. The analysis demonstrates that Hemipsalodon, a North American taxon, is a hyainailourine and is closely related to European Paroxyaena. Based on this analysis we hypothesize the biogeographic history of the Hyainailourinae. The group appeared in Africa with a first migration to Europe during the Bartonian that likely included the ancestors of Kerberos, Paroxyaena and Hemipsalodon, which further dispersed into North America at this time. We propose that the hyainailourines dispersed into Europe also during the Priabonian. These migrants have no ecological equivalent in Europe during these intervals and likely did not conflict with the endemic hyaenodont proviverrines. The discovery of K. langebadreae shows that large body size appears early in the evolution of hyainailourines. Surprisingly, the late Miocene Hyainailouros shares a more recent common ancestor with small-bodied hyainailourines (below 15 kg). Finally, our study supports a close relationship between the Hyainailourinae and Apterodontinae and we propose the new clade: Hyainailouridae