Ancient Amazonian populations left lasting impacts on forest structure

Amazonia contains a vast expanse of contiguous tropical forest and is influential in global carbon and hydrological cycles. Whether ancient Amazonia was highly disturbed or modestly impacted, and how ancient disturbances have shaped current forest ecosystem processes, is still under debate. Amazonian Dark Earths (ADEs), which are anthropic soil types with enriched nutrient levels, are one of the primary lines of evidence for ancient human presence and landscape modifications in settings that mostly lack stone structures and which are today covered by vegetation. We assessed the potential of using moderate spatial resolution optical satellite imagery to predict ADEs across the Amazon Basin. Maximum entropy modeling was used to develop a predictive model using locations of ADEs across the basin and satellite‐derived remotely sensed indices. Amazonian Dark Earth sites were predicted to be primarily along the main rivers and in eastern Amazonia. Amazonian Dark Earth sites, when compared with randomly selected forested sites located within 50 km of ADE sites, were less green canopies (lower normalized difference vegetation index) and had lower canopy water content. This difference was accentuated in two drought years, 2005 and 2010. This is contrary to our expectation that ADE sites would have nutrient‐rich soils that support trees with greener canopies and forests on ADE soils being more resilient to drought. Biomass and tree height were lower on ADE sites in comparison with randomly selected adjacent sites. Our results suggested that ADE‐related ancient human impact on the forest is measurable across the entirety of the 6 million km2 of Amazon Basin using remotely sensed data

Intermanifold similarities in partial photoionization cross sections of helium

Using the eigenchannel R-matrix method we calculate partial photoionization cross sections from the ground state of the helium atom for incident photon energies up to the N=9 manifold. The wide energy range covered by our calculations permits a thorough investigation of general patterns in the cross sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf 54}, 2080 (1996)]. The existence of these patterns can easily be understood in terms of propensity rules for autoionization. As the photon energy is increased the regular patterns are locally interrupted by perturber states until they fade out indicating the progressive break-down of the propensity rules and the underlying approximate quantum numbers. We demonstrate that the destructive influence of isolated perturbers can be compensated with an energy-dependent quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte

THE DENSITY OF LIQUID PLUTONIUM METAL

Measurements were made of the product of surface tension (ϒ) and the contact angle (θ) of liquid plutonium vs solid tantalum and of the density of liquid plutonium (p) as functions of temperature between 655 and 960°C. The following values were obtained: ϒ cos θ = 1030 - (0.967)T d/cm and p = [17.56$sub 7$ - (1.45$sub 1$ x 10$sup -3$)T] ± 0.021 g/cm$sup 3$. A single determination was also made of the liquid density of a plutonium-7.93 atomic percent iron alloy and he following value obtained: p = [16.88 - (1.36$sub 9$)T] ± 0.012 g/cm$sup 3$

Resonance structure in the Li^- photodetachment cross section

We report on the first observation of resonance structure in the total cross section for the photodetachment of Li^-. The structure arises from the autodetaching decay of doubly excited ^1P states of Li^- that are bound with respect to the 3p state of the Li atom. Calculations have been performed for both Li^- and H^- to assist in the identification of these resonances. The lowest lying resonance is a symmetrically excited intrashell resonance. Higher lying asymmetrically excited intershell states are observed which converge on the Li(3p) limit.Comment: 4 pages, 2 figure, 19 references, RevTeX, figures in ep

Ecological Science Infrastructure for Sustainability Transformations in Rangelands

Sustainability transformations—deliberate and radical shifts in values, governance, and management regimes to achieve sustainability—are needed in rangelands as in other components of the Earth system. We review four concepts comprising an ecological science infrastructure to support such transformations. The foundation is standard measurement of rangeland conditions in the field, especially vegetation and soil properties that underpin the environmental aspects of sustainability. Big data resources, especially gridded spatial datasets produced by models and remote sensing, can be combined with field data and computational approaches to upscale information about rangeland conditions and produce additional indicators of ecosystem functions and services. State and transition models (STMs) linked to land types provide a means to interpret indicators and link interpretations to sustainable land management practices to manage change. Technologies for climate adaptation in rangelands also need to be linked to STM databases. Web and mobile technologies can put multifaceted science knowledge into the hands of pastoralists worldwide to support transformational changes in how rangelands are managed