Charcoal chronology of the Amazon forest: A record of biodiversity preserved by ancient fires

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.he Amazon region holds a wide variety of ethnic groups and microclimates, enabling different interactions between humans and environment. To better understand the evolution of this region, ancient remains need to be analysed by all possible means. In this context, the study of natural and/or anthropogenic fires through the analysis of carbonized remains can give information on past climate, species diversity, and human intervention in forests and landscapes. In the present work, we undertook an anthracological analysis along with the 14 C dating of charcoal fragments using accelerator mass spectrometry (AMS). Charcoal samples from forest soils collected from seven different locations in the Amazon Basin were taxonomically classified and dated. Out of the 16 groups of charcoal fragments identified, five contained more than one taxonomic type, with the Fabaceae, Combretaceae and Sapotaceae families having the highest frequencies. 14 C charcoal dates span ∼6000 years (from 6876 to 365 yr BP) among different families, with the most significant variation observed for two fragments from the same sampling location (spanning 4000 14 C yr). Some sample sets resulted in up to five different families. These findings demonstrate the importance of the association between anthracological identification and radiocarbon dating in the reconstruction of paleo-forest composition and fire history.The authors thank the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ). KDM thanks CNPq for fellowship 305079/2014–0. CL thanks FAPEAM/FAPESP (09/53369-6, led by Flávia Regina Capellotto Costa) for financial support and Thaise Emílio, José Luiz Purri da Veiga Pinto, Rosineide Machado and Francislaide da Silva Costa for help with charcoal collection. TRF, BSM, and BHM acknowledge financial support from NERC (NE/N011570/1), CAPES/CNPq Science without Borders (PVE 177/2012 and PVE 401279/2014-6), CNPq/PPBio (457602/2012-0), CNPq/PELD (403725/2012-7) and the University of Exeter - College of Life and Environmental Sciences

Review of interactions between the Naval Postgraduate School and the Naval Undersea Warfare Engineering Station, 1973-1986

http://archive.org/details/reviewofinteract00wilsDept. of Physics.N

A statistical evaluation of the effects of a structured postdoctoral programme

Published© 2014 Society for Research into Higher Education. Postdoctoral programmes have recently become an important step leading from doctoral education to permanent academic careers in the social sciences. This paper investigates the effects of a large and structured postdoctoral programme in the social sciences on a number of academic and non-academic outcomes of fellows. Propensity score matching is employed to match fellows with applicants with similar characteristics who did not receive the fellowship; then the outcomes in the treatment and control groups are compared. The programme has a statistically significant positive effect on the general life satisfaction of former fellows and their publication activity. It is argued that an active and collegial research environment, with training in academic skills during postdoctoral employment, may improve the academic outcomes of postdoctoral fellows

Soil pyrogenic carbon in southern Amazonia: Interaction between soil, climate, and above-ground biomass

The Amazon forest represents one of the world’s largest terrestrial carbon reservoirs. Here, we evaluated the role of soil texture, climate, vegetation, and distance to savanna on the distribution and stocks of soil pyrogenic carbon (PyC) in intact forests with no history of recent fire spanning the southern Amazonia forest-Cerrado Zone of Transition (ZOT). In 19 one hectare forest plots, including three Amazonian Dark Earth (ADE, terra preta) sites with high soil PyC, we measured all trees and lianas with diameter ≥ 10 cm and analyzed soil physicochemical properties, including texture and PyC stocks. We quantified PyC stocks as a proportion of total organic carbon using hydrogen pyrolysis. We used multiple linear regression and variance partitioning to determine which variables best explain soil PyC variation. For all forests combined, soil PyC stocks ranged between 0.9 and 6.8 Mg/ha to 30 cm depth (mean 2.3 ± 1.5 Mg/ha) and PyC, on average, represented 4.3% of the total soil organic carbon (SOC). The most parsimonious model (based on AICc) included soil clay content and above-ground biomass (AGB) as the main predictors, explaining 71% of soil PyC variation. After removal of the ADE plots, PyC stocks ranged between 0.9 and 3.8 Mg/ha (mean 1.9 ± 0.8 Mg/ha–1) and PyC continued to represent ∼4% of the total SOC. The most parsimonious models without ADE included AGB and sand as the best predictors, with sand and PyC having an inverse relationship, and sand explaining 65% of the soil PyC variation. Partial regression analysis did not identify any of the components (climatic, environmental, and edaphic), pure or shared, as important in explaining soil PyC variation with or without ADE plots. We observed a substantial amount of soil PyC, even excluding ADE forests; however, contrary to expectations, soil PyC stocks were not higher nearer to the fire-dependent Cerrado than more humid regions of Amazonia. Our findings that soil texture and AGB explain the distribution and amount of soil PyC in ZOT forests will help to improve model estimates of SOC change with further climatic warming

Soil water-holding capacity and monodominance in Southern Amazon tropical forests

Background and aims: We explored the hypothesis that low soil water-holding capacity is the main factor driving the monodominance of Brosimum rubescens in a monodominant forest in Southern Amazonia. Tropical monodominant forests are rare ecosystems with low diversity and high dominance of a single tree species. The causes of this atypical condition are still poorly understood. Some studies have shown a relationship between monodominance and waterlogging or soil attributes, while others have concluded that edaphic factors have little or no explanatory value, but none has accounted for soil-moisture variation other than waterlogging. This study is the first to explicitly explore how low soil water-holding capacity influences the monodominance of tropical forests. Methods: We conducted in situ measurements of vertical soil moisture using electrical resistance collected over 1 year at 0–5; 35–40 and 75–80 cm depths in a B. rubescens monodominant forest and in an adjacent mixed-species forest in the Amazon-Cerrado transition zone, Brazil. Minimum leaf water potential (Ψmin) of the seven most common species, including B. rubescens, and soil water-holding capacity for both forests were determined. Results: The vertical soil moisture decay pattern was similar in both forests for all depths. However, the slightly higher water availability in the monodominant forest and Ψmin similarity between B. rubescens and nearby mixed forest species indicate that low water-availability does not cause the monodominance. Conclusions: We reject the hypothesis that monodominance of B. rubescens is primarily determined by low soil water-holding capacity, reinforcing the idea that monodominance in tropical forests is not determined by a single factor

Trees at the Amazonia-Cerrado transition are approaching high temperature thresholds

Land regions are warming rapidly. While in a warming world at extra-tropical latitudes vegetation adapted to higher temperatures may move in from lower latitudes this is not possible in the tropics. Thus, the limits of plant functioning will determine the nature and composition of future vegetation. The most temperature sensitive component of photosynthesis and a key component of plants is Photosystem II. Here we report the thermal safety margin (difference between Photosystem II thermotolerance (T50) and maximum leaf temperature) during the beginning of the dry season for four tree species co-occurring across the forest-savanna transition zone in Brazil, a region which has warmed particularly rapidly over the recent decades. The species selected are evergreen in forests but deciduous in savannas. We find that thermotolerance declines with growth temperature larger than >40 °C for individuals in the savannas. Current maximum leaf temperatures exceed T50 in some species and will exceed T50 in a 2.5 °C warmer world in most species evaluated. Despite plasticity in leaf thermal traits to increase leaf cooling in hotter environments, the results show this is not sufficient to maintain a safe thermal safety margin in hotter savannas. Overall, the results suggest that forest species may become increasingly deciduous and savanna-like in the future

Technology of production of Syrian lustre (11th to 13th century)

Lustre is a decoration consisting of a surface layer of silver and copper metal nanoparticles, a few hundreds of nanometres thick and incorporated into the glaze. It shows a colourful metallic and iridescent appearance which makes use of the quantum confined optical response of the metallic nanoparticles. Three apparently unrelated lustre decorations, yellow-orange golden (Tell Minis), a dark brown-reddish with iridescences (Raqqa) and yellow-brown golden (Damascus) were produced in the same area in successive periods over tin and lead-free glazes which is known to require specific strategies to obtain a metallic shiny lustre. The composition and nanostructure of the lustre layers are analysed and the materials and specific firing conditions followed in their production determined. The optical properties of the lustre layers have been analysed in terms of the nanostructure obtained and correlated to the specific processing conditions.Peer ReviewedPostprint (author's final draft

Fire Effects on Understory Forest Regeneration in Southern Amazonia

This is the final version. Available on open access from Frontiers Media via the DOI in this recordData Availability Statement: The datasets generated for this study are available on request to the corresponding author.Fire in tropical forests increases tree mortality, degrades forest structure, and reduces carbon stocks. Currently, there are large gaps in understanding how fire affects understory forest structure and composition, interactions with fire recurrence, and long-term impacts. Understanding these changes is critical to evaluate the present and future response of tropical forests to fire. We studied post-fire changes in understory regeneration in forests in Mato Grosso State, southern Amazonia, Brazil, aiming to answer the following questions: (i) does forest structure (basal area) and tree community composition vary with fire frequency and time since the last fire? (ii) does the response differ among strata (e.g., sapling, larger trees)? (iii) are changes in diversity associated with changes in forest structure? We surveyed trees and lianas in previously structurally intact forests that underwent selective logging, followed by different fire histories, including 5 and 16 years after once-burned, 5 years after three times burned, and unburned (control). Overall, species composition (abundance, richness, and number of families) and diversity were highest for the unburned treatment and lowest for the recurrent burned areas. Fire frequency negatively affected plant structure and basal area; basal area of small, medium, and large plants declined significantly by more than 50% in the most frequently burned areas. Richness was positively related to basal area in the three times burned sites and in the 16 years regenerating site for all strata. Our results demonstrate the negative influence of frequent fires on both the composition and structure of small trees in Amazonian forest. These changes to the cohort of small-sized trees may persist and have long-term impacts on forest structure, affecting the capacity, and direction of forest recovery. With wildfire widespread across the region and increasing in frequency, fire may negatively affect tree diversity in remaining selectively logged forests, and affect regional carbon cycling with consequences for the global vegetation carbon sink.Coordination of Improvement of Personnel in Higher Education, Brazil (CAPES

Author Correction: Tree mode of death and mortality risk factors across Amazon forests (Nature Communications, (2020), 11, 1, (5515), 10.1038/s41467-020-18996-3)

The original version of this Article contained an error in Table 2, where the number of individuals in the “All Amazonia” row was reported as 11,6431 instead of 116,431. Also, the original version of this Article contained an error in the Methods, where the R2 for the proportion of broken/uprooted dead trees increase per year was reported as 0.12, the correct value being 0.06. The original version of this Article contained errors in the author affiliations. The affiliation of Gerardo A. Aymard C. with UNELLEZGuanare, Herbario Universitario (PORT), Portuguesa, Venezuela Compensation International Progress S.A. Ciprogress–Greenlife