Explore the vast range of titles available.

Want to understand black holes, antimatter, physics, and space exploration? Looking for a guide to quantum physics that you can actually understand? Get a grip on even the most mysterious and complex sciences with Ben Gilliland's guide to dark matter, exo-planets, Planck time, earth sciences, and more.

Biochar is obtained by pyrolyzing biomass and is, by definition, applied in a way that avoids its rapid oxidation to CO2. Its use in agriculture includes animal feeding, manure treatment (e.g. as additive for bedding, composting, storage or anaerobic digestion), fertilizer component or direct soil application. Because the feedstock carbon is photosynthetically fixed CO2 from the atmosphere, producing and applying biochar is essentially a carbon dioxide removal (CDR) technology, which has a high‐technology readiness level. However, for swift implementation of pyrogenic carbon capture and storage (PyCCS), biochar use in agriculture needs to deliver co‐benefits, for example, by improving crop yields and ecosystem services and/or by improving climate change resilience by ameliorating key soil properties. Agronomic biochar research is a rapidly evolving field of research moving from less than 100 publications in 2010 to more than 15,000 by the end of 2020. Here, we summarize 26 rigorously selected meta‐analyses published since 2016 that investigated a multitude of soil properties and agronomic performance parameters impacted by biochar application, for example, effects on yield, root biomass, water use efficiency, microbial activity, soil organic carbon and greenhouse gas emissions. All 26 meta‐analyses show compelling evidence of the overall beneficial effect of biochar for all investigated agronomic parameters. One of the remaining challenges is the standardization of basic biochar analysis, still lacking in many studies. Incomplete biochar characterization increases uncertainty because adverse effects of individual studies included in the meta‐analyses might be related to low‐quality biochars, which would not qualify for certification and subsequent use (e.g. high content of contaminants, high salinity, incomplete pyrolysis, etc.). In summary, our systematic review suggests that biochar use in agriculture has the potential to combine CDR with significant agronomic and/or environmental co‐benefits. For the implementation of pyrogenic carbon capture and storage (PyCCS), biochar use in agriculture needs to deliver co‐benefits, e.g., by improving crop yields, ecosystem services, and/or by improving climate change resilience by ameliorating key soil properties. Here, we summarize 26 rigorously selected meta‐analyses published since 2016 that investigated a multitude of soil properties and agronomic performance parameters impacted by biochar application. All 26 meta‐analyses show compelling evidence of the overall beneficial effect of biochar for all investigated agronomic parameters.

During the twentieth century, Amazonia was widely regarded as relatively pristine nature, little impacted by human history. This view remains popular despite mounting evidence of substantial human influence over millennial scales across the region. Here, we review the evidence of an anthropogenic Amazonia in response to claims of sparse populations across broad portions of the region. Amazonia was a major centre of crop domestication, with at least 83 native species containing populations domesticated to some degree. Plant domestication occurs in domesticated landscapes, including highly modified Amazonian dark earths (ADEs) associated with large settled populations and that may cover greater than 0.1% of the region. Populations and food production expanded rapidly within land management systems in the mid-Holocene, and complex societies expanded in resource-rich areas creating domesticated landscapes with profound impacts on local and regional ecology. ADE food production projections support estimates of at least eight million people in 1492. By this time, highly diverse regional systems had developed across Amazonia where subsistence resources were created with plant and landscape domestication, including earthworks. This review argues that the Amazonian anthrome was no less socio-culturally diverse or populous than other tropical forested areas of the world prior to European conquest.

When excavating complex anthropogenic stratigraphies, the field archaeologist is often limited to prioritizing the sampling strategy based on in situ macroscopic interpretations. Not until months after the excavation do supporting information and interpretations such as micromorphological analysis offer a more nuanced picture. This article addresses this challenge by evaluating two methods for analyzing results as the excavation is ongoing: computer tomography (CT) and cone beam CT-scanning (CBCT-scanning) of soil blocks using commercially available medical scanners (0.6 mm and 0.3 mm resolution) and an impregnation and micromorphological sediment screening (MSS) approach. The combined methods were applied on samples from a Neolithic settlement ( n = 24), an Iron Age / Viking Age cult ( n = 9), and an Iron Age settlement ( n = 1) in Denmark. Results showed that the CBCT-scanning did not offer clear visual documentation of the different densities between, for example, organic-rich and sandy layers, while the micromorphological screening showed potential when a fluorescent agent (Epodye) was added to the epoxy. Hence, the results suggest that the epoxy impregnation makes it possible to detect microstratigraphical features, while further identification requires a traditional micromorphological thin-section analysis. It would require a larger quantity of samples to assess the procedure’s cost-efficiency on a larger scale. Al excavar estratigrafías antropogénicas complejas, el arqueólogo de campo a menudo se limita a priorizar la estrategia de muestreo basándose en interpretaciones macroscópicas in situ. No fue hasta meses después de la excavación que la información de apoyo y las interpretaciones, como el análisis micromorfológico, ofrecen una imagen más matizada. Este artículo aborda este desafío evaluando dos métodos para los resultados del análisis a medida que avanza la excavación: tomografía computarizada (CT) y escaneo por TC de haz cónico (CBCT) de bloques de suelo utilizando escáneres médicos disponibles comercialmente (resolución de 0,6 mm y 0,3 mm) y un escáner rápido. Enfoque de impregnación y detección micromorfológica de sedimentos (MSS). Los métodos combinados se aplicaron en muestras de un asentamiento neolítico ( n = 24), un culto de la Edad del Hierro / Edad vikinga ( n = 9) y un asentamiento de la Edad del Hierro ( n = 1), en Dinamarca. Los resultados mostraron que el escaneo CBCT no ofrecía una documentación visual clara de las diferentes densidades entre, por ejemplo, materia orgánica capas ricas y arenosas, mientras que el cribado micromorfológico mostró potencial al agregar un agente fluorescente (Epodye) al epoxi. Por lo tanto, los resultados sugieren que la impregnación con epoxi permite detectar características microestratigráficas, mientras que una mayor identificación requiere un análisis micromorfológico tradicional de sección delgada. Se necesitaría una mayor cantidad de muestras para evaluar la rentabilidad del procedimiento a mayor escala.

Spectroscopic techniques including X-ray photoelectron spectroscopy (XPS) can identify particular chemical groups of humic acids (HA) from “Terra Preta de Índios” (TPI) or Amazonian dark earth, the highly fertile anthropogenic soil found in the Amazonian region. The high fertility and resilience of these soils cannot be explained by their chemically inert pyrogenic C content alone, but the natural aging of this C generates reactive carboxyl functional groups attached directly to the recalcitrant polycondensed aromatic backbone. Through spectroscopic techniques used in this work, the HA fraction (the alkaline-soluble organic matter that precipitates at low pH) of the TPI soil was compared with humic and fulvic acids, obtained by oxidizing activated charcoal with sodium hypochlorite. The yields recovery of HA-like substances was 12 and 28 wt% by using 10 and 20 cmol L⁻¹ of oxidizing agent, respectively. X-ray photoelectron spectroscopy, energy dispersive X-ray, and solid-state ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopies were used to evaluate the elements and structures present in all samples. XPS C 1 s spectra of HA extracted from TPI soil and from prepared HA showed aromatic structures (C = C and π–π* shake-up satellite peak) bounded to carboxyl groups (COOH). The morphology and polycondensation level of aromatic C were evaluated by scanning electron microscopy (SEM). The similarities of the spectra indicated that the used method was efficient to obtain an organic amendment similar to TPI soil organic matter.

Aim: Our goal was to test the hypothesis that ancient humans substantially contributed to shaping the current distribution of Brazil nut (Bertholletia excelsa), an Amazonian tree species that has been important for human livelihoods since pre-Columbian times. We scrutinized the putative association between Brazil nut and Amazonian Dark Earth soils (ADE) and geometric earthworks called geoglyphs, and examined the existence of continental patterns in human footprints on Brazil nut stands. Location: Amazon Basin. Methods: We carried out a spatially explicit meta-analysis of the variation of Brazil nut stand metrics across the Amazon Basin based on 87,617 density estimates and 488 average stand diameter assessments, and related these to previously published datasets and suitability maps of Brazil nut, ADE and geoglyphs. Results: We found consistently higher Brazil nut suitability scores, stand densities and average stand diameters in the vicinities of ADE than at larger distances, regardless of their position along a gradient from south-western to north-eastern Amazonia. For geoglyph sites such a pattern was only found for Brazil nut habitat suitability scores. The available data further revealed an accumulation of Brazil nut stands with increasing densities and average diameters from south-western to central and eastern Amazonia. Main conclusions: Our findings suggest that the chance of encountering Brazil nut stands bearing the marks of past human influences increases from south-western to central and eastern Amazonia. In south-western Amazonia, the regeneration of Brazil nut seems to have been controlled predominantly by natural processes, whereas in central and eastern Amazonia, anthropogenic disturbance has been more important since pre-Columbian times. However, it remains challenging to disentangle human influences on the distribution and abundance of Brazil nut from existing environmental gradients across the Amazon Basin. In general, the results of this meta-analysis bode well for the future coexistence of Brazil nut with different forms of contemporary human land use.

Aims In West Africa, savannas are changing to either forest islands or arable lands arising from anthropogenic interference with the natural ecosystem. This study aimed at quantifying the trade-offs of this land use conversion on major soil quality indicators. Methods We evaluated soil organic matter (SOM) and other soil quality indicators such as macro- and micronutrients (including the absence of some hazardous trace metals) using standard methodologies across 11 settlements in Burkina Faso, Ghana, and Nigeria. The degree of soil quality improvement/degradation and soil quality were assessed using empirical models. Results The effects of savanna conversion were manifold and varied depending on the type of land use change, soil depth, and soil quality indicator. In savanna-forests, there was a substantial rise in SOM (37%—794%) and exchangeable cations (15% to 800%) and changes in SOM in the topsoil quadrupled that of the subsoil. A general loss in SOM (1% -74%) and soil macro-and micronutrients occurred under savanna-arable lands. Potassium, calcium and magnesium increased by ≥ 12%, ≥ 15% and 27% respectively while increases in Mn and Zn were 37% and ≥ 250% in the forests over the savannas. Trace quantities of Pb were detected which were below the contamination threshold. About 63% forest islands, 18% arable land, and 9% savannas had SQI % ≥ 50. Conclusion In marginal lands, land use conversion to forest islands presents great potential for improving soil fertility and overall ecosystem health as shown in the high organic matter and improved soil quality.

Aims Ecosystem changes in the mesic savannas of West Africa are resulting in the formation of patches of ‘forest islands’ around local communities in an otherwise open savanna landscape. There have been conflicting reports on the origin of these forest islands with a very limited understanding of their biogeochemistry. This study evaluated the soil mineralogical and chemical characteristics of forest islands and their surrounding ecosystems comprising croplands and open savannas in Burkina Faso, Ghana, and Nigeria to provide information on the processes leading to the formation of forest islands. Methods Soil mineralogy was determined using X-ray diffractometry (XRD) while the soil nutrients were analysed with ICP-OES and the other soil chemical properties were determined using standard conventional methodologies. Results Overall, we found that quartz, kaolinite with significant quantities of 2:1 silicate minerals dominated the soil matrix irrespective of land use type. The minerals identified in most of the locations were independent of land use type. This suggests that the forest island formation is not directly related to soil mineralogy. Forest islands showed differences in soil nutrient contents, being richer in exchangeable potassium and dibasic cations than their surrounding savannas and agricultural fields. This superior fertility status of the soils could contribute to the luxuriant growth of the vegetation leading to the development of forest island. The soil nutrient characteristics of the ecosystem types reflect the land use practices with the forest island having higher nutrient and organic carbon contents. Conclusions The study provided insight into how human-originated soil nutrient enhancement has induced forest island establishment in open savanna landscapes.

Homegardens may serve as reservoirs of agro-biodiversity on highly fertile, anthropogenic Amazonian Dark Earth (ADE) soils of the Amazon basin. However, as these soils are used more intensively for market-oriented agriculture, we suspected a decrease in their agro-biodiversity. We present data obtained from surveys on 16 farms where ADE was present in the region of Manaus, Amazonas, Brazil. When farms were separated into two groups by market orientation, species richness on the farms was not significantly influenced by market orientation, but there was less dominance (i.e., more diversity) for homegardens in the low-market orientation group (P < 0.1). The proportion of native species was not affected by market orientation. Hence, while the most market-oriented farms retained high species richness, homegardens located on them contained higher proportions of commercially interesting species.

European urban dark earth investigations have aided our understanding of Late Roman and early medieval populations and their activities. Deposits from two locations below Exeter Cathedral were compared in a geoarchaeological study and contrasting uses of space were identified. This supports the need for case-by-case investigations of urban deposits.