Criteria for the recognition of pedogenic/supergene and nonpedogenic/hypogene deposits and their relationship to the origin of calcite/opal deposits at Yucca Mountain. Special report No. 14

This study is part of the research program of the Yucca Mountain Project intended to provide the State of Nevada with a detailed assessment of the geology and geochemistry of Yucca Mountain and adjacent regions. The purpose of this report is to try and establish criteria for the recognition of pedogenic/supergene deposits of calcite/opal versus non-pedogenic/hypogene deposits of calcite/opal. Far from being of esoteric concern, this subject is of paramount importance to the pedogenic-hypogene debate which rages around the suitability of Yucca Mountain as a high-level radioactive waste repository site

Geomorphic-vegetation relationships using a geopedological classification system, northern Chihuahuan Desert, USA

Drylands typically have distinctive vegetative patterns that reflect the underlying physical landscape. We use a geopedological classification to organize the landscape into five categories from broad scale to fine scale: (1) physiographic divisions which describe regional topography, such as mountains and basin floors; (2) regolith type which identifies residuum versus transported sediments; (3) parent materials which describe mineralogy; (4) landforms which provide meso-scale descriptions of topography; and (5) soil texture, a fine-scale variable important for infiltration, erodibility, and available water holding capacity. The study was conducted in a 1753 km2 area of the White Sands Missile Range and easternmost Jornada Experimental Range and revealed the following. (1) At the broadest scale, mesquite is dominant on the basin floor when the parent material is siliceous sand, but (2) biological soil crust becomes dominant in the basin floor when the parent material is gypseous. (3) Creosotebush is dominant on rocky soils of the piedmont slopes regardless of parent material, but (4) grasslands become dominant on the bajadas upslope in the semiarid zone and into the semiarid mountain uplands regardless of bedrock type. This method provides a way of supplementing ecologic-edaphic studies and provides a framework within which mechanisms can be explored

Soil micromorphology and the anthropocene -Cross-scale connections and technology trends

The Anthropocene is a proposed geologic time period used to convey the profound influence humanity is having on the Earth. The term is controversial because of uncertainties about when to designate its beginning and whether a diagnostic feature of this era can survive millions of years into the future. Still, the Anthropocene has captured the imagination of many scientists and provides a framework for analyzing the broad-scale impacts of humanity. The purpose of this paper is to explore how soil micromorphology can contribute to a deeper understanding of the Anthropocene. We approached this issue by systematically examining how data gathered at the micromorphology scale is connected to data obtained at the soil profile, landscape, and global scales. In particular we look at world food production, climate change, groundwater pollution, and plastic decomposition. From this cross-scale analysis it becomes apparent that micromorphology (1) contributes to an understanding of feedbacks operating in complex adaptive systems and (2) provides evidence otherwise invisible for making inferences about climate change. As the human footprint increases, soil micromorphology, using both traditional and emerging technologies, can make a unique contribution to understanding the Anthropocene.El Antropoceno es un periodo de tiempo geológico que se ha propuesto para explicar la gran influencia que el ser humano está teniendo en los sistemas medioambientales terrestres. Se trata de un término controvertido debido a los problemas en establecer el comienzo de este periodo y a que se desconoce si algún rasgo diagnóstico de esta era sobrevivirá en el futuro dentro de millones de años. No obstante, el Antropoceno ha llamado la atención de numerosos científicos y constituye un marco para el análisis de los impactos de la humanidad a gran escala. El objetivo de este trabajo es explorar cómo la micromorfología de suelos puede contribuir a profundizar en el conocimiento del Antropoceno. Para ello se ha examinado de forma sistemática las conexiones entre los datos recogidos a escala micromorfológica y los datos obtenidos del perfil del suelo, del paisaje y a escalas globales. En particular, se ha prestado atención a la producción mundial de alimentos, el cambio climático, la contaminación del agua subterránea y la descomposición de plásticos. De este análisis cruzado se deduce que la micromorfología (1) contribuye a la comprensión de las retroalimentaciones que operan en sistemas adaptativos complejos y (2) proporciona evidencias que de otra forma permanecerían invisibles para realizar inferencias sobre el cambio climático. A medida que la huella humana se hace más evidente, la micromorfología de suelos, utilizando tecnologías tanto tradicionales como emergentes, puede representar una contribución indispensable para comprender el Antropoceno

Experimental micropedology: A technique for investigating soil carbonate biogenesis along a desert-grassland-forest transect, New Mexico, USA.

Manipulative experiments - characterized by comparing treatments to controls - are widespread in scientific investigations. This study uses experimental micropedology to investigate whether soil microbes precipitate carbonate if a liquid growth-medium is applied to soil in situ. This was undertaken using apparatuses designed to (1) obtain micromorphological images of biogenic carbonate on microscope slides, (2) to quantify carbonate formation in fiberglass cloths, and (3) to measure associated carbon-isotope fractionations. The apparatuses were buried and harvested at monthly intervals from December 2010 to June 2011. The study was conducted along an ecological transect in New Mexico, USA, at three sites: a low-elevation desert (C3 shrubs), an intermediate-elevation steppe (C4 grasses), and a high-elevation forest (C3 conifers). In addition to comparing bioclimatic zones, the effect of parent material was also tested using paired limestone and igneous soils at each site. Soil samples in their natural state and inserted microscope slides were analyzed with binocular, petrographic, and scanning electron microscopy equipped with an x-ray microanalyser (EDS), and the fiberglass traps were analyzed with x-ray diffraction and a mass spectrometer for carbon concentrations and isotope ratios. Naturally occurring calcified microbes were found at each site in the form of calcified hyphae, needle fiber, and calcified root hairs, with the exception of the forest site on igneous parent material. Liquid growth medium induced microbial calcification regardless of whether the vegetation was desert shrubs, grassland, or forest, and regardless of whether the parent material was igneous or limestone. Thus, the ability of soil microorganisms to biomineralize carbonate when supplied with liquid growth medium in situ is a phenomenon that crosses biomes and is not limited to microbes endemic to either limestone or igneous parent material.Os ensaios de manipulação - caracterizados pela comparação dos tratamentos com as testemunhas (controlos) - estão largamente difundidos em investigação científica. Este estudo utiliza a micro pedologia experimental para investigar se os microrganismos do solo precipitam carbonato quando se aplica um meio de crescimento líquido ao solo in situ. Este trabalho foi levado a cabo utilizando dispositivos projetados para (1) obter imagens micromorfológicas de carbonato biogénico em lâminas finas, (2) quantificar a formação de carbonato em tecidos de fibra de vidro, e (3) medir o fracionamento isotópico de carbono associado. Os dispositivos foram enterrados no solo e recolhidos com intervalos mensais de dezembro de 2010 até junho de 2011. O estudo foi realizado ao longo de um transecto ecológico no Novo México, EUA, em três locais: um deserto de relevo suave (arbustos C3), uma planície de relevo intermédio (gramíneas C4) e uma floresta de alto relevo (coníferas C3). Além de comparar áreas bioclimáticas foi também analisado o efeito do material parental estudando em cada local solos localizados sobre rochas carbonatadas e rochas magmáticas. As lâminas finas foram analisadas por microscopia binocular e petrográfica e microscopia eletrónica de varrimento equipada com um micro analisador de raios- X (EDS), e os tecidos de fibra de vidro foram analisados por difração de raios X e espectrometria de massa para obter concentrações de carbono e relações isotópicas. Em cada local foram encontrados microrganismos calcificados formados naturalmente em forma de micélios calcificados filamentosos e pelos de raízes calcificados, com exceção do local sobre material ígneo na zona de floresta. O meio de crescimento líquido induziu à calcificação microbiana, independentemente do tipo de vegetação ou material parental. Assim, a capacidade dos microrganismos do solo para biomineralizar carbonato mediante o fornecimento no local de um meio de crescimento líquido é um fenómeno transversal independente do bioma e não está limitado aos microrganismos endémicos de materiais calcários ou ígneos.Los experimentos manipulativos, caracterizados por comparar tratamientos con experiencias control, se utilizan ampliamente en las investigaciones científicas. Este estudio aplica la microedafología experimental para investigar si los microorganismos del suelo precipitan carbonato al aplicar in situ un medio de crecimiento líquido al suelo. Esto se llevó a cabo utilizando aparatos diseñados para (1) obtener imágenes micromorfológicas de carbonato biogénico sobre láminas delgadas, (2) cuantificar la formación de carbonato sobre telas de fibra de vidrio, y (3) medir fraccionamientos isotópicos de carbono asociados. Los aparatos fueron enterrados en el suelo y recogidos en intervalos mensuales desde diciembre de 2010 hasta junio de 2011. El estudio se realizó a lo largo de un transecto ecológico en New Mexico, USA, en tres localizaciones: un desierto de relieve suave (arbustos C3), una pradera de relieve intermedio (pastos C4) y un bosque de alto relieve (coníferas C3). Además de comparar las distintas zonas bioclimáticas también se analizó el efecto del material parental estudiando suelos sobre rocas carbonatadas e ígneas en cada lugar. Las láminas delgadas se analizaron con microscopía binocular, petrográfica y electrónica de barrido equipada con un mincroanalizador de rayos X (EDS), y las trampas de fibra de vidrio se analizaron mediante difracción de rayos X y un espectrómetro de masas para obtener las concentraciones de carbono y las razones isotópicas. En cada localización se encontraron microorganismos calcificados existentes de forma natural en forma de micelios calcificados filamentosos y pelos de raíces calcificados, con la excepción del lugar sobre material ígneo en la zona de bosque. El medio de crecimiento líquido indujo la calcificación microbiana independientemente del tipo de vegetación o de material parental. Así, la habilidad de los microorganismos del suelo para biomineralizar carbonato mediante la aportación in situ de un medio de crecimiento líquido es un fenómeno transversal independiente del bioma y que no está limitado a microorganismos endémicos de materiales calizos o ígneos