Shrub

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 185346 Experts worldwide ranked by ideXlab platform

Marcelle Marques Erthal - One of the best experts on this subject based on the ideXlab platform.

  • Shrub morpho types as indicator for the water flow energy tivoli travertine case central italy
    Sedimentary Geology, 2017
    Co-Authors: Hannes Claes, Jeroen Soete, Marcelle Marques Erthal, Enrico Capezzuoli, A Mancini, Rudy Swennen
    Abstract:

    Abstract Travertines from Tivoli area (Central Italy) possess abundant Shrub-like fabrics that are laterally continuous over hundreds of square meters. They occur dominantly in horizontal layers with aggradational and progradational stacking patterns. Their fabrics and morphologies are remarkably similar to the Shrubs lithotypes reported in literature for the Pre-Salt reservoirs, offshore Brazil and Angola, with huge oil accumulations. Petrographic and micro-computer tomography analyses allowed the identification of six Shrub morpho-types (i.e., narrow dendriform, wide dendriform, fili dendriform, arborescent, arbustiform and pustular). Dendriform Shrubs are the most common lithotype in Tivoli area, and three different subtypes could be distinguished according to the arrangement of their branches. The Shrubs consist largely of peloidal micritic aggregates engulfed in spar calcite, ranging in average from 1 to 3 cm in height. The Shrubs are interpreted to have developed in very shallow extensive waterlogged slightly inclined flat areas, changing laterally into a slope system with crusts as the main lithotype. Changes in the hydrodynamic conditions with episodes of stagnancy influenced the Shrub morpho-types making them very variegated. Shrub morphologies likely reflect specific (micro-) environments that are controlled by water flow rates, evaporation and microbial activity. The latter processes influenced Shrub fabric and morphology. Under high flow conditions, CO 2 degassing is the main process leading to carbonate precipitation. Consequently, denser and tightly packed morphologies will precipitate, composing mainly the crust lithotype. In this scenario microbes are less dominant. Dendriform Shrubs, with narrow, wide and fili morphologies are interpreted to occur in moderate to low energy water flows. Narrow dendriform Shrubs reflect faster flowing conditions, with decreasing impact of flow on the morphological aspects from wide dendriform Shrubs to fili dendriform Shrubs. Slow to very slow flowing waters are more characteristic for the arborescent, arbustiform and pustular Shrubs that possibly are highly influenced by evaporation. A decrease of water flow likely allows higher microbial activity, and consequently, Shrub morphologies become more fragile and enriched in peloidal micritic aggregate fabrics.

Florencia Cuassolo - One of the best experts on this subject based on the ideXlab platform.

  • when do nurse plants stop nursing temporal changes in water stress levels in austrocedrus chilensis growing within and outside Shrubs
    Journal of Vegetation Science, 2009
    Co-Authors: Cecilia I Nunez, Estela Raffaele, Martin A. Nuñez, Florencia Cuassolo
    Abstract:

    Question: Does the proximity of Shrubs affect seasonal water stress of young Austrocedrus chilensis trees (a native conifer of the Austral Temperate Forest of South America) in xeric sites? Location: A. chilensis xeric forest in northwest Patagonia, Argentina. Methods: We examined the dependence of predawn twig water potential on tree development (seedling to adult) and proximity to nurse Shrubs during spring and summer. We analysed spatial associations of seedlings, saplings and adult trees with nurse Shrubs, and also evaluated if trees affected Shrub canopy vitality. Results: Water stress in Austrocedrus trees was affected by Shrub presence. Small trees (i.e. 2 m in height) were not affected by Shrub presence. Austrocedrus trees were spatially associated with Shrubs in all height classes; however, the percentage of living Shrub canopy decreased with tree height. Conclusions: In xeric areas of northwest Patagonia, the strength and direction of interactions between A. chilensis and Shrubs, in terms of tree water stress, are dynamic and modulated by tree size and environmental conditions. Overall, positive effects of Shrubs on early developmental stages appear to be more important than subsequent negative interactions, since nursing effects could generate a spatial association of Shrubs and Austrocedrus trees that persists through later successional stages. These findings shed light on mechanisms behind successional changes, and have important conservation and management implications.

Martin A. Nuñez - One of the best experts on this subject based on the ideXlab platform.

  • when do nurse plants stop nursing temporal changes in water stress levels in austrocedrus chilensis growing within and outside Shrubs
    Journal of Vegetation Science, 2009
    Co-Authors: Cecilia I Nunez, Estela Raffaele, Martin A. Nuñez, Florencia Cuassolo
    Abstract:

    Question: Does the proximity of Shrubs affect seasonal water stress of young Austrocedrus chilensis trees (a native conifer of the Austral Temperate Forest of South America) in xeric sites? Location: A. chilensis xeric forest in northwest Patagonia, Argentina. Methods: We examined the dependence of predawn twig water potential on tree development (seedling to adult) and proximity to nurse Shrubs during spring and summer. We analysed spatial associations of seedlings, saplings and adult trees with nurse Shrubs, and also evaluated if trees affected Shrub canopy vitality. Results: Water stress in Austrocedrus trees was affected by Shrub presence. Small trees (i.e. 2 m in height) were not affected by Shrub presence. Austrocedrus trees were spatially associated with Shrubs in all height classes; however, the percentage of living Shrub canopy decreased with tree height. Conclusions: In xeric areas of northwest Patagonia, the strength and direction of interactions between A. chilensis and Shrubs, in terms of tree water stress, are dynamic and modulated by tree size and environmental conditions. Overall, positive effects of Shrubs on early developmental stages appear to be more important than subsequent negative interactions, since nursing effects could generate a spatial association of Shrubs and Austrocedrus trees that persists through later successional stages. These findings shed light on mechanisms behind successional changes, and have important conservation and management implications.

Rudy Swennen - One of the best experts on this subject based on the ideXlab platform.

  • Shrub morpho types as indicator for the water flow energy tivoli travertine case central italy
    Sedimentary Geology, 2017
    Co-Authors: Hannes Claes, Jeroen Soete, Marcelle Marques Erthal, Enrico Capezzuoli, A Mancini, Rudy Swennen
    Abstract:

    Abstract Travertines from Tivoli area (Central Italy) possess abundant Shrub-like fabrics that are laterally continuous over hundreds of square meters. They occur dominantly in horizontal layers with aggradational and progradational stacking patterns. Their fabrics and morphologies are remarkably similar to the Shrubs lithotypes reported in literature for the Pre-Salt reservoirs, offshore Brazil and Angola, with huge oil accumulations. Petrographic and micro-computer tomography analyses allowed the identification of six Shrub morpho-types (i.e., narrow dendriform, wide dendriform, fili dendriform, arborescent, arbustiform and pustular). Dendriform Shrubs are the most common lithotype in Tivoli area, and three different subtypes could be distinguished according to the arrangement of their branches. The Shrubs consist largely of peloidal micritic aggregates engulfed in spar calcite, ranging in average from 1 to 3 cm in height. The Shrubs are interpreted to have developed in very shallow extensive waterlogged slightly inclined flat areas, changing laterally into a slope system with crusts as the main lithotype. Changes in the hydrodynamic conditions with episodes of stagnancy influenced the Shrub morpho-types making them very variegated. Shrub morphologies likely reflect specific (micro-) environments that are controlled by water flow rates, evaporation and microbial activity. The latter processes influenced Shrub fabric and morphology. Under high flow conditions, CO 2 degassing is the main process leading to carbonate precipitation. Consequently, denser and tightly packed morphologies will precipitate, composing mainly the crust lithotype. In this scenario microbes are less dominant. Dendriform Shrubs, with narrow, wide and fili morphologies are interpreted to occur in moderate to low energy water flows. Narrow dendriform Shrubs reflect faster flowing conditions, with decreasing impact of flow on the morphological aspects from wide dendriform Shrubs to fili dendriform Shrubs. Slow to very slow flowing waters are more characteristic for the arborescent, arbustiform and pustular Shrubs that possibly are highly influenced by evaporation. A decrease of water flow likely allows higher microbial activity, and consequently, Shrub morphologies become more fragile and enriched in peloidal micritic aggregate fabrics.

Glen E Liston - One of the best experts on this subject based on the ideXlab platform.

  • changing snow and Shrub conditions affect albedo with global implications
    Journal of Geophysical Research, 2005
    Co-Authors: Matthew Sturm, Charles H Racine, Thomas A Douglas, Glen E Liston
    Abstract:

    [1] Observations suggest that Shrub abundance in the Arctic is increasing owing to climate warming. We investigated the ramifications of a tundra-to-Shrubland transition on winter energy exchange. At five sites in Alaska we suspended a 50-m-long cable above the vegetation and from this measured how the vegetation interacted with the snow and affected albedo. The sites defined a gradient from nearly Shrub-free tundra to a woodland with a continuous Shrub canopy. Where the Shrubs were small, thin-stemmed, and supple, they were bent and buried by snow. Where they were tall, thick-stemmed, and stiff, the Shrub canopy remained exposed all winter. Where Shrubs were buried, mid-winter albedo values were high (0.85), but where they were exposed, the values were 30% lower (0.60). At these latter sites, melting began several weeks earlier but proceeded more slowly. Consequently, all sites were free of snow about the same time. Using the measurements and a solar model, we estimate that a land surface transition from Shrub-free tundra to Shrubland could produce a 69 to 75% increase in absorbed solar radiation during the snow-cover period, depending on latitude. This is two thirds the increase associated with a tundra-to-forest transition. When combined with measurements showing that a tundra-to-Shrub transition would also produce a net increase in summer heating, our results suggest a positive feedback mechanism associated with a warming-induced increase in Shrubs. To our knowledge, ours is the first study to document that Shrubs could alter the winter energy balance of tundra in such a substantial way.

  • snow Shrub interactions in arctic tundra a hypothesis with climatic implications
    Journal of Climate, 2001
    Co-Authors: Matthew Sturm, Joseph P M Cfadden, Glen E Liston, F Tuart S Chapin, Charles H Racine, Jon Holmgren, Fort Wainwright
    Abstract:

    In the Arctic, where wind transport of snow is common, the depth and insulative properties of the snow cover can be determined as much by the wind as by spatial variations in precipitation. Where Shrubs are more abundant and larger, greater amounts of drifting snow are trapped and suffer less loss due to sublimation. The snow in Shrub patches is both thicker and a better thermal insulator per unit thickness than the snow outside of Shrub patches. As a consequence, winter soil surface temperatures are substantially higher, a condition that can promote greater winter decomposition and nutrient release, thereby providing a positive feedback that could enhance Shrub growth. If the abundance, size, and coverage of arctic Shrubs increases in response to climate warming, as is expected, snow‐Shrub interactions could cause a widespread increase (estimated 10%‐25%) in the winter snow depth. This would increase spring runoff, winter soil temperatures, and probably winter CO 2 emissions. The balance between these winter effects and changes in the summer energy balance associated with the increase in Shrubs probably depends on Shrub density, with the threshold for winter snow trapping occurring at lower densities than the threshold for summer effects such as shading. It is suggested that snow‐Shrub interactions warrant further investigation as a possible factor contributing to the transition of the arctic land surface from moist graminoid tundra to Shrub tundra in response to climatic warming.