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Tracing the lateral movement of sediment through an arid landscape at seasonal, centennial, and millennial scales.

机译：在季节，百年和千禧年尺度上通过干旱景观追踪沉积物的横向运动。

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摘要

As a result of desertification, semi-arid grasslands, in many parts of the world, have been displaced by woody shrubs, such as grasslands at the Jornada Experimental Range, New Mexico. In this northern Chihuahuan Desert ecosystem, grasslands on the piedmont slope and basin floor landforms have been exceptionally vulnerable to woody shrub expansion (Chapter 1). As shrubs invade perennial grasslands, the length, number, and arrangement of connected bare patches coalesce to create sediment transport corridors. Future droughts will likely result in the growth and coalescences of these bare erodible soil surfaces and lead to increased in wind and water erosion. Transport of sediments by wind and water are key components in our understanding of desertification. However, the lateral movement and transport of sediments over varying temporal time scales has been poorly characterized in arid landscapes.;This study used naturally occurring and anthropogenic radionuclides to study the rates of sedimentary processes and sediment redistribution at: seasonal, centennial, and millennial temporal scales. 7Be was used for seasonal processes on 3-6 month time scales to test new ways to alter the lateral movement of sediments (Chapter 2). Excess 210Pb and 137Cs was used for depositional processes in low-lying areas for centennial scales (Chapter 3), and optical and 14C dating were used to date periods for erosion and soil development, which occurred over millennial time scales (Chapter 4).;At the seasonal scale, short-lived radionuclide measurements indicated sediment retention structures (aka Connectivity-Modifiers) contained 30 to 50% higher surface activities than the neighboring control plots, which indicated that changes in connectivity can influence sediment movement. At the centennial scale, excess 210Pb and 137Cs measurements, in combination with optical and 14C dates, demonstrated that sedimentation in low-lying vegetated grasslands was ∼ 84% higher during the last 50 years than compared to late Holocene rates. At the millennial scale. Optical and 14C measurements, in addition to stable C isotopes, provides evidence that C3 ecosystem experienced periods of wind erosion, was present around 42 ka yrs. B.P., and was later impacted by higher water table at 13.9 ka yrs B.P.
机译：由于荒漠​​化，世界许多地方的半干旱草原被木本灌木丛所取代，例如新墨西哥州乔纳达实验山脉的草原。在这个奇瓦瓦沙漠北部的生态系统中，山前斜坡和盆地底部地貌的草地极易受到木本灌木丛扩张的影响（第1章）。灌木入侵多年生草地时，相连的裸露斑块的长度，数量和排列会聚在一起，形成泥沙输送通道。未来的干旱可能会导致这些裸露的易蚀土壤表面的生长和聚结，并导致风蚀和水蚀加剧。通过风和水输送沉积物是我们对荒漠化理解的关键组成部分。然而，在干旱的景观中，沉积物在不同时间尺度上的横向运动和运移的特征很差;该研究使用自然发生的和人为的放射性核素研究了季节性，百年和千禧年时间的沉积过程和沉积物再分配的速率。秤。 7Be用于3-6个月时间尺度的季节性过程，以测试改变沉积物横向运动的新方法（第2章）。多余的210Pb和137Cs被用于低洼地区百年尺度的沉积过程（第3章），光学和14C约会被用于记录侵蚀和土壤发育的时期，这些时期发生在千年尺度上（第4章）。在季节性尺度上，短期放射性核素测量结果表明，沉积物截留结构（又名连通性修饰剂）的表面活性比邻近的对照样地高30％至50％，这表明连通性的变化会影响沉积物的运动。在百年尺度上，超过210Pb和137Cs的测量值，加上光学和14C年代的数据表明，与新世晚期相比，低洼植被草地的沉积在过去50年中约高84％。千禧年规模。除了稳定的C同位素外，光学和14C测量还提供了证据，证明C3生态系统经历了风蚀时期，大约存在42 ka年。 B.P.，后来受到更高的地下水位（B.P. 13.9 ka年）的影响。

著录项

  • 作者

    Rachal, David Michael.;

  • 作者单位

    New Mexico State University.;

  • 授予单位 New Mexico State University.;
  • 学科 Geomorphology.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 117 p.
  • 总页数 117
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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