Doctoral Dissertation Research: Spatio-Temporal Soil Variability on Late Quaternary Fluvial Surfaces of the Southeastern Atlantic Coastal Plain

博士论文研究：东南大西洋沿岸平原晚第四纪河流表面土壤时空变化

• 批准号: 1202846
• 负责人: David Leigh
• 金额: $ 1.2万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-01 至 2013-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1202846&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Spatio; Temporal

The goal of this doctoral dissertation project is to understand the effect of time on soil formation processes. Soil spatial variability exists in all landscapes and may occur predictably, in response to known geomorphic and soil-forming factors, or unpredictably, without any apparent relationship to measureable changes in soil forming factors conditions. Such variability has important implications for soil chronosequence studies, which evaluate the influence of time on soil development. Understanding how soil properties change over time is critical for the restoration of degraded soils and the use of soils as relative-age dating tools in Quaternary geologic studies, and soil chronosequences remain the primary source for empirical data to evaluate rates and theories of soil development. However, spatial variability among soils of equivalent age can pose both theoretical and practical problems for the chronosequence approach. Within a chronosequence framework, adequate representation of soil spatial variability on even-aged surfaces is needed before dominant soil forming processes can be ascertained, models of soil formation can be tested, and rates of soil formation can be estimated. Nevertheless, relatively few studies have addressed this topic. Thus, the goal of this project is to characterize the range of soil development within and among late Quaternary fluvial surfaces of different ages in the southeastern Atlantic Coastal Plain in order to assess spatiotemporal trends of soil variability and development and evaluate drivers of these changes. This research will examine the morphology and chemistry of soils developed on the scrollbar components of three fluvial surfaces that span an age range of approximately two orders of magnitude (1,000 vs. 10,000 vs. 100,000 years) along the Oconee-Altamaha (Georgia) and Pee Dee (South Carolina) Rivers. Two scrollbars will be sampled per surface in each river valley, for a total of twelve sampled scrollbars, and sampling will be guided by a pilot study that will determine the number and spacing of profiles needed to adequately characterize soil variability on a single scrollbar. Soil properties will be evaluated that have been shown to be valuable chronosequence parameters in the region, including overall soil thickness; leaching (E) horizon thickness; as well as the thickness, clay content, redness, extractable iron, and total chemistry of the whole soil (2 mm) and fine sand (0.125-0.250 mm) fractions of the most well expressed horizon in which there is active soil formation occurring (B horizon). Multivariate statistical techniques will be used to identify drivers of soil variability, assess dominant soil forming processes, and evaluate the implications of spatial variability for the use of chronosequences as tools in soil formation and geomorphic research.By characterizing soil variability within a chronosequence framework, this research will directly address key problems that have emerged in soil geographic research in recent decades, such as 1) whether soils converge toward a spatially uniform, steady state condition or diverge into an increasingly complex spatial mosaic over time, and 2) the extent to which observed soil variability can be attributed to systematic drivers versus the degree to which variability is unexplained by measurable factors and possibly linked to chaotic behavior or stochastically random variation. Results will not only advance soil geographic thought, but have important implications for broader scientific questions about order and disorder, sources of spatial variability, and the evolution of natural systems through time that span disciplinary boundaries, from physical geography, to soil science and geology, to ecology and natural resources management. In addition, this project will provide valuable reference information for the restoration of degraded soils and ecosystems in alluvial bottomland settings. It will also evaluate the persistence of soil properties during the last glacial-interglacial cycle, a period when the Southeast experienced drastic fluctuations in environmental conditions, and will improve understanding of soil resistance to past and projected future climate change and its implications for land use. The project includes plans to collaborate with USGS on a map of the sediments of the region. There are also plans for academic and non-academic dissemination of the results, and an educational outreach module with a regional middle school will be developed. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish an independent research career.

这个博士论文项目的目标是了解时间对土壤形成过程的影响。土壤空间变异性存在于所有景观中，可以根据已知的地貌和土壤形成因素发生可预测的变化，也可以不可预测地发生，与土壤形成因素条件的可测量变化没有任何明显的关系。这种变异性对评价时间对土壤发育的影响的土壤时间序列研究具有重要意义。了解土壤性质如何随时间变化对于恢复退化土壤和将土壤用作第四纪地质学研究中的相对年龄测定工具至关重要，土壤年代序列仍然是评估土壤发展速度和理论的经验数据的主要来源。然而，相同年龄的土壤之间的空间变异性会给时间序列方法带来理论和实践上的问题。在时间序列框架内，在确定主导的土壤形成过程、测试土壤形成模型和估计土壤形成速率之前，需要在均匀年龄的表面上充分表示土壤的空间变异性。然而，关于这一主题的研究相对较少。因此，该项目的目标是描述东南部大西洋沿岸平原不同时代的晚第四纪河流表面内部和之间的土壤发育范围，以便评估土壤变异性和发育的时空趋势，并评估这些变化的驱动因素。这项研究将研究沿奥科尼-阿尔塔马哈(佐治亚州)和皮迪河(南卡罗来纳州)三个河流表面滚动条组成的土壤的形态和化学成分，这三个河流表面的年龄范围约为两个数量级(1000年对10000年对10万年)。将在每个河谷的每个表面上采样两个滚动条，总共采样12个滚动条，采样将由一项试点研究指导，该研究将确定在单个滚动条上充分描述土壤变异性所需的剖面的数量和间距。将对已被证明是该地区有价值的时间序列参数的土壤特性进行评估，包括土壤总厚度；淋溶(E)层厚度；以及整个土壤(2 Mm)和细沙(0.125-0.250 mm)部分的厚度、粘土含量、红度、可提取铁和出现活跃土壤形成的最好表现层(B层)的总化学成分。通过在时间序列框架内表征土壤变异性，这项研究将直接解决近几十年来土壤地理研究中出现的关键问题，例如：1)土壤是否收敛到空间上均匀、稳定的状态，或者随时间的推移而分化成越来越复杂的空间镶嵌；2)观测到的土壤变异性在多大程度上可以归因于系统的驱动因素，而不是可测量因素无法解释的变异性程度，并且可能与混沌行为或随机变化有关。这些结果不仅将推动土壤地理学思想的发展，而且对更广泛的科学问题具有重要意义，这些问题包括秩序和无序、空间变异性的来源以及自然系统在跨越学科边界的时间上的演变，从自然地理学到土壤科学和地质学，再到生态学和自然资源管理。此外，该项目还将为冲积滩地退化土壤和生态系统的恢复提供有价值的参考信息。它还将评估上一次冰川-间冰期周期期间土壤性质的持久性，这段时期东南部经历了环境条件的剧烈波动，并将增进对土壤对过去和预计未来气候变化的抵抗力及其对土地利用影响的了解。该项目包括与美国地质勘探局合作绘制该地区沉积物地图的计划。还制定了学术和非学术传播成果的计划，并将与一所区域中学一起开发一个教育推广单元。作为博士论文研究改进奖，该奖项还将为有前途的学生建立独立的研究生涯提供支持。