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Hillslope redistribution of soil organic carbon in the depressional landscape in Minnesota.

机译：土壤有机碳的山坡再分布在明尼苏达州的洼地景观中。

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摘要

Agricultural tillage has been estimated to cause a loss of 30-50% of the pre-settlement soil organic carbon (SOC) through enhanced decomposition and loss to the atmosphere or through erosion and subsequently loss to surface waters or burial in lower landscape positions. However, measures of whole landscape redistribution and fate of sediments and SOC are lacking. This research seeks to estimate change in SOC storage since agricultural settlement using soil-terrain modeling techniques in closed-depressional landscapes. The overall quantity of SOC in depressional landscapes may have not been lost to the atmosphere through enhanced decomposition but rather is redistributed downslope.;I conducted field observations and soil sampling in hillslope transects in Lake Rebecca Park Reserve in East-Central Minnesota. The thickness of re-deposited sediments (termed post-settlement alluvium, or PSA) was identified by morphological indicators in the field. The spatial distribution of PSA presence and its thickness were modeled with local and regional terrain attributes using a two-stage regression approach. The current SOC inventory (1.119 Pg) in top 1-m soil at the Lake Rebecca site was estimated by spatial predictive models of SOC contents at four soil depths (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm). I estimated pre-settlement SOC inventory for erosional uplands with spatial predictive models for an uncultivated grassland in Morristown, Minnesota; for depositional lowlands, I calculated pre-settlement SOC inventory by applying models for soil profiles below the PSA depth at the study site. Erosional losses and depositional gains were determined by subtracting current SOC inventory from pre-settlement values.;The results showed high SOC contents in surface soils at lower landscape positions, especially in wetlands near the surrounding marsh. Total SOC in the uppermost meter of this 6-ha study site was estimated as 1.528 Gg. The change in SOC density since European settlement was highly overestimated (36.7% increase). The prediction error is likely due to the lack of a mechanism to constrain the prediction of PSA under natural sedimentation patterns at the very bottom of the hillslope beyond the zone where PSA was observed. The model improvement is required to more accurately predict whole landscape SOC distribution and change over time.
机译：据估计，农业耕作通过增加的分解和向大气的损失或侵蚀，以及随后在较低景观位置的地表水或埋葬物的损失，会导致沉降前土壤有机碳（SOC）损失30-50％。但是，缺乏对整个景观重新分配以及沉积物和SOC命运的测量。这项研究试图估计自土壤沉降以来在封闭洼地景观中的农业定居以来土壤有机碳储量的变化。洼地景观中的SOC总量可能并没有通过增强的分解而损失到大气中，而是重新分布了下坡。；我在明尼苏达州中东部的丽贝卡湖公园保护区的山坡样带进行了实地观察和土壤采样。通过田间形态指标确定了再沉积沉积物的厚度（称为沉降后冲积物或PSA）。使用两阶段回归方法，利用局部和区域地形属性对PSA存在的空间分布及其厚度进行建模。通过四种土壤深度（0-10厘米，10-30厘米，30-60厘米，60-60厘米）土壤SOC含量的空间预测模型，估算了丽贝卡湖站点前1米土壤中的当前SOC量（1.119 Pg）。 100厘米）。我使用明尼苏达州莫里斯敦（Morristown）未耕种草地的空间预测模型，估算了侵蚀性高地的沉降前SOC清单。对于沉积低地，我通过应用研究地点PSA深度以下的土壤剖面模型，计算了沉降前的SOC清单。通过从沉降前的值中减去当前的SOC存量来确定侵蚀损失和沉积增加。结果表明，在较低景观位置的表层土壤中，尤其是在周围沼泽附近的湿地中，SOC含量较高。这个6公顷研究场地的最上面一米的总SOC估计为1.528 Gg。自从欧洲定居以来，SOC密度的变化被高估了（增加了36.7％）。预测误差很可能是由于缺乏在观测PSA区域以外的山坡最底部的自然沉积模式下限制PSA预测的机制所致。需要对模型进行改进，以更准确地预测整个景观SOC分布并随时间变化。

著录项

  • 作者

    Wu, An-Min.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Agriculture Soil Science.;Environmental Sciences.;Geodesy.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 194 p.
  • 总页数 194
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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