Actions for Land use versus climate controls on hillslope erosion at a farmed headwater catchment in central Pennsylvania

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Land use versus climate controls on hillslope erosion at a farmed headwater catchment in central Pennsylvania

Author
Silverhart, Perri
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2019.
Physical Description
1 electronic document
Additional Creators
Dibiase, Roman Alexander
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Open Access.
Summary
Throughout the Quaternary period, periglacial processes have set the pace and pattern of long-term erosion in central and southern Pennsylvania. In the low-lying Piedmont Physiographic Province of southeastern Pennsylvania, legacy sediment deposits trapped behind colonial milldams document extensive anthropogenic erosion throughout the region. The nearby heavily folded Valley and Ridge Physiographic Province of central Pennsylvania has experienced similar land use since European settlement, yet evidence of anthropogenic legacy sediment deposits is less obvious. Here, I evaluate the relative influences of long term (103 105 year) climate fluctuations and recent (200 years) land use on hillslope soil erosion at Cole Farm, a farmed calcareous shale watershed in the Valley and Ridge Physiographic Province of central Pennsylvania, and draw comparisons to the forested but lithologically similar Shavers Creek Environmental Center site and the forested Shale Hills site with shale bedrock.The hillslopes (mean slope = 9) of the 0.66 km2 Cole Farm catchment have been continuously farmed since the early 1800s and no till practices have been gradually implemented since the 1970s. To constrain shallow subsurface structure and patterns in soil thickness, I draw from hand augered depth of refusal measurements and valley axis push cores, which indicate thin (< 50 cm) midslope soils, thicker toeslope soils, and valley fill thicker than 4 m.At Cole Farm, the 137Cs inventory is distributed throughout the top 30 cm, whereas at Shavers Creek Environmental Center and Shale Hills it is highly concentrated in the top 5 cm.137Cs profiles with depth show evidence of the legacy of past land use. Cole Farm is no longer tilled, but the legacy of past tilling is apparent in the distribution of the 137Cs inventory throughout the top 30 cm of the soil profile.Total 137Cs inventories for samples collected along ridgetop to valley floor hillslope transects do not vary systematically based on distance down slope, hillslope curvature, orivcontributing area suggest minimal recent (< 60 years) stripping of hillslope soils has occurred. Variability in total inventory is greater across slope than downslope, indicating that localized redistribution on the hillslope, rather than downslope transport, is the dominant mechanism of soil redistribution in this landscape.The 4 m thick valley fill at Cole Farm is not an accumulation of anthropogenic sediments. Rather, it predates European settlement and has accumulated throughout the Holocene, which is indicated by bulk soil radiocarbon ages of 7 kyr at 150 cm depth increasing to 10 kyr at 200 cm depth, and a charcoal radiocarbon age of 695 20 BP at a depth of 67 cm depth. This valley fill has accumulated over a similar timescale as the forested Shale Hills catchment, which combined with the observed lack of recent hillslope erosion at Cole Farm and absence of legacy sediments behind mapped mill dams in the Shavers Creek Watershed, suggests that this landscape is resilient to agricultural erosion.
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Dissertation Note
M.S. Pennsylvania State University 2019.
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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