ERTH PhD Defense - Samantha Dow
Date: August 3rd, 2023 ΜΆ 10 am
Location: Beach Hall, Room 233
Webex Link: s.uconn.edu/gsci
Investigating historic land impacts as a source of legacy sediment in southern New England
Long-term erosion rates are primarily driven by the interactions between climate, topography,
and lithology, however, humans now outpace background rates by orders of magnitude.
Anthropogenic land use leads to accelerated soil erosion and sedimentation rates – with the
specific sediment that is deposited due to human activities being termed legacy sediment. The
northeast region of the US has a well-documented 300+ year history of land use changes
following European settlement, initiated by widespread 17–19th century deforestation and followed
by late 19th–early 20th century abandonment and reforestation. However, legacy sediment storage
in New England may be less than other areas of the US with comparable land use histories and
has not been as well studied. Additionally, little work has been done addressing the source of
legacy sediment from upland areas.
I investigate the source, mobilization, and storage of legacy sediment in southern New
England using geochemical records of anthropogenic activity and reconstructing the timing and
duration of historic land through a combination of field, lab, and GIS analyses. To determine
potential sources of legacy sediment, I develop a chronosequence and apply it to upland soils to
investigate the impact of historic land use on soil erosion and on changes in carbon and nitrogen
pools and isotopic signatures. To address the distribution and storage of legacy sediment, I
compile regional sediment core records along with new data to investigate the variability of
sediment accumulation rates and the distribution of legacy sediment between four different types
of depositional environments, and related to differences in land use, slope and surficial geology
between watersheds. A subset of cores from the compilation were used to investigate the δ15N
signature across various depositional environments and in relation to differences in land use type.
Overall, results from this work have importance for estimating sediment erosion and storage from
historic land use and determining the utility of 15N as an anthropogenic marker of land use.
For more information, contact: Christin Donnelly/Department of Earth Sciences at christin.donnelly@uconn.edu