RECORDS OF SEDIMENTATION IN RESPONSE TO 18TH–20TH CENTURY LAND USE IN NEW ENGLAND

Lakes, wetlands and reservoirs hold sedimentary records that can be used to study environmental change such climate variation through time, large storm events, and anthropogenic activity. Anthropogenic activity commonly leads to increased 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 17–19^th century deforestation and followed by late 19^th–early 20^th century abandonment and reforestation. The region experienced increased 20–21^st century urbanization, but still has isolated areas used for agriculture. Despite having seen intensive deforestation and agricultural activity in the 18–20^th century, previous studies suggest lower soil erosion and quantities of legacy sediment in New England compared to other areas of the U.S. that experienced similar timing and intensity of land use. In this study, we synthesize a regional dataset of ~150 sediment core records from kettle ponds, wetlands, lakes, and reservoirs in New England to address the spatial distribution of legacy sediment and sediment accumulation rates (SARs), both anthropogenic and background. Where available, we combine SARs data with geospatial analysis of watershed characteristics and mapping of extant land use features to evaluate controls of historic land use amount, slope, and surficial geology. Anthropogenic SARs are statistically higher than background rates in all depositional environments, with sites exhibiting a range of increases in sedimentation (1–100x). Kettle ponds, wetlands, and lakes consistently have lower amounts of legacy sediment and SARs compared to reservoirs. The type, magnitude, and timing of land use activity has a more dominant control on anthropogenic SARs than watershed slope, with surficial geology influencing sediment availability in some locations. Overall, the high degree of variability seen in legacy sediment and anthropogenic SARs likely reflects the discontinuous nature of watersheds in New England, with the arrangement of local sinks determining which sites received high amounts of sediment.