An Anthropocene chronosequence study on upland soils in the northeastern USA

Abstract

Intensive land use from agricultural activities fundamentally affects the physical structure and nutrient cycling of soils and can lead to increased erosion of sediment that gets stored downslope in legacy deposits. The northeastern USA provides the opportunity to study anthropogenic-induced changes to soils, with a well-documented ~300-year history of land modification. In this study, we investigate impacts on upland soils in northeast Connecticut at two sites used extensively in the 17–20th centuries that are now abandoned and forested along with two modern agriculture sites. We use stone walls present in LiDAR and aerial imagery from 1934 to 2019 to develop an Anthropocene chronosequence with four land use classes (T0, T1, T2, and T3) that vary in terms of duration of land use and time since abandonment. The two abandoned sites differ primarily in terms of average hillslope gradients, and we use transects at the steeper site to investigate the effect of catena position on sediment mobilization and downslope changes. Soil profiles within each class were described and sampled for standard soil analyses and trace metals using pXRF to address the processes of erosion and mixing in the soils. At both sites, A horizon thicknesses increase and B horizon thicknesses decrease with increasing land use duration. The consistent depth to the C horizon across all classes, lack of soil truncations and accumulation of sediment at the base of slopes, and inventories and patterns of Pb in soil profiles all suggest land use impacts led to soil mixing and redistribution along hillslope catenas, but no substantial erosion and soil loss. Therefore, depositional areas such as wetlands, floodplains and millponds in low relief deglaciated landscapes may not contain large quantities of legacy sediment. Furthermore, widely available LiDAR and aerial imagery datasets have the potential to scale up the chronosequence approach and soil impacts described here.