HISTORIC LAND USE IMPACTS ON UPLAND SOILS AND EROSION IN SOUTHERN NEW ENGLAND

Intensive land use fundamentally affects the physical structure and nutrient cycling of soils, and can lead to increased erosion. The northeast US provides the opportunity to study anthropogenic-induced changes to soils, with a rich and well documented history of land modification. In this study, we use stone walls present in LiDAR to determine the extent and intensity of land used for 17^th-early 20^th agriculture activities, and aerial images from 1934 onwards to develop a chronosequence, showing the progression of land abandonment and reforestation through the 20^th century. At two sites in Mansfield, CT, one high and one low slope, we used stone wall maps and aerial images to identify three main land use classes characterized by different durations of historic agriculture, and to quantify changes to soil chemistry. The difference in slope between the sites allows us to investigate the role that the duration of land use has on soil erosion using soil catenas. The first class has clearly delineated fields outlined by stone walls and is abandoned in the mid-20^th century, based on 1934-1950 aerial imagery – representing 150-250 years of agriculture. The second class is forested in 1934 aerial imagery (agriculture had been abandoned by that time), but still has clearly delineated fields outlined by stone walls – representing 75-150 years of agriculture. The third class exhibits minimal evidence of historic activity (few or no primitive walls) –representing 0-25 years of agriculture. In addition, we sampled residential and modern corn and hay fields in town that have been in continuous use (200+ years). Field work consisted of describing 5–10 soils pits for each of the classes; 2 pits for each type were sampled and analyzed for pH, organic content, trace metals, and stable C and N isotopes. Initial results show clear relationships between the thickness of the A horizon and mixing of trace metal profiles with the timing and duration of land use. Sediment mobilization appears greater on the high slope, longest use class. Detailed stone wall maps exist for large swaths of topography in the region, and future work aims to use these data to scale up the extent of the soil impacts. Furthermore, studies like this can lead to a better understanding of the generation and storage of legacy sediment in sites downslope of anthropogenically modified soils.