ANTHROPOGENIC MODIFICATIONS TO UPLAND SOILS FROM HISTORIC LAND USE IN SOUTHERN NEW ENGLAND

Human disturbance fundamentally affects critical zone processes, structure, and function. The northeastern US region provides a natural laboratory to study human-induced changes to the Critical Zone, with a rich and well documented history of land modification that includes clearing of forests, agriculture, pasture, logging and forest regrowth. 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 and pasture activities, and aerial images from 1934 onwards can be used to show the progression of land abandonment and reforestation through the 20^th century. At a site in Mansfield, CT, we used stone wall mapping to identify three main land use classes characterized by different durations of historic agriculture that are all forested today. The first class terrain that has clearly delineated fields outlined by stone walls and is not abandoned until the mid-20^th century, based on 1934-1950 aerial imagery – representing the longest duration of agricultural activity (150-250 yrs). The second class terrain that is forested in 1934 aerial imagery (hence agricultural activity had been abandoned by that time), but still has clearly delineated fields outlined by stone walls – representing a shorter duration of agricultural activity (75-150 yrs). The third class is terrain that exhibits minimal evidence of historic activity (minimal or no primitive stone walls) –representing the shortest duration of agricultural activity (0-25 yrs). Field work consisted of describing 10 soils pits for the first two classes, and 5 pits for the third class; a subset of 6 soil profiles (2 per type) were sampled and analyzed for soil pH, organic content, trace metals, and stable C and N isotopes. Initial results show a clear relationship between the thickness of the A soil horizon and the duration of land use for agriculture. 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 and calculate carbon stocks for each of the three land use classes. Furthermore, studies like this can lead to a better understanding of upland soil erosion and the generation and storage of legacy sediment in sites downhill and downstream of human impacted critical zone soils.