EVALUATION OF THE RESPONSE AND RECOVERY OF A FORESTED WATERSHED TO HUMAN DISTURBANCES BASED ON A MULTI-PROXY ANALYSIS OF SEDIMENTS IN TROUT POND, NEW HAMPSHIRE

The New England landscape has undergone significant changes since the arrival of European settlers. Variations in the accumulation of allochthonous and autochthonous sediment in lakes provides a unique opportunity to evaluate the response and recovery of a lake and its watershed to human disturbances in comparison with long-term natural variability. Trout Pond is a small (0.06 km²), 13 m deep lake in Lyme, New Hampshire (43.83° N, 72.09° W). In the late 19^th century a small logging camp was located near the lake and it is likely that much of the 1.5 square km watershed was deforested. Currently protected by a conservation easement, the Trout Pond watershed has completely reforested and is free of any direct human impacts, making it an ideal site for examining the response and recovery of a forested watershed to human disturbances. Two adjacent sediment cores, recovered from the deepest part of Trout Pond are being analyzed using a multi-proxy approach that includes evaluation of the bulk density, organic carbon content, total nitrogen content, bulk δ¹³C, magnetic susceptibility, and diatom content of the sediments. Initial results from a 145 cm long core show a trend of gradually increasing organic carbon content and decreasing bulk density up to ~40 cm below lake bottom. The relatively consistent trend in the lower part of the record is interrupted by a spike in the C:N ratio at 40 cm depth and two large oscillations in bulk density and organic carbon between 40 and 20 cm depth. The uppermost 20 cm of the record is characterized by a sharp decrease in organic carbon content, increase in bulk density, and increase in δ¹³C. The uniqueness of the upper section of the record suggests a significant, recent alteration of the lake system, although the precise timing of these events is not yet known. Nonetheless, sedimentation rates in other similar lakes in New England suggests that the 145 cm core from Trout Pond should include at least several centuries of sediment accumulation prior to the arrival of European settlers. Pb-210 and Cs-137 profiles will be combined with radiocarbon dating to establish an age model for the sediment cores and evaluate changes in the composition of the sediments and the rate of accumulation in relation to the historical record of human disturbance and forest recovery in the surrounding watershed.