Department or Program

Geology

Abstract

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 19th century a small logging camp was located near the pond and 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. A 1.45 m sediment cores, recovered from the deepest part of Trout Pond, was analyzed using a multi-proxy evaluation of the bulk density, organic carbon content, total nitrogen content, bulk δ13C, magnetic susceptibility, and diatom content of the sediments. A chronology, derived from 137Cs, bulk Pb, and two, radiocarbon dates, was used to evaluate the geochemical results over time.

Results show a constant period of sedimentation for the first ~1800 years of the core. We attribute the onset of human landscape to changes in the watershed between 1820 and 1890 AD. These changes are evident in the geochemical and biological proxies, with sharp increases in bulk density, total organic carbon and nitrogen, more negative d13C values and increases in the centric to pennate ratio and total abundance of diatoms. Historical evidence of three, active sawmills in the Trout Pond watershed during this time period support our findings. Only in the past 60 years (~1950 AD- present) has there been a decrease in bulk mass, carbon and nitrogen accumulation rates to pre-disturbance values. While land use rapidly changed the landscape during the early 20th century from deforestation to re-growth, the land use signal recorded in the Trout Pond sediments show a lag period between reforestation and a decrease in bulk mass accumulation.

Level of Access

Open Access

First Advisor

Timothy Cook

Date of Graduation

Spring 5-2012

Degree Name

Bachelor of Science

Number of Pages

83

Components of Thesis

1 pdf file

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