USING TREE RING DATA AS A PROXY FOR SUMMER PRECIPITATION AND THE TIMING OF LAND USE CHANGES IN NORTHEAST OHIO

Tree rings can be used to analyze past summer moisture and changes in environmental conditions brought about by settlers in the late 18^th to early 19^th centuries. Settlement had a profound impact on forests through land use modifications such as logging and agriculture, as well as perturbations of biogeochemical cycles from draining and fossil fuel burning. The effects of these human activities are recorded in the tree ring records as increases in ring widths over a few decades. Timing of the onset of changes can be inferred from these calendar-dated records often to the year. Before settlement, the lands of northeast Ohio were covered in thick forests and grasslands. As settlers began to arrive, however, the land was transformed from vast tree-filled expanses to drained croplands with occasional tracks of forest dotting the landscape that bore witness to these changes. Settlers in Ohio generally moved from the south along the Ohio River to the north, founding cities such as Marietta and Cincinnati before traveling northward to found Cleveland. Accordingly, the effects on tree rings should also be sequential, observed first in the south and later in the north. By plotting ring widths and their releases, we can see trends that indicate the changing forest conditions due to settlement. Our initial research sites are old-growth forests and forest remnants in northeast Ohio at Stebbin’s Gulch, Holden Arboretum, and Brown’s Lake Bog, located in Shreve, Ohio. An abrupt release and sustained twofold increase in ring width was observed in both chronologies, indicating a rapid change in these trees’ environment. This change was caused by a combination of increased precipitation and human activities, as the release coincides with the timing of settlement in both locations. Settlement led to decreased vegetative competition from logging, increased fertilization from windblown sediment, and increased CO₂ and NO_x from coal burning. With a surprising number of old growth forest remnants across northeast Ohio, we are now mapping out the timing of the initiation of land use change and comparing it with independent records of settlement to explore various hypotheses that cause and sustain the release.