PS 4-51 - Soil carbon pools along yard-field-forest land use gradients

Monday, August 7, 2017
Exhibit Hall, Oregon Convention Center
Morgan E. Peach, Ecology, Evolution, Ecosystems & Society, Dartmouth College, Hanover, NH, Andrew J. Friedland, Environmental Studies, Dartmouth College, Hanover, NH and Laura A. Ogden, Anthropology, Dartmouth College, Hanover, NH

Soils store more carbon (C) than the atmosphere and terrestrial plants combined. Humans alter soil ecosystem C pools from the urban core to rural periphery. Urban and suburban land uses, such as yards and parks, often store more soil C than undisturbed lands, while the effect of exurban land use on soil C storage is lesser known. How do soil C pools differ across residential exurban yard-field-forest land use gradients? Does varying intensity of yard management affect soil C pools? Is soil solution dissolved organic carbon (DOC) transport related to differences in soil C pools?

In the Upper Connecticut River Valley, VT and NH, yards (n = 19) were selected adjacent to mown fields (n = 8) and second-growth forests (n = 7) to control for land use history. Participating residents were interviewed about their property history and management. Yards were categorized as either intensively (n = 9; mowing, clipping removal, irrigation and fertilizing) or non-intensively (n = 10; mowing as needed) managed. Three soil cores were extracted to 60-cm depth within land uses, and analyzed for C, N, pH, bulk density, and moisture content by upper (0-10 cm & 10-20 cm) and deep soil (20-40 cm & 40-60 cm). Across one land use gradient site, soil solution DOC concentrations were monitored in upper and deep soil.


Yards stored less soil carbon to 60-cm depth (10.43 kg C m-2) than forest (13.28 kg C m-2) and field soils (12.08 kg C m-2). Across six land use clusters (LUC), defined by a yard-field-forest gradient, land use and depth explained soil C pools in a linear mixed effects model, with LUC as a random effect. Yard soil C pools, averaged over depths, were lower than adjacent forests (p < 0.05). Field (1.32 g cm-3) and yard (1.21 g cm-3) soil bulk density, averaged over depths, were significantly greater than forest soils (1.04 g cm-3). The interaction of yard management (mean 26 y.) and house age (mean 99 y.) explained yard soil C pools to 60-cm depth. Preliminary soil solution data suggested higher DOC concentrations in yard and field deep soil relative to forest. Land-use conversion, a legacy of soil disturbance, limits the magnitude of soil C pools. Exurban land-use change alters soil carbon pools and the function of soils to provide essential ecosystem services.