Below the Radar

A forest's ability to store carbon depends significantly on the bedrock beneath, according to Penn State researchers who studied forest productivity, composition, and associated physical characteristics of rocks in the Appalachian Ridge and Valley region of Pennsylvania.

The results have implications for forest management, the researchers suggest, because forests growing on shale bedrock store 25 percent more live, aboveground carbon and grow faster, taking up about 55 percent more carbon each year than forests growing on sandstone bedrock.

The findings, published in Forest Ecology and Management, demonstrate that forests underlain by shale in this region provide more ecosystem services such as carbon uptake and biodiversity, explained researcher Margot Kaye, associate professor of forest ecology. Shale forests also make up a smaller portion of the landscape and should be high-priority candidates for management or conservation.

Forest managers--now realizing the disparity of productivity--may target forests growing over shale for conservation and carbon sequestration, Kaye said. In contrast, they may decide that forests growing over sandstone are better suited for wildlife habitat management or recreation.

To reach their conclusions, the team analyzed forest inventory data from 565 plots on state forest and game lands managed by Pennsylvania state agencies in the Appalachian Ridge and Valley region. They used a suite of GIS-derived landscape metrics, including measures of climate, topography, and soil physical properties, to identify drivers of live forest carbon dynamics in relation to bedrock.

Forests grow faster over shale bedrock than sandstone bedrock because of soil characteristics that generally make water more available to trees, hypothesized lead researcher Warren Reed, a doctoral student in ecology.

--Jeff Mulhollem