Converting hardwood stands to loblolly pine reduces streamflow in the Piedmont of North Carolina

Forest Service scientists are undertaking a study to improve how we manage forested watersheds for water resources. Watersheds that are converted from hardwood trees to pine trees typically use more water and can reduce streamflow, leaving less water to flow downstream into rivers and reservoirs – especially during droughts. 

Young Loblolly Pine standIn the 1950s, there were almost no pine plantations in the southern United States. Now there are over 39 million acres of planted pine (about the size of the state of Georgia) with most of that expansion occurring over the last twenty-five years. Managing our forests so they can continue to release enough water to streams and reservoirs that will supply the needs of the rapidly growing population in the Piedmont region is a challenge for land and water managers. In partnership with several North Carolina state agencies, scientists from the Eastern Forest Environmental Threat Assessment Center started the first study in the Piedmont that quantifies changes in streamflow after a watershed is converted from a hardwood stand (dominated by oaks, tulip poplars, sweetgums, and red maples) to a loblolly pine stand. The researchers found that eight years after the conversion, streamflow was about 15 percent less than if the hardwood trees had not been cut. This study is ongoing and the growth of the young pine trees will continue to be linked to streamflow measurements. Data from this project will help public and private landowners decide how to most effectively sustain forest and water resources together with silvicultural activities across the Piedmont region.

Pictured: Eight year old loblolly pine stand in the Piedmont of North Carolina. USDA Forest Service.

External Partners/Collaborators: North Carolina Forest Service, North Carolina State University, North Carolina Department of Agriculture and Consumer Services.

Contact: Johnny Boggs, Biological Scientist, Eastern Forest Environmental Threat Assessment Center,

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