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Goal: Apply Knowledge Globally More carbon dioxide, more forest biomass production

After 15 years of growing in an environment enriched with extra carbon dioxide, loblolly pine trees grew taller than expected and stored more carbon underground, in their roots. The long-term study was conducted at the Duke Free-Air Carbon Enrichment Study CO2 (FACE) site to assess how rising carbon dioxide in the air could affect forests.

A person shoveling soil from around an exposed tree stump and roots.
Excavation of loblolly pine root systems at the Duke Free-Air Carbon Enrichment Study where loblolly pine and associated broadleaved species were exposed to elevated CO2 for 15 years. USDA Forest Service photo by Chris Maier.

At the Duke FACE site, loblolly pine trees grew for 15 years surrounded by pipes that emitted carbon dioxide—enough to raise the concentration by 200 parts per million. Under the higher levels of carbon dioxide, the loblolly pines grew taller than expected for their width. The trees also stored more carbon underground. Combined, pine and broadleaved root biomass increased by 48% and root to shoot ratio increased by 16%.

The sustained increase in biomass production shows likely long-term effects of rising atmospheric carbon dioxide on loblolly pine development. The research indicates that the trees had enough soil nutrients to maintain growth. Results from other long-term FACE experiments have been inconsistent—some suggest that forests will grow faster as carbon dioxide increases in the atmosphere, while others report that forest growth will not change.

Southern pine forests store large amounts of carbon. When estimating the amount of carbon stored in these forests, both above- and belowground, their response to increased carbon dioxide in the atmosphere must be considered over a range of soil nitrogen availability.

Principal Investigators
Chris A. Maier, Team Leader, Research Biological Scientist
Kurt Johnsen, Plant Physiologist
4160 - Forest Genetics and Ecosystems Biology
Strategic Program Area
Resource Management and Use
Biomass increases attributed to both faster tree growth and altered allometric relationships under long‐term carbon dioxide enrichment at a temperate forest
External Partners
Ram Oren - Duke University and University of Helsinki
Sari Palmroth - Duke University
Dohyoung Kim - University of Notre Dame