Temporal dynamics and spatial variability in the enhancement of canopy leaf area under elevated atmospheric CO2

Increased canopy leaf area (L) may lead to higher forest productivity and alter processes such as species dynamics and ecosystem mass and energy fluxes. Few CO2 enrichment studies have been conducted in closed canopy forests and none have shown a sustained enhancement of L. We reconstructed 8 years (1996-2003) of L at Duke's Free Air CO2 Enrichment experiment to determine the effects of elevated atmospheric CO2 concentration ({[}CO2]) on L before and after canopy closure in a pine forest with a hardwood component, focusing on interactions with temporal variation in water availability and spatial variation in nitrogen (N) supply. The dynamics of L were reconstructed using data on leaf litterfall mass and specific leaf area for hardwoods, and needle litterfall mass and specific leaf area combined with needle elongation rates, and fascicle and shoot counts for pines. The dynamics of pine L production and senescence were unaffected by elevated {[}CO2], although L senescence for hardwoods was slowed. Elevated {[}CO2] enhanced pine L and the total canopy L (combined pine and hardwood species; P

Duke Scholars

Author Ram Oren Environmental Sciences and Policy