Skip to Main Content
Temporal dynamics and spatial variability in the enhancement of canopy leaf area under elevated atmospheric CO2Author(s): Heather R. McCarthy; Ram Oren; Adrien C. Finzi; David S. Ellsworth; Hyun-Seok Kim; Kurt H. Johnsen; Bonnie Millar
Source: Global Change Biology, Vol. 13: 2479-2497
Publication Series: Miscellaneous Publication
PDF: View PDF (459 KB)
DescriptionIncreased canopy leaf area (L) may lead to higher forest productivity and alter processes such as species dynamics and ecosystem mass and energy fluxes. Few CO2enrichment 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 senescencewere 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; Po0.050); on average, enhancement following canopy closure was 16% and 14% respectively. However, variation n pine L and its response to elevated [CO2] was not random. Each year pine L under ambient and elevated [CO2was spatially correlated to the variability in site nitrogen availability (e.g. r2=0.94 and 0.87 in 2001, when L was highest before declining due to droughts and storms), with the [CO2]-induced enhancement increasing with N (P50.061). Incorporating data on N beyond the range of native fertility, achieved through N fertilization, indicated that pine L had reached the site maximum under elevated [CO2] where native N was highest. Thus closed canopy pine forests may be able to increase leaf area under elevated [CO2] in moderate fertility sites, but are unable to respond to [CO2] in both infertile sites (insufficient resources) and sites having high levels of fertility (maximum utilization of resources). The total canopy L, representing the combined L of pine and hardwood species, was constant across the N gradient under both ambient and elevated [CO2], generating a constant enhancement of canopy L. Thus, in mixed species stands, L of canopy hardwoods which developed on lower fertility sites (3gNinputsm-2 yr-1) may be sufficiently enhanced under elevated [CO2] to compensate for the lack of response in pine L, and generate an appreciable response of total canopy L (~14%).
- You may send email to email@example.com to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationMcCarthy, Heather R.; Oren, Ram; Finzi, Adrien C.; Ellsworth, David S.; Kim, Hyun-Seok; Johnsen, Kurt H.; Millar, Bonnie. 2007. Temporal dynamics and spatial variability in the enhancement of canopy leaf area under elevated atmospheric CO2. Global Change Biology, Vol. 13: 2479-2497
Keywordsbroadleaf leaf area, drought, leaf area index, leaf area profile, Liquidambar styraciflua, nitrogen availability, Pinus taeda
- Branch growth and gas exchange in 13-year-old loblolly pine (Pinus taeda) trees in response to elevated carbon dioxide concentration and fertilization
- Effects of Fertilization on the Vegetation Dynamics of Yougn Loblolly Pine Plantations
- Short-term effects of fertilization on photosynthesis and leaf morphology of field-grown loblolly pine following long-term exposure to elevated CO2 concentration
XML: View XML