Effects of long-term elevated CO₂ treatment on the inner and outer bark chemistry of sweetgum (Liquidambar styraciflua L.) trees

Journal Article · Thu Jul 23 00:00:00 EDT 2015 · Trees

DOI:https://doi.org/10.1007/s00468-015-1254-8· OSTI ID:1261487

Eberhardt, Thomas L. ^[1]; Labbé, Nicole ^[2]; So, Chi-Leung ^[3]; Kim, Keonhee ^[2]; Reed, Karen G. ^[4]; Leduc, Daniel J. ^[4]; Warren, Jeffrey M. ^[5]

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1. USDA Forest Service, Pineville, LA (United States); USDA Forest Service, Madison, WI (United States)
2. Univ. of Tennessee, Knoxville, TN (United States)
3. Louisiana State Univ., Baton Rouge, LA (United States)
4. USDA Forest Service, Pineville, LA (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Long-term exposure of sweetgum trees to elevated atmospheric CO₂ concentrations significantly shifted inner bark (phloem) and outer bark (rhytidome) chemical compositions, having implications for both defense and nutrient cycling. Changes in plant tissue chemistry due to increasing atmospheric carbon dioxide (CO₂) concentrations have direct implications for tissue resistance to abiotic and biotic stress while living, and soil nutrient cycling when senesced as litter. Although the effects of elevated CO₂ concentrations on tree foliar chemistry are well documented, the effects on tree bark chemistry are largely unknown. The objective of our study was to determine the effects of a long-term elevated CO₂ treatment on the contents of individual elements, extractives, ash, lignin, and polysaccharide sugars of sweetgum (Liquidambar styraciflua L.) bark. Trees were harvested from sweetgum plots equipped with the Free-Air CO₂ Enrichment (FACE) apparatus, receiving either elevated or ambient CO₂ treatments over a 12-year period. Whole bark sections were partitioned into inner bark (phloem) and outer bark (rhytidome) samples before analysis. Moreover, principal component analysis, coupled with either Fourier transform infrared spectroscopy or pyrolysis-gas chromatography-mass spectrometry data, was also used to screen for differences. Elevated CO₂ reduced the N content (0.42 vs. 0.35 %) and increased the C:N ratio (109 vs. 136 %) of the outer bark. For the inner bark, elevated CO₂ increased the Mn content (470 vs. 815 mg kg^-1), total extractives (13.0 vs. 15.6 %), and residual ash content (8.1 vs. 10.8 %) as compared to ambient CO₂; differences were also observed for some hemicellulosic sugars, but not lignin. Shifts in bark chemistry can affect the success of herbivores and pathogens in living trees, and as litter, bark can affect the biogeochemical cycling of nutrients within the forest floor. Our results demonstrate that increasing atmospheric CO₂ concentrations have the potential to impact the chemistry of temperate, deciduous tree bark such as sweetgum.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1261487
• Journal Information: Trees, Vol. 29, Issue 6; ISSN 0931-1890
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
Ash
Climate change
Extractives
Lignin
Phloem
Rhytidome
RISING ATMOSPHERIC CO2
PRINCIPAL COMPONENT ANALYSIS
STEM WOOD PROPERTIES
CARBON-DIOXIDE
ENRICHMENT FACE
PELLET QUALITY
NORWAY SPRUCE
PICEA-ABIES
PINE BARK
RESPONSES