Tree bark is comprised of living inner bark (phloem) that transports the products of photosynthesis and dead outer bark that protects the living tissues and seals in moisture. Active and passive defenses against destructive agents (e.g., insects, fungal pathogens) are provided by the inner bark and outer bark, respectively (Eberhardt 2013). For sweetgum (Liquidambar styraciflua
L.), the bark comprises 23 percent by mass of the sapling-sized stems and 31 percent of the branches (Koch 1985); the percentage of bark in larger trees would be less. Trees debarked during processing by the forest products industry sector generate significant amounts of bark residue for conversion to mulch products or for fuel value recovery. The chemical composition of tree bark is important as it has the potential to significantly impact the utilization of bark, particularly for biofuel applications.
Eberhardt, Thomas L.; So, Chi-Leung; Labb , Nicole; Leduc, Daniel J.; Warren, Jeffrey M. 2016. Changes in bark composition from long-term elevated CO2 treatment: Implications for the management of sweetgum as a wood energy crop. In: Proceedings of the 18th biennial southern silvicultural research conference. e-Gen. Tech. Rep. SRS-212. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 3 p.