The Carbon Quandary: Essential and Detrimental - Sustainable Design: The Science of Sustainability and Green Engineering - page 284

Woody plants have connecting systems that link modules together and that
connect the modules to the root system. These connecting systems do not rot
away after the growing season. In fact, for years a tree thickens these connect-
ing tissues. Actually, most of the mass of a woody tree is dead, with only a thin
layer of living tissue below the bark. However, this living stratum regenerates
Figure B7.2 Configuration of a lignin polymer.
From Institute of Biotechnology and Drug Research, Environmental Biotechnology and Enzymes , IBDR, Kaiser-
slautern, Germany. Adapted from E. Adler, “Lignin chemistry:past, present and future,” Wood Science Technol-
ogy , 11, 169-218, 1977.