ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

I
HCOH
Figure 1. -- Proposed structure of Zignin polymer depicting
interunit linkages found {n angiospemnous and gymnosper-
mous Zipins (Kirk and Fen 2980).
DECAY SYSTEMS
Types of decay in the major groups of woody plants are of two major kinds:
white rots and brown rots. Typically, whi te-rot fungi depolymerize cell ulose and
hemicellulose at similar rates and lignin at a similar or somewhat faster rate.
Brown-rot fungi depolymerize cellulose and hemicellulose and 1 eave the 1 ignin
essentially unchanged, though there is demethylation of the olymer and the accumu-
lation of lignin degradation products (Highley and Kirk 1980 !' ,
There are also indications that the extractlve content of heartwood and sapwood,
particularly in coniferous substrata, exerts a limiting or selective influence on
the activi ties of both brown-rot and whi te-rot fungi. In coniferous residues,
initial sapwood decay appears to be of the white-rot type, which eventually shifts
to brown-rot. Heartwood is usually decayed by the brown-rot fungi. The present
understanding of the distribution is not a clear one.
In the intermountain regions of the western United States, the principal decay
process for large-dimensional dead coniferous woody materials is the brown-rot type.
The end products are apparently a function of the interaction between li nin-ty e,
temperature-moisture (T-M) regimes, and associated decay microorganisms 9 fig. 2 ! .