13CPMAS-NMR spectroscopy and chemical analysis of coarse woody debris in coastal forests of Vancouver Island

The coastal forests of British Columbia have large accumulations of coarse woody debris, and information on this pool is considered essential in developing sustainable management practices. We characterized coarse woody debris (7-12 and >12 cm diameter) in forest chronosequences of four age classes located on the eastern and western sides of Vancouver Island. For three species (Douglas-fir (Pseudotsuga menziesii (Mirb.) France), western hemlock (Tsuga heterophylla (Raf.) Sarg), western red cedar (Thuja plicata Donn.)) and unidentified samples, increases in decay class (I to V, assigned in the field) were associated with decreasing density, and small increases in concentrations of C, N, and P. Sulfur concentrations (0.6-2.4 g/kg) were higher than those found elsewhere for wood and did not show any significant changes with decay class. C-13 nuclear magnetic resonance spectroscopy with cross polarization and magic-angle spinning (C-13-CPMAS-NMR) was used to analyze organic components in a subset of samples >12 cm. Logs up to decay class III generally showed little change in composition or a slight increase in polysaccharide C. After this, polysaccharide was lost more quickly and logs of decay class V were composed almost entirely of lignin, a pattern consistent with decay by brown-rot fungi. However, two samples of western red cedar decay class III and IV showed accumulation of polysaccharide, the pattern expected from white-rot fungi. The results of the density, chemical and NMR analysis indicate that for management purposes, a system with fewer decay classes would suffice. (C) 1998 Elsevier Science B.V.