Decomposing coarse woody debris (CWD) is a conspicuous and important component of forest ecosystems. Seasonal temperature and precipitation patterns influence heterotroph activity, which determines the rate of CWD decomposition. We tested the hypothesis that moisture content and heterotroph community composition influence carbon flux in freshly-cut Douglas fir (Pseudotsuga menziesii) logs. To evaluate the effects of physical penetration of bark and wood and transmission of basidiomycete compared with ascomycete fungi by insects, 360 experimental logs were assigned to five replicate sites, each with 12 heterotroph脳moisture treatment combinations in 1995. Half of the logs in each heterotroph treatment received normal rainfall and half were placed individually under elevated clear plastic tents to reduce water inputs. Respiration was measured every 1-3 months. In 1996 and 1997 a different log representing each treatment combination was harvested from each replicate and analyzed for the presence of inoculated and colonizing fungi. Logs inoculated with decay fungi had higher respiration than uninoculated logs but this effect only approached significance (P=0.08) during the first season. Respiration was significantly higher in sheltered than in exposed logs. Our results indicate that respiration and wood decomposition rates may be depressed by high moisture content in the wet forests of the coastal Pacific Northwest.
The effect of wood/plastic ratio and the presence of a boron compound on resistance to biodegradation of wood plastic composites (WPC's) by the brown rot fungus Gloeophyllum trabeum was investigated in a soil block exposure. Weight losses of all WPC's were generally lower than those of solid wood, even when only the wood component of the WPC was used in calculating weight loss. Higher wood content was associated with greater weight losses, suggesting that the plastic encapsulated wood at lower wood levels. Borates markedly reduced weight losses at all wood/plastic ratios. Weight losses tended to be slightly lower with a Na/Ca borate than with similar levels of zinc borate. Mechanical properties did not correlate well with weight losses under the conditions evaluated, but these effects may have been masked by moisture sorption. The causes and implications of these differences are discussed.
Three extractives from China-fir were obtained by a sequential extraction processes with hexane, ethyl acetate, and methanol. The components of the three extractives were analyzed: (1) The gas chromatography-mass spectrometry (GC-MS) analysis showed that in addition to the presence of cedrol, naphthalenes comprised a relatively large percentage of both the hexane extract (10.39%) and the ethyl acetate extract (9.43%). (2) Total phenolic contents analysis showed that phenols took up 6.66 % of the ethyl acetate extract and 22.8% of the methanol extract. All extracts, even with low concentrations, presented fair antifungal activities against two white-rot fungi, Trametes versicolor and Irpex lacteusand two brown-rot fungi, Postia placenta and Gloeophyllum trabeum. Cedrol and naphthalenes were partly responsible for the bioactivities. The synergistic effect of phenols and antifungal compounds also contributed to the wood decay resistance.
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