Multivariate analysis of CWD visual characteristics

Multivariate analysis was used to analyze the changes in CWD visual characteristics occurring as a result of the decomposition process. Non-metric Multidimensional Scaling (NMS) analysis with rotation of the axes was performed. The axes rotation to one degree resulted in the first axis having the higher coefficient of determination (r²) of the two.

Variables in the approximate sequence of their appearance and correlation coefficients
between them and scores on the ordination axes

Variables	Axis 1	Variables	Axis 2
BARKBOLE BARKBR BRANCHES TWIGS BCOVER NEEDLES BEETLES WOODBORER CONKS LICHENS ANTS CASEHARD WHITEROT STUBSMOV SCATTER MOSS BROWNROT COLLAPSE HWFRIAB SAPSLOUG SAPFRIAB	-0.746 -0.733 -0.716 -0.700 -0.648 -0.459 -0.393 -0.129 -0.109 0.073 0.115 0.211 0.464 0.623 0.647 0.659 0.697 0.718 0.743 0.763 0.858	BARKBR TWIGS NEEDLES BRANCHES SCATTER BCOVER COLLAPSE HWFRIAB STUBSMOV BROWNROT BARKBOLE CASEHARD MOSS LICHENS SAPFRIAB ANTS CONKS SAPSLOUG WHITEROT BEETLES WOODBORER	-0.312 -0.299 -0.261 -0.215 -0.177 -0.172 -0.138 -0.082 -0.065 -0.028 -0.018 -0.01 0.073 0.078 0.118 0.127 0.159 0.159 0.261 0.346 0.381

Variables associated with early stages of decomposition (bark on bole, bark on branches, branches, and twigs) had lower scores, whereas variables associated with late stages of decomposition (heartwood friable, sapwood sloughing, and sapwood friable) had higher axis scores.

Correlations of indicator variables in ascending order to scores on the ordination axis one for five taxa well represented in the study area

Betula pendula		Pinus siberica/koraiensis		Larix spp.		Picea spp.		Pinus sylvestris
Variables	r	Variables	r	Variables	r	Variables	r	Variables	r
BRANCHES BARKBR TWIGS NEEDLES BCOVER LICHENS BARKBOLE BEETLES ANTS WOODBORER CONKS CASEHARD WHITEROT BROWNROT MOSS STUBSMOV SAPSLOUG SCATTER COLLAPSE HWFRIAB SAPFRIAB	-0.817 -0.799 -0.707 -0.435 -0.257 -0.226 -0.200 0.008 0.023 0.038 0.075 0.215 0.479 0.496 0.549 0.665 0.669 0.683 0.787 0.793 0.846	BARKBOLE BARKBR BCOVER TWIGS BEETLES NEEDLES BRANCHES WOODBORER CONKS CASEHARD ANTS LICHENS WHITEROT SCATTER COLLAPSE STUBSMOV MOSS HWFRIAB BROWNROT SAPSLOUG SAPFRIABPFRIAB	-0.854 -0.795 -0.788 -0.787 -0.739 -0.650 -0.586 -0.444 -0.356 0.102 0.166 0.259 0.563 0.652 0.667 0.668 0.703 0.767 0.810 0.859 0.870	BARKBOLE BCOVER BRANCHES BARKBR TWIGS BEETLES NEEDLES WOODBORER CONKS ANTS LICHENS CASEHARD STUBSMOV WHITEROT SCATTER MOSS COLLAPSE HWFRIAB BROWNROT SAPFRIAB SAPSLOUG	-0.814 -0.801 -0.769 -0.710 -0.704 -0.660 -0.429 -0.331 -0.214 0.094 0.175 0.311 0.543 0.544 0.730 0.746 0.766 0.787 0.834 0.862 0.874	BARKBOLE BARKBR BRANCHES BCOVER TWIGS BEETLES NEEDLES LICHENS WOODBORER CONKS ANTS CASEHARD WHITEROT MOSS BROWNROT SCATTER COLLAPSE SAPFRIAB SAPSLOUG STUBSMOV HWFRIAB	-0.724 -0.702 -0.663 -0.635 -0.567 -0.496 -0.395 -0.151 -0.113 -0.100 0.102 0.254 0.441 0.477 0.546 0.567 0.617 0.638 0.657 0.680 0.686	BARKBOLE BRANCHES BARKBR BCOVER TWIGS NEEDLES BEETLES WOODBORER CONKS ANTS CASEHARDSEHARD WHITEROT LICHENS SCATTER STUBSMOV MOSS SAPSLOUG BROWNROT HWFRIAB COLLAPSE SAPFRIAB	-0.792 -0.776 -0.708 -0.704 -0.694 -0.519 -0.435 -0.148 -0.092 0.148 0.272 0.404 0.420 0.642 0.667 0.668 0.722 0.754 0.78 0.797 0.881

There were no significant differences among five best-represented species in terms of the variables correlated to the scores on ordination axis one. However, correlation coefficients of birch bark cover (-0.257) and bark on bole (-0.200) were low, and indicate little change in birch bark presence on bole and percent bark cover over the course of decomposition. This contrasts the coniferous species, which have a high correlation of these variables to first ordination axis, with correlation coefficients ranging from -0.635 to -0.801 and from -0.724 to -0.854 for bark cover and bark on bole, respectively. These indicate a decrease in percent bark cover and bark presence on bole for conifers occurring over the course of decomposition.

Frequency of an indicator (in percent) occurring in CWD of different decay classes by species

A plot of percent frequency of indicator occurrence suggests that the presence of bark on boles may be the single most important indicator separating birch from all coniferous species. Due to the extended bark presence in birch the presence of characteristics such as beetles, wood borers, conks and their traces (galleries, holes) can be detected in birch in more advanced decay classes than in conifers. The latter loose their bark early in decomposition, so it is almost impossible to detect the presence of these biotic indicators in coniferous logs of decay classes four and five. Also, the difference between birch and conifers was indicated by early occurrence (decay class one) of white rot in birch logs and snags, while in conifers the appearance of this type of rot was recorded for decay classes two, three, four and five.

Another difference among the species was the high percent of occurrence of friable sapwood and sapwood sloughing in decay class two CWD of Korean and Siberian pines and low percent of bark on bole occurrence in decay class three of the same species. For example, by decay class two about 60 percent of the white pine CWD pieces sampled had friable sapwood or sapwood sloughing as opposed to less than 20 percent in the other species; and less than 20 percent of the white pine boles had bark present by decay class three, while the bark presence was observed on 65 to 95 percent of other species' boles. This pattern in white pines may be explained by the slow decomposition of heartwood of these species.

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Questions? Email Dr. Mark Harmon at mark.harmon@orst.edu or Dr. Olga Krankina at olga.krankina@orst.edu

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