Stage 3: Xylemic examination

Stage 3 provides the most conclusive evidence of the presence or absence of birdseye, but it does damage the tree and should be implemented cautiously. This stage should only be used on standing timber immediately before harvest or on harvested trees because exposure of the phloem and xylem tissues to pathogens can result in substantiM decay arid lost log value.

In this stage, it is necessary to remove all bark and cambial tissues to view the sur_face of the wood. Birdseyes will appear as indentations in the wood from a tangential view_point (figs. 12b, 12c), and as faint traces in the radial and cross sectional views (figs. 13a-13b). Birdseye size may range (figs. 12a, 12b, arid 12c) from small dimples in young (Pillow 1955) and newly initiating trees, to indentations a half inch or more in diameter in advanced cases.

No guarantee can be made that exposing the xylem will reveal birdseyes because normal tissue growth will at times obscure previously figured wood, and layers of wood may have to be removed before figure is found. Pillow (1930) noted that veneer manufacturers occasionally find birdseyes only after removing several inches of the outer layers of a log. Bark samples, however, may sometimes indicate the presence of birdseye when no evidence can be found on the surface of the wood. This would appear to reflect the discontinuance of birdseye production, with normal tissue being tayered over figured wood. The birdseyes still present in the bark are artifacts that have yet to slough off the tree.

CONCLUSIONS AND RECOMMENDATIONS

Further research is needed to determine the cause of birdseye in sugar maple and to ensure that this resource is properly maintained. Attempts to grow birdseye maple from seedlings (Anonymous 1929) or to vegetatively propagate using root cuttings (Bailey 1948) have been unsuccessful to date, suggesting the need to investigate the cause of birdseye as a function of manageable stand or site characteristics rather than an inheritable phenomenon. Field identification of birdseye in sugar maple should be a component of timber cruising in regions where birdseye is historically significant. Substantial timber revenues may be lost if birdseye is not identified, especially when wood's-run birdseye may bring more than 40 times the value of comparably graded non-birdseye timber (Mroz et al. 1990). This field identification guide has been developed to give foresters the means to identify birdseye maple in standing timber, maximizing the potential of their sugar maple resource.

Localities in which birdseye maple is relatively common should modify cruising practices to account for the value differences presented by birdseye veneer. Foremost, these adjusted cruising methods should include identification of birdseye in standing sugar maples. The forest manager should also realize that increased monetary return is not guaranteed by locating the trees with birdseye--the bole quality and size of the tree must be sufficient (grade 1 saw logs or veneer, usually) to provide high value logs. In lower quality logs, birdseye can actually be a defect in the wood and downgrade its value, Logging crews should also take care to separate birdseye logs from non-birdseye material to avoid decreasing birdseye's value through improper bucking of the logs. Suspect logs can be inspected by using [he methods previously described and by searching for the faint birdseye traces that may be seen in the cut face of the log (fig. 14). Pickens et at. (1992) demonstrated that improved bucking practices can achieve 39 to 55 percent gains in northern hardwood log gross value, which can substantially increase financial return when applied to valuable birdseye maple logs. Harvest methods should also be modified to protect the residual stand from logging damage. For example, a simple method to minimize logging damage is to switch from stringer-length skidding to forwarding of timber.

Consumer demand has significantly increased the value of birdseye over the past century. There is no guarantee that prices will keep rising (or even remain stable), making it necessary to maximize the current value of the timber. Birdseye maple has provided an economic boom to the northern hardwood timber industry, especially in the Upper Peninsula of Michigan, yet many forest resource managers remain unaware of the potential value of this unique figured wood. Identification is relatively quick and easy; and where birdseye is somewhat common and quality logs are found, it is also very cost effective.

<ACKNOWLEDGMENTS & LITERATURE CITED>