The desirable wood characteristics of yellow-cedar put great pressure on the resource of this species for timber production. The large acreage of yellow-cedar decline, coupled with the value of wood from dead trees suggest salvage opportunities. Before salvage recovery could proceed, information was needed on how the characteristics of wood from dead trees compared to that of live trees. Thus, several years ago, we initiated a series of studies to evaluate the value of wood from dead yellow-cedar.
Each of the studies employed the same snag classification system for trees dead up to 100 years that was developed for epidemiological studies (Hennon et al., 1990). It provided time-since-death estimates for dead standing yellow-cedar trees in five recognizable stages of deterioration.
The 5-class snag system is the common link between these studies. Most declining forests have dead trees in each class, as well as surviving yellow-cedars and trees of other species. To evaluate recovery from dead trees, we selected and tracked 300 logs according to snag class as they were sawn into boards, then classified by grade.
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| Class 1 | Class 2 | Class 3 | Class 4 | Class 5 |
| 4 years | 14 years | 26 years | 51 years | 81 years |
Pattern of Deterioration
As a yellow-cedar tree dies, the sapwood is quickly colonized by stain and decay fungi. The narrow sapwood on yellow-cedar is fully colonized by fungi and insects and begins to slough away at the third snag class. Up to this stage, however, any defect factors (stain, decay, checking) are restricted to the sapwood and do not penetrate the heartwood.
This snag class 4 cross section shows some slight checking near the edges.
By class 4 snags, however, the sapwood is nearly gone and the heartwood is exposed to drying checks--the most serious defect. This pattern of deterioration helps explain the high volume and grade of recovery that is yielded from the first 3 snag classes.
Volume Recovery
With assistance from Pacific Rim Cedar, Inc., we measured the cubic volume recovery from over 300 logs from dead and live yellow-cedar trees that were harvested near Nemo Point on Wrangell Island. This was possible by marking trees in the woods and following their logs to individual boards as they were sawn at the mill site. Each board was given a domestic and export grade. Class 4 and 5 snags yielded significantly less domestic volume than the more recent classes of snags or live trees, but the reduction was less than 15%. Recovery of wood meeting the more restrictive export rules was considerably lower and more variable among tree/snag classes but showed the same general pattern as domestic recovery. Generally, these results demonstrate an encouraging rate of recovery from snags.
Grade Recovery
A high-grade 5”x5” piece of lumber produced from a class 5 snag, dead about 80 years.
The lumber grade for recovered volume did not differ greatly by tree/snag class, but there was a trend for more of the volume recovered in poorer grades to be from the older snag classes. Results below are the percentage of the volume recovered in each lumber grade for each of the tree/snag classes.
Strength Properties
Yellow-cedar is known for the strength of its wood. Results from the first phase of testing at the Forest Products Laboratory indicated no reduction in the strength properties of wood from snags, even long after death. Note that the “Handbook value” comes from published tests of wood from live yellow-cedar growing throughout its range. Larger sample sizes were included in the second round of sampling of dead trees from Wrangell Island.
Stakes were placed in the ground for 2 and 4 years at two sites to test the decay rate of yellow-cedar.
Decay resistance
We addressed the question of whether wood from dead yellow-cedar retains its remarkable decay resistance when used in service. This work included laboratory and field tests on the durability of snag wood with the Forest Products Laboratory.
Heartwood chemistry – defensive compounds
We measured the concentration of nootkatin and other heartwood constituents from the wood of each of our snag classes to determine if these compounds are lost or altered through time as snags remain standing in the woods. Heartwood chemistry begins to change in the class 3 snags, dead about 30 years. The defensive compounds continue to degrade somewhat as snags age, but relatively high concentrations persist even 80 years after death.
Conclusions
- Heartwood chemistry greatly limits deterioration of snags
- Allows high rate of recovery, even in trees dead 81 years
- Recovery and all wood properties from snags 1, 2, 3 (dead 4, 14,
- and 26 years) do not differ from live trees.
- Strength properties are retained in snags 4 and 5 (dead 51 and 81 years), but chemistry, decay resistance and recovery reduced slightly.
- Large acreage dead + dead wood value = promising recovery
- Hennon, P.; Woodward, B.; Lebow, P.K. 2007. Deterioration of wood from live and dead Alaska yellow-cedar in contact with soil. Forest Products Journal. 57(6): 23-30.
- Kelsey, R.G.; Hennon, P.E.; Huso, M.; Karchesy, J.J. 2005. Changes in heartwood chemistry of dead yellow-cedar trees that remain standing for 80 years or more in Southeast Alaska. Journal of Chemical Ecology. 31: 2653-2670.
- Morales-Ramos, J.A.; Rojas, M.G.; Hennon, P.E. 2003. Black stain fungus effects on the natural resistance properties of Alaskan yellow-cedar to the Formosan subterranean termite (Isoptera: Rhinotermitidae). Environmental Entomology Physiological and Chemical Ecology. 32: 1234-1241.
- Green, D.W.; McDonald, K.A.; Hennon, P.E.; Evans, J.W.; Stevens, J. H. 2002. Flexural properties of salvaged dead yellow-cedar. J. For. Prod. 52(1): 81-88.
- Hennon, P.E.; Wittwer, D.; Stevens, J.; Kilborn, K. 2000. Pattern of deterioration and recovery of wood from dead yellow-cedar in southeast Alaska. Western Journal of Applied Forestry. 15: 49-58.
- DeGroot, Rodney C.; Woodward, Bessie; Hennon, Paul E. 1999. Natural decay resistance of heartwood from dead, standing yellow-cedar trees: laboratory evaluations. Forest Products Journal 50: 53-59.