Glenn R. Ahrens
GBA Forestry, Inc. and the Western Hardwood Association
Recent increases in both the value of red alder (Alnus rubra) and our knowledge of alder forestry provide opportunities for improved returns to landowners. Historically viewed as an overabundant weed tree, red alder now sustains a major hardwood industry. Red alder is the most abundant broadleaf tree in the Pacific Northwest comprising 7 % of the total timber inventory and 61% of the hardwood inventory in western Oregon and Washington. Both the value and utilization of alder have increased substantially since the 1980’s
Figure 1. Increases in red alder stumpage values reported by the Washington Department of Revenue for the Puget Sound Area. Values are the 5-year running average of real prices adjusted for inflation.
Increased Value of Alder in Managed Stands
By thinning young alder on appropriate sites, we expect substantial increases in stand value compared to typical unmanaged alder.
Higher stand values result from:
In the tall timber of the Northwest, the difference between 6-, 8-, or 10-inch alder logs seems insignificant. But it is often the relative abundance of 6 vs. 8 vs. 10-inch logs that determines most of the value in a stand of alder. This is because log prices for red alder increase dramatically with increasing log size and lumber recovery potential (Table 1). High-quality lumber for furniture and cabinets drives the current market for red
- An increased proportion of sawtimber vs. pulpwood, and
- Reduced logging costs with fewer, larger trees per acre.
||4 - 8 in.
||8 - 10 in.
|$ / ton
|22 - 32
175 - 250
|48 - 62
350 - 450
|69 - 85
450 - 550
Table 1. Delivered log prices for red alder increase dramatically with increasing log size.
Prices represent the range of general quotes from mills in western Washington for “Good” quality logs, August 1999.
In many unmanaged alder forests, a large portion of the wood falls in the 4 to 8-inch diameter range due to overcrowded stand conditions. By thinning young alder on appropriate sites, we expect to produce stands with a much higher proportion of logs in the 8 to 12-inch diameter range at harvest time, which dramatically increases log value and reduces logging costs (Table 2). This is achieved by a 15-25% increase in crop tree diameter, along with improved diameter distributions and stocking levels in managed stands.
|Red Alder stand conditions
||Percentage sawlogs 8 in. +
||Delivered $ / ton, green logs 4 in. +
||Net stand value / acre (after logging costs)
|40 years - typical yield table
|40 years - thinned
Table 2. Much better returns are expected from thinned stands compared to typical unmanaged alder stands via an increase in the proportion of sawlog volume recovered from managed stands.
40 years - yield table is SI 100 at 100% Normal Basal Area, from “Empirical yields for predominantly alder stands in western Washington”, DNR Report 31, Charles Chambers, 1983.
40 years thinned projection - hypothetical yield assuming a 20% increase in crop tree diameter and diameter distributions similar to those observed in 25-30 year old thinned stands.
Other assumptions: Scribner vol. to 6”top, Log lengths 30 ft. ave., 16 ft. min. Prices: <8” logs $22/ton, 8-10” $450/mbf, 10”+ $500/mbf, logging costs $22/ton thinned, $25/ton unthinned
Alder Density Management Guidelines
When and how much to thin alder depends on factors such as current stand density, stand age, site quality, and competing vegetation. Using guidelines provided by the Density management guide for red alder (Puettmann et al. 1993), an appropriate spacing can be determined based on the average size of crop trees (“leave trees”) in prospective thinning units (Table 3).
|Ave. dbh inches
||Number of "leave trees per acre
||Tree spacing feet
||760 - 1300
||5.7 - 7.6
||470 - 850
||7.2 - 9.6
||310 - 570
||8.7 - 11.9
||250 - 450
||9.8 - 13.2
||190 - 330
||11.5 - 15.4
Table 3. Spacing guidelines for red alder based on the Density management guide for red alder.
Lower densities (wider spacing) within the ranges in Table 3 may be appropriate on better quality sites and with low levels of competing vegetation. Higher densities may be more appropriate on lower quality sites, sites with high levels of competing vegetation, or sites with very crowded conditions. Very dense alder patches must be thinned down gradually due to the risk of sunscald, wind, and ice/snow breakage.
Making the Most of Rapid Juvenile Growth
To make the most of alder’s rapid juvenile growth potential, it is essential to avoid the early overcrowding that often occurs. Alder is short-lived; its growth pattern is initially very rapid but tapers off quickly such that alder reach about 80% of their lifetime height in only 30 years (Figure 2). Thinning is most effective when it is done while growth potential is still high, generally before age 15 to 20 years.
Figure 2. Red alder displays a pattern of rapid juvenile height growth that slows dramatically by age 30.
In well-spaced, managed forests, we expect to grow alder to sawtimber-quality in 30-40 years. The target condition for alder at harvest age is a stand density in the range of 100-200 trees per acre with trees averaging 12 to 14 inches in dbh. In typical unmanaged stands it takes 50-70 years to reach this condition.
Management of stand density in red alder can greatly improve sawtimber yields and economic returns compared to typical unmanaged stands. The major reasons for this are:
- Sawlog values are much greater than pulpwood values.
- Typical unmanaged alder stands are mostly pulpwood less than 8 in.
Density management can easily shift the balance toward sawlog material 8-in. and larger.
Many landowners are still faced with patches of alder dominating substantial areas in young forests (age 10-20 years). In this case, the question is how to make the best of the alder, and there could be much to gain from the effort to manage the alder on appropriate sites.
Density management guide for red alder. Puettmann, K.J., D.S. DeBell, D.E. Hibbs. 1993. Oregon State University, Forest Research Lab. Research Contribution 2.
The biology and management of red alder. Hibbs, D.E., D.S. DeBell, and R.F. Tarrant (editors). 1994. Oregon State University Press, Corvallis, Oregon.