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Ten-year data on growth and survival of two red alder provenance-progeny test trials located in the southern and northern coastal regions in British Columbia, Canada, were analysed and their implications for the genetic improvement of this species were discussed. A total of 42 and 41 provenances, each represented by two to five open-pollinated families were evaluated at each site, respectively. Results indicate that red alder provenances responded differently to the environmental conditions of the two sites. At age 10, red alder provenances tended to perform better at sites near their origin. The results support earlier work that two breeding zones should be delineated with the boundary at approximately 52° N. One may expect an average of about 5% decrease in stem volume and 6% increase in mortality, respectively, for each degree of southward and northward transfer of seed sources from their origins. Individual, family, and within-family heritabilities for height, diameter, stem volume were moderately high (0.22–0.42), for the southern zone, implying good potential for genetic improvement. Heritabilities were somewhat lower (0.12–0.39) for the northern zone because of greater environmental heterogeneity of the test site. Selecting the top 20 unrelated individuals for seed orchard establishment would result in 29% and 23% gain in stem volume at a rotation age of 40 years in the southern and northern zones, respectively. Correlation between ranks of the predicted breeding values for height at different ages and stem volume at age 10 increased rapidly when plantation was young and became relatively stable after 6 years of out-planting. Stem volume had much stronger correlation with diameter (≥0.84) than with height (≤0.67). Early selection at age 6 based on stem volume is therefore recommended.

The genetic structure of 19 red alder (Alnus rubra Bong.) populations representing the natural range of the species in British Columbia was investigated at 19 allozyme loci. The estimated average number of alleles per locus (1.79), percentage of polymorphic loci (52.6), and total expected genetic diversity (0.113) were all lower than those reported for most long-lived woody species but comparable to early successional species. About 8% of the total genetic variation was attributable to among-population differentiation, the majority being detected at the Aat-2 locus between the Mainland and the Islands regions. Phylogenetic analysis grouped the 19 populations into two distinct clusters that perfectly coincided with their geographical arrangement. Genetic differentiation between populations within both the Mainland and the Islands regions was very weak, accounting for about 3% of the total genetic variation within each region. Red alder is predominantly an outcrossing species with an average outcrossing rate of 0.85. The rate of outcrossing also varied widely among populations, ranging from 0.56 to 0.98. Practical implications of these findings with respect to tree improvement and in situ gene conservation are discussed.

This study evaluates the performance of Alnus rubra inthree square spacings (0.5-, 1.0- and 2.0-m), two irrigationregimes (low and high), and two pre-planting fertilizer treatments (0 and 300 kg P ha−1). Initial survival and growthwere excellent, and differences among various cultural treatmentswere apparent by the end of the second growing season. At ageten, mean tree sizes in specific regimes ranged from 4.8 cm to11.5 cm in diameter and 7.7 m to 13.1 m in height, with largesttrees produced in regimes with wide spacing and high irrigation. Beneficial effects of fertilizer were minimal and were limitedprimarily to enhanced early survival during the first two yearsin the closest spacing. Growth of the plantings was greater thanthat estimated for fully stocked, natural stands of the same ageand site index (or height). Data from our study provided generalconfirmation of the level and slope of the tree size-standdensity lines currently used in density management guidelines foralder, except that mortality in the densest spacing occurred atdiameters smaller than those assumed to indicate the thresholdfor inter-tree competition. This difference, however, waslessened by irrigation.

Interest in managing red alder (Alnus rubra Bong.) for pulp, lumber and improving site quality is increasing. Proper management of this species requires growth and yield information. Height-age and years to breast height models developed for western Washington and northwestern Oregon are being used in British Columbia. It is unknown whether these models are suitable for British Columbia's conditions. Therefore, new models were developed from thirty stem analysis plots established in red alder stands in coastal areas of British Columbia. The sample trees in the plots were intensively sampled by taking sections out of the tree stems and counting the annual growth rings on each section. This led to height-age data for each tree, which was then averaged by age to get plot height-age data. Years to breast height and height-age models were developed from these data and are summarized in this paper. The height-age model was anamorphic, which contrasts with the model previously used in British Columbia. The new years to breast height model provides more resolution than the previous model.

The success of various grass-legume mixtures in controlling competing vegetation, and their effect on subsequent survival and growth of Sitka spruce seedlings was studied on a coastal alluvial site in northwestern British Columbia. Mechanically scarified (bladed) strips were hand seeded to pure and combined mixtures of legumes, bunchgrasses, and sodforming grasses. An unseeded control (bladed but not seeded) was also established.

To determine if inoculation increases nodulation and yield of bare-root red alder (Alnus rubra Bong.), fumigated nursery plots were treated with inoculum and ammonium sulfate (28 kg N ha−1) in a factorial experiment. Inoculum was alder soil with 100 infective units of Frankia g−1. Seedlings were evaluated for nodulation at age 10 wk and when lifted, at age 9 mo. Inoculation produced earlier and more extensive nodulation and increased seedling root collar diameter, height, and dry weight. Fertilization decreased seedling height, but did not decrease nodulation. No interaction of fertilization with inoculation was found. Inoculated unfertilized plots had the highest yield of packable seedlings (257 m−2), and uninoculated fertilized seedlings had the lowest yield (126 m−2).

Two- to four-week stratification of red alder seeds slightly increased the speed of germination but did not improve total germination under alternating warm temperatures (30°C/20°C), yet significantly improved speed and total germination under cool temperatures (15°C/5°C) that simulated early spring outdoor nursery bed conditions. Only seeds that received four-week stratification achieved complete germination at the cooler temperatures. Strong seed source variation in response to seed treatments was observed at the cool regime. The Yacolt source germinated well regardless of seed treatments, even without stratification, while five other sources needed two to four weeks of stratification to achieve above 50% germination. Possible reasons for this variation are discussed.

Underplanting conifers beneath thinned hardwood stands could shorten conversion to a more valuable crop species. Thinning the hardwoods to final crop-tree spacing could increase growth and marketable volume while releasing the site resources necessary to support conifers planted in the understory. In western Oregon, an experimental thinning of a 14-year-old red alder (Alnus rubra Bong.) stand provided an opportunity to test this concept. Initial efforts were directed toward testing survival and growth of wilding seedlings of western hemlock (Tsuga heterophylla [Raf.] Sarg.) planted in thinned and unthinned alder stands. Survival averaged 78% and 52% after the first and fifth growing seasons. Fifth-year height growth of surviving seedlings averaged from 38 to 49 cm under various thinning regimes but only 9 cm in the unthinned. Wildlife browsing and the pinning of seedlings by falling debris reduced growth and survival.

Tests were conducted to assess rootability of red alder softwood cuttings from shoots of young trees and epicormic sprouts of mature individuals. Ortets were 3 to 34 years old, and treatments with and without indole-3-butyric acid (IBA) were compared. The extent of rooting and root vigor on the cuttings varied greatly among ortets and treatments. Among nonterminal cuttings, the best overall rooting success, with and without IBA, was obtained with cuttings of the youngest ortet. Average rooting of terminal and nonterminal cuttings of one clone were 100% and 64%, respectively. Although cuttings of some trees rooted well without IBA, the IBA treatment appeared to be generally beneficial. For all nonterminal cuttings of all clones, best results (80.0%/x) were obtained with a 10-sec dip in 2,000 or 4,000 ppm IBA. Vigorous planting stock was obtained from the rooted cuttings of all clones. Using epicormic sprouts from mature trees of proven performance will presumably allow propagation of superior trees and establishment of new plantations with improved stock.

Clonal micropropagation was demonstrated as feasible on a commercial basis for several clones of five Alnus species. Approximately 60,000 ready-to-root individual shoots were multiplied in vitro on modified MS medium supplemented with 2.5–5 μM BAP. A total of 15,500 shoots from different clones were rooted in vitro on half strength MS medium including 1–5 μM IBA. They were transferred under mist conditions within a growth chamber illuminated with high pressure sodium lamps. Those conditions gave 99–100% plantlet survival after four weeks. Plantlets were then inoculated with selected Frankia sp. strains. These nodulated alder plants are under field evaluation at the Petawawa National Forestry Institute, Canadian Forestry Service in Chalk River, Ontario.