GENETIC VARIATION IN WOOD MECHANICAL PROPERTIES OF CALYCOPHYLLUM SPRUCEANUM AT AN EARLY AGE IN THE PERUVIAN AMAZON Carmen Sotelo Montes Ph.D. Candidate Jean Beaulieu Senior Scientist Natural Resources Canada, Canadian Forest Service, Canadian Wood Fibre Centre 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy Québec (Quebec) Canada, G1V 4C7 and Roger E. Hernández† Professor Centre de recherche sur le bois Département des sciences du bois et de la forêt Université Laval Québec (Quebec) Canada, GIK 7P4 (Received February 2007) ABSTRACT Calycophyllum spruceanum (Benth.) Hook. f. ex Shum. is an important timber species of the Peruvian Amazon Basin. Due to overexploitation in natural populations, users are turning to young trees of potentially lower quality. Therefore, variation in juvenile wood properties should be investigated to determine whether wood quality can be maintained or, if necessary, improved by breeding. A provenance/ progeny test was established to evaluate genetic variation in growth and wood properties of young trees, the strength of their genetic control, as well as their interrelationships both at the genetic and phenotypic ␴ levels. This paper presents results obtained for ultimate crushing strength ( L), the static compliance coefficient (s11) in longitudinal compression, the dynamic s11 in the longitudinal direction (determined by ultrasound), and air-dry density at 39 months. Results indicate that the mechanical properties of juvenile wood of this species are adequate for structural uses. There was significant variation in all wood properties due to families within provenances, and in all but dynamic s11 due to provenances. Families accounted for a larger percentage of the total phenotypic variance than provenances. Heritability estimates were higher ␴ for L and static s11 than for dynamic s11 and density. Genetic correlations indicate that selecting trees with denser wood and/or faster growth would have a positive effect on some mechanical properties. A non-destructive ultrasonic method appeared suitable for estimating juvenile wood strength and stiffness of this species. Keywords: Provenance, family, environment, heritability, phenotypic and genetic correlations, juvenile wood. INTRODUCTION under these conditions usually have a higher portion of juvenile wood compared with trees in Plantation forestry is an attractive manage- natural stands, and this can affect wood proper- ment option in the tropics given the high growth ties (Zobel and Sprague 1998; Bowyer et al. rates normally observed. However, trees grown 2003; Saranpää 2003). Understanding this varia- † Member of SWST. tion and the factors involved is essential to main- Wood and Fiber Science, 39(4), 2007, pp. 578 – 590 © 2007 by the Society of Wood Science and Technology Sotelo Montes et al.—VARIATION IN MECHANICAL PROPERTIES OF CALYCOPHYLLUM SPRUCEANUM 579 tain or, if required, improve wood properties for populations, without considering management specific uses (Tsoumis 1991). There has been plans that would ensure that the genetic quality is relatively little research on genetic variation in maintained for subsequent generations. As a re- wood properties of juvenile wood, their herita- sult, users are becoming dependent on young bility, their correlation with tree growth, and trees, which may have lower genetic quality for their impact on end-use products (Zobel and timber. In response to this problem, efforts have Sprague 1998). This research is essential to de- been made to set up seed orchards to produce sign tree improvement programs that provide high-quality seed for the establishment of small- high-quality seed for plantation forestry in the scale forestry/agroforestry plantations in farm- tropics (Simons et al. 1994). ing communities (Weber et al. 2001). Strength and stiffness are important mechani- A provenance/progeny test of C. spruceanum cal properties that determine the wood’s suitabil- was established in the Peruvian Amazon Basin, ity for structural uses (Jozsa and Middleton and results evaluated at 39 months indicated that 1994). Wood density is usually a good predictor there was significant variation in tree growth and of strength and stiffness (Panshin and de Zeeuw wood density due to provenances and families 1980), but these properties can be influenced by within provenances. Wood density had a higher other factors, including the variability among heritability than growth, and these variables trees within species and environmental condi- were positively correlated at the genetic and tions that affect tree growth (Tsoumis 1991). phenotypic levels (Sotelo Montes et al. 2006). Destructive methods are usually used to evaluate This paper presents additional results from the mechanical properties. However, a large number same provenance/progeny test. The main objec- of living trees need to be evaluated using non- tives were to (a) determine the relative magni- destructive methods in order to create breeding tude of variation in juvenile wood mechanical ␴ or production populations with trees possessing properties (ultimate crushing strength, L, and the best attributes. Non-destructive acoustical static and dynamic parallel compliance coeffi- methods have been developed to evaluate wood cients, s11) due to provenances and families properties (Herzig 1991; Bucur 2005), and sev- within provenances, (b) evaluate the heritability eral researchers have used these methods suc- of the mechanical properties, (c) evaluate the cessfully (Kyokong and Bello 1977; Hernández phenotypic and genetic correlations among tree et al. 1998; Oliveira et al. 2002; Ilic 2003). growth, wood density, and mechanical proper- Calycophyllum spruceanum (Bentham) ties, and (d) evaluate the usefulness of non- Hooker f. ex Shumann (Rubiaceae family), destructive methods for predicting crushing known as capirona in Peru, is an important hard- strength and static stiffness. Results are com- wood species for farming communities in the pared with those of other species, and some Peruvian Amazon (Sotelo Montes and Weber practical implications are discussed. 1997). Its dense, diffuse-porous wood (Keenan and Tejada 1984) is mainly used for construction poles, charcoal, and firewood, but there is also MATERIALS AND METHODS demand in national and international markets for Sample region, study area, experimental furniture, wall paneling, and parquet floors (To- design, and management of the ledo and Rincón 1996). Capirona is a pioneer provenance/progeny test species that colonizes the floodplain and dis- turbed forests in the Amazon of Peru, Brazil, The sample region and provenance/progeny Ecuador, and Colombia (Linares et al. 1992). test are located in the Aguaytía watershed of the Trees can attain heights of 35 m and stem diam- western Peruvian Amazon (Fig. 1). Open- eters of 1.8 m at breast height (Sears 2003). In pollinated seeds were collected on 200 selected Peru, farmers and industry have been harvesting mother trees of Calycophyllum spruceanum the best canopy-level trees in accessible natural growing in natural stands located in seven geo- 580 WOOD AND FIBER SCIENCE, OCTOBER 2007, V. 39(4) FIG. 1. Geographic location of the sample region and study area in the Aguaytía watershed of the Peruvian Amazon. Inset shows the location of the seven provenances of Calycophyllum spruceanum and the three planting zones (bold ellipses). graphic locations (provenances) distributed in on each site. Dead trees were replaced during the the lower, middle, and upper parts of the water- first dry season, but data collected on replants shed. Seeds collected from the same mother tree were not included in the analyses. Although are referred to as a family because they share the each replication was established on a relatively same maternal parent. The test was established homogenous site, the size of the replication with on sites with upland, non-alluvial soils. In gen- border rows was relatively large (∼0.3 ha), and eral, soil fertility and mean annual rainfall in- this could have resulted in fairly large microen- crease from the lower to the upper parts of the vironmental differences within replications. watershed. Details about the distribution of C. Management practices included a cover crop, spruceanum in the sample region, sampling pro- fertilizer application, branch pruning, and cedures, tree selection criteria, and the climate manual weeding (Sotelo Montes et al. 2006). and soils in the sample region and study area are One tree in each experimental plot was selec- given elsewhere (Sotelo Montes et al. 2006). tively thinned 39 months after planting, based on The experimental design was a randomized tree form (primarily stem bifurcations in the complete block with 15 replications: five repli- canopy) and growth. cations were established on different farms in each of the lower, middle, and upper parts of the Traits measured in the provenance/ watershed (hereafter called planting zones). In progeny test each replication, each of the 200 families was randomly assigned to one of 200 experimental Measurements of mechanical properties were plots, with two trees per plot. Spacing was 2.5 made on the thinned trees of only six of the by 2.5 m within and between rows. Two rows of fifteen replications: three each in the middle and border trees surrounded the experimental design upper zones of the watershed. The other nine Sotelo Montes et al.—VARIATION IN MECHANICAL PROPERTIES OF CALYCOPHYLLUM SPRUCEANUM 581 replications (two each in the middle and upper sections of the sticks were 2.5 × 2.5