Heterosis at Allozyme Loci under Inbreeding and Crossbreeding in PINUS ATTENUATA

The dependence of heterosis at isozyme loci on inbreeding and crossbreeding was studied in 10-yr-old trees of knobcone pine (Pinus attenuata Lemm.). Heterozygosity was determined at 24 polymorphic isozyme loci and related to the rate of vegetative growth and cone production. The inbreds, created by selfpollination, had 46% of the heterozygosity of their mothers; the crossbreds, created by interpopulation crossing, had 155% of the heterozygosity of their mothers. Within the crossbreds, heterozygosity was positively correlated with trunk growth, but negatively correlated with cone production. Results in the crossbreds, however, were strongly influenced by a few individuals that showed unusually slow growth, high reproduction and low heterozygosity. Without those individuals, there was no relationship of heterozygosity to either growth or reproduction.—Within the inbreds, heterozygosity was positively correlated with both trunk growth and cone production. Each locus that was heterozygous in the mothers was calculated to mark about 3% of the genome for identity by descent in the inbred progeny; the total proportion of the genome marked was between 10 and 11%. Using these estimates to relate heterozygosity to the inbreeding coefficient (F) gave estimates of inbreeding depression per unit of F that fell within the range of published values for conifers. The strength of heterosis found among the inbreds suggests that single-locus or multilocus overdominance should be exceedingly difficult to detect in natural populations of predominantly outcrossing species.     

GENETIC PATTERNS ASSOCIATED WITH GROWTH VARIABILITY IN PONDEROSA PINE

Variability in annual growth increment in Pinus ponderosa was measured and heterozygosity level estimated in order to examine the relationship between genetic heterozygosity and phenotypic homeostasis in natural populations of a long-lived perennial plant. Pollen was collected from 190 ponderosa pine trees in the upper montane region of the Front Range in Colorado and four isozyme systems were resolved electrophoretically from these samples. Each tree was cored, aged, and each annual ring width measured. Statistics estimating within-tree variation in growth increment were then related to heterozygosity levels. The results indicated a significant positive association between level of heterozygosity and growth variability. Two speculations are offered to account for this relationship.     

Factors influencing size inequality in peatland black spruce and tamarack: evidence from post-drainage release growth

1 We used tree ring analysis to determine stem radius and thus examine size variation over time in two even-aged (approximately 40-year-old) mixed populations of black spruce and tamarack established on peatlands in a boreal forest. We also followed the response of one of these populations to improved edaphic conditions over 8 years following drainage.
2 Populations of trees in undrained areas showed a decline in size variability over time until age 20–25 years, after which size heterogeneity was relatively stable.
3 For trees in undrained areas there was a relationship between age and size for the first 20–25 years, but this relationship then broke down due to a period where relative growth rate and size were inversely related.
4 For the population of trees in the drained area, smaller trees (i.e. those that had been growing more slowly prior to drainage) showed significantly greater drainage-induced release growth, while larger trees (those growing faster prior to drainage) showed an initial reduction in growth following drainage and, overall, less release growth.
5 The response of tamarack to drainage was more dramatic than for black spruce.
6 Despite extensive variation in tree size, drainage dramatically reduced variability in growth rate among trees of each species, such that size variability in the populations declined.
7 We postulate that the heterogeneity of microsites with respect to edaphic conditions, perhaps associated with the hummock to hollow microtopographic gradient, has a major influence on growth variation, and hence size inequality, in peatland populations of black spruce and tamarack.     

Coordination between water transport capacity,biomass growth,metabolic scaling and species stature in co‐occurring shrub and tree species

The significance of xylem function and metabolic scaling theory begins from the idea that water transport is strongly coupled to growth rate. At the same time, coordination of water transport and growth seemingly should differ between plant functional types. We evaluated the relationships between water transport, growth and species stature in six species of co‐occurring trees and shrubs. Within species, a strong proportionality between plant hydraulic conductance (K), sap flow (Q) and shoot biomass growth (G) was generally supported. Across species, however, trees grew more for a given K or Q than shrubs, indicating greater growth‐based water‐use efficiency (WUE) in trees. Trees also showed slower decline in relative growth rate (RGR) than shrubs, equivalent to a steeper G by mass (M) scaling exponent in trees (0.77–0.98). The K and Q by M scaling exponents were common across all species (0.80, 0.82), suggesting that the steeper G scaling in trees reflects a size‐dependent increase in their growth‐based WUE. The common K and Q by M exponents were statistically consistent with the 0.75 of ideal scaling theory. A model based upon xylem anatomy and branching architecture consistently predicted the observed K by M scaling exponents but only when deviations from ideal symmetric branching were incorporated.     

The effects of genetic diversity,climate and defoliation events on trembling aspen growth performance across Canada

Tree genetic makeup may provide an important control of growth dynamics; however, no studies have previously attempted to evaluate its effects in natural trembling aspen stands. In this study, we examined the relative contribution of genetics (i.e. clonal diversity, observed heterozygosity) and environmental conditions (i.e. insects, climate) on aspen growth as represented by mean inter-tree correlation (RBAR), tree basal area increment (TBAI) and inter-annual growth variability (MS). We sampled 440 trees in 22 even-aged natural stands dominated by aspen along an east-west continental gradient of decreasing annual precipitation in the Canadian boreal forest. Linear and mixed-effect models tested the relationships between tree growth, genetics and environmental factors. We showed that clonal diversity and number of years with forest tent caterpillar (FTC) defoliation (N_FTC) reduced and increased the level of growth synchronicity (RBAR), respectively. Clonal diversity explained 30 % of variation in RBAR among sites. TBAI was positively influenced by high moisture conditions while N_FTC and climate explained the variation in MS among trees for each site. No genetic effect could explain either TBAI or the MS variation. Climate and N_FTC drive annual growth variability in trembling aspen at stand and subcontinental scales. Tree genetic makeup contributed to these dynamics, the annual growth dynamics of multi-clonal stands being less homogeneous than those of monoclonal stands. Maintaining diverse aspen stands may ensure a wider range of growth responses to environmental variability, which in turn may help maintain resilience of aspen stands under future climate.     

Insights into intraspecific wood density variation and its relationship to growth,height and elevation in a treeline species

• The wood economics spectrum provides a general framework for interspecific trait–trait coordination across wide environmental gradients. Whether global patterns are mirrored within species constitutes a poorly explored subject. In this study, I first determined whether wood density co‐varies together with elevation, tree growth and height at the within‐species level. Second, I determined the variation of wood density in different stem parts (trunk, branch and twigs).
• In situ trunk sapwood, trunk heartwood, branch and twig densities, in addition to stem growth rates and tree height were determined in adult trees of Nothofagus pumilio at four elevations in five locations spanning 18° of latitude. Mixed effects models were fitted to test relationships among variables.
• The variation in wood density reported in this study was narrow (ca. 0.4–0.6 g cm^?3) relative to global density variation (ca. 0.3–1.0 g cm^?3). There was no significant relationship between stem growth rates and wood density. Furthermore, the elevation gradient did not alter the wood density of any stem part. Trunk sapwood density was negatively related to tree height. Twig density was higher than branch and trunk densities. Trunk heartwood density was always significantly higher than sapwood density.
• Negative across‐species trends found in the growth–wood density relationship may not emerge as the aggregate of parallel intraspecific patterns. Actually, trees with contrasting growth rates show similar wood density values. Tree height, which is tightly related to elevation, showed a negative relationship with sapwood density.

     

Allozyme variation in populations, full-sib families and selfed lines in Betula pendula Roth

Changes in genetic variability in populations (stand origins), full-sib (FS) families and three generations of selfed lines of Betula pendula were observed based on 15 allozyme loci. Growth vigour, measured as stem volume, and its relationship with heterozygosity was studied to determine the effect of inbreeding. Pooled FS families showed a higher percentage of polymorphic loci (P) and allelic numbers per locus (A) than those of natural populations, but no difference in heterozygosity. There was no difference in allozyme variability between fast-and slow-growing family groups, and heterozygosity was not correlated with stem volume among FS families. Allozyme variability was significantly decreased in advancing generations of selfing, and the further the selfing generation, the lower the heterozygosity and the slower the growth. Observed heterozygosity after advancing generations of inbreeding was increasingly higher than expected, indicating overdominance effects or, alternatively, selection against deleterious homozygotes.     

Bayesian analysis of Douglas-fir hydraulic architecture at multiple scales

We used a Bayesian hierarchical model to analyze the variation in xylem anatomy, hydraulic properties, and the relationship between anatomy and properties within Douglas-fir trees. The hierarchical scales in our study included fertilization treatments (fertilized and unfertilized), trees within the treatments, and positions within the trees. We measured tracheid diameter, tracheid length, percent latewood, number of pits per cell, density, and specific conductivity (K _s) on seven positions in each of 16 fertilized and 16 unfertilized trees: the trunk at cambial age 52 (breast height), 25, and 5; a branch at cambial age 20 and 7; and a root at cambial age 42 and 22. Vulnerability to embolism was also measured on the oldest trunk, branch, and root positions. For any measurement, there was little variation between treatments, however, there was great variation among positions. Tracheid diameter, tracheid length, number of pits per cell, K _s, and vulnerability to embolism decreased vertically from the roots to the branches. Correlations were evident between some positions for tracheid diameter, percent earlywood, pits per cell, and vulnerability to embolism, mostly in the fertilized treatment. We found evidence for large-scale relationships (among all observations from all trees) between density and tracheid diameter, K _s and diameter, vulnerability and diameter, K _s and pits per cell, and vulnerability and pits per cell. At a smaller scale of within position, however, usually only the branches and roots maintained the relationship.     

Spatial structuring of bacterial communities within individual Ginkgo biloba trees

Plant‐associated microorganisms affect the health of their hosts in diverse ways, yet the distribution of these organisms within individual plants remains poorly understood. To address this knowledge gap, we assessed the spatial variability in bacterial community diversity and composition found on and in aboveground tissues of individual Ginkgo biloba trees. We sampled bacterial communities from > 100 locations per tree, including leaf, branch and trunk samples and used high‐throughput sequencing of the 16S rRNA gene to determine the diversity and composition of these communities. Bacterial community structure differed strongly between bark and leaf samples, with bark samples harbouring much greater bacterial diversity and a community composition distinct from leaves. Within sample types, we observed clear spatial patterns in bacterial diversity and community composition that corresponded to the samples' proximity to the exterior of the tree. The composition of the bacterial communities found on trees is highly variable, but this variability is predictable and dependent on sampling location. Moreover, this work highlights the importance of carefully considering plant spatial structure when characterizing the microbial communities associated with plants and their impacts on plant hosts.     

Climate controls act at different scales on the seasonal pattern of Quercus ilex L. stem radial increments in NE Spain

Long-term data on radial increment dynamics in Mediterranean species may identify which climatic variables are the main constraints for radial growth and at which temporal scales they act. To this end, we examined stem radial fluctuations in Quercus ilex L., the dominant evergreen oak species in the Western Mediterranean Basin, over a period of 11 years (1994–2004) at a coastal site in north-eastern Spain. We used manual band dendrometers to record girth changes in trees on north- and south-facing slopes. Annual increments measured by dendrometers showed good agreement with annual tree-ring width. North-facing trees showed a lower long-term cumulative radial increment than south-facing trees. The seasonal radial increment pattern of Q. ilex was bimodal, being characterized by a greater increase in May and a lesser, more variable increase peak in September. Both phases corresponded to warm and moist climatic conditions, whereas radial increase of stems stopped in winter and occasionally in summer. Considering the whole year, mean maximum air temperature was the main factor positively affecting radial increment of Q. ilex from short- (5 days) to- long (30 days) time scales, whereas the accumulated precipitation exerted a similar effect at longer (30 days) scales, but only on south-facing trees. In summer, all trees were positively correlated with precipitation at long-time scales (30 days); however, only stem increment of south-facing trees showed a significant relation to the temperature at short-time scales (10 days). We confirmed the dominant role of temperature as the major constraint on radial increment at short time scales, despite most previous studies were mostly biased towards precipitation effects at monthly scales.     

New method for rapidly estimating population densities of the concealed wood‐borer Monochamus alternatus (Coleoptera: Cerambycidae) in the field

To rapidly estimate pine sawyer, Monochamus alternatus Hope, population densities in forests, the vertical distributions of M. alternatus oviposition sites and larvae on infested Masson pines (Pinus massoniana Lamb.) were studied. Results showed that the number of oviposition sites on sections of trunks between 0 and 2 m above ground was significantly greater than on sections of trunk above 2 m, and the vertical distribution had a significant logarithmic relationship with trunk height. The larval number of M. alternatus on dead infested trees had a significant difference among heights of trunks. Sections on trunks at 2–4 m usually contained the largest number of M. alternatus larvae, while the number of larvae on trunks above 10 m declined significantly, as well as in the 1 m section of trunk at the base. The vertical distribution of M. alternatus larvae on dead infested pines showed a distinct parabolic relationship with trunk height. The number of oviposition sites of M. alternatus on infested Masson pine trunks revealed a significant exponential relationship with the diameter at breast height (DBH) of trees. A significant positive linear relationship also was observed between M. alternatus larval number and DBH on the host pine trees, as well as between the numbers of larvae and oviposition sites on an individual tree. The total number of larvae in an infested tree could be calculated easily using an established equation, through counting the number of oviposition sites at 3–4 m of trunk aboveground. This study developed a practical method for rapid estimation of M. alternatus populations.     

Climatic Stress during Stand Development Alters the Sign and Magnitude of Age-Related Growth Responses in a Subtropical Mountain Pine

The modification of typical age-related growth by environmental changes is poorly understood, In part because there is a lack of consensus at individual tree level regarding age-dependent growth responses to climate warming as stands develop. To increase our current understanding about how multiple drivers of environmental change can modify growth responses as trees age we used tree ring data of a mountain subtropical pine species along an altitudinal gradient covering more than 2,200 m of altitude. We applied mixed-linear models to determine how absolute and relative age-dependent growth varies depending on stand development; and to quantify the relative importance of tree age and climate on individual tree growth responses. Tree age was the most important factor for tree growth in models parameterised using data from all forest developmental stages. Contrastingly, the relationship found between tree age and growth became non-significant in models parameterised using data corresponding to mature stages. These results suggest that although absolute tree growth can continuously increase along tree size when trees reach maturity age had no effect on growth. Tree growth was strongly reduced under increased annual temperature, leading to more constant age-related growth responses. Furthermore, young trees were the most sensitive to reductions in relative growth rates, but absolute growth was strongly reduced under increased temperature in old trees. Our results help to reconcile previous contrasting findings of age-related growth responses at the individual tree level, suggesting that the sign and magnitude of age-related growth responses vary with stand development. The different responses found to climate for absolute and relative growth rates suggest that young trees are particularly vulnerable under warming climate, but reduced absolute growth in old trees could alter the species’ potential as a carbon sink in the future.     

Effects of understory dwarf bamboo on soil water and the growth of overstory trees in a dense secondary <Emphasis Type="Italic">Betula ermanii</Emphasis> forest,northern Japan

The effects of understory dwarf bamboo (Sasa kurilensis) on soil water and the growth of overstory trees were studied in a dense secondary forest of Betula ermanii in northern Japan. Four plots were established in a Betula ermanii forest with Sasa kurilensis in the understory. The Sasa was removed in two of the plots. The annual increment of the trunk diameter for each tree was measured in the first two years from the commencement of the experiment. Soil water potential was similar in the plots following significant rainfall, but was found to be greater in the plot without Sasa between rainfall events. This suggests that the removal of Sasa slows the reduction of soil water after rainfall. The relative growth rate of the trunk diameter of Betula ermanii increased with tree size in all of the plots because taller trees strongly suppressed smaller ones in the dense forest. The growth rates of Betula ermanii were higher in the plots without Sasa. However, the difference in growth rates between all of the plots tended to be smaller in smaller size classes, possibly because smaller trees were strongly suppressed by larger ones, irrespective of the presence/absence of Sasa. Therefore, the removal of Sasa increased soil water and encouraged the growth of larger Betula ermanii in dense forest during the first two years after the Sasa was removed. The present study suggests that Sasa can reduce the growth of larger Betula ermanii in dense forest by limiting available soil water to these trees.     

Isolated Trees and Grass Removal Improve Performance of Transplanted Trema micrantha (L.) Blume (Ulmaceae) Saplings in Tropical Pastures

Cattle pastures established in areas previously covered by tropical rainforest can be abandoned in unproductive and degraded conditions. Transplanting native tree species to pastures is one common practice among rainforest restoration techniques, but several environmental barriers compromise transplant success. We assessed whether the presence of isolated trees and the removal of pasture grasses affect survival, growth, and allometry of transplanted saplings of the pioneer tree Trema micrantha (L.) Blume (Ulmaceae) into abandoned pastures in southeast Mexico. An isolated tree was selected in the center of each of four pasture sites of one hectare, and grass treatments were applied under the tree's canopy (0–10 m from the trunk) and in open pasture (15–48 m from the trunk). Grass removal treatments were control (grass present), cut with machete, herbicide application, and total grass removal with a gardening hoe. After 1 year, sapling survival was not different between the canopy and pasture areas (53%). Saplings showed higher survival probability (p < 0.05) in the hoe treatment (63 ± 9%) than in the control treatment (38 ± 9%). Height and crown cover growth rates were faster under the canopy of isolated trees compared with the open pasture. Saplings showed significantly greater crown area/height ratios under the canopy of isolated trees. Stressful environmental conditions restricted sapling growth in the open pasture. We conclude that complete removal of grasses and transplanting T. micrantha saplings in the vicinity of isolated trees can improve transplant success.     

Presence and Abundance of Birds in an Atlantic Forest Reserve and Adjacent Plantation of Shade-Grown Yerba Mate,in Paraguay

In the Atlantic forest region, there is a need to develop economic activities that can be carried out in buffer zones around parks, with minimal impact on forest bird species. One such possibility is the farming of yerba mate, Ilex paraguariensis, under native trees. We compared bird speciesȁ9 presence and abundance between a forest reserve and an adjacent plantation of shade-grown yerba mate, to determine which species might use such plantations. Of the 145 species that were regularly recorded in the forest, 66%, including five globally threatened species, were also regularly recorded in the plantation. Most canopy species and tree trunk insectivores showed similar abundance in both habitats, but forest floor and understory species were absent from the plantation. Within the plantation, higher tree density did not lead to a greater abundance of forest birds. Yerba mate grown under native trees could be used to rehabilitate cleared land and allow recolonization by some Atlantic forest bird species.     

Growth and water relations of Liquidambar styraciflua L. in an urban park and plaza

Summary Growth and water relations of 10-year-old sweet gum (Liquidambar styraciflua L.) street trees were studied in sites with low and high potential evapotranspiration to determine how these differences are integrated by growth and water relations over time. The trees were located in the parking strip between the curb and sidewalk at a partially vegetated urban park and an urban plaza in Seattle, Washington. Crown size, and seasonal and diurnal stomatal conductance and water potential, as well as diurnal air temperature and humidity, were measured over 2 growing seasons. Yearly trunk growth since transplanting was measured from increment cores. Vapor pressure deficits and air temperatures averaged 18% greater at the plaza, but whole-tree water loss appeared to be much lower than the park trees due to more restricted stomatal conductance and crown size. In addition, yearly diameter increment declined progressively once the plaza trees were established in the existing soil several years after transplanting. Lower water potential in the plaza trees indicated greater internal moisture deficits than the park trees, and tissue analysis revealed lower nutritional status, particularly nitrogen. A manipulative study of water and fertilizer to several additional plaza trees showed an interaction between water and nutrient deficiencies in the coarse and shallow soil that apparently limited growth. Furthermore, soil limitations probably interacted with paved surface conditions over time by reducing nutrient recycling from leaf litter, and generating higher vapor pressure deficits that would contribute to prolonged stomatal closure. Restricted growth and water relations status of the plaza trees represented an equilibrium between chronic high-resource demand above ground and limited below ground.     

水杉原生种群结构及空间分布格局

水杉(Metasequoia glyptostroboides)是我国特有濒危极小种群物种, 其种群的状态一直被国内外学者广泛关注。分析现存水杉原生种群结构和空间分布格局及其空间关联性, 可以从空间格局角度深入认识水杉原生种群结构和分布格局及可能的形成机理。本文基于湖北利川境内水杉原生种群的野外调查数据, 分析其径级和高度级结构, 同时运用点格局分析中的成对相关函数g(r)以及3个零模型(完全空间随机模型、异质泊松模型、先决条件模型)分析水杉原生种群空间分布格局、各龄级空间分布格局及空间关联性。结果表明: (1)分布于研究区域内的水杉原生种群个体数共5,663株, 已死亡33株, 现存活5,630株, 其中40株濒临死亡, 465株处于衰弱状态, 部分个体呈现不同的形态特征和生长状况, 断梢和蚁害最为常见, 雷击是最致命的危害。(2)水杉原生种群结构分析显示, 其径级结构和高度级结构均呈纺锤型, 自然更新不良。(3)基于完全空间随机模型, 水杉原生种群在各尺度下均呈现聚集分布, 中龄树在较小尺度(r < 3,300 m)上呈现聚集分布, 成年树和老龄树在较大尺度(r < 4,700 m)上呈现聚集分布; 排除生境异质性影响后, 聚集尺度均减小, 所以种群及不同龄级的聚集尺度分别为0-3,000 m、0-2,100 m、0-2,900 m和0-2,500 m, 随后呈现为微弱的随机分布和均匀分布。(4)基于完全空间随机模型, 3个龄级之间在所有尺度均为正关联; 在排除生境异质性影响后, 不同龄级的正关联尺度减小, 均在0-2,800 m呈正关联。综上, 水杉原生种群个体数量正呈现逐步减少的趋势, 种群主要呈聚集分布, 各个龄级间具有正向的关系, 从现有的空间格局来看, 生境异质性、扩散限制和种内竞争是导致该格局的主要原因。     

Genetic diversity and seed production in Santa Lucia fir (Abies bracteata), a relict of the Miocene Broadleaved Evergreen Forest

Santa Lucia fir (Abies bracteata), is a unique fir, the sole member of the subgenus Pseudotorreya. It is a relict of the Miocene broadleaved evergreen sclerophyll forest, and is now restricted to a highly fragmented range in the Santa Lucia Mountains of central coastal California. Expected heterozygosity for 30 isozyme loci in 18 enzyme systems, averaged over six populations that spanned the species’ north–south range, was only 0.036. Despite a fragmented range and isolated populations, differentiation (F _ST) was only 0.080 for mature trees, and the number of migrants per generation (Nm) was 2.88 or 3.83, depending on the method of estimation. F _ST for embryos was lower, 0.025, and Nm correspondingly higher, 9.75. Nei’s genetic distances were small and unrelated to geographic distances between populations. The proportion of full seeds per cone was only 0.082–0.488, depending on population, which suggests a high incidence of selfing followed by embryo abortion. However, the level of accumulated inbreeding, F _IS, in mature trees was low, only 0.049. By contrast, F _IS for embryos was 0.388, which indicates a high proportion of selfed progeny, in agreement with the low seed yields. The difference in inbreeding coefficients between seed trees and their progeny suggest that most inbreds are eliminated before maturity and, therefore, seed production, already low, overestimates the true potential for regeneration of these populations. These results have implications for conservation.     

Environmental sensitivity and heterosis for egg laying in Drosophila melanogaster

Summary Genotype × temperature interactions for egg laying were studied in Drosophila melanogaster using two sets of half diallel crosses: one between inbred lines of the same geographic origin, and the other between established laboratory, newly derived inbred lines from different geographic origins. The sensitivity of most genotypes to changes in temperature was adequately described as a linear regression of mean in temperature. The regression coefficients (linear sensitivities) were heterogeneous between genotypes. Hybrids were more affected by temperature variation than were inbreds. All the heterogeneity of linear sensitivities was accounted for by a linear function of the genotypic means, which strongly suggests that a scale effect is responsible for the differences in sensitivity to temperature. In contrast, no general relationship was found between standard error deviation (sensitivity to small environmental changes) and mean performance between genotypes, although hybrids tended to be less variable than inbreds. This shows that the sensitivity to environmental variation depends not only on the genotype, but also on the nature of the environmental variation. The variability within temperatures may be affected by the general homeostasis of individual genotypes, while the variability between temperatures could be the result of genes directly affecting the trait and their multiplicative interaction with the environment.     

A method for determining knotty core sizes of standing Pinus patula trees based on tree ring sampling

The objectives of this study were to develop and assess a method of using tree ring measurements in standing pruned Pinus patula trees for modelling the knotty core of the pruned section of a tree and to assess variability in knotty core diameters in the tree stem. A total of 170 trees from 17 compartments on a wide variety of growth sites from the Mpumalanga escarpment in South Africa were selected and destructively sampled. We show that ring width measurements at breast height can be used to predict growth in the upper pruned section which in turn can be used to reconstruct the internal knotty core through the full pruned section of the log.Analysis of variation for the entire data set from ring width measurements showed that there was far greater variation in knotty core percentages (the percentage of diameter occupied by knotty core) between different compartments than within compartments. Within a tree, the knotty core percentages between three stem sections, 0.0–2.4 m, 2.4–4.8 m, and 4.8–7 m, differed significantly. As expected the knotty core percentages were found to increase from the bottom section (49.1%) to the top section (65.4%).A comparison of the actual measured knotty core size and the modeled knotty core size of a sub-sample of trees showed only a modest relationship (R² = 0.62). Reasons for this might be variability in pruning quality, inaccurate pruning records, nodal swellings, and the methodology used to measure the actual knotty core sizes.Knowledge of knotty core sizes can be used as a decision aid in the forest and forest products industry.