Stem Slenderness Research Articles

Fiber flax varieties of domestic selection under conditions of the Tomsk region

The results of the study of 20 samples of cultivated flax (Linum usitatissimum L.) of the Federal Scientific Center of Bast Crops in 2021–2023 are presented. The field studies were conducted in the sub-taiga zone of the Tomsk region. Natural and climatic conditions corresponded to the requirements of fiber flax cultivation. As a result of the conducted research, valuable and flexible source material for the creation of varieties with high productivity traits has been identified. The varieties of the Pskov selection – Antey, Voskhod, Nord, Chance, Tver (Torzhok) selection – Polet, Universal, Smolensk selection – Phoenix, Impulse and standard Pamyati Krepkova – stood out in terms of total and technical length of the stems. The total stem length reached 90 cm and above, the technical stem length was more than 80 cm. The leaders in terms of fiber content in the technical part of the stems were varieties of the Tver selection (Torzhok): Tonus, Visit, Pskov varieties – Kvartet, Orion, Peresvet – 40% and higher. The highest value for the characteristic of stem slenderness (the ratio between technical length and stem thickness) was observed in the varieties Voskhod (681.0) and Peresvet (652.6). In terms of linear stem density, the varieties differed insignificantly among themselves, with most varieties having values in the range of 5.0–6.0 mg/cm. The influence of the factor " The year of inclusion in the State Register of BA of the Russian Federation" was also studied. The factor had the greatest influence on the fiber content trait. Varieties with earlier dates of inclusion in the State Register showed low fiber yield. Russian flax varieties are recognized as promising and are included in the breeding process as male and female seed parents during hybridization.

Application of microalgae in cauliflower fertilisation

In a circular bioeconomy, balancing inorganic fertilisers and microalgae supplementation is important for ensuring sustainable agriculture. This study aimed to evaluate the fertilising effects of live microalgae (mostly Chlorella vulgaris and a mixture of Chlorophyceae and Trebouxiophyceae) on cauliflower (Brassica oleracea L. subsp. botrytis) plant morphology, yield, and quality of cauliflower heads. Microalgae fertilisation effects were analysed by employing an experimental factorial design with two factors: inorganic fertiliser and microalgae, each at high and low dosage levels, and the results revealed higher plant height, wider stem diameter, and lower stem slenderness in high-dose combinations than those in other combinations. In addition, an increase in nitrate, calcium, potassium, and sodium content was observed in the sap of cauliflower leaves in high-dose combinations compared to those in low-dose combinations. The high-dose combination also increased the yield, number of commercial heads, weight of the heads, and number of curds per head of cauliflower. Overall, the study demonstrates that increasing the dose of inorganic fertilisers and microalgae significantly increases nutrient concentration in the sap, which translates into a larger plant, an increase in the number of leaves and yield, and an improvement in the quality of cauliflower heads. These findings underscore the necessity for further research to ascertain the optimal combination of inorganic fertilisers and microalgae to maximise crop yield and cauliflower head quality.

Realised genetic gains from past Finnish silver birch seed orchards

Genetic gains realised through silver birch (Betula pendula Roth) seed orchards were studied using data from common-garden trials established at 34 sites in southern and central Finland. The test materials include seedlots representing 19 commercial seed orchards that operated between 1972 and 2009, and 21 natural stands. All the trials were assessed for several growth and quality traits between the ages of 9 and 24. Realised gains were estimated based on univariate linear mixed models with corrections for latitudinal seed transfer effects. Overall, seed orchard materials outperformed unimproved reference materials in all the traits but results for individual seed orchards varied substantially. Stem volume gains ranged from 1.0% to 31.1%. Improved trees had, on average, 6.8% (up to 26.7%) fewer ramicorn branches and 16.2% (up to 57.6%) fewer forks than unimproved trees. Branch and overall quality showed consistently positive gains. More recently established seed orchards performed better than older ones, and seed orchards with fewer clones outperformed those with dozens of clones. "JR-1" and "JR-2" bi-clonal seed orchards fared differently, with "JR-1" showing modest genetic gains and "JR-2" emerging as the top overall performer across all seed orchards. An alternative statistical concept, the D-value, was utilised to assess the magnitude of genetic gain for different scaled, normally distributed traits. Average D-values implied a similar level of improvement for stem volume, branch quality, and forking, and a smaller gain for stem slenderness and the number of ramicorn branches. The results for individual seed orchards suggest a slight trade-off between stem volume growth and branch quality.

Modeling spatial variation in radiata pine slenderness (height/diameter ratio) and vulnerability to wind damage under current and future climate in New Zealand

Wind is a significant disturbance agent in forests that is likely to become more prevalent as plantation forests are increasingly grown at high stand density to maximize yields and carbon sequestration. Although research has used models to characterize plantation wind risk at discrete sites, little research has regionally scaled these predictions under both current and future climate. Stem slenderness, or height/diameter ratio, has been found to be a useful proxy for stand stability in the widely grown species, radiata pine (Pinus radiata), which constitutes 90% of the New Zealand plantation area. Stands with a slenderness that exceed 80 m m–1 are likely to be at risk when exposed to strong winds. In this study, slenderness was derived from 4,004 radiata pine permanent growth monitoring plots, that covered the spatial distribution of the species, and matched with stand density, age and key climatic and edaphic variables derived from surfaces. Using these data, the objectives of this study were to (i) develop a model to predict slenderness using machine learning and partition the impacts of key factors on slenderness, (ii) use this model to spatially predict slenderness throughout New Zealand for three contrasting silvicultural regimes, under current and future climate, and (iii) identify any regions that may be particularly vulnerable to wind risk. The final model of slenderness developed using the random forest algorithm included, in order of importance, stand density, stand age, mean annual air temperature and total annual rainfall. Predictions made on a withheld independent dataset (n = 401) were both unbiased and accurate (R2 = 0.85). Spatial predictions of slenderness under current climate showed wide regional variation with mean slenderness at age 30 years increasing from 62.1 m m–1 for low stand density clearwood regimes to 73.5 m m–1 for medium stand density structural grade regimes and 79.5 m m–1 for high stand density carbon regimes. Mean changes in slenderness were relatively low to 2040 and 2090 within the North Island. In contrast, within the South Island there were moderate increases in slenderness for the three silvicultural regimes that were markedly higher for 2090 than 2040.

Tree-level differences in Norway spruce and Scots pine growth after extreme thinning treatments

ABSTRACT We studied tree-level dynamics (stem slenderness and growth) in spruce- and pine-dominated stands after intermediate commercial thinning of different type (low, crown normal, and crown strict) and intensity (standard and extreme), for two 5-years growth periods. Thinning treatments were included in modeling as numerical variables based on how they changed the stand- and tree-level conditions (in terms of mean diameter of remaining trees and basal area of larger trees removed). Stem slenderness significantly decreased with time for both species and all types only in the extreme intensity (excluding low thinning for pine). Regarding basal area growth, for both species it was slightly higher in low than crown thinning, and much higher in extreme intensity for all thinning types. Pine had a lower basal area growth in the second period after thinning compared with the first one. Height growth differences were not found across treatments. Concluding, extreme thinning increased individual tree basal area growth and decreased stem slenderness for both species compared with thinning carried out according to the standard guidelines. Across types, there were only small differences, hence crown thinning seems a viable option to the widely used low thinning in Fennoscandia.

Genetic Variation and the Effect of Herbicide and Fertilization Treatments on Wood Quality Traits in Loblolly Pine

Abstract The effect of silvicultural treatments (herbicide, fertilization, herbicide + fertilization) and the interactions with genetic effects were investigated for wood quality traits in a 16-year-old loblolly pine (Pinus taeda L.) genetic test established in southwest Georgia, USA. Fertilizer and herbicide treatment combinations were applied multiple times to main plots containing 25 open-pollinated families as sub plots. Significant differences among treatments were found for all traits. Squared acoustic velocity, used as a surrogate for wood stiffness, was higher in herbicide-only plots compared with other treatments. Wood density was considerably lower in fertilization plots. A large proportion of variance observed for wood quality traits was explained by additive genetic effects, with individual-tree heritabilities ranging from 0.78 (ring 7–16 section wood density) to 0.28 (ring 2–6 section wood density). Corresponding family-mean heritability values were well over 0.86. Genotype-by-treatment interactions were nonsignificant for all traits, indicating no need to match families to silvicultural treatments. Wood quality traits had weak genetic correlations with growth and stem quality traits (stem slenderness, sweep, and branch angle) with a range of −0.33 to 0.43, suggesting that recurrent selection on growth or stem quality traits would not adversely affect wood quality in loblolly pine.

Wider crown shyness between broad‐leaved tree species than between coniferous tree species in a mixed forest of Castanopsis cuspidata and Chamaecyparis obtusa

AbstractPersistent openings (gaps) between adjacent crowns at similar heights can be found in tall forests. Such openings are called “crown shyness” and are formed through the collision of tree crowns during high winds. While crown shyness has been studied in plantations, much less studied in natural forests despite its importance for light acquisition, competition, and coexistence. In this study, we focused on a mixed forest in Japan, and examined a hypothesis that broad‐leaved tree species, which often have top‐wide crowns, have wider crown shyness than coniferous tree species, which often have narrow cone‐shape crowns, because top‐wide crowns may be more exposed to wind and more likely to collide with their neighbors. Crown shyness, which was measured by drone imagery, was clearly found between individuals of the broad‐leaved tree species Castanopsis cuspidata but not between the coniferous tree species Chamaecyparis obtusa. This interspecific difference may be associated with differences in crown shape; Castanopsis had wider (1.57‐fold) and shallower (0.64‐fold) crowns than Chamaecyparis. Within Castanopsis, the size of crown shyness tended to negatively correlated with stem diameter and positively correlated with stem slenderness. Our study showed that the difference in crown shape among species is one of the key factors in determining the size of crown shyness. Top‐wide crowns of broad‐leaved trees compared to conifers may have a competitive advantage in light interception, but it may come at the cost of crown collisions with adjacent crowns and resulting in persistent openings at the canopy layer.

Structure, growth and growing space efficiency of Pinus radiata (D. Don) trees as affected by their social position

Currently, silvicultural prescriptions such as thinning monospecific stands from above and transitioning from monospecific to mixed-species stands are scrutinised regarding their ability to reduce stress and damage. That the quantity and quality of the trees harvested by intermediate and final cuts will vary depending on the chosen prescription is likely but more or less neglected so far. Here we analyse 60 Pinus radiata (D. Don) trees earmarked for removal from the Jonkershoek thinning experiment at the West Cape, South Africa. The experiment comprises both thinning from above and below allowing for comparison of the structure and growth of dominant and subdominant trees removed at 11 years old. Thinning from above removed mainly dominant trees which were on average 44.3% larger in tree diameter, only 8.5% larger in tree height, but 83% larger in crown projection area and more than 25% tapering than subdominant trees extracted by thinning from below. The courses of diameter growth over age of the dominant trees were degressively asymptotic; those of subdominant trees were S-shaped, due to competitive pressure. The volume growth was exponential in both groups. However, the dominant trees achieved 2–3 times higher stem volumes at 10 years of age. Tree structure and growth were highly correlated: the mean annual volume increment showed a Pearson correlation of r = 0.64 with crown length, r = −0.76 with the current ratio of stem slenderness, and r = −0.70 with the competition index by Hegyi. Thus, crown length, slenderness and the competition index were most relevant in explaining tree growth. The analysis of the mode of competition indicated in both groups and in total a sub-proportional increase of stem growth with increasing size. Interestingly, growing space efficiency in terms of mean annual volume growth per crown projection area was similar in both groups.

Lianas explore the forest canopy more effectively than trees under drier conditions

Abstract Lianas rely on trees for support and access to high‐light positions in the forest canopy, but the implications for how lianas explore the canopy compared to trees remain understudied. We present an in situ forest canopy study to test the hypotheses that: (1) lianas favour leaf display over stem investment compared to trees and (2) lianas have greater potential to colonize non‐shaded, high‐light areas effectively than trees. We compared branches of 16 liana species with those of 16 sympatric tree species in the canopy of two lowland tropical forests with contrasting rainfall regimes in Panama using 40–50 m tall canopy cranes. One forest was relatively dry and seasonal in rainfall and associated solar radiation. The other forest was relatively wet and had a weaker seasonality. We observed that lianas were more efficient in leaf display over stem investment than trees, particularly in the forest with lower precipitation and stronger seasonality. Specifically, lianas had a lower LMA (leaf mass per unit leaf area), stronger apical dominance, higher stem slenderness and fewer leaf layers than trees. In the forest with higher precipitation and weaker seasonality, lianas also had stronger apical control and fewer leaf layers than trees, but both lianas and trees were relatively similar in LMA and stem slenderness. Our study shows that lianas more effectively explore the canopy than trees under drier conditions, but much less so under wetter conditions. We argue that lianas display a functional strategy that allows them to better intercept light than the tree species in forests with low precipitation and strong seasonality, while they are constrained to display such strategy at high precipitation – light‐limited – sites. A free Plain Language Summary can be found within the Supporting Information of this article.

The Effects of Wind Exposure on Scots Pine Trees: Within-Stem Variability of Wood Density and Mechanical Properties

Survival in variable conditions of wind exposure depends on the strategy of trees in adapting to environmental constraints. There are many studies investigating the effect of wind on the adaptation of trees, but little attention is paid to the properties of the wood, particularly within-stem variability. In the present work, an analysis was made of within-stem variability of the density and mechanical properties of Scots pine wood from parts of stands with different wind exposure (stand edge, forest interior). The research was carried out in north-western Poland, in seven selected pine stands (without other species in the canopy) aged from 82 to 87 years. In each stand, three trial plots were marked, each at a different distance from the edge of the stand. The first plot was immediately adjacent to the edge (0–20 m), the second was at a distance of 30–50 m, and the third was at a distance of 60–80 m. Generally, wind exposure, defined by the distance from the windward edge, did not significantly affect the tree morphology and wood properties. A statistically significant difference was found only for the modulus of elasticity (MOE), between stand edge and forest interior. Trees growing at a distance from the stand edge compensate for their greater stem slenderness with higher elasticity. A certain growth response to wind loads is also represented by the within-stem variability of wood. We found that within-stem variability of wood at the stand edge is higher than in the forest interior. At various points along the stem, the wood density and strength were generally higher on the eastern radius (on the leeward side of the stem). Different wind resistance requirements at the stand edge and in the interior lead to combinations of tree architecture and wood properties that enable the best resistance to wind loads.

Performance of genetically improved Norway spruce in one-third rotation-aged progeny trials in southern Finland

ABSTRACT Growth data from 15 progeny trials were analyzed to assess realized and expected genetic gains associated with improved Norway spruce (Picea abies Karst.) stock in southern Finland. The study materials included 257 seedlots originating from 9 wild stands and 17 seed orchards. The measurement data were collected between 22 and 30 years of age. First-generation seed orchard progenies showed a clear superiority over unimproved trees with a realized genetic gain of 8.4% in height growth, 9.0% in diameter growth, and 20.6% in stem volume growth. The respective genetic gains expected from 1.5-generation seed orchards were 12.8%, 13.5% and 36.9%. Stem slenderness and survival did not differ between groups of improved and unimproved trees. The interaction between genetic groups and sites was insignificant for all the traits, suggesting overall robustness of the gains across environments. The results do not include the additional genetic gain due to genetic thinnings and thus, they are likely to underestimate the currently realizing gains from genetically thinned first-generation seed orchards. The results are suggested to be primary information for further studies needed to model growth and yield of genetically improved Norway spruce stands over a full rotation.

Where to find structural grade timber: A case study in ponderosa pine based on stand and tree level factors

Using portable acoustic tools, measurements of dynamic modulus of elasticity (Ed) were made in standing ponderosa pine (Pinus ponderosa (Dougl. ex Laws)) trees (n = 437) growing in 22 stands encompassing the range of environmental site conditions and ages of the plantations that have been established in NW Patagonia, Argentina. The objectives of this research were to (i) identify the stand and tree-level factors associated with the variation in Ed and, with the most suitable variables (ii) develop a descriptive model to Ed for ponderosa pine grown in NW Patagonia Argentina as the first step of a predictive model.Tree and stand variables showed a wide range of variation and Ed ranged ten-fold, from 2.13 GPa to 22.1 GPa, with a mean value of 11.2 Gpa. The cross-correlations analysis performed among Ed and independent tree and stand variables showed almost all variables to be significantly related to Ed. The main positive and significant correlation was found for total tree height (H, r = 0.78, p < 0.001), top height of the stand (H100, r = 0.78, p < 0.001) and basal area of the stand (G, r = 0.68, p < 0.001). Nevertheless, the most suitable independent variables for modelling Ed were two stand variables: age at breast height (ABH) and site index (SI20) and two tree variables: stem slenderness (S, tree height/diameter at breast height) and social status or relative height (RH = H/H100).In combination, ABH, SI20, S and RH accounted for 68.4% of the variation in Ed within the sample population. This model could be readily applied by managers to estimate stand-level Ed, giving them greater understanding of how they can manipulate stands to achieve desired end product outcomes.

Development of a generic model describing modulus of elasticity of Pinus radiata in Chile and New Zealand

Using three national datasets collected across Chile and New Zealand we developed a model of Modulus of Elasticity (E) for Pinus radiata D. Don to ascertain whether predictions can be generalised across countries. Data used within the model covered a wide range in E (3.1–19.0 GPa) and tree age (6–25 years). The temperature range of 8.2–15.9 °C and rainfall range of 636–3276 mm covered the variation present within plantations in both countries. A range of models were tested that varied in complexity with the simplest including only the tree dimensions (diameter (DBH), height (H) and stem slenderness (S)), to tree dimensions and stand age, and finally, for the most complex models, all of these variables as well as climatic data and stand density. Modelling approaches included general linear models, and for the models with more variables, elastic net, partial least squares and sparse partial least squares.Analyses show S to be a more precise predictor of E than either H or DBH. The most precise model of E, which had R2 of 0.82 and RMSE of 1.57 GPa, included stand age, S, air temperature and rainfall as significant predictors. This model was constructed using a linear modelling approach and predictions using more sophisticated methods were not significantly more precise. Predictions were applicable across both Chile and New Zealand as evidenced by the lack of bias, with respect to country level datasets, in the final model.

Disturbance history mediates climate change effects on subtropical forest biomass and dynamics.

The responses of forest communities to interacting anthropogenic disturbances like climate change and logging are poorly known. Subtropical forests have been heavily modified by humans and their response to climate change is poorly understood. We investigated the 9‐year change observed in a mixed conifer‐hardwood Atlantic forest mosaic that included both mature and selectively logged forest patches in subtropical South America. We used demographic monitoring data within 10 1 ha plots that were subjected to distinct management histories (plots logged until 1955, until 1987, and unlogged) to test the hypothesis that climate change affected forest structure and dynamics differentially depending on past disturbances. We determined the functional group of all species based on life‐history affinities as well as many functional traits like leaf size, specific leaf area, wood density, total height, stem slenderness, and seed size data for the 66 most abundant species. Analysis of climate data revealed that minimum temperatures and rainfall have been increasing in the last few decades of the 20th century. Floristic composition differed mainly with logging history categories, with only minor change over the nine annual census intervals. Aboveground biomass increased in all plots, but increases were higher in mature unlogged forests, which showed signs of forest growth associated with increased CO2, temperature, and rainfall/treefall gap disturbance at the same time. Logged forests showed arrested succession as indicated by reduced abundances of Pioneers and biomass‐accumulators like Large Seeded Pioneers and Araucaria, as well as reduced functional diversity. Management actions aimed at creating regeneration opportunities for long‐lived pioneers are needed to restore community functional diversity, and ecosystem services such as increased aboveground biomass accumulation. We conclude that the effects of climate drivers on the dynamics of Brazilian mixed Atlantic forests vary with land‐use legacies, and can differ importantly from the ones prevalent in better known tropical forests.

Modelling the influence of environment on juvenile modulus of elasticity in Pinus radiata grown in Chile

Measurements of modulus of elasticity (E) were taken from Pinus radiata D. Don growing at 88 sites that encompass the range of environmental conditions over which forest plantations have been established in Chile. Using this dataset the objectives of this research were to (i) identify the key determinants of E across sites and (ii) develop a robust tree level model to predict E across the environmental range over which P. radiata is grown in Chile.Variance components analysis showed variation between sites to account for almost twofold more variation in E than variation within sites. Across the studied region, mean site values of E varied widely ranging fourfold from 3.41 to 14.1GPa, with a mean of 8.52GPa. The mean within site variation at each site was 4.50GPa, ranging from 1.50 to 14.6GPa.Of the climatic and stand level variables used in analyses stem slenderness, S, (tree height/diameter at breast height) exhibited the strongest correlation with E accounting for 43% of the variance in the property. The final model of E at the site level included S and minimum air temperature during May, both of which were positively related to E. This model was extended to the tree level through inclusion of a term that accounted for the random intercept between S and E. This model accounted for 75% of the variation in the data and exhibited little apparent bias.

From seedling to sapling: tree species responses to spatial and temporal understory light heterogeneity in disturbed tropical montane forests

Difficulties in measuring small-scale light heterogeneity in forest understories is reflected in the classification of species, conventionally based on their responses to gaps or shade, rarely present in uniform conditions in space and time. Spatial and temporal heterogeneity expressed as a contrast between direct vertical light and light coming from the surroundings allows for a better assessment of the understory light environment and thus of the effect of its variation on species performance. Using repeated measures, we evaluated the effect of vertical light, contrast, and distance to the gap center on the performance of transplanted seedlings of Alnus acuminata , Cornus excelsa , Liquidambar styraciflua , Quercus laurina and Persea americana . Highlands of Chiapas between 999 and 2005 in eight plots of pine-oak forest, each one with a small gap in the middle. Illumination was evaluated with hemispherical photographs at the beginning and the end of the study. We measured stem slenderness and survival after one, two, four, and six years following transplantation. Distance had an effect on survival of Alnus and Liquidambar. Vertical light only had an effect on Liquidambar slenderness. Contrast explained slenderness of Liquidambar , Cornus and Quercus , and survival of Liquidambar , Quercus and Persea conditional on plant age. Initial light contrast predicted the final condition well, which vertical light did not. Contrast between two gradients of the same resource produced a remarkable improvement in the predictive power of light over the performance of the studied species describing the small variations of light in forest understory.

Structure of different stand layers and management optimization strategies in a Masson pine plantation in southern subtropical, China

Forest vertical structure has significant influences on a series of structural and functional properties of forest ecosystems, and is often manipulated by silvicultural practices. However, how forest structure changes with stand height has not been well understood although their occurrence is highly correlated with forest management. An across-stand analysis of forest structure was conducted to characterize the structure of different stand heights in a Masson Pine plantation in southern subtropical China. Totally 238 plots were measured. We categorized all tree individuals into four layers according to tree height: the regeneration, lower, middle and upper layers. Species composition, species richness, abundance, diversity, DBH, volume, and slenderness were quantified and compared among four different stand layers. The results showed that (1) species richness and abundance index increased firstly and then decreased with increasing stand layer. (2) Tree individuals with diameter >20 cm dominated at the upper stand layer (tree height >15.6 m). (3) Although tree individuals at the lower layer contributed substantially to forest area at both plot and stand levels, their volume was less influential than larger trees because about 12.6% of the total tree individuals at the upper layer provided 46.5% of total volume. (4) Trees with stem slenderness values smaller than 100 and DBH >20 cm were predominantly located at the upper layer. The findings suggest that the features of vertical structure were useful for designing silvicultural systems of Masson pine plantation. Future research is needed to gain a better management strategy linked with structure characteristics.

Detecting ecological groups from traits: a classification of subtropical tree species based on ecological strategies

We evaluated the frequently assumed but rarely tested hypothesis that in tropical and subtropical forests species form discontinuities along gradients in trait variation, which can be detected to classify species into ecologically meaningful and statistically defined groups. We also tested the hypothesis that the dominant conifer Araucaria angustifolia have a contrasting trait syndrome from the pool of angiosperms. Data were collected in subtropical mixed conifer-hardwood forests in southern Brazil. Eleven trait variables (relative growth rates, growth rates under favourable conditions, annual mortality rates, seed length, seed dispersal mode, wood density, maximum height, crown depth, stem slenderness, specific leaf area, and leaf blade length) were measured for 66 large tree species. The conifer Araucaria angustifolia differed significantly in most traits and vital rates from the angiosperm distributions. The Simple Structure Index criterion was used to identify the optimum number of non-hierarchical k-means groups. This index was largest for a solution with five groups. Non-hierarchical groups were more strongly related with the resource capture and height gradients than groups formed by hierarchical clustering. We propose the recognition of seven ecological species groups in the studied forests depending on growth rates, leaf size, wood density, height, stem slenderness, dispersal, and crown depth: Conifers, Palms, Pioneers, Large-seeded Pioneers, Wind-dispersed Large trees, Large shade-tolerant trees, and Small Shade-tolerant trees. The classification produced was coherent with the ecological strategies present in the community and represents a subdivision of Westoby’s leaf-height-seed plant strategy scheme.

Magnesium fertilizer, weed control and clonal effects on wood stiffness of juvenile Pinus radiata at two contrasting sites

Two field trials established at contrasting sites (Kaingaroa and Rolleston) with different silvicultural treatments [magnesium (Mg) fertilizer or plus or minus weed control (±WC)] but identical clones of Pinus radiata were measured at age 6 for tree height (Ht), diameter at breast height (DBH) and ground-line (GLD), and modulus of elasticity (MOE) of standing trees. This study was undertaken to (i) quantify the main and interactive effects of clone, site, Mg fertilizer or WC on stem slenderness and corewood MOE of juvenile radiata pine, and (ii) examine the relationships between clonal means of corewood MOE and stem slenderness from 15 selected clones.At the Kaingaroa site, clone had a significant (P<0.001) influence on stem slenderness and corewood MOE, which exhibited a 1.5-fold variation (1.48–2.33GPa). The Mg fertilizer effect on MOE was not significant. At the Rolleston site, both WC and clone had significant (P<0.001) influence on corewood MOE. Compared to −WC, +WC reduced MOE by 7%. The MOE exhibited a 1.7-fold variation (1.67–2.83GPa) among the 15 clones. Across both sites, MOE exhibited a 1.5-fold variation (1.65–2.55GPa) among the 15 clones. Overall, clonal differences in MOE were substantial and larger than the differences due to site and WC. Significant interactions were also found between clone and Mg fertilizer, clone and WC, and clone and site.This study for the first time showed the clonal means of MOE was strongly and positively correlated to clonal means of stem slenderness. This study has the important implication for forest managers that clonal material can be closely matched to site conditions and management regimes to optimise product value.

Stand variation in Pinus radiata and its relationship with allometric scaling and critical buckling height

Allometric relationships and the determination of critical buckling heights have been examined for Pinus radiata in the past. However, how they relate to more mature Pinus radiata exhibiting a wide range of stem diameters, slenderness and modulus of elasticity (E) at operationally used stand densities is largely unknown. The aim of this study was to examine the relationship between Pinus radiata stand structure variables and allometric scaling and critical buckling height. Utilizing a Pinus radiata Nelder trial with stand density and genetic breed as variables, critical buckling height was calculated whilst reduced major axis regression was used to determine scaling exponents between critical height (Hcrit), actual height (H), ground line diameter (D), slenderness (S), density-specific stiffness (E/ρ) and modulus of elasticity (E). Critical buckling height was highly responsive to decreasing diameter and increasing slenderness. Safety factors in this study were typically considerably lower than previously reported margins in other species. As density-specific stiffness scaled negatively with diameter, the exponent of 0·55 between critical height and diameter did not meet the assumed value of 0·67 under constant density-specific stiffness. E scaled positively with stem slenderness to the power of 0·78. The findings suggest that within species density-specific stiffness variation may influence critical height and the scaling exponent between critical height and diameter, which is considered so important in assumptions regarding allometric relationships.