Juvenile genetic parameter estimates for vigour,stem form,branching habit and survival in three radiata pine (<Emphasis Type="Italic">Pinus radiata</Emphasis> D.Don) progeny tests in Galicia,NW Spain

Individual and family heritabilities, as well as phenotypic and genetic correlations were estimated 2 and 3 years after plantation, in progeny tests carried out in plantations of open-pollinated Pinus radiata D.Don progeny located at three different sites in Galicia (NW Spain). The following factors were considered: survival, growth (free growth, height, diameter, volume, height/diameter ratio), form (number of branches, number of whorls, number of branches per whorl, number of branches per tree height meter, number of ramicorn branches, diameter of the thickest branch, internode length, branch angle, stem straightness, stem sinuosity, number of forks) and resistance (frost and insect resistance). Each plantation contained 50 female parents that had been selected as plus trees in genetically unimproved plantations in Galicia, as well as 6 female parents selected from the radiata pine breeding programme in the Basque Country (northern Spain) and two commercial lots of seed from Galicia, as controls. Individual heritabilities varied from low to high levels for each trait studied. Family heritabilities followed similar trends for individual heritabilities, but were of much greater magnitude. The results suggested that all traits except the number of branches per whorl and insect resistance could be expected to respond to selection based on individual performance. The less heritable traits could be improved by progeny testing. Height and diameter were strongly and positively correlated, and both traits were also correlated with the number of branches, the number of whorls and the branch diameter. The results are compared with previously published data and discussed in relation to the implications for breeding activities.     

Optimum pruning intensity for reducing crop suppression in a <Emphasis Type="Italic">Gmelina</Emphasis>–maize smallholder agroforestry system in Claveria,Philippines

On-farm trials were conducted to assess the effects of four branch pruning levels on maize grain yield, tree growth and stem shape. The experimental plots consisted of Gmelina (Gmelina arborea R.Br.) trees planted at 1 × 10 m with maize intercropped in the 10 m-wide alleys between lines of trees. Pruning levels consisted of retaining a live crown ratio of 60–70% (T ₁), 40–50% (T ₂); 30–40% (T ₃) and of 20–30% (T ₄). At the end of the experiment, the total maize grain yield was highest under the high pruning intensity (T ₄) (18.06 t ha⁻¹) and lowest under T ₁ (14.48 t ha⁻¹). Maize grain yield under the pruning regime T ₂ and T ₃ were 16.08 and 17.21 t ha⁻¹, respectively. Mean annual increment (MAI) in tree diameter was greater (5.0 cm year⁻¹) under T ₁ than those at T ₄ (4.1 cm year⁻¹). Pruning regimes T ₂ and T ₃ resulted in a MAI of 4.7 and 4.5 cm year⁻¹, respectively. Financial analysis showed that maize-tree systems under T ₄ were more profitable than under T ₁ as long as the reduction of the average dbh at harvest were not greater than 1 cm. Pruning trees intensively also generated greater returns from labour than moderate pruning, as the greater maize grain yields under T ₄ compensated for the cost of pruning and the lower timber yield. In the context of resource-poor farmers, intensive branch pruning was a practice that prolonged the period of profitable intercropping and was compatible with commercial timber production.     

Effects of pruning on radial growth and biomass increment of trees growing in homegardens of Kerala, India

To evaluate the effects of pruning on stem radial growth increment and leaf and twig biomass production, an experiment with four pruning intensities (0, 50, 75 and 90%) on ten locally important tree species (Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bombax malabarica, Bridelia crenulata, Erythrina indica, Grewia tiliifolia, Macaranga peltata, Terminalia paniculata and Xylia xylocarpa ), was carried out. The results did not support the contention that a certain level of pruning promotes stem growth in trees. Instead, all species have a level of pruning that reduces annual increment in stem diameter. In Ailanthus triphysa and Artocarpus hirsutus trees subjected to different pruning intensities showed a decline in the annual increment in stem diameter while in other species diameter increment reduced when the pruning intensity was 75% and 90%. Response to pruning in terms of biomass production also varied from species to species. In Erythrina indica, Macaranga peltata and Terminalia paniculata annual foliage and branch production in pruned trees was significantly more than that of the un-pruned trees. However, in Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa pruned trees produced comparatively more amount of foliage and branches produced annually than that by the un-pruned trees when the pruning was carried out once in 2 years. Based on these observations it is recommended that trees of Erythrina indica, Macaranga peltata and Terminalia paniculata may be pruned at 50% level annually while the trees of Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa may be pruned at the same pruning intensity once in 2 years.     

Growth of pruned eucalypt clone in an agroforestry system in southeastern Brazil

This study aimed to identify pruning intensity and frequency that can be applied to eucalypt without imposing growth reduction, in an agroforestry system in Brazil (17°36’ S and 46°42’ W). Pruning treatments included removal of 0, 1/4 and 1/3 of the live crown height (LCH) with or without the removal of some thick branches above this height (TBA), in three or four lifts, which started at 9 months. There was no effect of pruning on tree height. Diameter (dbh) and volume per tree decreased (P ≤ 0.05) only with the removal of 1/3 of the LCH + TBA, of all trees of the stand, in three lifts, up to 36 months. The Weibull diameter distribution curves showed a higher proportion of trees in the greatest diameter classes with the removal of 1/4 or 1/3 of the LCH + TBA of selected trees, in four lifts, at the age of 36 months. The time required for applying pruning to a height of 6 m did not differ among treatments (P > 0.05). Pruning up to 1/3 of the LCH + TBA of selected trees, in 4 lifts (6-month intervals) is recommended because there was a higher proportion of trees in the greatest diameter classes and the dbh at the time of the last pruning was smaller than for the other treatments, which implies in reduced knotty core. The production of trees with larger diameter and reduced knotty core may increase farmers’ income and reduce the pressure on native forests.     

The effects of early and intense pruning on light penetration,tree growth,and epicormic shoot dynamics in a young hybrid larch stand

We examined the effect of early and intense pruning on light intensity under the canopy, individual growth, diameter–height relationships, and epicormic shoot dynamics in young hybrid larch (Larix gmelinii var. japonica × L. kaempferi) to establish a new effective management method for hybrid larch plantations. The objective is to produce high-quality wood while reducing silviculture costs using a combination of low-density planting and early and intense pruning. In a young hybrid larch plantation, we pruned branches to two different heights (2 and 4 m above ground level) using a no-pruning treatment as a control. Although the growth rates were lower in the heavy pruning treatment (4 m above the ground level) than in other treatments in the year following pruning, when measured 4 years later, growth did not differ between treatments. The number of epicormic shoots increased in the year following pruning, as did the relative photosynthetic photon flux density (rPPFD). The number of epicormic shoots was also dependent on the size of individual trees. However, survival of epicormic shoots was not sufficiently high to be problematic for high-quality timber production. If branches are pruned carefully such that the rPPFD does not rise above 20%, the emergence of epicormic shoots can also be controlled. Our results indicate that early and intense pruning is an effective component of a new management system for hybrid larch plantations.     

Influence of tree shelters,irrigation and branch pruning on early field performance of micropropagated wild cherry cv. F12/1

The growth potential of micropropagated wild cherry cv. F12/1 under field conditions was assessed. Relatively short trees (19–22 cm tall) were planted in the field just seven months after transfer from tissue culture to soil. Irrigation and shelters promoted shoot heights in the first (establishment) year. If planting techniques can be developed which reduce branch production, then the cost of corrective pruning to achieve clean stems is also reduced. Shelters, but not irrigation almost totally inhibited outgrowth of branches produced in spring. Outgrowth of spring branches by unsheltered trees was strongly influenced by tree height at planting, with shorter trees producing fewer branches. In the second and third years of the trial, pruning branches from trees that had been planted in shelters, resulted in taller trees. By the end of the third year, pruned trees had smaller stem diameters than unpruned trees. These results are discussed with respect to using cv. F12/1 as a productive timber tree.     

Quantitative assessment of fungal colonization in Norway spruce after green pruning

In July and in October of 1978, 1979, 1980 five Picea abies stands in Baden-Württemberg, Germany were green-pruned up to a tree height level of c. 10 m. In 1993–94, 30 pruned trees and five control trees from each stand were harvested for investigation. The quality of pruning proved to be excellent because only few branch collar, bark injuries or too long branch stubs were detected. Based on isolations from more than 6000 wood specimens of c. 20 mm³ obtained from 175 trees, specific infection rates are given for different tree compartments. Wood decay fungi as well as important blue stain fungi were only rarely present. Tolerable discolourations were limited to the stub containing core of a few trees. Wood formed after pruning showed neither more fungal infections nor other related disadvantages compared with the respective increment from unpruned control trees. Nectria fuckeliana, proved to be the most abundant fungus in pruned trees especially in the branch stubs. Respective infection rates in and close to dry branches were compared. Bacteria could be found in the pruned branch stubs, however, they did not penetrate into the heartwood or sapwood of the stems. Both summer and autumn pruning involve only very low risk of wood deterioration. However, summer pruning shows some advantages with respect to lower infection rates by N. fuckeliana.     

Effect of wide spacing on increment and branch properties of young Norway spruce

The effects of stand density on increment and branch properties were studied in three spacing experiments of Norway spruce [Picea abies (L.) Karst.]. The stand densities ranged from 350 stems ha⁻¹, regarded as open-grown trees, up to 1,600 stems ha⁻¹, corresponding to the density recommended for forestry practice. Properties of all the branches were measured from the stem apex downwards. The study material included a total of 5,661 branches from 45 trees. Increasing stand density resulted in a decrease in radial increment as well as shorter and narrower crowns, but it had no effect on height increment. The average number of spike knots per tree was 0.87, 0.27, and 0.33 in densities of 350, 700 and 1,600 ha⁻¹, respectively. Additionally, in the widely spaced stands of 350 stems ha⁻¹, the fraction of trees having spike knots was high (over 50%). At a density of 1,600 ha⁻¹, the sample trees had somewhat less branches in a whorl compared with the more widely spaced plots. The most pronounced effect of stand density was the increase in branch diameter with decreasing stand density. At a density of 350 ha⁻¹, the maximum branch diameter of all the sample trees exceeded the diameter limit of quality class B in the European quality requirements for round wood. The results give some indication that trees subjected to severe competition would produce smaller branches per unit of crown projection area. However, the possibilities for reducing branch dimensions relative to stem and crown size through competition appear quite restricted.     

Transformation of western hemlock (Tsuga heterophylla) tree crowns by dwarf mistletoe (Arceuthobium tsugense,Viscaceae)

Dwarf mistletoes (Arceuthobium species) are arboreal, hemiparasitic plants of conifers that can change the structure and function of the tree crown. Hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) principally parasitizes western hemlock (Tsuga heterophylla) and effects 10.8% of all western hemlock trees in Oregon, USA. In this study, we climbed 16 western hemlock trees (age 97–321 years, height 33–54.7 m) across a gradient of infection (0%–100% of branches infected) and measured occurrence of all dwarf mistletoe infections, dwarf mistletoe caused deformities, foliage, branch and crown metrics, and sapwood area. We then modelled over 25 different response variables using linear and generalized linear models with three metrics of severity as explanatory variables: total infection incidence, proportion of all live branches infected, and proportion of all live, infected branches with 33 per cent or more foliage distal to infection. A strong effect of dwarf mistletoe intensification was the reduction of branch foliage and an increase in the proportional amount of foliage distal to infections, with severely infected trees having the majority of foliage distal to infections. Increasing severity led to an apparent crown compaction as crown volumes decreased and became increasingly comprised of deformities. Sapwood area was unrelated to infection severity. Branch length and diameters were unrelated to increasing infection severity despite severely infected branches supporting 1–70 infections. The most severely infected tree had 3,615 individual plants in the crown. Our results suggested that shifts in crown structure and branch deformation, foliage amount, and foliage distal to infection, reflected a likely reduction of capacity for tree growth that coincided with a hypothesized increase in resource demand by dwarf mistletoe plants as infection severity intensified.     

Biomass dynamics of Erythrina lanceolata as influenced by shoot-pruning intensity in Costa Rica

Pruning of agroforestry trees, while reducing shade of the crops, usually reduces both biomass production and nitrogen fixation. Short pruning cycles are often not sustainable on the long run, because tree production declines over subsequent pruning cycles. We compared biomass and labile carbohydrate dynamics of Erythrina lanceolata Standley (Papilionaceae) shade trees under total and partial pruning regimes in a vanilla (Vanilla planifolia L.) plantation in South-western Costa Rica. The highest biomass production was measured in the unpruned control, followed by trees with 50% of the leaf pruned every three months, while total pruning every six months resulted in the lowest biomass pruduction. In the more productive treatments, a higher proportion of the production was in branches. Because, the N content of woody branches was high, they were important for nitrogen cycling. In the partial pruning treatment more nitrogen was returned to the soil from litter and woody branches than from pruned leaf. Sugar concentrations were not different between treatments and the dynamics of non-structural carbohydrates (sugar and starch) seems to depend more on plant phenology than pruning treatment. However, the starch concentrations in the total pruning were lower than in the other treatments.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effects of groundcover management on soil properties, tree physiology, foliar chemistry and growth in a newly established Fraser fir (Abies fraseri [Pursh] Poir) plantation in Michigan, United States of America

Incorporating cover crops into Christmas tree plantations may potentially improve soil fertility, tree growth and quality and be an alternative to commercial nitrogen (N) fertilizers. However, cover crops may compete with the trees for water and other nutrients than N. This study was carried out to assess whether soil fertility, tree survival and growth could be improved by incorporating leguminous and non-leguminous cover crops into the Fraser fir (Abies fraseri) production system. Dutch white clover (Trifolium pratense), alfalfa (Medicago sativa) and perennial ryegrass (Lolium perenne) were grown in a newly established Fraser fir plantation using two cover crop management practices; no banding (NB) by growing each cover crop throughout the entire plot and banding (B) by creating a 61 cm-wide bare zone centered on the tree rows. A conventionally-managed system (CONV) was used as a control. The cover crop aboveground biomass and N content were assessed. Soil available N (NO₃ ⁻ and NH₄ ⁺) and N mineralization were measured at 0–15, 15–30 and 30–45 cm soil depths. Tree survival, growth, photochemical efficiency of photosystem II (F_v/F_m), branch water potential (Ψ_w) and foliar nutrients were also evaluated. Biomass production was as high as 13.9, 10.2 and 5.9 Mg DM ha⁻¹ year⁻¹ for clover, alfalfa and ryegrass, respectively. Cover cropping increased soil available N by 1.5- and 2.2-fold relative the CONV in the top soil layer in 2007 and 2008, respectively. Tree seedling survival and growth in the B and CONV systems were similar. In contrast, NB treatments resulted in poor seedling survival and growth relative to the B and CONV plots. Plant Ψ_w and F_v/F_m decreased significantly for A. fraseri seedlings on the NB treatments relative to their counterparts on the B and CONV plots. However, cover cropping had marginal effects on foliar nutrients. Cover cropping with banding can be an efficient strategy for maintaining productivity in Fraser fir Christmas plantations.     

Apical control of branch movements in white pine: Compression wood action

Summary The movements of branches or control stem girdled white pine (Pinus strobus L.) were analyzed using beam theory. The stresses generated in the compression wood (CW) produced bending moments to counter the added bending moments due to new branch growth. The branches on the treated trees produced additional CW after untreated trees stopped elongation and diameter growth. The intensity of the stresses in this additional CW was greater than in the other CW. Thus, branches on treated trees moved up vertically well beyond their initial orientation due to both more CW and more active CW. The branches on untreated trees all deflected downward as branch weight continued to increase after CW production stopped.     

Impacts of long-term elevation of atmospheric carbon dioxide concentration and temperature on the establishment,growth and mortality of boreal Scots pine branches

Abstract

The aim of this study was to investigate the impacts of elevated carbon dioxide (CO₂) and temperature on the establishment, growth and mortality of the branches of Scots pine (Pinus sylvestris L). In 1997, 16 young trees were individually enclosed in chambers, in eastern Finland, for a period of 5 years (1997–2001), in an environment that simulated the future climate for the region. There were four replicates of each treatment, including combinations of ambient and elevated CO₂ and temperature. Measurements were carried out on the establishment of new branches, branch diameter growth and branch mortality. Elevated temperature and elevated CO₂ had no positive effect on the number of branches that established each year or branch diameter growth. They were, instead, related to tree height growth and stem diameter growth, respectively. However, elevated CO₂ and temperature caused an increase in branch mortality.     

Impact of artificial pruning on growth and secondary shoot development of wild cherry (Prunus avium L.)

Producing high value veneer wood requires that the tree bole be branch-free. This can be accomplished by natural or artificial pruning. Since wild cherry does not self prune well, pruning artificially is the only practical option. The study analysed the effect of conventional whorl-wise pruning and selective pruning, on height growth, diameter growth and secondary shoot development of wild cherry. Four pruning treatments were applied on cherry trees in summer 2007, one group of cherries was left unpruned to serve as a control: treatment C1 (upper 5 whorls left), C2 (upper 3 whorls left), S1 (removal of branches larger than 3 cm or with an angle to the stem < 40°), S2 (removal of branches larger than 2 cm or with an angle to the stem < 40°), N (unpruned). Data showed that height growth was not affected by pruning. In contrast, diameter growth at breast height of the C2 pruned cherry was reduced by approximately 5% (SE = 2.7%) in the year of pruning (trees were pruned in July). This pruning treatment produced significant (p = 0.028) nine percent less diameter growth than the control in the second year following pruning. The diameter increment of the C1 pruned trees with five whorls left after pruning and the selective pruned cherries were only about 4% (SE = 4.0%) smaller than the control after two years. This loss was statistically not significant. Analyses showed that on selective pruned trees the survival rate of secondary shoots was significantly reduced compared to those on whorl-wise pruned trees. Significant differences in the size of the secondary shoots were only found between the C1 and S1 (p < 0.05) pruned trees. We did not find differences in the total number of secondary shoots per tree among pruning treatments. Solely from a tree growth perspective, the moderate whorl-wise pruning treatment C1 and the selective prunings were equally effective in minimizing the reduction of diameter growth and are recommended in practice. However it was found that the survival of secondary shoots was reduced on selective pruned trees although the amount of pruning work needed in selective pruning was slightly greater than conventional moderate pruning.     

Nitrogen and fine root length dynamics in a tropical agroforestry system with periodically pruned Erythrina poeppigiana

The effect of pruning all branches (complete pruning) or retaining one branch (partial pruning) on the dynamics of nitrogen cycling in aboveground biomass, nitrogen supplying power of an amended Eutric Cambisol, and fine root length, was studied in an Erythrina poeppigiana (Walp.) O.F. Cook—tomato (Lycopersicon esculentum Mill.) alley cropping practice in Turrialba, Costa Rica during 1999–2000. Over the 1 year pruning cycle, in which trees were completely or partially pruned four times, respective aboveground biomass production was 4.4 Mg or 7 Mg ha⁻¹ (2-year-old trees) and 5.5 Mg or 9 Mg ha⁻¹ (8-year-old trees); N cycled in aboveground biomass was 123 kg or 187 kg ha⁻¹ (2-year-old trees) and 160 kg or 256 kg N ha⁻¹ (8-year-old trees); mean fine root length was 489 or 821 m (2-year-old-trees), 184 or 364 m per tree (8-year-old-trees). Pruning intensity did not significantly affect net N mineralisation and net nitrification rates during the tomato-cropping season. For the tomato crop, pre-plant mean net N mineralisation rate of 2.5 mg N kg⁻¹ soil day⁻¹ was significantly lower than 16.7 or 11.6 mg N kg⁻¹ soil day⁻¹ at the end of vegetative development and flowering, respectively. Mean net nitrification rates of 3.5, and 4.3 mg N kg⁻¹ soil day⁻¹, at pre-plant and end of vegetative development, respectively, were significantly higher than 0.3 mg N kg⁻¹ soil day⁻¹ at end of flowering. In humid tropical low-input agroforestry practices that depend on organic inputs from trees for crop nutrition, retention of a branch on the pruned tree stump appears to be a good alternative to removal of all branches for reducing N losses through higher N cycling in aboveground biomass, and for conserving fine root length for higher N uptake, although it might enhance competition for associated crops.     

A model for the relationship between branch number and biomass in Pinus sylvestris crowns and the effect of crown shape and stand density on branch and stem biomass

The branch biomass of young Scots pines (Pinus sylvestris L.) was inversely related to the branch number per projected crown area giving greater branch density and smaller branch biomass for narrow crowns than for broad crowns. In particular, in dense stands the small share of branches from the total biomass of narrow‐crowned trees was emphasized. The productivity of narrow crowned trees was, however, smaller than that of trees with broad crowns. The concept of the tree ideotype has been discussed on the basis of theoretical calculations.     

华北落叶松不同修剪方式对新生枝条生长及雌花量影响

为了明确不同修枝方式对促进新生枝条生长及雌花量影响,我们对华北落叶松种子园的9个家系的母树进行不同修剪方式的树体管理试验。结果表明,疏剪、短剪及中剪形式的的侧枝修剪对新生枝条生长具有促进作用,且疏剪可促进结实。     

Impacts of Teratosphaeria leaf disease on plantation Eucalyptus globulus productivity

The effects of Teratosphaeria leaf disease (TLD) on Eucalyptus globulus are varied, and it is currently poorly understood whether infection by TLD can cause long‐term growth effects. Such information would greatly assist disease management and pruning regimes on E. globulus plantation sites, resulting in both financial and ecological benefits. Two trials were established to quantify the effects of TLD on long‐term growth. The first was a 2‐year fungicide exclusion trial that aimed to determine initial growth losses between trees treated with fungicide and untreated trees. It was found that tree growth was not affected until a threshold value of 20% damage was reached. Volume was reduced by 17% between treated and untreated trees over the course of the 2‐year trial. The second trial, a 5‐year growth study, used differentially affected adjacent stands (one infected and the other unaffected) to look at the longer term effects of more severe defoliation (44–60%) caused by an epidemic of TLD. Results recorded 5 years after the epidemic showed that trees recovered to regain normal growth trajectories after the epidemic, but growth was retarded by ca. 1.2 years for both height and diameter compared with that of the adjoining unaffected stand. As the growth of trees was not permanently reduced by the epidemic, it is concluded that the financial impacts of TLD are more likely to be associated with the loss of income resulting from extensive branch death in the lower crown after leaf and stem infection, which makes the affected stands not suitable for pruning and hence prevents them from being managed as a higher value solid wood crop.     

Crown architecture of Abies balsamea from four canopy positions

Data collected from four distinct canopy positions from each of 39 Abies balsamea (L.) Miller trees were used to construct models to describe the cumulative leaf area distribution within the crown and to predict the needle mass of individual branches, the average branch angle, branch diameter, branch length, and crown radius per whorl, and the average number of living branches per whorl. We tested the hypotheses that regression models are equal among canopy positions and that a model to predict branch needle mass is valid at the northern and southern extremes of the central climatic zone of Maine. Canopy position had an effect on the models constructed to predict needle mass, branch angle, branch diameter, branch length, crown radius, and the number of living branches per whorl. However, compared with an expanded model that incorporated parameters calculated for each crown class, there was only a small loss in model precision when a general model constructed from data pooled from all crown classes was used to predict needle mass, branch angle, and branch diameter. Regression equations unique to each crown class were needed to predict crown shape and leaf area distribution in the crown satisfactorily. Our branch needle mass model, which was constructed from data collected at the southern extreme of the central climatic zone of Maine, consistently underestimated needle branch mass when applied to the northern extreme of the central climatic zone.     

Effect of wide spacing on tree growth, branch and sapwood properties of young Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in south-western Germany

The influence of stand density on Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is conceptually understood, but for wide spacings not well quantified, particularly in Europe. This study used 41 trees from 7 different locations in south-western Germany to compare important tree- and branch-level attributes across three different densities, namely 100, 200, and 1,200 stems ha⁻¹. In general, there were only a few tree and branch attributes that were significantly different between the 100 and 200 ha⁻¹ densities. Crown projection area and diameter of the thickest branches were the most important differences between the 100 and 200 ha⁻¹ densities. The most obvious and significant differences in this study were between 100 and 1,200 ha⁻¹ densities, where nearly every examined tree and branch attributes were statistically significant. However, relative sapwood area, the number of branches, branch angle, and the occurrence of spike knots were insensitive to stand density. Although the two lowest stand densities in this study represent rather extremely wide spacings, these results still have important implications for the development of effective thinning regimes for Douglas-fir in south-western Germany. Important management recommendations from this study include thinned stands should be maintained to at least 200 stems ha⁻¹ to maintain high log quality and stand stability. Furthermore, even at stand densities exceeding more than 1,200 trees ha⁻¹ planted trees, artificial pruning may even be necessary to produce high quality logs.