Tree Height Diversity Research Articles

Do birds see the forest for the trees? Scale-dependent effects of tree diversity on avian predation of artificial larvae.

The enemies hypothesis states that reduced insect herbivory in mixed-species stands can be attributed to more effective top-down control by predators with increasing plant diversity. Although evidence for this mechanism exists for invertebrate predators, studies on avian predation are comparatively rare and have not explicitly tested the effects of diversity at different spatial scales, even though heterogeneity at macro- and micro-scales can influence bird foraging selection. We studied bird predation in an established forest diversity experiment in SW Finland, using artificial larvae installed on birch, alder and pine trees. Effects of tree species diversity and densities on bird predation were tested at two different scales: between plots and within the neighbourhood around focal trees. At the neighbourhood scale, birds preferentially foraged on focal trees surrounded by a higher diversity of neighbours. However, predation rates did not increase with tree species richness at the plot level and were instead negatively affected by tree height variation within the plot. The highest probability of predation was observed on pine, and rates of predation increased with the density of pine regardless of scale. Strong tree species preferences observed may be due to a combination of innate bird species preferences and opportunistic foraging on profitable-looking artificial prey. This study therefore finds partial support for the enemies hypothesis and highlights the importance of spatial scale and focal tree species in modifying trophic interactions between avian predators and insect herbivores in forest ecosystems.

Sub-footprint analysis to uncover tree height variation using ICESat/GLAS

Detailed forest height data are an indispensable prerequisite for many forestry and earth science applications. Existing research of using Geoscience Laser Altimeter System (GLAS) data mainly focuses on deriving average or maximum tree heights within a GLAS footprint, i.e. an ellipse with a diameter of 65m. However, in most forests, it is likely that the tree heights within such ellipse are heterogeneous. Therefore, it is desired to uncover detailed tree height variation within a GLAS footprint. To the best of our knowledge, no such methods have been reported as of now. In this study, we aim to characterize tree heights’ variation within a GLAS footprint as different layers, each of which corresponds to trees with similar heights. As such, we developed a new method that embraces two steps: first, a refined Levenberg–Marquardt (LM) algorithm is proposed to decompose raw GLAS waveform into multiple Gaussian signals, within which it is hypothesized that each vegetation signal corresponds to a particular tree height layer. Second, for each layer, three parameters were first defined: Canopy Top Height (CTH), Crown Length (CL), and Cover Proportion (CP). Then we extracted the three parameters from each Gaussian signal through a defined model. In order to test our developed method, we set up a study site in Ejina, China where the dominant specie is Populus euphratica. Both simulated and field tree height data were adopted. With regard to the simulation data, results presented a very high agreement for the three predefined parameters between our results and simulation data. When our methods were applied to the field data, the respective R2 become 0.78 (CTH), CL (R2=0.76), CP (R2=0.74). Overall, our studies revealed that large footprint GLAS waveform data have the potentials for obtaining detailed forest height variation.

Sub-Compartment Variation in Tree Height, Stem Diameter and Stocking in a Pinus radiata D. Don Plantation Examined Using Airborne LiDAR Data

Better information regarding the spatial variability of height, Diameter at Breast Height (DBH) and stocking could improve inventory estimates at the operational Planning Unit since these parameters are used extensively in allometric equations, including stem volume, biomass and carbon calculations. In this study, the influence of stand stocking on height and DBH of two even aged radiata pine (Pinus radiata D. Don) stands were investigated using airborne Light Detection and Ranging (LiDAR) data at a study site in New South Wales, Australia. Both stands were characterized by irregular stocking due to patchy establishment and self-thinning in the absence of any silvicultural thinning events. For the purpose of this study, a total of 34 plots from a 34 year old site and 43 plots from a nine year old site were established, from which a total of 447 trees were sampled. Within these plots, DBH and height measurements were measured and their relationships with stocking were evaluated. LiDAR was used for height estimation as well as stem counts in fixed plots (stocking). The results showed a significant relationship between stem DBH and stocking. At both locations, trees with larger diameters were found on lower stocking sites. Height values were also significantly correlated with stocking, with taller trees associated with high stocking. These results were further verified of additional tree samples, with independent field surveys for DBH and LiDAR-derived metrics for height analysis. This study confirmed the relationship between P. radiata tree heights and stem diameter with stocking and demonstrated the capacity of LiDAR to capture sub-compartment variation in these tree-level attributes.

Do wide crowns in arid woodland trees reflect hydraulic limitation and reduction of self-shading?

In arid regions many tree species develop broad crowns. A number of hypotheses involve trade-offs between growth in height and horizontal spreading, but there is no explanation for the switch from vertical to horizontal growth during development. Using Acacia papyrocarpa Benth as a model, we measured tree height and crown shape across different sites and topographic positions. We also measured δ13C of phyllodes from crown tops and lateral spreading branches. Trees were significantly taller at the base of a hill, where water availability is typically greater, than on the adjacent steep hillslope. In contrast, δ13C from the treetops was not significantly different across this topographic gradient, despite variation in tree height. In addition, δ13C was higher at treetops than in lower, lateral branches. These observations are consistent with hydraulic limitation to tree height. The shape of mature and young crowns in open environments was not symmetrical. At all sites, branches were shortest, but tree crowns tallest, on south-facing (i.e. shadiest) aspect of crowns. This suggests that light limitation may also affect crown development. If upper branches become water-limited and lower branches light-limited, then middle lateral branches become the less-stressed part of the crown and may grow more, producing a broad crown.

Modelling tree size diversity from airborne laser scanning using canopy height models with image texture measures

The aim of this study is to investigate the relationships between the plot-level tree size diversity and variables derived from airborne laser scanning (ALS) data, which is a type of LiDAR measurement. We conducted a study using forest stands with a range of managed and near-natural stands with a broad range of species. 33 Plots that represent the forest stand variety in the study area were sampled; within each plot four biophysical variables were measured by ground-based methods, these were height (TH), diameter at breast height (DBH), crown length (CL), and crown width (CW). The resultant tree size diversity was parameterised as Lmoments (t) statistics and compared with both point-based and grid-based laser scanning diversity variables. Point-based measures included the ratios of the Percentile means (P99/P25, P99/P50, P99/75, and P99/P90), Coefficient of variation, Skewness, Kurtosis, and Lmoments (t). The grid-based texture measures derived from the ALS Canopy Height Models (CHMs) included first-order texture, Standard Deviation of Grey Levels (SDGL), and three second-order texture measures, including Contrast, Entropy and Correlation. Furthermore, we tested the influence of scale by analysing the effect of grid cell sizes when generating CHMs from the raw point cloud ALS data. Using linear regression analysis, we show that the grid-based texture measures are superior predictors of tree height diversity than the point-based metrics. Sixty percent of the variance in the tree height diversity and 51% of the variance in the DBH Diversity were explained by the SDGL and Correlation texture measures, respectively (p<0.01). The associations between the texture features and the CL Diversity and CW Diversity were weaker compared to the TH Diversity and DBH Diversity (The highest R2 was 0.46 and 0.45, respectively, p<0.01). While the CHM calculated from a 3×3m grid cell had the strongest correlation with TH Diversity (0.60, p<0.01), the CHMs calculated from 1×1m and 2×2m cell size had the strongest association with DBH Diversity (0.51, p<0.01). Combining selected point- and grid-based variables accounted for up to 85% of the variance of tree height diversity, 68% of the variance of DBH Diversity and 52% of the variance of CL Diversity. Our study shows that the combination of laser-based height percentile ratios and texture measures derived from the ALS–CHM can be used to estimate tree size diversity across forest landscapes.

Estimation of shielding failure number of transmission lines for different trace configurations using leader progression analysis

The electrogeometric model (EGM) is a technique used for analyzing the termination of lightning flashes on transmission lines and masts, etc. When using the EGM for modeling the lightning stroke to transmission lines, the power line has normally been represented by a set of horizontal wire and both the sag of the wire, the existence of the towers and effect of uneven way have been ignored. This approach has serious short comings including inability to determine the percentage of the strokes terminating on the towers, failure to correctly predict the effect of height, and giving an approximate value for the number of collected strokes. This paper presents the development of a method for estimating the shielding failure number of power transmission lines in different trace configurations by using the charge simulation method. The effects of towers, sags of conductors, and a perfectly conducting ground are represented in 3-D computation. In addition, the stepwise descending nature of a downward negative leader–streamer systems taken into account by using an appropriate progression model. Upward leader inception and propagation is also modeled utilizing critical equivalent streamer-length criterion. The method is applied to compute the shielding failure of power transmission line for different trace configurations. In this paper the 3-D method is extended by modeling the effect of sloppy trace, trees on both and one side of the transmission line with extensive simulation results. Also, in this paper the effect of variation of tree height, its distance from transmission line and the number of trees on SFN are analyzed and results are shown in curves.

Improvement in accuracy of aboveground biomass estimation in Eucalyptus nitens plantations: Effect of bole sampling intensity and explanatory variables

Two sets of aboveground biomass equations were fitted for stem only and stem plus crown predictive variables in Eucalyptus nitens plantations in Northern Spain. A sample of 40 trees was chosen after a complete study of variation in tree height and diameter in the region. The trees were felled and the biomass was divided into the following components: wood, bark, thick branches, thin branches, twigs, leaves and dead branches along the stem. Bole biomass was estimated by systematic subsampling of one 5 cm-thick disk every 0.5 m. Such intensive subsampling enabled determination of the effect of subsampling intensity on accuracy and bias of wood estimation, considering two ratio-type estimators: stem weight to dry matter, determined by the complete weighing (CW) method (i.e. of the fresh weight of the entire stem) and volume to dry matter, determined by the partial weighing (PW) method. The changes in moisture content and basic density along the stem explained the serious risk of dry mass or weight overestimation when a systematic subsample is considered. The average basic density was usually found at a relative height of 30–35% along the stem. The default choice of the bottom disk or log as the first section resulted in overestimations for the CW method and underestimations for the PW one. The biomass equations were fitted by seemingly unrelated regression, with corrections for heteroscedasticity carried out by weighted fitting. Diameter at breast height was the best explanatory variable, and the inclusion of height did not improve the accuracy, except for wood. The inclusion of crown variables improved the predictive ability for crown fractions, increasing the accuracy for estimating thick branches (by 10.8%), twigs (by 19.1%) and leaves (by 17.3%). The biomass of each fraction decreased in the following order: wood > bark > thick branches > dead branches along the stem > leaves > thin branches > twigs. The changes in these percentages with diameter class and the predictive ability of the fitted equations were also studied.

Phytostabilisation of arsenical gold mine tailings using four Eucalyptus species: Growth, arsenic uptake and availability after five years

Arsenic (As) contamination is a worldwide problem. Where arsenic is highly concentrated and confined within a limited area, such as in many mine tailings facilities, phytostabilisation is an attractive technology for long-term remediation. Important characteristics of a plant to be useful for phytostabilisation include As tolerance and low levels of As accumulation, as well as the ability to limit As availability. Performance needs to be monitored over the long term to ensure an ongoing vegetation community, though this is rarely done. In this study, the suitability of four Eucalyptus species ( E. cladocalyx, E. melliodora, E. polybractea, E. viridis) for the phytostabilisation of arsenical, sulphidic gold mine tailings was assessed after five years. All four species accumulated low As concentrations, the highest being recorded in mature leaves, ranging from 0.29 to 5.14 μg g − 1 As. E. polybractea had significantly higher foliar As than the other three species but there was also great variation within the species. Between 5–10 times lower concentrations were recorded in stem samples and no As was detected in young leaf tips. There was also significant variation in the growth of trees upon the site. Eucalyptus cladocalyx grew significantly taller than other species although greater variation was detected within the species than between. The variation in tree heights was not correlated with As concentrations in either stems or leaves. Arsenic availability was determined to depths of 2.2 m and found to be low when compared to total As in the tailings. Importantly, no effect of trees on As availability or soil pH was detected. We conclude that E. cladocalyx, in particular is an ideal candidate for the long-term phytostabilisation of As-contaminated land and mine tailings. The variation detected in both As accumulation and growth is also promising for the selection of desirable traits.

Determination of soil-related factors controlling initial mangrove (Rhizophora apiculata BL.) growth in an abandoned shrimp pond

To elucidate factors contributing to plant growth in a mangrove plantation, the height of mangrove trees (Rhizophora apiculata BL.) was measured in addition to relative ground level and soil properties in an abandoned shrimp pond in Thailand. Tree height was measured at 1,853 points in the 25 ha experimental site. Soil was sampled from 74 points and physical (hardness, water content) and chemical (e.g. total C and N) properties were determined. The mean tree height of 58.3 cm was relatively small for 2-year-old trees, and varied considerably with a coefficient of variation of 32.4%. The relatively low total C content of the soil, 0.68 × 10−2 kg kg−1, indicated a decline in organic matter content during the conversion from mangrove into shrimp pond. The negative correlation of tree height with relative ground level (P < 0.01) suggested that better growth was observed at a lower area. The important role of soil properties in determining tree height was demonstrated. By combining geostatistics with multivariate analysis, as much as 90% of the spatially structured or non-random variation of tree height was explained by taking into account soil properties in addition to topography. Together, the results suggest that site-specific management, such as site-specific organic matter application, is a feasible and effective option for mangrove rehabilitation.

HeightߝDiameter Equations for 12 Upland Species in the Missouri Ozark Highlands

Abstract We calibrated a model predicting total tree height as a function of tree diameter for nine tree species common to the Missouri Ozarks. Model coefficients were derived from nearly 10,000 observed trees. The calibrated model did a good job predicting the mean heightߝdiameter trend for each species (pseudo-R2 values ranged from 0.56 to 0.88), but for a given tree diameter observed tree heights were highly variable. We also present a technique for incorporating the observed variation in tree heights in the predicted values.

Effects of extractive disturbance on bird assemblages, vegetation structure and floristics in tropical scrub forest, Sariska Tiger Reserve, India

A study was carried out in a tropical scrub forest in India, to investigate the effects of extractive activities such as fodder and firewood collection, on native bird communities and to study the relative influences of altered vegetation composition and structure. The study was based on comparison between six ‘disturbed’ (extracted) and four ‘undisturbed’ (non-extracted) sites that were delineated using quantitative disturbance indicators. Birds were sampled seven times over two different seasons utilising the fixed radius point count method. Six different variables related to vegetation structure (canopy cover, basal area, average forest height, tree density, tree height diversity and tree species richness) were quantified, as was tree species composition. There was no significant difference in number of recorded species or bird abundance between disturbed and undisturbed sites. However, bird species diversity was significantly lower in disturbed sites in comparison to undisturbed sites. Overall, bird species composition also differed significantly between disturbed and undisturbed sites. Nine of 38 locally abundant bird species (23.6%) showed significant selection for either disturbed or undisturbed habitats. Of these nine species, seven chose undisturbed habitats and two chose disturbed. All seven species adversely affected by disturbance are primarily insectivorous. Canopy cover, tree basal area and height of trees were significantly lower in disturbed sites in comparison to undisturbed sites. In both habitats, bird species composition was significantly dependent on these components of altered vegetation structure. Tree species composition was also significantly altered by disturbance in scrub forest. However, altered tree species composition did not significantly affect bird species composition. Partial Mantel's tests confirmed that there were no significant residual effects of tree species composition on bird composition after the effects of vegetation structure were accounted for. Our study indicates that rural biomass extraction can have significant effects upon bird species composition of tropical scrub forest which is caused principally by alteration of vegetation structure, rather than by changes in forest tree composition.

Growth Intercept Methods for Predicting Site Index in White Pine Plantations in the Glaciated Areas of Ohio

Abstract Growth intercept (GI) techniques were evaluated for estimating site quality in white pine stands planted on old-field sites in the Wisconsin-aged glaciated areas of northern and western Ohio. Correlations between growth of trees below the breast high (bh) annual growth increment andheight growth from bh and above were not statistically significant. Site index estimates were made using age at bh and height from the bh annual growth increment to the growing tip. Three-year and 5-year growth beginning 3 years above the bh annual increment and 10-year growth beginning oneinternode above bh were significantly more correlated with height than were intercepts beginning at bh. In multiple regression equations developed for predicting site index, 3-, 5- and 10-year intercepts, along with age at bh, accounted for 76, 77, and 80%, respectively, of the variationin tree heights and 35-year site indices varied from 60 to 83 ft. Combining clay content of the B2 soil horizon with GI and age increased the variation accounted for by 3-, 5-, and 10-year GI equations to 79, 78, and 81%, respectively, and the improvement in site index estimatesover those using GIs alone was not more than ±2 ft within any given GI measurement.

Effects of light and microsite conditions on tree size of 6-year-old Cryptomeria japonica planted in a group selection opening

We examined the extent to which direct and indirect measures of light and microsite conditions could explain variation in tree height and diameter at the base of 6-year-old Cryptomeria japonica trees planted in a group selection opening of about 0.32 ha on a steep slope at Shiiba, Miyazaki Prefecture, southern Japan. We first used the gap light index (GLI) and soil thickness (ST) as directly measured indices. For an indirect measure of light, we used a between-cohort competition index (BCI) estimated from the position and total height of residual trees. For indirect measures of microsite, we examined topographic indices (slope, plan and profile curvature, average slope gradient, and relative elevation) derived from digital elevation models (DEMs) with different resolutions ranging from 2 to 10m. The multiple linear regression using GLI and ST explained about 45% of variation in tree size, while simple regression using only GLI explained about 35%. The contribution of ST was about half of GLI. The multiple regressions using BCI and the topographic indices did not explain any more variation than using BCI alone (R2 of about 0.26). We conclude that microsite conditions with shallower soil and steeper slope have negative effects on tree growth in group selection openings, although the relative importance is smaller than light conditions. More comprehensive studies considering several openings with more heterogeneous topography including different species are needed to generalize our growth prediction using the indirect measures, which are useful for practical forest management.

Growth potential of Gmelina arborea at 3 years of age in Colombia

Smurfit Carton de Colombia, a pulp and paper company based in Cali, established six genetic and growth and yield trials of Gmelina arborea (gmelina) in the North and Southwest Regions of Colombia. The objective of the trials was to evaluate the potential productivity of gmelina as a source of raw material for corrugated medium. The trials were evaluated at age 3 years for survival, height and total volume (over bark). Variation in tree height and volume among the six sites were the result of differences in soil texture (a surrogate for water holding capacity) and natural soil drainage, which are the main soil characteristics that affect gmelina productivity. The most productive plots (Lote 80, 37.0 m3/ha/yr and La Estancia, 31.6 m3/ha/yr) were those with loamy–clay or clay textures on well-drained sites that received between 1000 and 1300 mm of rainfall per year. The least productive site (Vanessa, 15.5 m3/ha/yr) was one with a clay texture that was poorly drained and received more than 2000 mm of annual precipitation.

Stand characteristics in colour-infrared aerial photographs as indicators of epiphytic lichens

Information about forest biodiversity has so far been collected mostly by using field inventories, but it is desirable to find other methods that can cover large areas at a lower cost. In a forest landscape covering 2000 ha in southern Sweden we tested if colour-infrared (CIR) aerial photographs on the scale of 1:30000 can be used to interpret forest stand characteristics correlated to the occurrence of epiphytic lichens that are Red-listed or otherwise indicate high nature conservation value ('signal species'). Using logistic regression we found that the interpreted stand variables tree height and crown structure class were significantly correlated to the occurrence of Red-listed species. For signal species, the variables tree height, percentage of southern deciduous trees and crown structure class were significantly correlated to the occurrence. The logistic regression models successfully predicted a significantly higher probability to find Red-listed species in the stands that actually contained such species compared to stands without Red-listed species. The same was true for stands with signal species. We conclude that interpretation of CIR aerial photographs could be a useful method to find certain groups of epiphytic lichens in surveys covering large areas. (Less)

WINDA—a system of models for assessing the probability of wind damage to forest stands within a landscape

An integrated system of models, WINDA, is presented for calculating the stand-wise probabilities of wind damage, uprooting and breakage of trees within a landscape. The calculations are made point-wise at exposed stand edges. WINDA integrates a modified version of the dose/response model HWIND [Can. J. For. Res. 29 (1999) 647], the airflow model WASP [Wind Atlas Analysis and Application Program (WASP), Risø National Laboratory, Roskilde, Denmark], and a component for calculating the zero-plane displacement and surface roughness and uses a GIS for geographical computations. The likelihood of damage is calculated using extreme value theory. WINDA was able to predict damage that compared well with observed extensive damage within 6.7 km 2 large landscape in southern Sweden. Output from the system of models was most sensitive to modifications in the input variables tree height and diameter at breast height and to the internal parameter critical friction velocity. The mechanistic modelling approach makes WINDA useful for evaluating effects on the probability of wind damage of silvicultural treatments and forestry activities as well as of a changed climate.

DO RESIDUAL TREES INCREASE STRUCTURAL COMPLEXITY IN PACIFIC NORTHWEST CONIFEROUS FORESTS?

Green-tree retention has been promoted as an alternative management tool to create structurally complex forests that would resemble late-successional forests faster than single-aged stands planted after clearcuts. To evaluate if and how overstory residual trees were associated with a higher structural complexity, nine pairs of naturally regenerated stands, initiated between 55 and 110 yr ago with and without residual trees, were investigated. The new Structural Complexity Index (SCI) was used to relate the observed structure to residual trees and other structural components such as tree density, tree size variation, species composition, and environmental variables such as aspect, slope, and elevation. The SCI-ht, which is based on tree height variation, was negatively associated with residual trees, indicating that residual trees reduced vertical structural complexity. The SCI-dbh, which is based on the tree diameter variation, was positively associated with residual trees up to a density of 40 residual t...

The influence of body movement on subjective presence in virtual environments.

We describe an experiment to assess the influence of body movements on presence in a virtual environment. In the experiment 20 participants were to walk through a virtual field of trees and count the trees with diseased leaves. A 2 x 2 between subjects design was used to assess the influence of two factors on presence: tree height variation and task complexity. The field with greater variation in tree height required participants to bend down and look up more than in the lower variation tree height field. In the higher complexity task participants were told to remember the distribution of diseased trees in the field as well as to count them. The results showed a significant positive association between reported presence and the amount of body movement in particular, head yaw--and the extent to which participants bent down and stood up. There was also a strong interaction effect between task complexity and gender: Women in the more-complex task reported a much lower sense of presence than in the simpler task. For applications in which presence is an important requirement, the research in this paper suggests that presence will be increased when interaction techniques are employed that permit the user to engage in whole-body movement.

Hybrid poplars: present status and potential in Britain

Past and potential future use of hybrid poplars for wood production in Britain is considered, and preliminary results of trials with new clones imported from Belgium in 1985 are given. A series of nine field experiments established in 1991, to a common protocol, was analysed using stepwise multiple regression. The superior vigour of 'Beaupre' compared with 'Ghoy', 'Robusta' and 'Trichobel' was clear in almost every case. For 'Beaupre' (Populus trichocarpa X P. deltoides) altitude emerged as the variable explaining most variation in tree height after six growing seasons, height declining with increasing altitude. The four best sites were characterized by low elevation and low rainfall. At the two older sites planted in 1987, at Ampthill and Bedgebury, the 'interamerican' hybrids (P. trichocarpa X P. deltoides) were the most vigorous, and the clones 'UnaP and 'Raspalje', which were thought to be too rust susceptible to release for commercial use in 1990, achieved similar stem sizes to those of 'Beaupre' and 'Bolelare'. The General Yield Class (based on a reference spacing of 8 X 8 m) calculated for 'Beaupre' was 8 at Ampthill and 24 at Bedgebury. Future prospects for poplar planting are considered in relation to possible reform of the Common Agricultural Policy.

Structural heterogeneity and spatial autocorrelation in a natural mature Pinus sylvestris dominated forest

The tree species composition, vertical stratification and patterns of spatial autocorrelation at the tree and quadrate (25 × 25 m) scales were studied in a natural mature PinuS sylvestris dominated forest in eastern Finland. For the analyses we mapped the locations and dimensions of trees taller than 10 m in a 9 ha (300 × 300 m) area, and within this area we mapped all trees taller than 0.3 m on a core plot of 4 ha (200 × 200 m). The overall tree size distribution was bimodal. the dominant layer and the understory forming the peak frequencies. Pinus sylvestris dominated the main canopy, together with scattered Betula pendula and Picea abies. Alnus incana, Populus tremula, Salix caprea, Sorbus aucuparia and Juniperus communis occurred only in the under‐ and middlestories. Autocorrelation analysis (semivarianee) of tree size variation revealed spatial patterns, which were strongly dependent on the size of trees included in the analysis. When all living trees, including the understory regeneration, were taken into account, the autocorrelation pattern ranged up to 35 m inter‐tree distances, reflecting the spatial scale of understory regeneration patches. Competitive interaction among middle‐ and upperstory trees (height&gt;10 m) had contrasting effects on autocorrelation pattern depending on spatial scale. At the fine scale, dominant trees suppressed their smaller close neighbors (asymmetric competition), which was shown as increased tree size variation at small inter‐tree distances (&lt;2 m). At slightly larger inter‐tree distances, specifically among large trees of similar size, competition was more symmetrical, which resulted in decreased tree size variation at these inter‐tree distances (3–4 m). This effect was seen most clearly in the dominant trees, there being a clear autocorrelation pattern in tree size up to inter‐tree distances of ∼4 m. At the quadrate scale (25 × 25 m) the analysis revealed high local variation in structural characteristics such as tree height diversity (THD), tree species diversity (H) and autocorrelation of tree height. The analysis suggests that naturally developed P. sylvestris forests exhibit complex small‐scale patterns of structural heterogeneity and spatial autocorrelation in tree size. These patterns may be important for stand‐scale habitat diversity and can have aggregated effects on ecosystem dynamics at larger spatial scales though their influence on the spread of disturbance and regeneration after disturbance.