Multi-layered Stands Research Articles

Hizmet amaçlı işletilen ormanlarda optimal kuruluşların belirlenmesi

A regulated forest structure exists that will best fulfill the expected forest value for both protection and service purposes. For the forest functions designated or to be assigned for service production purposes, optimal formations have not been disclosed yet. For this purpose, the optimal forest structure in the aesthetic and recreation managed forest unit in Odayeri planning unit, reserved to the service production function is explained theoretically, and afterwards presented by numerically and graphically. The optimum rotation age obtained with the calculations for the aesthetic management unit was determined as 198 years, the diameter of the target 72 cm and the target volume 270 m3/ha. Since the aesthetic management unit consists of multi-layered and mixed stands, the continuous forest form has been adopted as the management method and the optimal structure has been determined using the French volume method. The recreation management unit consists of fir and beech mixed stands and was managed according to the age class method. In this study, an example of determining the optimal formation for a management unit consisting of mixed forests has been presented.

Voxel-Based Automatic Tree Detection and Parameter Retrieval from Terrestrial Laser Scans for Plot-Wise Forest Inventory

This paper presents a fully automatic method addressing tree mapping and parameter extraction (tree position, stem diameter at breast height, stem curve, and tree height) from terrestrial laser scans in forest inventories. The algorithm is designed to detect trees of various sizes and architectures, produce smooth yet accurate stem curves, and achieve tree height estimates in multi-layered stands, all without employing constraints on the shape of the crown. The algorithm also aims to balance estimation accuracy and computational complexity. The method’s tree detection combines voxel operations and stem surface filtering based on scanning point density. Stem diameters are obtained by creating individual taper models, while tree heights are estimated from the segmentation of tree crowns in the voxel-space. Twenty-four sample plots representing diverse forest structures in the south boreal region of Finland have been assessed from single- and multiple terrestrial laser scans. The mean percentages of completeness in stem detection over all stand complexity categories are 50.9% and 68.5% from single and multiple scans, respectively, while the mean root mean square error (RMSE) of the stem curve estimates ranges from ±1.7 to ±2.3 cm, all of which demonstrates the robustness of the algorithm. Efforts were made to accurately locate tree tops by segmenting individual crowns. Nevertheless, with a mean bias of −2.9 m from single scans and −1.3 m from multiple scans, the algorithm proved conservative in tree height estimates.

Insect abundance in managed forests benefits from multi-layered vegetation

Retention forestry intends to promote biodiversity by retaining deadwood and tree-related microhabitats. Simultaneously, production forests undergo major structural changes by conversion into near-natural forests. As insect biomass is declining, it is important to understand how insect communities respond to management-related changes in forest structure. While some structural elements, such as deadwood, are studied extensively, three-dimensional forest structure is often neglected. Terrestrial laser scanning offers new approaches to quantify three-dimensional structure but their suitability has not been evaluated with field-based insect surveys.To test how insect communities respond to forest structure, we examined insects from window traps from 122 sites in the Black Forest. For total insect abundance and for the seven most abundant taxa, we related deadwood, microhabitats, various conventional stand properties and novel remote sensing-based indices for vegetation structure to total and taxon-specific abundances. Additionally, we assessed the influences of these structural elements on community composition.Total insect abundance and abundances of most taxa were positively related to multi-layered stands, as derived from remote sensing techniques. Furthermore, each taxon responded to some additional forest structural elements. Higher tree diameter, canopy gap fraction and share of deciduous trees increase abundances of the predominantly herbivorous taxa Heteroptera, Sternorrhyncha and Auchenorrhyncha. Community composition was influenced by mean tree diameter and share of deciduous trees. Neither tree-related microhabitats nor deadwood diversity had a detectable effect on insect abundance.We conclude that more elements of forest structure than previously acknowledged are related to insect populations. In particular, multi-layered forest stands have higher insect abundances in the midstorey. The current conversion in continuous-cover forestry in Europe from even-aged, often conifer-dominated forests to uneven-aged, mixed species stands can therefore increase the abundance of a wide range of insect taxa and is possibly one strategy to halt insect decline in forests.

Can forest structural diversity be a response to anthropogenic stress? A case study in old-growth fir Abies alba Mill. stands

Key messageFrom 1973 to 1991, Polish SO2emissions above 3250 Gg/year resulted in a decline of firAbies albaMill. After stresses connected with these emissions, five main diameter at breast height (DBH) structural types were described. This type of heterogeneous forest structure is supposed to increase forest resistance and resilience to abiotic, biotic and anthropogenic disturbances.ContextThe analyses of forest structure are important under the current scenario of global change, since heterogeneous structures allow for better responses to disturbances. Forests with more complex structures should present greater vitality.AimsThe main hypotheses were as follows: (1) the temporal changes of atmospheric SO2 emissions caused (a) the abrupt changes in the tree DBH radial increment and (b) the death of fir trees; and (2) atmospheric SO2 emissions and related fir decline and recovery processes ultimately result in the development of stands characterised by diverse DBH structures.MethodsRadial growth trends of 49 and 215 fir trees in the older and younger generations, respectively, and 85 dead fir trees were evaluated. Using data collected in 32 stands, the DBH structural types were identified, and the shapes of these types were illustrated.ResultsThe structural diversification of forest patches may influence forest resistance and resilience to disturbances; five main structural types were identified: ML1 and ML2 represent DBH distributions of multi-layered stands, and OS, TS1 and TS2 represent DBH distributions of one- and two-storied stands.ConclusionStructural diversity of forests was a response to SO2 emissions; fir trees had the ability to increase their radial growth, although there were still high SO2 emissions.

Toward a issue of box elder invasion into the forests around Moscow

Anthropogenic and natural disturbances, such as damage to spruce forests by the eight-dentated bark beetle, favor the invasion of Acer negundo into the strongly fragmented forests close to Moscow. A crown closure of more than 0.5 as well as dense rowan understory or A. platanoides young growth, prevents the penetration of A. negundo into forest communities. Being less shade tolerant but more fertile and fast growing than A. platanoides, A. negundo gradually invades only slightly disturbed woodlands. Its ability to form multilayered stands faster than other wood species hampers the regeneration of local species. The progressing affection of A. negundo leaves by Phyllosticta negundinis fungus and noninfectious leaf toxicosis observed in Moscow may decrease its invasive potential.

Enriching ALS-Derived Area-Based Estimates of Volume through Tree-Level Downscaling

Information on individual tree attributes is important for sustainable management of forest stands. Airborne Laser Scanning (ALS) point clouds are an excellent source of information for predicting a range of forest stand attributes, with plot and single tree volume being among the most important. Two approaches exist for estimating volume: area-based approach (ABA) and individual tree detection (ITD). The ABA is now routinely applied in operational forestry applications, and results in generalized plot- or stand-level attribute predictions. Alternatively, ITD-based estimates provide detailed information for individual trees, but are typically biased due to challenges associated with individual tree detection. In this study, we applied an ABA to estimate tree counts and individual tree volumes by downscaling plot-level predictions of total volume derived using ALS data in a highly productive and complex coastal temperate forest environment in British Columbia, Canada, characterized by large volumes and multi-species and multi-age stand structures. To do so, a two-parameter Weibull probability density function (PDF) was used to describe the within-plot tree volume distribution. The ABA approach was then used to model the total plot volume and the two Weibull PDF parameters. Next, the parameters were used to calculate mean tree volume and derive the number of trees and the individual tree volume distribution. Tree count estimates were minimally biased with RMSE of 149 trees·ha−1 or 24.4%. The volume distributions showed good agreement with reference data (mean Reynold’s error index = 71.7). We conclude that the approach was suitable for enriching ABA-derived forest stand attributes in the majority of the studied forest stands; however the accuracy was lower in multi-layered stands that had a multimodal individual tree volume distribution.

Guild-specific responses of forest Lepidoptera highlight conservation-oriented forest management – Implications from conifer-dominated forests

The loss of biodiversity in forest ecosystems has led to a discussion on conservation-oriented forest management, particularly in intensively managed coniferous forest of the northern hemisphere. Two conservation-oriented management strategies, namely advancement of multi-layered forests stands and benign neglect of naturally disturbed stands, are currently being promoted over conventional management strategies of single-layered stands and salvage logging after natural disturbances. However, the effect of these conservation-oriented strategies on nocturnal Lepidoptera has not yet been assessed, despite the high contribution of this order to biodiversity. Here we used full assemblage data of forest-dwelling micro-moths and macro-moths to compare species densities and relative abundance of moths of the larval feeding guilds in single-layered and multi-layered stands, and in naturally disturbed salvaged or unsalvaged stands. We demonstrate that forest moth assemblages are sensitive to conservation-oriented forest management strategies. The relative abundance of moths of the saproxylic and detritus-feeding larval guilds was higher in naturally disturbed unsalvaged stands and in multi-layered stands, whereas that of moths of the moss-feeding larval guild was lower in multi-layered stands. These results corroborate the benefit of a benign-neglect strategy in the management of naturally disturbed stands in conserving saproxylic and detritus-feeding moths and in using natural disturbance to guide the enhancement of stand complexity. Our results demonstrate both the power of functional approaches to reveal slight changes in species communities and the importance of including micro-moths (a frequently disregarded group) in studies aimed at developing management implications for forest managers.

Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR), and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level) models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

BackgroundForest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR), and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies.MethodsThe stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures.ResultsThe stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level) models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters.ConclusionThis model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

Does forest stand structure impact the dynamics of snow on winter grazing grounds of reindeer (Rangifer t. tarandus)?

The landscape in boreal Sweden is dominated by even-aged, single-layered forest monocultures and clear cuts. Few forest stands with a more complex, multi-layered structure remain as landscape elements. We studied the impact that different forest management regimes have on snow conditions and the metamorphosis of snow, and discuss how these factors may affect suitability for reindeer grazing.Over two winters, we recorded the development of snow depth and hardness in clear cuts and two different forest types, and their changes with weather events. In the forests, the dynamics of snow characteristics were analyzed in relation to stand structure and at the level of individual trees.There were no clear differences in snow characteristics between single-layered and multi-layered stands, although snow hardness was more variable in the latter. In single-layered stands, snow depth and hardness were spatially uniformly distributed in relation to stand characteristics. Contrastingly, the complex structure of multi-layered stands did influence snow depth significantly. However, hardness was highly heterogeneous in these stands. Due to the absence of tree effects, clear cuts had deeper but softer snow than forested stands, although hardness increased towards spring.Weather affected the metamorphosis of the snow blanket. The magnitude of the effects depended on both timing and severity of discrete weather events and forest structure, but generally weather had a greater influence on snow cover characteristics than forest structure per se. In their interaction with weather, different forest structures affect the snow and thus suitability as winter grazing area for reindeer. Reindeer herders, therefore, require diversity in the landscape in order to respond to such weather variations and their impact on grazing conditions.

Understory trees in airborne LiDAR data — Selective mapping due to transmission losses and echo-triggering mechanisms

Understory trees in multilayered stands are often ignored in forest inventories. Information about them would benefit silviculture, wood procurement, and biodiversity management. Cost-efficient inventory methods are needed and airborne LiDAR is a promising addition to fieldwork. The overstory, however, obstructs wall-to-wall sampling of the understory using LiDAR, because transmission losses affect echo-triggering probabilities and intensity (peak amplitude) observations. We examined the potential of LiDAR in mapping of understory trees in pine (Pinus sylvestris L.) stands (62°N, 24°E), using careful experimentation. We formulated a conceptual model for the transmission losses and illustrated that loss normalization is highly ill-posed, especially for vegetation. The losses skew the population of targets that produce a subsequent echo. Losses up to 10–15% can occur even if an overstory echo is not triggered. In LiDAR sensors, quantized intensity values start from binary zero, but actually should include an offset, the noise level. We estimated these empirically. Constraining to low-loss pulses and ground data, we estimated parameters for compensation models that were based on the radar equation and employed the geometry of the pulse, as well as the overstory intensity observations as predictors. Intensity variation of second-return data was reduced, but, the intensity data were deemed of low value in species discrimination. Our results highlight differences between sensors in near-ground echo-triggering and height data. Area-based LiDAR height metrics from the understory had reasonable correlation with the density and mean height of the understory trees, whereas tree species seemed out of reach even if the transmission losses were compensated for. We conclude that transmission losses are a general impediment for radiometric analysis of multi-echo pulses in discrete-return and waveform LiDAR data.

Creation of multi-layered canopy structures in young oak-dominated urban woodlands – The ‘ecological approach’ revisited

We investigated the stand structure of ten young urban woodlands established in Southern Scandinavia during the 1970s and 1980s according to the ecological approach, which advocated the use of many different species of trees and shrubs to create complex canopy structures as soon as possible after establishment to promote recreation and biodiversity. Tree height and live crown depths were measured and analysed using a combination of quantitative and qualitative approaches to assess the forest structure in terms of canopy stratification. The results show that the current canopy structures could be classified into seven different two- and three-layered structural types which had evolved as a combination of differences in management frequency and the initial species composition. Two layered stands were characterized by lower management frequency compared to three layered stands and stands in transition to three layers. They were also established with a lower proportion of understory species and a higher proportion of shade tree species. The total number of species at the establishment did not influence how stands were categorized. The two main conclusions are that recurrent thinnings is a key factor for successful management of young, species rich forest plantations, and that species composition can increase the resilience towards management neglect. Instead of aiming at maximising total species number it is more reasonable to focus on a few key species in each layer. We conclude that three-layered canopy structures can be created already after twenty five years, which should encourage planners and practitioners to incorporate multilayered stands in future urban woodland creation.

Diversity of patch structure in Central European forests: are tree diameter distributions in near‐natural multilayered Abies–Fagus stands heterogeneous?

AbstractNear‐natural multilayered Abiesalba Mill.–Fagus sylvatica L. forests form structural mosaics and consist of patches in different developmental stages and phases. Knowledge of the diversity of patch structure and adequate methods to describe the diameter structure is essential for modeling forest dynamics. The hypotheses tested in the study are that near‐natural multilayered stands are structurally heterogeneous (i.e., tree diameter (DBH) distributions of these stands are heterogeneous) and, that in these forests the finite‐mixture models are suitable for modeling the empirical DBH distributions. Diversity of patch structure was studied based on data collected from 33 sample plots. In multilayered stands, four groups of empirical DBH distributions were distinguished using hierarchical cluster analysis (HCA) and correspondence analysis (CA). Stands investigated are structurally heterogeneous; 27% multilayered stands showed the slightly rotated sigmoid (SRS) type of empirical DBH distribution, 34% the distinctly rotated sigmoid (DRS) type, 18% the bimodal M‐shaped (BMS) type, and 21% the unimodal highly skewed (UHS) type. The gamma distribution, the two‐component mixture gamma model, and the two‐component mixture Weibull model were more flexible for the SRS type of DBH distributions. The average p‐values (Chi‐square test) for these theoretical distributions were 0.4712, 0.4718, and 0.4660, respectively. The two‐component mixture gamma model and the two‐component mixture Weibull model were a good choice for modeling the DRS, BMS, and UHS types of DBH distributions. The average p‐values (Chi‐square test) for these models ranged from 0.2684 to 0.4854. In near‐natural multilayered Abies–Fagus forest patches of different DBH distributions occur together. The empirical DBH distributions in these stands are characterized by irregular and complicated shapes and therefore are best approximated by finite‐mixture models.

Modifiche compositive e strutturali in soprassuoli in evoluzione naturale della riserva M.a.B. di Montedimezzo (Isernia)

Tree species composition and structural dynamics in forest stands under natural evolution in the Montedimezzo M.a.B. reserve. This study is included in an experimental protocol established in 1954 aimed at examining the natural dynamics in mixed broadleaves high forests dominated by Turkey oak (Quercus cerris L.) and beech (Fagus sylvatica L.). Stand development patterns in the last fifteen years are reported. Repeated quantitative and qualitative inventories were carried out in two permanent plots (3 ha each) and in two structural transects (0.2 ha each) located in Collemeluccio-Montedimezzo M.a.B. reserve (Is). The study highlighted, as already observed in 1954, the differences between the two multilayered stands. In the higher elevation beech is the predominant species recording 53% of importance value index (I), followed by Turkey oak (I=25%). In the lower elevation the dominant species is Turkey oak (I=46%), followed by hornbeam (Carpinus betulus L.) (I=28%) and beech (I=12%). The decreased presence of Turkey oak and the increase of beech density are confirmed in each plot over the last fifteen years. Among the other tree species, importance values rise only for silver fir (Abies alba Mill.) (introduced) and holly tree (Ilex aquifolium L.), while hornbeam and hedge maple have been reducing their own presence.

Multipurpose conversion management of Scots pine towards mixed oak–birch stands—A long-term simulation approach

The forest growth model 4C was used to investigate how conversion management of a Scots pine ( Pinus sylvestris L.) stand towards a mixed oak–birch stand would affect stand structural development – and hence biodiversity and productivity – in the long term. For this purpose the 4C model was parameterised for natural regeneration of light demanding species and extended for management of multi-layered stands. A series of structural indicators was selected to describe key factors of forest biodiversity at the stand scale. Two consecutive aspects of Scots pine conversion were tested: (1) the choice of conversion strategy between thinning and gap creation and (2) the choice of conversion regime in terms of cutting cycle, thinning type and pine tree retention. Three simulated conversion strategies aim at the gradual removal of the pine canopy but differ in the spatial organisation of pine cuttings and hence result in different light conditions for regeneration. Only the directed gap creation strategy was able to maintain and increase birch admixture to the stand and to approach natural stand structural development. Simulation of 12 conversion regimes for the directed gap creation strategy indicated that thinning type (from above or from below), pine tree retention at final felling (50% of the standing volume or none) and cutting cycle (6, 9 or 12 years) all significantly influence stand structural development. These effects were clearest for oak development. Birch occurred in a few mixed clusters, but tended to disappear when longer cutting cycles were used. Based on a multi-criteria analysis we conclude that the optimal conversion regime – in which both stand productivity and biodiversity objectives can be combined – implies thinning from above, pine tree retention, and cutting cycles of 6 years. The conceptual validity of the model as well as the applicability of the results are discussed.

Comparison of selected statistical distributions for modelling the diameter distributions in near-natural Abies–Fagus forests in the Świętokrzyski National Park (Poland)

The aim of the study is to compare selected theoretical distributions (normal, lognormal, Weibull, gamma, logistic, and exponential) in describing the tree diameter (DBH) distributions of mixed near-natural forests consisting of fir Abies alba Mill. and beech Fagus sylvatica L. growing in various vertical structures. Tree DBH data were collected between 1997 and 2008 from 51 sample plots established in the Świetokrzyski National Park in Poland. The empirical data represent differentiated DBH distributions, ranging from almost symmetric to extremely asymmetric ones. The chi-square test and the modified Kolmogorov–Smirnov test were chosen for the goodness-of-fit testing. In addition to the test statistics, the bias (B), the root mean square error (RMSE) and the graphical method (quantile–quantile plots) were used. In one-storied stands, the most suitable distributions were the normal and logistic distributions; in two-storied and multilayered stands, the Weibull and gamma distribution were the most suitable; and in selection stands, the exponential distribution was the most appropriate to describe the DBH distribution. The order of precision of the tested distributions (from the highest to the lowest) was Weibull, gamma, logistic, normal, exponential, and lognormal. The normal and exponential distribution should be applied only to one-storied and selection forests, respectively. The least suitable distribution for DBH distribution modelling was the lognormal one.

Overstory and understory development in thinned and underplanted Oregon Coast Range Douglas-fir stands

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests managed for timber in western Oregon frequently lack structure and diversity associated with old-growth forests. We examined thinning effects on overstory and understory development for 8 years after treatment. Three 30- to 33-year-old Oregon Coast Range plantations were partitioned into four overstory treatments: unthinned (~550 trees/ha) and lightly (~250 trees/ha), moderately (~150 trees/ha), and heavily (~75 trees/ha) thinned. Within each overstory treatment, two understory treatments were established: underplanted with Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.) or not underplanted. Thinning increased overstory stem growth, crown expansion, and retained crown length. Thinned overstory canopies began to close rapidly the third year after thinning, decreasing % skylight by approximately 2%/year, whereas % skylight in unthinned stands increased slightly. All seedlings planted in unthinned stands died, whereas eighth year survival in thinned stands averaged 88%. Natural regeneration densities and distributions were highly variable. Understory shrub cover was reduced by harvesting disturbance but recovered by the fifth year. Thinning increased understory plant species diversity, and no shrub species were lost. Thinning to low densities and underplanting has the potential to accelerate development of multilayered stands characteristic of old-growth Douglas-fir forests.

Identifying and quantifying structural characteristics of heterogeneous boreal forests using laser scanner data

Structural characteristics of forest stands, e.g. in relation to carbon content and biodiversity, are of special interest. It has been stated in numerous publications that discrete return laser scanner data produce accurate tree canopy information since the quantiles of the height distribution of laser scanner data are related to the vertical structure of the tree canopy. Since some of the laser pulses will penetrate under the dominant tree layer, it is also possible to analyse multi-layered stands. In this study, the existence and number of understory trees were examined. This was carried out by analysing the height distributions of reflected laser pulses. In the laser data of this study, (Toposys Falcon, survey May 2003 in Kalkkinen, Finland, flight altitude 400 m AGL) the average number of laser pulse hits/1m 2 was 12. The reference data consisted of 28 accurately measured field sample plots. These plots include highly heterogeneous structures of boreal forests. The existence of lower canopy layers, i.e. understory trees, was analysed visually by viewing the plotwise 3D-images of laser scanner-based canopy height point data and examining distributions of canopy densities which were computed as proportions of laser hits above different height quantiles. Furthermore, a developed histogram thresholding method (HistMod) was applied to the height distribution of laser hits in order to separate different tree storeys. Finally, the number and Lorey's mean height of understory trees were predicted with estimated regression models. The results show that multi-layered stand structures can be recognised and quantified using quantiles of laser scanner height distribution data. However, the accuracy of the results is dependent on the density of the dominant tree layer.

Tree crown ratio models for multi-species and multi-layered stands of southeastern British Columbia

The ratio of live crown length to tree height (crown ratio; CR) is often used as an important predictor variable for tree level growth equations, particularly for multi-species and multi-layered stands. Also, CR indicates tree vigour and can be an important habitat variable. Measurement of CR for each tree can be time-consuming and difficult to obtain in very dense stands and for very tall trees where the base of live crown is obscured. Models to predict CR from size, competition and site variables were developed for several coniferous and one hardwood tree species growing in multispecies and multi-layered forest stands (complex stands) of southeastern British Columbia. Simple correlations indicated the expected relationships of CR decreasing with increasing height, and with increasing competition. A logistic model form was used to constrain predicted CR values to the interval [0,1]. Also, predictors were divided into tree size, stand competition, and site measures, and the contribution of each set of contributors was examined. For all models, height was an important predictor. The stand competition measure, basal area of larger trees, contributed significantly to predicting CR given that crown competition factor was also included as a measure of competition. Logical trends in CR versus size and competition variable groups were reflected by the models; site variable slightly improved predictions for some species. Much of the variability in CR was not accounted for, indicating that other variables are important for explaining CR changes in these complex stands. Key words: crown ratio, multi-species stands, multi-layered stands, basal area of larger trees

Habitat features of the capercaillie (Tetrao urogallus) leks in the West Carpathians

Habitat characteristics of 43 capercaillie (Tetrao urogallus) leks were studied in the mountains of Central Slovakia (West Carpathians) in 1984–2002. Macro-habitat was described with respect to topography and succession stage. Micro-habitat was described with respect to forest type and forest stand structure. Twenty-seven out of forty-three display grounds were situated in the upper half of the lateral ridges. Sixteen leks were located on hills of the lateral ridges (slope < 10%). All the leks were situated in old succession stages of the forest (80–200 years old). Twenty-seven display grounds were located in natural forests, sixteen leks were situated in man-managed stands more than 80 years old. Leks were situated in a variety of forest types with overstorey tree-density between 400–1,050 stems per ha. Distribution of leks was limited above all by macro-habitat characteristics (elevated sites, old stands). Age-space structure seemed to be a significant micro-habitat feature (preference of multi-layered stands).