Tree Dimensions Research Articles

The overall effect of research years, rootstocks, and cultivars on the morphological attributes of pear trees

This research was conducted to determine the combined effect of 3 factors including rootstocks, cultivars, and research years on the morphological characteristics in Samsun/Türkiye ecological conditions in the research years of 2021 and 2022. Eight rootstocks consisting of quince BA29 (BA29), quince A (QA), FOX9, FOX11, OHxF333, OHxF87, FAROLD40, and European pear seedlings were used in the study, while the cultivars were 'Santa Maria', 'Williams', and 'Deveci'. The study results revealed the significance of the combined factors on all leaf characteristics of European pear. While rootstock diameter, scion diameter, tree length, and trunk cross-sectional area showed insignificant variations. It was determined that the canopy characteristics of ‘Williams' pear cultivar in combination with the FAROLD40 and OHxF333 in the research year 2022 were higher than other combinations, while the same combination was obtained with lower values in the case of other morphological characteristics. Generally, all the morphological attributes were obtained higher in the rootstocks and cultivars combination in the research year of 2022. In conclusion, the genetic capacity of rootstocks, cultivars, and variations of the climate situations in two consequent research years, resulted in variations in the morphological attributes of pear trees.

Effects of canopy structure on the diversity and structure of tree species in omo biosphere reserve, Ogun state, Nigeria

This study assessed the effects of canopy structure on tree species diversity and forest structure in OmoBiosphere Reserve. Landsat imagery was used; supervised maximum likelihood classification was used to classify the reserve into two canopy structures (closed and open canopies). Random sampling technique was used to delineate 10 sample plots of 30m x 30m in each canopy type. Tree species with a diameter at breast height (Dbh) ≥10cm were enumerated in each sample plot. Shannon Weiner and Simpson’s indices were used to assess the tree diversity, while diameter and height stratification were used to evaluate the forest structure. Shannon Weiner and Simpson’s indices were 3.507 and 0.953, respectively, in open canopy structure (OCS) and 3.396 and 0.951, respectively, in closed canopy structure (CCS). Species richness and population were higher in OCS (64 and 575, respectively) than in CCS (56 and 531, respectively). Milletia thonningii andStrombosia pustulata were the dominant tree species in OCS and CCS, respectively. The mean Dbhand height in OCS were 40.09cm and 22.86 cm; and 50.21cm and 23.05cm in CCS, respectively. The basal area was 110.01m2/ha in OCS and 207.97m2/ha in CCS. The volume yield per hectare in OCS was 343.35m3/ha and 842.49m3/ha in CCS. The OCS was dominated by younger trees than the CCS. Canopy structure affects tree species richness, population, and diversity, as well as tree attributes.

Changes in the provision of ecosystem services based on sidewalk tree-composition scenarios

Cities have been experiencing environmental and social issues due to urban expansion processes, be them planned or not. However, several environmental solutions have been proposed and sidewalk tree planting stands out among them. The aim of the current research is to assess the process to estimate ecosystem services under different sidewalk tree composition scenarios in Irati and Curitiba cities, Paraná State. In order to do so, 10 street segments from neighborhoods sampled in city-wide inventories were selected. Information about sidewalk length, curb ramps’ width, and number of utility poles was collected for each street segment. The number of trees to be fit in each segment and sampled neighborhood was determined based on safety recommendations for these urban structures. Tree dimensions (Diameter at Breast Height - DBH, total height and crown diameter) were projected for the 55th year post-planting, based on using minimum dimensions of seedlings from small, medium and large-sized species. It was done to estimate ecosystem services in i-Tree Eco software. Significant differences among floristic composition scenarios (p<0.05) were observed for all ecosystem services in both cities. Compositions featuring large-sized species have show higher ability to provide ecosystem services, as well as higher monetary valuation, despite fitting a smaller number of trees in the assessed street segments. The herein formulated scenarios have shown the potential to increase the number of planted trees and to select compositions capable of maximizing ecosystem services’ provision and trees’ monetary value.

A Scoping Review of Urban Planning Decision Support Tools and Processes That Account for the Health, Environment, and Economic Benefits of Trees and Greenspace.

Compelling evidence shows that trees and greenspaces positively impact human well-being and the environment and offer economic benefits. Nevertheless, there exists a knowledge gap regarding the extent to which this evidence is efficiently incorporated into existing urban planning decision-making processes. This scoping review identified the extent to which urban planning decision-making frameworks, models, and tools consider the health, environmental, and economic benefits of trees and greenspace. Out of 28 reviewed studies, 11 (39%) reported on frameworks, models, and tools that take into account the health, environmental, and economic dimensions of trees and greenspace. Additionally, seven studies provided comprehensive coverage of at least one of the three key dimensions. However, none of the decision support frameworks, models, or tools comprehensively integrated all three dimensions, with only two tools (7%) scoring above 50% (five or more out of nine) in terms of comprehensiveness. This review highlights the urgent need to incorporate the true economic and monetary values of the health and environmental benefits of trees and greenspace to inform urban development decision making.

Growth, fruit bearing behaviour, yield and quality of some apple cultivars

Apple is a temperate climate fruit species grown almost worldwide. Research and past experiences have shown that apples have different growth and fruiting behaviours. Knowing the growth and fruiting behaviours of apples, determining the training system, how to prune, will shed light on the cultural practices that need to be done in order to obtain quality and early high yield. In light of the above, the study aimed to determine the growth and fruiting behaviours of different apple. In the experiment, eight apple cultivars, ‘Jeromine’, ‘Fuji Zehn Astec’, ‘Granny Smith Challenger’, ‘Buckeye Gala’, ‘Rosy Glow’, ‘Golden Reinder’, ‘Ginger Gold’ and ‘Amasya’, grafted on M9 rootstock were used. The growth and fruiting behaviours of the cultivars were determined by phenological observations, canopy dimensions, tree dimensions, canopy volume, tree volume, number and size of annual shoots on the leader, number of spurs, internode distance, distribution of flowers on the tree and similar measurements and evaluations. In addition, yield and some quality characteristics of fruits were also recorded. It was determined that ‘Rosy Glow’ and ‘GS Challenger’ cultivars showed the best performance in terms of growth, and ‘Fuji Zehn Astec’, ‘Rosy Glow’, ‘Buckeye Gala’, ‘GS Challenger’ cultivars in terms of cumulative yield. Additionally, this study found that there was a positive relationship between yield and branch angles in the first two years. Considering all the years, it was determined that ‘Fuji Zehn Astec’ and ‘Granny Smith Challenger’ cultivars produced larger fruits than the others. In conclusion, it was revealed that the growth and fruiting behaviours of apple cultivars cannot be classified very clearly, and it would be more accurate to group them as spur, semi-spur, standard and tip bearer in general. It was claimed that the number of flowers in the cluster is not a characteristic of apples. Besides, ‘Fuji Zehn Astec’, ‘Rosy Glow’, ‘GS Challenger’ was suggested for high yield in the new training systems.

DETECTION OF SILVER BIRCH GROWTH DYNAMICS AND TIMING WITH DENSE SPATIO-TEMPORAL LIDAR TIME-SERIES

Abstract. Silver birch (Betula pendula Roth) is a deciduous pioneer tree species with significant economic and ecological importance due to its rapid growth, high genetic variability and adaptability to diverse climates and environments. In this regard, understanding the factors that influence silver birch tree growth variability and its seasonal patterns has been a subject of research interests, which aim at effective forest management and ecological analyses. Tree size, competition, light availability, and topography has been considered significant factors affecting tree growth patterns. However, their relative contributions are not well understood. This is because, to study the interactions between neighbor trees and their competitive responses requires complex measurements. Accurately measuring tree attributes, such as 3D canopy shape and arrangement, is challenging but has been made possible through advancements in high-resolution 3D remote sensing, specifically laser scanning technology. This study shows the potential of high-spatial and temporal resolution LiDAR time-series from a permanent laser scanning setup to detect detailed structural changes and timing in individual tree canopies, focusing on assessment of the structural canopy growth characteristics of silver birch trees. We first investigate how silver birch trees respond to competition and neighboring species. Our results focusing on canopy height increment show that tree size, competition, neighboring species, and water availability affect the rate of vertical (height) growth of the studied silver birch trees. Further, we detect the timing in canopy vertical and horizontal growth using LiDAR time-series. Significant variations of up to one week were detected among trees, providing insights for future studies on growth dynamics of silver birch in coniferous-dominant forests.

Adjustment of Thinning Equations for Forest Management Area in the Western Amazon

Logging in the Amazon using reduced impact methods has high potential. However, one of the problems of forest management is an accurate estimation of the wood stock of a forest. Thinning equations allow for the analysis of the volume and fluctuations in diameter along the trunk of a tree, making it possible to estimate the volume, diameter, or height based on known dimensions of the trunk. Therefore, this study aimed to adjust and evaluate two thinning equations in a forest management area in the Western Amazon, in the municipality of Xapuri, state of Acre, Brazil, comparing them and selecting the one that presented the best performance for the study area. The study involved sampling in the Chico Mendes Extractive Reserve, utilizing 53 work units and employing the Kozak and linearized Demaerschalk models. These models were assessed based on their determination coefficient, standard error percentage, and graphical analysis of residues. The Demaerschalk model exhibited superior performance, with R² adj. of 92.88% for commercial height and 95.68% for total height. This research contributes to efficiently estimating tree dimensions, essential for sustainable forest management in the Western Amazon. The application of the Demaerschalk model provides precise measurements, enhancing the accuracy of volume calculations and facilitating effective forest management practices. Keywords: allometry, Amazon, Demaerschalk model, dendrometry, Kozak model

Drought-related mortality modifies mixing effects on light absorption and growth in mono-specific and mixed stands of Fagus sylvatica, Alnus glutinosa, and Betula pendula

Abstract Little is known about how drought-related mortality influences light absorption of surviving trees and consequent changes in tree species interactions. Here, we used the detailed tree-level light model (Maestra) in combination with measurements of tree dimensions, crown architectures, and stand structures to examine experimental mixing effects of Fagus sylvatica, Alnus glutinosa, and Betula pendula on light dynamics following a drought in Bangor, Wales. The experimental stands, planted in 2004, were composed of clusters with one to three species in different combinations. Droughts occurred in 2011 and 2014 during the growing seasons, and trees were measured in 2014 and 2015. Species mixing resulted, on average, in higher tree growth, absorption of photosynthetically active radiation (APAR), and light-use efficiency (LUE) compared with the mean of the monocultures. An exception was the monoculture of B. pendula, which was the most productive species and had higher growth, APAR, or LUE than some mixtures. Drought-related mortality reduced the stand basal area across all plots by an average of 8.3% and tree density by 11%. This moderate change in the structure did not result in significant increases in individual tree APAR, LUE, or growth. From a management perspective, mortality might need to reduce stand density more strongly than it did in this study before light absorption or LUE is altered.

Assessing the Allometric Scaling of Vectorized Branch Lengths of Trees with Terrestrial Laser Scanning and Quantitative Structure Modeling: A Case Study in Guyana

Allometric scaling is closely related to the morphology, function and behavior of trees, which are of great significance to the study of ecology. However, most of the traditional allometric scaling studies used the scalar attributes of trees, without considering the 3D vector mode of tree growth. In order to investigate the allometric relationships between branch lengths in 3D vector mode, in this study, an accurate and detailed quantitative structure model was used to reconstruct tree architectures from 3D point cloud data collected by terrestrial laser scanning and extract the structural parameters of each branch (length, branching level and zenith angle). The standardized major axis was used to establish and analyze the scalar and vector allometric relationships between branch lengths. Our results show that at the same branching level and using the same allometric model, the scaling exponents between the lengths of branches and the lengths of cumulative child (descendant) branches (no matter whether the lengths are in scalar or vector form) are similar among trees, and there is no significant difference between the scaling exponents of most trees. And the scaling exponents between the lengths of the horizontal components of branches and the cumulative lengths of the horizontal components of the child (descendant) branches are much larger than those between the lengths of the vertical components of branches and the cumulative lengths of vertical components of the child (descendant) branches. At different branching levels, the scaling exponents between the lengths of branches and the cumulative lengths of descendant branches tend to decrease with the increase in the branching level. The allometric models in terms of the cumulative lengths of horizontal components of the child (descendant) branches and the allometric models in terms of the cumulative lengths of child (descendant) branches have similar model accuracy and scaling exponents. The study results of allometric relationships between tree branch lengths in 3D mode are of great importance for understanding the crown morphology and the branching rule, which is helpful to further understand the growth strategies and adaptation mechanisms of trees and explain the growth and development mechanisms of trees from a physiological perspective.

Dead Better than Alive—The Case of Retention Trees and Tree-Related Microhabitats in Young Stands of Hemiboreal Forests in Latvia

This study examines microhabitat abundance and composition on retention trees in 20 young stands in Latvia that were clear-cut between 2002 and 2004. Retention trees play a vital role in sustaining biological diversity after clear-cutting, but their mortality rate is often high due to post-harvest environmental changes. This study compares tree-related microhabitat (TreM) abundance and composition on retention trees of different dimensions, species, and vitality. The tree height and diameter were measured, and the living status and position of each tree were determined. The research questions of the study were to assess the relationships between TreMs, tree dimensions, and species, as well as to compare the occurrence of TreMs on living and dead wood. The comprehensive analysis revealed that larger tree diameters and specific tree species (Populus tremula, Fraxinus excelsior, and Salix caprea) lead to a higher abundance of TreMs. The results also highlighted the importance of preserving deadwood within forest stands as it enhances the observed abundance of TreMs. This study provides the missing information on TreMs in Latvia, thus providing data for comparison in a wider region.

Impacts of tending on attributes of radiata pine trees and stands in New Zealand – a review

Impacts of tending on attributes of radiata pine trees and stands in New Zealand – a review

Recreating structurally realistic tree maps with airborne laser scanning and ground measurements

The estimation of forest attributes representing aspects of structural biodiversity from vast areas is difficult not only because of the lack of agreement on what constitutes a structurally diverse forest, but also due to difficulties in the detection of small trees. However, a structurally diverse forest should have large variation in tree size (i.e., height and diameter), as well as some clustering of trees, as regular tree pattern is typical for managed forests. In this work we developed a framework for building structurally representative tree maps using airborne laser scanning data and a limited number of ground measurements using data from two locations in Finland. In the proposed method, an individual tree detection algorithm is optimized so that the number of undetected trees and false detections is minimized. The ground measurements are then used to train models for predicting the number and location of undetected trees and false detections by resampling the attributes of undetected trees in the training data. This model can then be applied to other areas in the proximity of the ground measurements to build tree maps, with the location, height, and diameter for each tree. The methodology was shown to reproduce the number of trees, the height distribution, and the spatial pattern of the trees with sufficient accuracy for practical use in large-scale mapping of forest attributes. For example, the individual tree detection could find at best about 54% of the trees with an additional 7% of false detections, resulting in a bias of approximately −30%, while with the new method the bias was reduced to ±10% of the stem density. Further research is needed on how to account for tree species when building tree maps.

Multi-scale assessment of roost selection by 'ōpe'ape'a, the Hawaiian hoary bat (Lasiurus semotus).

The Hawaiian hoary bat (Lasiurus semotus; Chiroptera: Vespertilionidae), commonly and locally known as 'ōpe'ape'a, is a solitary, insectivorous, and foliage-roosting species distributed across a wide range of habitats in lowland and montane environments. The species, as with many others in the Hawaiian archipelago, are facing a suite of challenges due to habitat loss and degradation, introduced predators and pests, and climate change. An understanding of the roost requirements of foliage-roosting tree bats is critical to their conservation as these habitats provide several important benefits to survival and reproduction. Because little is known about 'ōpe'ape'a roost ecology and considerable effort is needed to capture and track bats to roost locations, we examined resource selection at multiple spatial scales-perch location within a roost tree, roost tree, and forest stand. We used a discrete choice modeling approach to investigate day-roost selection and describe attributes of roost trees including those used as maternity roosts. 'Ōpe'ape'a were found roosting in 19 tree species and in an assortment of landcover types including native and non-native habitats. Our results are largely consistent with findings of other studies of foliage-roosting, insectivorous tree bats where bats selected roost locations that may offer protection and thermoregulatory benefits.

Effects of historical land use and recovery pathways on composition, structure, ecological function, and ecosystem services in a Caribbean secondary forest

Regenerated secondary forests in the tropics are resilient ecosystems. Differences in land-use history and disturbance, abiotic and biotic site conditions, and successional pathways can influence secondary forest biodiversity, structure, ecological functions, and ecosystem services. However, studies assessing the supply of ecosystem services of secondary forests are limited. We examined trees in plots located across late successional stage secondary forest in the Luquillo Experimental Forest, Puerto Rico with three combinations of historical canopy cover (circa 1936) and post-agricultural recovery pathways: (1) > 50% canopy cover and passive regeneration (>50 P), (2) < 50% canopy cover and passive regeneration (<50 P), and (3) < 50% canopy cover and assisted + passive regeneration (<50 A+P). Using i-Tree Eco methodology, we investigated if differences in historical cover and passive vs assisted natural regeneration resulted in differences in composition and structure, hydrological functions, and estimated regulating ecosystem services, and compared the results between native and non-native species. The <50 P plots had greater species richness than the >50 P and <50 A+P plots, while the <50 A+P plots had significantly greater DBH, height, basal area, aboveground biomass, and estimated quantities of evaporation and transpiration, carbon storage, and removal of airborne contaminants compared to the other recovery pathways. Differences among plot groups can be attributed to historical management actions in concert with successional trajectories characteristic of novel secondary forests. Native species dominated throughout these secondary forests and cumulatively exhibited services that were 1.3 to 3.5 times greater than those of non-native species. However, non-native trees contributed disproportionally to basal area and aboveground biomass, and thus to some ecosystem services. Both natives and non-natives exhibited service provision that varied significantly with diameter size class and service type, and large trees were observed to be dominant service providers irrespective of species origin. Our study marks the first landscape-scale quantitative assessment of forest composition, structure and ecological functioning that is explicitly linked to exploring regulating ecosystem services within the montane secondary forest in Puerto Rico and expands representation of this research from the Caribbean. The findings underscore the role of historical land use and recovery pathways in driving services of tropical forests and show how ecosystem functions can vary in accordance with dynamic structural attributes of individual trees. This research can provide a useful point of comparison for analysis of biomass accumulation, ecosystem service provision, and evaluating service tradeoffs associated with forest structure in other recovering and old-growth tropical landscapes.

Improving Estimation of Tree Parameters by Fusing ALS and TLS Point Cloud Data Based on Canopy Gap Shape Feature Points

Airborne laser scanning (ALS) and terrestrial laser scanning (TLS) are two ways to obtain forest three-dimensional (3D) spatial information. Due to canopy occlusion and the features of different scanning methods, some of the forest point clouds acquired by a single scanning platform may be missing, resulting in an inaccurate estimation of forest structure parameters. Hence, the registration of ALS and TLS point clouds is an alternative for improving the estimation accuracy of forest structure parameters. Currently, forest point cloud registration is mainly conducted based on individual tree attributes (e.g., location, diameter at breast height, and tree height), but the registration is affected by individual tree segmentation and is inefficient. In this study, we proposed a method to automatically fuse ALS and TLS point clouds by using feature points of canopy gap shapes. First, the ALS and TLS canopy gap boundary vectors were extracted by the canopy point cloud density model, and the turning or feature points were obtained from the canopy gap vectors using the weighted effective area (WEA) algorithm. The feature points were then aligned, the transformation parameters were solved using the coherent point drift (CPD) algorithm, and the TLS point clouds were further aligned using the recovery transformation matrix and refined by utilizing the iterative closest point (ICP) algorithm. Finally, individual tree segmentations were performed to estimate tree parameters using the TLS and fusion point clouds, respectively. The results show that the proposed method achieved more accurate registration of ALS and TLS point clouds in four plots, with the average distance residuals of coarse and fine registration of 194.83 cm and 2.14 cm being much smaller compared with those from the widely used crown feature point-based method. Using the fused point cloud data led to more accurate estimates of tree height than using the TLS point cloud data alone. Thus, the proposed method has the potential to improve the registration of ALS and TLS point cloud data and the accuracy of tree height estimation.

Associations between tree characteristics and street crime: A case study in downtown Austin, TX

Urban trees play a critical role in livable and safe communities. Few studies have attempted to comprehensively examine a set of tree-related characteristics by using multiple measures through aerial imagery, street view imagery, and tree inventories in relation to street crime, especially in downtowns with busy street activities. This study examined to what extent tree attributes were associated with street crime at the street segment scale. This study also aimed to investigate the relationships of proxy measures for view-obstructive levels of trees with street crimes. Using downtown Austin, Texas as a study area, we analyzed micro-level crime incidents at a street segment level: 518 street segments in total within the downtown neighborhood. We used violent and property crime incidents that occurred on the streets between 2014 and 2019. A series of negative binomial regressions were employed to explore the associations of the characteristics of trees with street crime. After adjusting for socioeconomic and built environment variables, tree canopy coverage using aerial imageries and tree coverage using Google Street View images had inverse relationships with both violent and property street crime rates while size-weighted tree density using tree inventory was only associated with violent street crime rate. The tree coverage in the bottom-half of GSV images was inversely associated with violent street crime rate but not with property street crime rate. Additionally, we found that large-sized tree density (DBH≥30 cm and 40 cm) was inversely associated with both types of crime rates while small-sized tree density (DBH≤20 cm) was positively associated with property crime rate. While further research is needed to validate the view-obstructing effects of small-sized tree density and tree coverage in the bottom-half of GSV images, it is important to consider factors such as appropriate tree size and the potential for view-obstruction to maximize the benefits of urban trees in crime prevention.

Estimation of fractal dimension of trees using LiDAR point data with sequential data decimation

Fractal dimensions of trees provide key ecological information regarding tree and forest stand structure. Although LiDAR scanning has the potential to reduce the intensive labor required to estimate fractal dimensions with manual measurements, neither an accuracy assessment comparing with true dimensions nor a guide or method for accurately measuring the dimensions using LiDAR scanners has been presented. This study examined the accuracy of fractal dimensions estimated using terrestrial LiDAR scanning (TLS) and unmanned aerial LiDAR scanning (ULS) through computer simulations and developed an approach to reduce the estimation bias. The true fractal dimensions of digitized trees of red pine (Pinus densiflora), ubame oak (Quercus phillyreoides), and giant timber bamboo (Phyllostachys bambusoides) in 18 site scenarios were calculated by applying the box-counting method to the tree object data. The true fractal dimensions were compared with the estimated dimensions in four TLS and ULS scenarios. Furthermore, a method to reduce the estimation bias was developed by introducing sequential point decimation and modeling the acquisition rate decay, thereby extrapolating the number of voxels before decay. Simple box-counting on highly dense and precise TLS data collected from four positions could retrieve the true fractal dimensions for all 18 site scenarios. However, sparse and less accurate TLS underestimated fractal dimensions in 8 out of 18 cases, and ULS overestimated the dimensions in 29 of 36 cases. The change in the relationship between the number of voxels and mesh size on a log-log plot with sequential decimation could be used to judge whether a set of TLS data can retrieve accurate fractal dimensions by applying simple box-counting to the TLS data. The developed method improved the estimations of fractal dimensions for 30 of the 37 cases where the simple box-counting on the TLS and ULS data provided biased estimations. In contrast, the estimation bias increased in 27 of the 35 cases where the simple box-counting on the TLS and ULS data successfully retrieved the true fractal dimensions.

Pelatihan Pengukuran Dimensi Pohon dan Pembuatan Label Pohon QR Code di Hutan Adat Ghimbo Pomuan

Sustainable forest management and support for the preservation of honey bee cultivation habitat requires collecting forest potential by measuring tree dimensions and presenting them on tree information labels. Furthermore, partners also do not have the knowledge and skills regarding measuring tree dimensions, namely measuring tree diameter and height and making QR Code tree information labels. Therefore, the service team provides a solution by increasing partners' knowledge by holding socialization about the meaning and benefits of measuring tree dimensions, the tools used in measuring tree dimensions. The team also improved partner skills by providing training on measuring tree dimensions and making QR Code tree information labels. The stages of community service carried out are the socialization of the meaning and benefits of measuring tree dimensions, the tools used in measuring tree dimensions, the advantages and disadvantages of tree dimension measurement tools and how to use tree dimension measurement tools. The team also conducted training on using tree dimension measurement tools, making QR Code tree information labels containing species, families, Latin and local names, tree coordinates, tree uses and photos with practice and field assistance as well as evaluations using questionnaires and observing partners' skills. After the service is completed, partners have or increase their knowledge about tree diameter and height, tools used for measuring tree diameter and height, how to use phiband and hagameter and knowledge of making QR Code tree labels of 89.16%. Partners have also been able to measure tree dimensions and make QR Code tree labels according to the knowledge they have received.

Influence of Tree Attributes on Silver Fir (Abies alba Mill.) Transitioning to Higher Defoliation Classes Determined by Logistic Regression

The age, size and morphology of trees, including crown dimensions, can influence crown defoliation. In Croatia, the selection management of silver fir (Abies alba Mill.) forests involves pure or mixed stands, either of which can be affected by various disturbances, resulting in unbalanced stand structures. The aim of this study was to estimate the probability of trees transitioning from one defoliation class to the next, examine the influence of tree attributes on that process and analyze the changes in survival over time. The study was conducted over a 18-year period (1990–2007) on two sites with contrasting stand structures: a uniform stand with a dominant share of silver fir (Site A) and an uneven-aged mixed beech–fir stand (Site B). Logistic regression was used to model tree transitions between defoliation classes. Uniform stand structure increased the likelihood of silver fir trees transitioning to a higher defoliation class, with limited dependence on the tree crown position. In contrast, suppressed and central trees in uneven-aged stands were more likely to transition to a higher defoliation due to greater competition between them. Diameter at breast height (DBH) was found to be a significant predictor of tree transition to higher defoliation classes, with a linear trend of increasing probability with increasing DBH. Crown position and crown length were also found to be significant predictors of changing defoliation class, with observed differences between sites occurring due to differences in stand structure. To ensure a balanced stand structure and enhance tree vitality, careful consideration of easily measurable tree elements such as DBH, crown length, and tree crown position is imperative when selecting trees for felling.

Allometry of the quasi-pipe (qPipe) model for estimating tree leaf area and tree leaf mass applied to plant functional types

The allometry of the pipe model quantifies the approximate proportionality between the tree leaf amount and the stem cross-sectional area at the crown base (ACB). It is useful for estimating and modeling carbon fixation abilities of trees but requires climbing the tree and is thus unsuitable for large-scale studies. Here, we adopted a previously proposed allometry (hereafter the quasi-pipe (qPipe) model allometry) formulating the relationship between the tree leaf amount and a surrogate of ACB, ACB_Est, calculated from tree dimensions measurable from the ground. Using published/unpublished data for 962 trees of 159 species collected between tropical rainforests and boreal forests, we established pipe and qPipe model allometries for evergreen-conifer, deciduous-conifer, evergreen-broadleaf, and deciduous-broadleaf plant functional types (PFTs). For the leaf area per tree (LA), allometric lines on a log–log plane were almost identical among the four PFTs in both models, with slopes of ~ 1. For the leaf mass per tree (LM), however, the allometric lines separated among the four PFTs in both models and had slopes greater than 1, indicating that the proportionality assumed in the pipe model held for LA but not LM. The applicability of the qPipe model in estimating the stand-scale leaf amount was further examined.