Intermediate Trees Research Articles

Temporal variations in burn severity among various vegetation layers in subtropical Pinus Roxburghii (Chir Pine) forest of Hindu Kush mountain range

The Sub-tropical forests of Pinus roxburghii (chir pine) provide various ecosystem services and act as watershed for low lying regions. However, this species is prone to human induced fire primarily due to local communities' dependence for various resources exacerbated by the current dry conditions. The impact of fire across various vegetation layers and developmental stages has not been thoroughly studied. Bearing to this, the present study was conducted using composite burn index to assess the severity on various layers of vegetation and their long-term impact through a chronological approach. The impact of fire on 40 representative circular plots with a radius of 30 m, categorized into five forest strata: large and intermediate trees, seedlings/saplings, pole stage, shrubs, and soil were investigated and compared across four different time interval: unburnt (B0), burnt two years ago (B2), burnt five years ago (B5), and burnt 15 years ago (B15). The results were statistically proved using Kruskal–Wallis followed by Dunn's Post Hoc and Friedman test with the Holm correction in R Language. The study revealed significant variations in the average burn severity for each treatment, with shrubs having the highest average score of burn severity (average = 1.4) and soil showing the lowest (average = 0.408). The results of the Friedman test indicated non-uniform distribution of burn severity across different ecological treatments. This study is contributing significant insights into the effects of forest fires and their severity on different vegetation layers, which can be instrumental in devising and executing successful restoration strategies.

Carbon budget at the individual-tree scale: dominant Eucalyptus trees partition less carbon belowground.

Large trees in plantations generally produce more wood per unit of resource use than small trees. Two processes may account for this pattern: greater photosynthetic resource use efficiency or greater partitioning of carbon to wood production. We estimated gross primary production (GPP) at the individual scale by combining transpiration with photosynthetic water-use efficiency of Eucalyptus trees. Aboveground production fluxes were estimated using allometric equations and modeled respiration; total belowground carbon fluxes (TBCF) were estimated by subtracting aboveground fluxes from GPP. Partitioning was estimated by dividing component fluxes by GPP. Dominant trees produced almost three times as much wood as suppressed trees. They used 25 ± 10% (mean ± SD) of their photosynthates for wood production, whereas suppressed trees only used 12 ± 2%. By contrast, dominant trees used 27 ± 19% of their photosynthate belowground, whereas suppressed trees used 58 ± 5%. Intermediate trees lay between these extremes. Photosynthetic water-use efficiency of dominant trees was c. 13% greater than the efficiency of suppressed trees. Suppressed trees used more than twice as much of their photosynthate belowground and less than half as much aboveground compared with dominant trees. Differences in carbon partitioning were much greater than differences in GPP or photosynthetic water-use efficiency.

Modelling the spatial abundance of invasive deer and their impacts on vegetation at the landscape scale

Deer populations and their impacts on forest ecosystems are increasing globally. Given the imperative and expense to mitigate impacts of invasive deer, we aimed to elucidate critical drivers of (i) deer density, (ii) deer impacts, and (iii) the relationship between them, to facilitate targeted management. We used quantile regression forests to model deer density (faecal pellet counts at 1948 locations) and impacts (browsing and other impacts on > 23,000 woody plants at 343 locations) across a mosaic of agricultural and forested ecosystems in Victoria, Australia (12,775 km2). Climate, topography, vegetation cover, and distance to water features were included as model covariates. Modelled deer density (r2 = 0.71, MAE = 0.56 pellets/m2) was most influenced by distance to waterbodies (> 10 ha, 31.2%), elevation (14.3%) and woody vegetation cover (12.9%). Modelled deer impact (r2 = 0.32, MAE = 6.9%) was most influenced by deer density (21.0%), mean annual precipitation (12.8%) and elevation (12.2%). Deer density was typically highest near large waterbodies, at low elevation, and with intermediate tree cover (40–70%). Impacts increased steadily with deer density up to ~ 2 pellets/m2. Our study demonstrates the importance of forest water and forest agricultural interfaces for both deer density and impacts. Deer are likely to be most abundant near waterbodies due to the availability of high-quality forage and water, and prefer lowland locations that have access to both open and forested habitats. Spatial models can be used to predict deer density and associated impacts to facilitate targeted invasive deer management.

Responses of the Crown Shape of Larix kaempferi Plantations to Site Index in Subtropical Areas of China

This study addresses how site index may affect crown shape by developing a crown shape regression model for the planted L. kaempferi at high altitudes in the subtropical climate of China. A total of 9241 branches from 78 trees, including 39 dominant trees and 39 intermediate trees, were measured in Hubei Province, southern China. The branch characteristics, including branch length, branch angle, and branch chord length of all living branches, were measured by felling trees. The models that showed good performance in crown shape modeling were used and compared in the present study. The goodness of fit statistics and stability of parameter estimation of the modified Kozak equation were better than those of the segmented polynomial equation. A nonlinear mixed-effect crown shape model was developed based on the modified Kozak equation. In addition to the tree level variables of diameter at the breast height (DBH), crown ratio (CR), and tree height-to-DBH ratio, an attempt was made to incorporate the site index into the crown shape model for the planted L. kaempferi. However, the site index was not a significant variable in the crown shape model. The purpose of our study was to lay the foundation for further study of the growth of the trees and the effects of crown morphology on stem growth in the future.

Assessment of Potential Prediction and Calibration Methods of Crown Width for Dahurian Larch (Larix gmelinii Rupr.) in Northeastern China

Crown width (CW) is an important indicator for assessing tree health, vitality, and stability, as well as being used to predict forestry models and evaluate forest dynamics. However, acquiring CW data is laborious and time-consuming, making it crucial to establish a convenient and accurate CW prediction model for forest management. In this study, we developed three models capable of conducting calibration: generalized models (GM), quantile regression models (QR), and mixed-effects models (MIXED). The aim was to effectively improve the prediction accuracy of CW using data from Dahurian larch (Larix gmelinii Rupr.) in Northeastern China. Different sampling designs were applied, including selecting the thickest, thinnest, intermediate, and random trees, with 1 to 10 sample trees for each design. The results showed that all models achieved accurate CW predictions. MIXED displayed the most superior fitting statistics than GM and QR. In model validation, with the increase in the number of sample trees, the model prediction accuracy gradually improved and the model differences gradually reduced. MIXED produced the smallest RMSE, MAE, and MAPE across all sampling designs. The intermediate tree sampling design with the best validation statistics for the given sample size was selected as the final sampling design. Under intermediate tree sampling design, MIXED required a minimum of five sample trees, while GM and QR required at least five and six sample trees for calibration, respectively. Generally, we suggested selecting MIXED as the final CW prediction model and using the intermediate tree sampling design of five trees per plot. This study could provide ideas and support for forest managers to accurately and efficiently predict CW.

Geodesics to characterize the phylogenetic landscape.

Phylogenetic trees are fundamental for understanding evolutionary history. However, finding maximum likelihood trees is challenging due to the complexity of the likelihood landscape and the size of tree space. Based on the Billera-Holmes-Vogtmann (BHV) distance between trees, we describe a method to generate intermediate trees on the shortest path between two trees, called pathtrees. These pathtrees give a structured way to generate and visualize part of treespace. They allow investigating intermediate regions between trees of interest, exploring locally optimal trees in topological clusters of treespace, and potentially finding trees of high likelihood unexplored by tree search algorithms. We compared our approach against other tree search tools (Paup*, RAxML, and RevBayes) using the highest likelihood trees and number of new topologies found, and validated the accuracy of the generated treespace. We assess our method using two datasets. The first consists of 23 primate species (CytB, 1141 bp), leading to well-resolved relationships. The second is a dataset of 182 milksnakes (CytB, 1117 bp), containing many similar sequences and complex relationships among individuals. Our method visualizes the treespace using log likelihood as a fitness function. It finds similarly optimal trees as heuristic methods and presents the likelihood landscape at different scales. It found relevant trees that were not found with MCMC methods. The validation measures indicated that our method performed well mapping treespace into lower dimensions. Our method complements heuristic search analyses, and the visualization allows the inspection of likelihood terraces and exploration of treespace areas not visited by heuristic searches.

Elevated mortality rates of large trees allow for increased frequency of intermediate trees: A hypothesis supported by demographic model comparison with plot and LiDAR data

Tree diameter distributions are important indicators of forest structure, are a principal element of forest carbon stock estimates, and are theoutcome of forest demography. Hump-shaped tree diameter distributions, also known as rotated-sigmoid diameter distributions, are characterized by an increased frequency of intermediately-sized trees over what would be extrapolated from the small tree size distribution and are common in temperate forests. One hypothesis to explain hump-shaped tree size distributions is the U-shaped mortality curve, where the mortality rates of the largest canopy trees are higher than those of intermediately-sized canopy trees. However, studies that have directly tested this hypothesis by comparing tree diameter distributions predicted from forest demographic models with empirical diameter distributions are lacking, and how the U-shaped mortality curve influences other aspects of forest structure such as canopy height is not well understood. We used model-data comparisons to test the hypothesis that the U-shaped mortality curve generates the hump-shaped tree diameter distribution. We used two versions of a forest demographic model (the PPA model) to predict tree diameter distributions, one that assumed that tree demographic rates varied only between understory and canopy trees, and a second that assumed tree demographic rates varied among understory trees, small canopy trees, and large canopy trees, consistent with the U-shaped mortality curve. We compared predictions from each form of the model with empirical tree diameter distributions from the Wind River Forest Dynamics plot, a 27.2 ha forest dynamics plot with a hump-shaped diameter distribution. We found that the model that accounted for the higher mortality rates of larger canopy trees generated a hump-shaped distribution, whereas the model that did not account for the higher mortality rates of larger trees was not able to generate a hump-shaped diameter distribution. To understand how the assumptions of forest demographic patterns affected other aspects of forest structure that could be derived from remote sensing, we compared predictions of forest canopy height from each form of the model with measurements of forest canopy height derived from airborne LiDAR. We found that accounting for the higher mortality rates of larger trees became even more critical to accurate prediction of forest canopy height because intermediate-sized trees occupy large areas in the canopy. Our results demonstrate the link between the U-shaped mortality curve and hump-shaped diameter distributions, and suggest that accurate characterization of the demography of large trees may be particularly important for predicting forestcanopy structure and carbon stocks.

Agromorphological characterization of cacao (Theobroma cacao L.) accessions from the germplasm bank of the National Institute of Agrarian Innovation, Peru

Agromorphological characterization of cacao accessions in Peru is currently an important tool in the conservation and genetic improvement of cacao germplasm. The objective of this study was to carry out the morphological and agronomic characterization of 113 cacao accessions from the Huarangopampa germplasm bank. Tree, leaf, flower, fruit and seed descriptors were used. The data collected were processed by descriptive statistics using multivariate techniques. Five groups were formed according to similar characteristics. The accessions of group 1 are vigorous trees with an pod index of 19.27 pods/kg of seeds; the groups that presented better differential characteristics were group 2 with erect tree architecture, intermediate vigorousness, purple seed color and pod index of 20.07 pods/kg of seeds and group 3, which had the highest number of accessions with the lowest pod index of 18.77 pods/kg of seeds, besides being vigorous trees and having purple seeds. On the other hand, group 4 presented a particular characteristic of white seed color and high pod indexes with 22.11 pods/kg of seeds. Finally, group 5 accessions were characterized by intermediate tree architecture and vigor with an pod index of 21.3 pods/kg of seeds. The morphoagronomic characterization constitutes a first advance in the identification of cacaos with potential for genetic improvement and advances in the Peruvian chocolate industry.

Predicting and calibrating height to crown base: a case for Dahurian larch (Larix gmelinii Rupr.) in Northeastern China

The applicability of height to crown base (HCB) appears to be particularly broad given the important impact on explaining tree growth dynamics. Given the high cost of measuring HCB, accurate prediction with a few trees is popular in forestry practice. In this study, a fixed-effects model (FEM), a mixed-effects model (MEM), and quantile regressions (QR) were adopted to predict HCB using data from natural secondary forests of Dahurian larch ( Larix gmelinii Rupr.) in Northeastern China. Corresponding calibration techniques were applied to trees with different sample designs (random selection, the thickest tree selection, the intermediate tree selection, and the thinnest tree selection) and sample sizes (1–10 trees per plot). The results showed that all models achieved accurate HCB predictions. The QR calibration technique of 3-quantiles achieved simple and accurate consequences compared to 5-quantiles and 9-quantiles. MEM displayed the most robust and superior statistics. The selection of the two thickest trees was recommended for the MEM. For FEM and QR, the sample size should be exceeded by 5. Generally, a combination of MEM and sampling two thickest trees per plot to predict HCB is recommended as a win–win solution that neither sacrifices model prediction accuracy nor minimizes the required measurement cost.

Hydroclimatic adaptation critical to the resilience of tropical forests.

Forest and savanna ecosystems naturally exist as alternative stable states. The maximum capacity of these ecosystems to absorb perturbations without transitioning to the other alternative stable state is referred to as ‘resilience’. Previous studies have determined the resilience of terrestrial ecosystems to hydroclimatic changes predominantly based on space‐for‐time substitution. This substitution assumes that the contemporary spatial frequency distribution of ecosystems’ tree cover structure holds across time. However, this assumption is problematic since ecosystem adaptation over time is ignored. Here we empirically study tropical forests’ stability and hydroclimatic adaptation dynamics by examining remotely sensed tree cover change (ΔTC; aboveground ecosystem structural change) and root zone storage capacity (S r; buffer capacity towards water‐stress) over the last two decades. We find that ecosystems at high (>75%) and low (<10%) tree cover adapt by instigating considerable subsoil investment, and therefore experience limited ΔTC—signifying stability. In contrast, unstable ecosystems at intermediate (30%–60%) tree cover are unable to exploit the same level of adaptation as stable ecosystems, thus showing considerable ΔTC. Ignoring this adaptive mechanism can underestimate the resilience of the forest ecosystems, which we find is largely underestimated in the case of the Congo rainforests. The results from this study emphasise the importance of the ecosystem's temporal dynamics and adaptation in inferring and assessing the risk of forest‐savannah transitions under rapid hydroclimatic change.

A Bimodal Pattern and Age-Related Growth of Intra-Annual Wood Cell Development of Chinese Fir in Subtropical China.

Age plays an important role in regulating the intra-annual changes in wood cell development. Investigating the effect of age on intra-annual wood cell development would help to understand cambial phenology and xylem formation dynamics of trees and predict the growth of trees accurately. Five intermediate trees in each stand (total of 5 stands) in five age groupings of Chinese fir (Cunninghamia lanceolata Hook.) plantations in subtropical China were monitored on micro-cores collected weekly or biweekly from January to December in 2019. We modeled the dynamics of wood cell development with a mixed effects model, analyzed the age effect on intra-annual wood cell development, and explored the contribution of rate and duration of wood cell development on intra-annual wood cell development. We found a bimodal pattern of wood cell development in all age classes, and no matter the date of peak or the maximal number of cells the bimodal patterns were similar in all age classes. In addition, compared with the older trees, the younger trees had the longest duration of wood cell development because of the later end of wood cell development and a larger number of wood cells. The younger trees had the faster growth rate than the older trees, but the date of the maximal growth rate in older trees was earlier than younger trees, which led to the production of more wood cells in the younger trees. Moreover, we found that the number of cells in wood cell formation was mostly affected by the rate (92%) rather than the duration (8%) of wood cell formation.

Characterizing subcanopy structure of Mediterranean forests by terrestrial laser scanning data

Vegetation structure is one of the key factors in forest ecosystems. Especially understory structure has major implications for wildlife habitat selection, reproduction, and survival. Structural indices traditionally used to characterize understory vegetation are based on field vegetation surveys describing general features such as leaf area index (LAI), canopy cover or vegetation height, hiding much of the three-dimensional vegetation structure complexity. The application of terrestrial laser scanning (TLS) in forest ecological and management applications is becoming more effective. In this study, we use TLS data to quantify spatial attributes of forest subcanopy in four different forest strata ranging from 0.5 m to 10 m from the ground. We collected data in 12 plots of mature European beech (Fagus sylvatica L.) forests and 12 plots of mature black pine (Pinus nigra subsp. laricio Maire) forests, located in the Sila National Park, Italy. We propose a TLS-based approach to estimate a fine-scale vegetation density using the Plant Density Index (PDI) and to test the PDI at different height classes. We found a significant relationship between the PDI and the number of trees belonging to the dominant layer, using the Spearman correlation coefficient (r = 0.83, pval = 0.001). Basing on PDI values, a cluster analysis of the four subcanopy strata was carried out for deriving clusters of structurally homogeneous forest plots. Results identified three clusters in terms of the vegetation features in the horizontal height classes: the first cluster primarily includes Beech forests characterized by plots with the highest tree densities; the second one includes both Beech and Pine forests characterized by dense ground vegetation and shrubs and an intermediate tree density; the third group is represented by Pine forests with massive presence of vegetation lower strata and moderate tree density. Then, PCA allowed identifying the relationship between the considered subcanopy layers and forest plots.

Canopy status modulates formation of wood rays in scots pine under hemiboreal conditions

Non-structural carbohydrates (NSC) reserves are crucial for trees to cope with weather extremes, thus to ensure their survival and ecological plasticity. The NSC reserves can depend on social status, suggesting uneven plasticity of trees at the stand level. In stemwood of Scots pine (Pinus sylvestris L.), which is a widespread and important species, NSC reserves are stored in parenchyma in wood rays (WR). The quantity of WRs is adjusted intra-annually, allowing retrospective analysis of factors affecting their formation. Accordingly, the differences in WR quantity in stemwood of dominant and intermediate (canopy trees with reduced and narrow crowns) maturing Scots pine were assessed by quantitative wood anatomy. Tangential cuts from the outermost 30 tree-rings were analysed. The relative ray area was intermediate, i.e. covering about 5% of the tangential cut, yet expressed high individuality among the trees. The size and amount of WR mainly differed between the earlywood and latewood; WRs in latewood were higher although narrower in comparison to earlywood, yet their total amount was higher in earlywood. Canopy status had only a slight effect, as quantity and height of WR tended to be higher for the intermediate trees, particularly in earlywood. The size and quantity of WR expressed inter-annual variation, which was mainly related to the meteorological conditions prior to the formation of the tree-ring (previous summer and autumn) indicating legacy effects of climatic factors on NSC and susceptibility of trees to cumulative effects of weather extremes. However, the climatic signals in the inter-annual variation of WR were weaker than observed before, likely due to location of the studied stand in the mid-part of the species range. Nevertheless, the observed differences in mean values and inter-annual variation of WR suggested a within-species diversity of carbon allocation patterns, supporting adaptability of the species.

Pomological and phenological characteristics of the main pistachio cultivars in Greece

The present study aimed to evaluate the pomological and phenological traits, as well as kernel antioxidant potential of the dominant Greek pistachio cultivars, ‘Aegina’ and ‘Pontikis’ (Pistacia vera L.). Blooming of ‘Aegina’ cultivar occurred from early to mid of April, and nut maturation at middle to late of August. Production started at 6 to 7 years from grafting and full production observed at year 13. Blooming and nut maturation of ‘Pontikis’ occurred about 1 to 2 days later than ‘Aegina’ and production started 6 to 7 years from grafting, with full production observed in the 14th year. Mean tree yields reached 18.0 ± 1.0 kg and 17.4 ± 1.1 kg of dry nuts, in ‘Aegina’ and ‘Pontikis’ cultivar, respectively. ‘Aegina’ cultivar presented intermediate tree vigour and spreading growth habit, whereas ‘Pontikis’ high tree vigour and semi-erect growth habit. ‘Aegina’ nut had a narrowly cordate shape and the percentage of split nut was found at 78.5 ± 6.5. ‘Pontikis’ nut had ovoid shape and the percentage of split nut was 84.1 ± 6.2. In ‘Aegina’ cultivar 100 nuts weighted 101.0 g and in ‘Pontikis’ 114.4 g. Color of kernel was green externally and green to green-white internally, greener in ‘Pontikis’. The antioxidant potential of pistachio kernel measured by FRAP assay, total polyphenolic substances, flavonoids, flavanols and hydroxycinnamic acids content, did not differ (P &gt; 0.05) between cultivars. Evaluation of ‘Aegina’ and ‘Pontikis’ pistachio cultivars revealed that both are high yielding, with large nut sizes of acceptable appearance and high quality.

Is field-measured tree height as reliable as believed – Part II, A comparison study of tree height estimates from conventional field measurement and low-cost close-range remote sensing in a deciduous forest

Tree height is one of the most important tree attributes in forest inventory. However, using conventional field methods to measure tree height is a laborious and time-consuming process. Despite the great interest in the past to facilitate tree height measurements, new, upcoming solutions are not yet thoroughly investigated. In this study, we investigated the applicability of different close-range remote sensing options for tree height measurement in a complex lowland deciduous forest. Six sample plots in a pedunculate oak forest were measured in detail using conventional methods. Close-range remote sensing datasets used in this study represent solutions from low-cost sensors used for hand-held personal laser scanning (PLShh), unmanned–borne laser scanning (ULS) and unmanned aerial vehicle photogrammetry (UAVimage). Each tree in the sample plots was interactively measured directly from the point cloud, and correspondence of the field- and remote sensing measured trees was verified using tree positions collected during fieldwork. Cross-comparisons of different datasets were performed to evaluate the performances of different data sources in the tree height estimation with respect to crown class, tree height and species. All remote sensing data sources correlated well, e.g. biases between remote sensing sources were around ± 1%. The field-measured tree height in general correlated well with remote sensing data sources. The uncertainties and bias of the field measurements were dependent on the tree height and crown class. Field measurements tended to underestimate codominant and intermediate trees at the approximately 1 m magnitude, whilst remote sensing data sources were robust to crown classes. Low-cost ULS used in this study, and very likely in general, may not have enough penetration capability when measuring low and mostly occluded trees, causing missed treetops. PLShh gave tree height estimates closer to the real tree height than those derived from conventional field measurements for trees above 21 m height.

UCDiff: Difference Detection in Use Case Models of Healthcare System

Development of large-scale healthcare software projects essentially need the efficient management of the created software artifacts during software development process. In such projects different versions of an artifact are created at different times. Traditional software configuration management systems, such as Git, Subversion (SVN), etc., are designed for later phases of software development, which mainly handle the source code document. These systems are unable to perform difference detection and version management tasks on models such as unified modeling language diagrams. UML use case model is used for capturing functional requirements at analyses phase. Different versions of the use case model are created during analyses phase. This paper addresses the detection of differences between two versions of a use case model. In order to perform difference detection, we need to perform three main tasks, i. e., extract the contents of the model, comparison of models and difference representation. Most of the existing approaches in literature of model comparison deal with UML class diagrams. To the best of our knowledge, so far no appropriate approach addresses difference computation of use case model. Existing approaches are not applicable on use case model due to different semantics of use case model. In this research, the concept of model-based software configuration management (SCM) for use case difference detection is proposed. The use case models are created in an open source tool, starUML. The proposed difference algorithm is applied on intermediate tree structure representation of models. As a case study, different versions of a patient appointment healthcare system is used to evaluate different evaluation parameters, such as accuracy, domain independence, high conceptual level and tool independence.

UCDiff: Difference Detection in Use Case Models of Healthcare System

Development of large-scale healthcare software projects essentially need the efficient management of the created software artifacts during software development process. In such projects different versions of an artifact are created at different times. Traditional software configuration management systems, such as Git, Subversion (SVN), etc., are designed for later phases of software development, which mainly handle the source code document. These systems are unable to perform difference detection and version management tasks on models such as unified modeling language diagrams. UML use case model is used for capturing functional requirements at analyses phase. Different versions of the use case model are created during analyses phase. This paper addresses the detection of differences between two versions of a use case model. In order to perform difference detection, we need to perform three main tasks, i. e., extract the contents of the model, comparison of models and difference representation. Most of the existing approaches in literature of model comparison deal with UML class diagrams. To the best of our knowledge, so far no appropriate approach addresses difference computation of use case model. Existing approaches are not applicable on use case model due to different semantics of use case model. In this research, the concept of model-based software configuration management (SCM) for use case difference detection is proposed. The use case models are created in an open source tool, starUML. The proposed difference algorithm is applied on intermediate tree structure representation of models. As a case study, different versions of a patient appointment healthcare system is used to evaluate different evaluation parameters, such as accuracy, domain independence, high conceptual level and tool independence.

Modelling the responses of crown profiles to competition in terms of different tree classes and directions in two coniferous tree species in northeastern China

Using branch data from 63 L.kaempferi and 36 L.gmelinii sampled trees in northeastern China, the responses of crown profiles with different tree classes (dominant, intermediate and suppressed trees) and aspects (north, east, south and west) to competition were studied. Crown displacement, defined as the distance between the centre of gravity of the crown and the stem base, was calculated for all the sampled trees to estimate the crown plasticity. The horizontal crown overlapping area (COAH) between sampled trees and the closest neighbouring trees was calculated to estimate the neighbour competition. A crown profile model that includes COAH as the explanatory variable was developed, and the effect of COAH on the crown profile of two tree species was analysed. The results showed that more than half of the trees had the largest crown radius and upper crown surface area on the north and east sides for L.kaempferi and on the north and south sides for L.gmelinii. The crown displacement of L.kaempferi was greater on the north and east sides, and that of L.gmelinii was greater on the south and east sides. COAH had a significant effect on the crown profile model for both species. The mean square error reduction (MSER) for the crown profile model including COAH relative to the model without COAH was 1.68% and 2.10% for L.kaempferi and L.gmelinii, respectively. The COAH had a greater impact on the crown profile of L.gmelinii than that of L.kaempferi. The inflexion point of the dominant and intermediate trees for both species was sensitive to COAH and gradually moved towards the crown base as the neighbour competition intensified, while the inflexion point of the suppressed tree showed a weak response to COAH. The crown profile in the four directions was closely related to the current radial stem growth.

Application of growth traits and qualitative indices for selection of Scots pine (Pinus sylvestris l.) elite trees. A case study from Volyn region, western ukraine

Abstract Since the plus trees are selected based on phenotype, it is necessary to evaluate them in progeny test. The aim of this study is an indication of selecting elite mother trees based on the results from half-sib progeny test trials. As study sites, two Scots pine half-sib progeny tests were selected. During evaluation, the progenies had reached the age of 38 and 40 years, respectively. In both progeny trials, quantitative parameters and qualitative traits of Scots pine half-sib progenies were investigated. Based on these data, complex evaluation of half-sib families was carried out. We concluded that, Scots pine progenies at the age of 38 and 40 years in fresh and moist mixed forests are characterised by acceptable quality, with the survival being 25%–33% per progeny test trial. Based on a complex evaluation of 38- and 40-year-old half-sib progenies of plus trees, we proposed to select 31% of tested plus/mother trees as candidates for elite trees. Further, the list of candidates for elite trees was created with five plus trees from the Volyn region (26% of the total tested from the region) and four plus trees from the Lviv region (40% of the total tested from the region). With age, the share of the best and undesirable trees decreases, while the proportion of intermediate trees increases in both control trees and half-sib progenies. At the age of 38 and 40 years, the proportion of fast-growing offspring was from 0% to 36%, while the declining trend that was observed in previous years was being continued. Thus, due to the declining trend in the proportion of fast-growing offspring observed at the age of 38 and 40 years, we propose to select candidate trees for an elite group not early than after 40 years of test their progenies.

Flammability thresholds or flammability gradients? Determinants of fire across savanna-forest transitions.

Vegetation-fire feedbacks are important for determining the distribution of forest and savanna. To understand how vegetation structure controls these feedbacks, we quantified flammability across gradients of tree density from grassland to forest in the Brazilian Cerrado. We experimentally burned 102 plots, for which we measured vegetation structure, fuels, microclimate, ignition success and fire behavior. Tree density had strong negative effects on ignition success, rate of spread, fire-line intensity and flame height. Declining grass biomass was the principal cause of this decline in flammability as tree density increased, but increasing fuel moisture contributed. Although the response of flammability to tree cover often is portrayed as an abrupt, largely invariant threshold, we found the response to be gradual, with considerable variability driven largely by temporal changes in atmospheric humidity. Even when accounting for humidity, flammability at intermediate tree densities cannot be predicted reliably. Fire spread in savanna-forest mosaics is not as deterministic as often assumed, but may appear so where vegetation boundaries are already sharp. Where transitions are diffuse, fire spread is difficult to predict, but should become increasingly predictable over multiple fire cycles, as boundaries are progressively sharpened until flammability appears to respond in a threshold-like manner.