Crown Volume Research Articles

Measuring tree growth using terrestrial laser scanning

Forests are dynamic ecosystems that are constantly changing. The most common natural reasons for change in forests are the growth and death of trees, as well as the damage occurring to them. Tree growth appears as an increment of its structural dimensions, such as stem diameter, height, and crown volume, which all affect the structure of a tree. Repeated measurements of tree characteristics enable observations of the respective increments indicating tree growth. According to current knowledge, the tree growth process follows the priority theory, where trees aim to achieve sufficient lightning conditions for the tree crown through primary growth, whereas increment in diameter results from the secondary growth. Tree growth is known to have an effect on the carbon sequestration potential of trees as well as on the quality of timber. To improve the understanding of the underlying cause–effect relations driving tree growth, methods to quantify structural changes in trees and forests are needed. The use of terrestrial laser scanning (TLS) has emerged during the recent decade as an effective tool to determine attributes of individual trees. However, the capacity of TLS point cloud-based methods to measure tree growth remains unexplored. This thesis aimed at developing new methods to measure tree growth in boreal forest conditions by utilizing two-date TLS point clouds. The point clouds were also used to investigate how trees allocate their growth and how the stem form of trees develops, to deepen the understanding of tree growth processes under different conditions and over the life cycle of a tree. The capability of the developed methods was examined during a five- to nine-year monitoring period with two separate datasets consisting of 1315 trees in total. Study I demonstrated the feasibility of TLS point clouds for measuring tree growth in boreal forests. In studies II and III, an automated point cloud-based method was further developed and tested for measuring tree growth. The used method could detect trees from two-date point clouds, with the detected trees representing 84.5% of total basal area. In general, statistically significant changes in the examined attributes, such as diameter at breast height, tree height, stem volume, and logwood volume, were detected during the monitoring periods. Tree growth and stem volume allocation seemed to be more similar for trees growing in similar structural conditions. The findings obtained in this thesis demonstrate the capabilities of repeatedly acquired TLS point clouds to be used for measuring the growth of trees and for characterizing the structural changes in forests. This thesis showed that TLS point cloud-based methods can be used for enhancing the knowledge of how trees allocate their growth, and thus help discover the underlying reasons for processes driving changes in forests, which could generate benefits for ecological or silvicultural applications where information on tree growth and forest structural changes is needed.

Estimation of Larch Growth at the Stem, Crown, and Branch Levels Using Ground-Based LiDAR Point Cloud

Tree growth is an important indicator of forest health and can reflect changes in forest structure. Traditional tree growth estimates use easy-to-measure parameters, including tree height, diameter at breast height, and crown diameter, obtained via forest in situ measurements, which are labor intensive and time consuming. Some new technologies measure the diameter of trees at different positions to monitor the growth trend of trees, but it is difficult to take into account the growth changes at different tree levels. The combination of terrestrial laser scanning and quantitative structure modeling can accurately estimate tree structural parameters nondestructively and has the potential to estimate tree growth from different tree levels. In this context, this paper estimates tree growth from stem-, crown-, and branch-level attributes observed by terrestrial laser scanning. Specifically, tree height, diameter at breast height, stem volume, crown diameter, crown volume, and first-order branch volume were used to estimate the growth of 55-year-old larch trees in Saihanba of China, at the stem, crown, and branch levels. The experimental results showed that tree growth is mainly reflected in the growth of the crown, i.e., the growth of branches. Compared to one-dimensional parameter growth (tree height, diameter at breast height, or crown diameter), three-dimensional parameter growth (crown, stem, and first-order branch volumes) was more obvious, in which the absolute growth of the first-order branch volume is close to the stem volume. Thus, it is necessary to estimate tree growth at different levels for accurate forest inventory.

Ground-based/UAV-LiDAR data fusion for quantitative structure modeling and tree parameter retrieval in subtropical planted forest

Light detection and ranging (LiDAR) has contributed immensely to forest mapping and 3D tree modelling. From the perspective of data acquisition, the integration of LiDAR data from different platforms would enrich forest information at the tree and plot levels. This research develops a general framework to integrate ground-based and UAV-LiDAR (ULS) data to better estimate tree parameters based on quantitative structure modelling (QSM). This is accomplished in three sequential steps. First, the ground-based/ULS LiDAR data were co-registered based on the local density peaks of the clustered canopy. Next, redundancy and noise were removed for the ground-based/ULS LiDAR data fusion. Finally, tree modeling and biophysical parameter retrieval were based on QSM. Experiments were performed for Backpack/Handheld/UAV-based multi-platform mobile LiDAR data of a subtropical forest, including poplar and dawn redwood species. Generally, ground-based/ULS LiDAR data fusion outperforms ground-based LiDAR with respect to tree parameter estimation compared to field data. The fusion-derived tree height, tree volume, and crown volume significantly improved by up to 9.01%, 5.28%, and 18.61%, respectively, in terms of r RMSE. By contrast, the diameter at breast height (DBH) is the parameter that has the least benefits from fusion, and r RMSE remains approximately the same, because stems are already well sampled from ground data. Additionally, particularly for dense forests, the fusion-derived tree parameters were improved compared to those derived from ground-based LiDAR. Ground-based LiDAR can potentially be used to estimate tree parameters in low-stand-density forests, whereby the improvement owing to fusion is not significant. • Mitigation of the limitations of tree localization in case of ground-based/ULS LiDAR data co-registration using virtual keypoints. • Fusion of ground-based/ULS LiDAR data based on removal of redundant and noisy points. • Investigation and evaluation of the utility of ground-based/ULS LiDAR data fusion for tree parameter estimation. • Ground-based/ULS LiDAR data fusion improved estimation of tree height, tree volume, and crown volume. • Ground-based/ULS LiDAR data fusion has strong potential in QSM of trees particularly in high-stand-density forest.

A Robust Deep Learning Approach for the Quantitative Characterization and Clustering of Peach Tree Crowns Based on UAV Images

The accurate large-scale measurement of peach crowns is vital in horticultural science and the optimization of orchard management. Nowadays, numerous crown parameters (e.g., crown area, height, and volume) can be obtained via the analysis of point clouds or photographs. Current laser-based sensors provide the required reliable and accurate information; however, they are costly and time-consuming. Therefore, a simpler approach for crown measurement is required. For this purpose, this study presents a pipeline for the monitoring and clustering of 259 peach tree crowns based on unmanned aerial vehicle (UAV) images of a peach orchard in Southeast China. Considering the limitation that the original aerial image dataset contains little information, a data augmentation process is adopted, and an efficient deep learning architecture based on conditional generative adversarial networks (cGANs) was designed to extract the crown area. Then, the shape of the crown area was clustered using an edge detection process and a <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula>-means algorithm. Finally, an ellipsoid volume method (EVM) was applied to estimate the crown volume. Five indicators&#x2014;namely, <inline-formula> <tex-math notation="LaTeX">$Q_{\mathrm {seg}}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$S_{\mathrm {r}}$ </tex-math></inline-formula>, Precision, Recall, and F-measure&#x2014;were employed to evaluate the crown extraction effects, and the average results for testing samples were 0.832, 0.847, 0.851, 0.828, and 0.846, respectively. Compared with other approaches&#x2014;namely, fully convolutional network (FCN), U-Net, SegNet21, the excess green index (ExG), and the color index of vegetation extraction (CIVE)&#x2014;the proposed cGAN model performs better, achieving an accuracy improvement of 5&#x0025;&#x2013;25&#x0025;. For the estimation of crown volume, using measurements from a light detection and ranging (LIDAR) scanner as a reference, the correlation coefficient and relative-root-mean-square error (R-RMSE) were found to be 0.836&#x0025; and 14.93&#x0025;, respectively. Overall, the results demonstrate that the proposed method is feasible for measuring peach tree crowns. The wide application of such technology would facilitate applied research in plant phenotyping and precision horticulture.

Variability and plus tree selection in Swietenia macrophylla, from Kerala, South India

Big leaf mahogany (Swietenia macrophylla, King) is a valuable Neotropic timber species. It is the first extensively traded timber species to be listed in Appendix II of the CITES in 2002. The tree was introduced to India in 1795 and Kerala in 1872. The present study aimed at selecting plus trees of Swietenia macrophylla and evaluating their genetic variability. Forty-five plus trees were selected from 593 candidate trees spread over fifteen locations in Kerala based on baseline regression of trunk volume to crown volume, followed by scoring for qualitative characters. The clean bole height, GBH, crown width, crown volume and wood density of CPTs ranged from 6 to 13.4 m, 0.75 to 2.00 m, 8 to 15 m, 7 to 16 m and 21 to 23 mm, respectively. The plus trees were grouped into five clusters based on their quantitative and qualitative characters. Clustering was independent of the geographical location indicating a lack of development of any land races in the species. Key words: Swietenia macrophylla, Mahogony, Plus tree selection, CPT, Genetic variability

Yield and crown structure characteristics in a red oak (Quercus rubra L.) stand: Case study

The paper provides the results of a detailed analysis of timber volume and several important crown variables of red oak (Quercus rubra L.) based on an experimental plot in eastern Hungary. At the age 32 years the crop trees belonged to different height classes. If the volume of the mean tree from height class I was considered as 100%, the volume of the mean tree of class II was 59%, and the mean tree of class III was only 36%. It appeared that there was a significant correlation between crown indices and yield. For this reason, diameter at breast height showed a positive linear correlation with crown diameter (R2= 0.6211). Additionally, there was also positive linear relationship between crown diameter and volume (R2= 0.6908). The variation of crown indices is height even within the same stand and indicates the importance of following a selective thinning operation method.

Quantifying Crown Morphology of Mixed Pine-Oak Forests Using Terrestrial Laser Scanning

Mixed forests make up the majority of natural forests, and they are conducive to improving the resilience and resistance of forest ecosystems. Moreover, it is in the crown of the trees where the effect of inter- and intra-specific interaction between them is evident. However, our knowledge of changes in crown morphology caused by density, competition, and mixture of specific species is still limited. Here, we provide insight on stand structural complexity based on the study of four response crown variables (Maximum Crown Width Height, MCWH; Crown Base Height, CBH; Crown Volume, CV; and Crown Projection Area, CPA) derived from multiple terrestrial laser scans. Data were obtained from six permanent plots in Northern Spain comprising of two widespread species across Europe; Scots pine (Pinus sylvestris L.) and sessile oak (Quercus petraea (Matt.) Liebl.). A total of 193 pines and 256 oaks were extracted from the point cloud. Correlation test were conducted (ρ ≥ 0.9) and finally eleven independent variables for each target tree were calculated and categorized into size, density, competition and mixture, which was included as a continuous variable. Linear and non-linear multiple regressions were used to fit models to the four crown variables and the best models were selected according to the lowest AIC Index and biological sense. Our results provide evidence for species plasticity to diverse neighborhoods and show complementarity between pines and oaks in mixtures, where pines have higher MCWH and CBH than oaks but lower CV and CPA, contrary to oaks. The species complementarity in crown variables confirm that mixtures can be used to increase above ground structural diversity.

Extracting Crown Morphology with a Low-Cost Mobile Lidar Scanning System in the Natural Environment

To meet the demand for intelligent measurements of canopy morphological parameters, a mobile LiDAR scanning system with LiDAR and IMU as the main sensors was constructed. The system uses a LiDAR-IMU tight coupling odometry method to reconstruct a point cloud map of the area surveyed. After using the RANSAC algorithm to remove the map ground, the European clustering algorithm is used for point cloud segmentation. Finally, morphological parameters of the canopy, such as crown height, crown diameter, and crown volume, are extracted using statistical and voxel methods. To verify the algorithm, a total of 43 trees in multiple plots of the campus were tested and compared. The algorithm defined in this study was evaluated with manual measurements as reference, and the morphological parameters of the canopy obtained using the LOAM and LeGO-LOAM algorithms as the basic framework were compared. Experiments show that this method can be used to easily obtain the crown height, crown diameter, and crown volume of the area; the correlation coefficients of these parameters were 0.91, 0.87, and 0.83, respectively. Compared with the LOAM and LeGO-LOAM methods, they were increased by 0.004, 0.12, and 0.13 and 0.07, 0.15, and 0.04, respectively. The test results for this new system are positive and meet the requirements of horticulture and orchard measurements, indicating that it will have significant value as an application.

Opportunities for winter prescribed burning in mixed conifer plantations of the Sierra Nevada

BackgroundYoung, planted forests are particularly vulnerable to wildfire. High severity effects in planted forests translate to the loss of previous reforestation investments and the loss of future ecosystem service gains. We conducted prescribed burns in three ~35-year-old mixed conifer plantations that had previously been masticated and thinned during February in order to demonstrate the effectiveness of winter burning, which is not common in the Sierra Nevada, California.ResultsOn average, 59% of fine fuels were consumed and the fires reduced shrub cover by 94%. The average percent of crown volume that was damaged was 25%, with no mortality observed in overstory trees 1 year following the fires. A plot level analysis of the factors of fire effects did not find strong predictors of fuel consumption. Shrub cover was reduced dramatically, regardless of the specific structure that existed in plots. We found a positive relationship between crown damage and the two variables of Pinus ponderosa relative basal area and shrub cover. But these were not particularly strong predictors. An analysis of the weather conditions that have occurred at this site over the past 20 years indicated that there have consistently been opportunities to conduct winter burns. On average, 12 days per winter were feasible for burning using our criteria. Windows of time are short, typically 1 or 2 days, and may occur at any time during the winter season.ConclusionsThis study demonstrates that winter burning can be an important piece of broader strategies to reduce wildfire severity in the Sierra Nevada. Preparing forest structures so that they can be more feasible to burn and also preparing burn programs so that they can be nimble enough to burn opportunistically during short windows are key strategies. Both small landowners and large agencies may be able to explore winter burning opportunities to reduce wildfire severity.

Growth features of apple varieties and forms with natural and compact crown types

This research explores the compactness of apple varieties and forms with different types of crown. Orchards on semi-vigorous rootstocks with density and high density planting systems are cost-effective in modern horticulture. For making such gardens, it is necessary to have trees with special compact crown shape. They ensure the high-quality fruits production, meeting the requirements of world standards. To date the most perspective apple varieties and forms for domestic intensive gardening from the rich gene pool of the Selection and Genetic Center of Federal State Scientific Institution «I. V. Michurin Federal Scientific Center» are identified. Varieties of folk domestic and foreign breeding took part in the creation of new genotypes. Apple varieties and promising forms (more than 160 genotypes), including from near and far abroad selection, were used as materials for crown features studying. We conducted our study by the following indicators: tree height, crown volume, “degree of compactness” and the shoot-forming ability. We found that the genotypes Sholokhovskoye, Zvezda Artemyeva, 25-7(11), 40-9(8), 36-8(21), 40-9(6), 8-7(72), 40-9(7), 36-8(17), 62-5(140) have optimal crown parameters. We recommend their use for industrial horticulture and further breeding to create restrained growth, low-volume crown, and a high degree of compactness varieties.

Live Crown Ratio Models for Loblolly Pine (Pinus taeda) with Beta Regression

The growth and production potential of a tree depends on its crown dimensions as these are closely related to a tree’s photosynthetic capacity. However, tree crowns have been studied less compared to their main stems because of their lower market value and because the measurement of crown dimensions, such as crown volume or surface area, is difficult. Frequently, an individual tree’s live crown ratio (LCR) is predicted by linear or nonlinear models that are a function of easy-to-measure dendrometric variables using ordinary least-squares techniques. Using the long-term data from established genetic and spacing trials, we developed and evaluated the predictive performance of three nonlinear models and introduced a new generalized linear model for predicting LCR. The nonlinear models were fit using exponential, Weibull, and Richards functions. The generalized linear model was based on beta regression. This resulted in a slightly smaller error than the other models in predicting the LCR of loblolly pine trees used in this study. Crown ratio is measured in percentage unit and should be modeled using generalized linear models that assume a beta distribution for error terms.

Agroecological coverings for the sustainable production of Rambutan (Nephelium lappaceum L.)

Objective: To evaluate the influence of living and dead covers on the yield and quality of rambutan fruits (Nephelium lappaceum L.) in Soconusco, Chiapas, Mexico.&#x0D; Design / methodology / approach: Five treatments were evaluated, two live covers, two dead covers and an always clean control without covers. The following were evaluated: plant height, crown volume, fruit quality, fruit yield (t ha-1). The data were analyzed under a randomized block experimental design.&#x0D; Results: All the agroecological modalities of hedging evaluated produced fruits with the quality required for national and international commercialization.&#x0D; Study limitations / implications: The morphological and physiological response of the crop can change with the age of the tree.&#x0D; Findings / conclusions: An agroecological management strategy is presented to develop rambutan cultivation in Soconusco region.

Tree-ring density and carbon isotope composition are early-warning signals of drought-induced mortality in the drought tolerant Canary Island pine

Tree death is not always preceded by a visible decline in vigor (canopy dieback) or a progressive loss in crown volume. Identifying early-warning signals of incipient decline can help to implement the necessary measures to prevent tree death. The aim of this work is to understand what functional alterations preceded the massive drought-induced death of adult Pinus canariensis trees in an arid stand, located in the Canary Islands. To this aim, we analyzed interannual variations in earlywood and latewood width, wood density and anatomy, and carbon isotope composition, and the relationships among these variables, in dead and living trees from 1980 to 2013. Dead trees grew less since the 1990′s, produced fewer parenchyma rays and resin canals, and exhibited a trend of decreasing latewood density and a marked shift in carbon isotope discrimination over the last 34 years that were reversed in living trees. Higher wood density in living trees resulted from thicker tracheid cell walls rather than narrower lumens. The intrinsic water use efficiency shifted from higher to lower values in dead trees after the 2000s. These results suggest a carbon limitation to maintain hydraulic safety under xylem tension, as well as to maintain storage and defense capacity, which can render trees more vulnerable to severe drought episodes. A long-term trend of decreasing tree-ring density and a reduced intrinsic water use efficiency in the short-term can be early-warning signals of carbon limitation and tree decline in drought-stressed P. canariensis. The analysis of these variables can be used to assess tree decline risks in similarly vulnerable conifer populations inhabiting drought-prone regions.

Investigation of stem anatomy in relation to hydraulic conductance, vegetative growth and yielding potential of ‘Summit’ cherry trees grafted on different rootstock candidates

Abstract Severe climate alterations that seriously challenge fruit production, combined with the demand for healthy, pesticide-free fruits, continuously direct rootstock/cultivar selection towards high adaptable varieties breeding. This study aimed to investigate the rootstocks’ influence on the performance of grafted ‘Summit’ cherry trees, including potentially dwarfing Prunus cerasus, Prunus fruticosa and Prunus mahaleb rootstock candidates. Anatomical properties of rootstock and scion stems were investigated to determine variation among different rootstocks and scion-rootstock combinations and to establish the link between trunk hydraulic conductivity, effective tree crown volume and yielding potential. Cross-section anatomical characteristics varied significantly both in rootstock and scion stems, indicating a clear influence of rootstock genotype on grafted sweet cherry trees. It was observed that all investigated cherry rootstock candidates belong to the low-vigorous rootstocks, based on the estimated effective crown volume of grafted trees compared to ‘Gisela 5’, with values ranging from 0.86 to 2.97 m3 in the fifth year after planting. Results showed a statistically significant positive correlation between trunk hydraulic conductivity, effective tree crown volume and yielding potential, with correlation coefficients up to 0.96. Significantly higher effective crown volume and trunk hydraulic conductance of trees grafted on P. cerasus compared to the trees on control, as well as highest yielding potential, showed better adaptation of these rootstock candidates in the trial without irrigation implemented. It was found that PC_05_04 rootstock candidate could be considered as the most appropriate choice when raising the high-density sweet cherry plantations, due to assessed parameters of vegetative and generative growth.

Single-tree crown shape and crown volume models for Pinus nigra J. F. Arnold in central Italy

Key message The crown volume of Pinus nigra trees can be modelled as a function of the total crown length and the crown radius at crown base to support forest management practices. ContextThe crown volume of trees is rarely considered in forest management practices and is often approximated to a simple cone or paraboloid whose volume can be broadly derived from costly measurements.AimsWe developed two equations to predict single-tree crown volumes for Pinus nigra plantations in Italy based on the analysis of a database with 3578 trees.MethodsTwo key crown parameters (total length of the crown and crown radius at crown base) were here modelled using directly measurable mensurational data using Generalise Additive Mixed-effect Model. Afterwards, two functions were then proposed to predict single-tree crown volumes.ResultsThe fitted models were statistically significant and explaining 57.6% for crown radius at crown base and 87.1% for crown length of the total variance. The power model for single-tree crown volumes calculation showed a mean absolute error around 4.1 m3 for the upper portion of the crown and 12.1 m3 for the lower part for a mean absolute relative error of 12.5% and 32.0% respectively for a global value of 16.4%.ConclusionSingle-tree and stand-level data are fundamental to balance forest management trajectories. The provided functions may be used in external dataset to derive indication on the single-tree or stand-level crown volume to be used as indicators of ground coverage.

The influence of urban tree characteristics on environmental noise in Montreal, Canada

BACKGROUND AND AIM: Vegetation can reduce environmental noise, but limited information exists regarding how specific characteristics of trees of the urban forest influence environmental noise. We investigated the physical characteristics of urban trees that influence environmental noise measurements in Montreal, Canada. METHODS: We used Light Detection and Ranging (LiDAR) point cloud data from 2015 to extract the characteristics of all trees across the island of Montreal. Needle and broadleaf trees were distinguished with a Random Forest algorithm. Based on individual tree characteristics, we computed the total area of the tree crown footprint, the mean tree crown centroid height, the mean volume of tree crowns, and the percentage of broadleaf trees within various buffers (250 to 1000m) around 87 noise measurement sites across the city. Noise measurements were taken over a two-week period in the spring of 2010. Random Forest regression models were used to estimate the variation in noise around measurement sites related to tree characteristics, the Normalized Difference Vegetation index (NDVI), and distances of the measurement sites to major noise sources (highways, railways, and roads). RESULTS:The 24-hour equivalent noise levels averaged across the 87 monitoring sites were 57.5 + 5.1 dBA. The mean crown centroid tree height (5.2 + 0.4m) and the total area of crown footprint (130.7k + 63.4m2) within 500m of each site location were the strongest predictors of measured noise levels. The percentage increased mean squared errors indicated that in 500m buffers, the total area of the crown footprint (29.2%) and the mean crown centroid height (12.6%) were associated with a stronger noise decrease than NDVI (3.2%); similar patterns were observed with other buffers. CONCLUSIONS:Our findings suggest that tree crown footprint and centroid height, and not just the overall amount of vegetation, may play a vital role in reducing urban noise levels. KEYWORDS: Built environment, Green space, Noise

Tree characteristics and environmental noise in complex urban settings – A case study from Montreal, Canada

Field studies have shown that dense tree canopies and regular tree arrangements reduce noise from a point source. In urban areas, noise sources are multiple and tree arrangements are rarely dense. There is a lack of data on the association between the urban tree canopy characteristics and noise in complex urban settings. Our aim was to investigate the spatial variation of urban tree canopy characteristics, indices of vegetation abundance, and environmental noise levels. Using Light Detection and Ranging point cloud data for 2015, we extracted the characteristics of 1,272,069 public and private trees across the island of Montreal, Canada. We distinguished needle-leaf from broadleaf trees, and calculated the percentage of broadleaf trees, the total area of the crown footprint, the mean crown centroid height, and the mean volume of crowns of trees that were located within 100m, 250m, 500m, and 1000m buffers around 87 in situ noise measurement sites. A random forest model incorporating tree characteristics, the normalized difference vegetation index (NDVI) values, and the distances to major urban noise sources (highways, railways and roads) was employed to estimate variation in noise among measurement locations. We found decreasing trends in noise levels with increases in total area of the crown footprint and mean crown centroid height. The percentages of increased mean squared error of the regression models indicated that in 500m buffers the total area of the crown footprint (29.2%) and the mean crown centroid height (12.6%) had a stronger influence than NDVI (3.2%) in modeling noise levels; similar patterns of influence were observed using other buffers. Our findings suggest that municipal initiatives designed to reduce urban noise should account for tree features, and not just the number of trees or the overall amount of vegetation.

Competition in Abies kawakamii forests at subtropical high mountain in Taiwan.

The spatial patterns of plant species reflect the competitive pressures on individuals. To generate Competition indices (CI), we measured the diameter at breast height (DBH), crown volumes (CV) and the distances between trees. In this study, Abies kawakamii were divided based on the dominant component of the understory (moss or bamboo) to (1) investigate the relationship between the CI and stand structural attributes (SSAs); (2) compare the inter- and intraspecies; CIs as well as living and dead individual CIs; and (3) examine the relationship between the DBH and CI. The current findings indicate that the understory composition affected the CI and SSAs. The interspecies CI was larger than the intraspecies CI when bamboo-dominated the understory. In contrast, the intraspecies CI was larger than the interspecies CI when the understory was dominated by moss. The CI of dead individuals was higher than that of live individuals due to the biological characteristics and regeneration needs of Abies. Additionally, sensitivity to the environment and available resources may exert more pressure on young individuals than mature individuals.

Calcium and Silicon Fertiliser Influence on Fungicide Efficacy Against Guignardia Leaf Blotch and Apple Scab Management

Management of fungal diseases within urban landscapes relies heavily on repeat fungicide sprays. Environmental concerns have led to a need to eliminate or reduce fungicide use. Foliar sprays of calcium- (Ca) and silicon- (Si) based fertilisers have been shown to reduce symptom severity of several fungal pathogens. The aim of our research was to evaluate the influence of Ca chloride, Ca metasolate, tetra ethyl silicate, and potassium silicate fertilisers, applied independently and in combination with a synthetic fungicide (penconazole) at full and half strength, on apple scab (Venturia inaequalis) and Guignardia leaf blotch (Guignardia aesculi) symptom severity, as well as leaf chlorophyll content, fruit yield, and crown volume. Trials used container-grown Aesculus hippocastanum and field-grown Malus domestica cv. ‘Golden Delicious’. Applications of Ca, Si, and penconazole sprays alone significantly reduced scab and leaf blotch severity compared to water-sprayed controls; however, a significant difference between the type of Ca and Si fertilisers was recorded. A combined mix of a Ca or Si fertiliser with a full or half dose of penconazole was more effective at reducing symptom severity of both foliar pathogens than a full or half dose of penconazole alone. Data analysed with Limpel’s formula indicated positive synergistic effects between Ca and Si and penconazole in some, but not all, cases. The integration of Ca and Si foliar sprays as an alternative to, or additive with, penconazole for scab and leaf blotch management appears feasible based on results of our studies and may have applicability against other fungal pathogens.

Tree-size dimension inequality shapes aboveground carbon stock across temperate forest strata along environmental gradients

It is generally well-explored that overstorey stratum regulates understorey stratum through the dominant role over the available resources in forests. However, the relationships amongst topography, soil nutrients, species diversity, tree-size dimension inequality and aboveground carbon (AGC) stock across forest strata remain debated in forest ecosystems. Here, we assumed that soil nutrients, species diversity and tree-size dimension inequality promote AGC stock in overstorey stratum, which in turn regulate AGC stock in understorey stratum in natural temperate forests. To do so, using several structural equation models (SEMs) on the data from 104 temperate forest plots in Northern Iran, we assessed the effects of tree-size dimension inequality as well as the individual effects of either inequality in tree diameter, height, basal area, crown volume, or crown area, species diversity, soil nutrients and topographic factors on AGC in each forest stratum and at whole-community level as well as the effects of overstorey on understorey (i.e., joint SEMs). Results show that AGC stock in overstorey stratum was mainly determined by tree-size dimension inequality rather than by species diversity on nutrient-rich soils but controlled by topographic factors related to light availability. In understorey stratum, only basal area inequality was the strong driver of AGC stock, but overstorey overruled the effects of understorey drivers on understorey AGC stock. Specifically, overstorey tree-size dimension inequality increased but AGC stock decreased the AGC stock of understorey. The observed mechanism and effects at overstorey stratum were nearly similar to whole-community level. This study shows that overstorey stratum regulates understorey through dominant occupancy on the light availability and soil nutrients. We suggest that integrative modeling of overstorey and understorey strata based on tree height, diameter and crown inequality may better enhance our understanding and extend the existing debate based on multiple drivers of forest functioning, which may help to provide specific guidelines for forest management.