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In this paper, empirical relationships between diameter at breast height (DBH), crown diameter (CD), and stem number per hectare (N) were improved in a Paulownia Shan Tong plantation. Various functions of these variables were defined, focusing on growing space (Gs) and stem number per hectare. The linear crown index between CD and DBH seems to be particularly important in predicting stem number per hectare. Based on an analysis of the relationships, a CD-DBH (R2 = 0.7254) and a DBH-N graphic model (R2 = 0.7302) can be applied widely in plantation forestry. Under suitable site conditions, the investigated Paulownia hybrid can provide a higher increment in DBH than most of poplar hybrids at a certain age. The aim of this study was to explore the relationships between the Gs based on CD and DBH. These types of investigations are of fundamental importance in terms of the growing technology of tree plantations.

In this paper, empirical relationships between diameter at breast height (DBH), crown diameter (CD), and stem number per hectare (N) were improved in a Paulownia Shan Tong plantation. Various functions of these variables were defined, focusing on growing space (Gs) and stem number per hectare. The linear crown index between CD and DBH seems to be particularly important in predicting stem number per hectare. Based on an analysis of the relationships, a CD-DBH (R² = 0.7254) and a DBH-N graphic model (R² = 0.7302) can be applied widely in plantation forestry. Under suitable site conditions, the investigated Paulownia hybrid can provide a higher increment in DBH than most of poplar hybrids at a certain age. The aim of this study was to explore the relationships between the Gs based on CD and DBH. These types of investigations are of fundamental importance in terms of the growing technology of tree plantations. [ABSTRACT FROM AUTHOR]

Minimum stand densities necessary to achieve crown closure is an important aspect of stocking assessment that merits more attention. Managers concerned with optimizing individual-tree and stand-level responses will benefit from improved guidance on minimum densities when designing intermediate silvicultural treatments. To do so we generated a dataset of crown projection areas using previously published crown width models and considered various assumptions about crown packing and the spatial arrangement of stems. Implied stem densities based on predicted crown sizes were used to determine the minimum stand density index (SDI MIN) by species. These values were integrated with published information about maximum stand density index (SDI MAX) providing estimates of minimum relative density (RD MIN =SDI MIN /SDI MAX). Mixed-effects models were used to predict RD MIN and determine the slope of the minimum size-density relationship (mSDR) for common softwood and hardwood species in northern New England, USA. Large differences in crown-stem allometry were revealed between open- and forest-grown trees (ΔRD ∼0.2). Hardwoods occupied more growing space than softwoods (ΔRD ∼0.05), a finding primarily attributed to differences in crown architecture, though species shade-tolerance may also play a role. Minimum stem densities capable of achieving crown closure span a wide range determined by species composition and stand history. Importantly, the implied slope of mSDR (∼ −1.0) differed substantially from that of the benchmark maximum size-density relationship (MSDR; −1.605), corresponding to lower values of RD MIN for smaller-sized stems and earlier in stand development than when stems are larger and older. Our models and resulting estimates of RD MIN can be used to locate the lower boundary of stocking space on size-density diagrams. • In contrast to maximum stem densities, the quantification of minimum numbers has not received adequate attention. • The slope of the relationship between minimum stem density and average size diverges substantially from that for the maximum. • Full site occupancy is possible at surprisingly low levels of relative density, and more so for hardwoods than softwoods. • tand history is important to consider when interpreting and using size-density management charts. [ABSTRACT FROM AUTHOR]

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Key message: TLS scans of three surveys before, during and after gypsy moth gradation, allowed high-resolution tracking of defoliation and subsequent inter-annual growth losses on an individual tree level. Foliation strongly determines all tree growth processes but can be reduced by various stress factors. Insect defoliation starts at variable times and is one stress factor that may affect photosynthetic processes and cause immediate reactions like refoliation, which are difficult to detect by surveys repeated at 1-year intervals. This study used a large-scale field experiment in German oak/mixed forests affected by gypsy moths (Lymantria dispar) to test the use of terrestrial laser scanning (TLS) for detecting inter-annual foliation and growth losses at the individual tree level caused by the gypsy moth. The experiment comprised two levels of gypsy moth defoliation risk, high (H) and low (L), as well as two pest control treatment levels: spraying with the insecticide Mimic (M) or unsprayed control (C). The factorial design consisted of four treatment combinations (HC, HM, LC, and LM), applied to 11 spatial blocks with a total of 44 plots. The TLS approach detected the defoliation caused by the gypsy moth, estimated as leaf area and crown perforation parameters. For the first time, TLS-derived tree foliation was evaluated based on inter-annual stem growth. Leaf area and crown perforation showed a correlation of + 0.6 and – 0.35, respectively, with basal area increments. Furthermore, this study revealed subsequent growth losses in the same year due to defoliation. Our results show that TLS can offer new opportunities to develop new indicators that monitor foliation at the individual tree level. The crown perforation can describe defoliation or the tree's vitality based on one scanning campaign, whereas the leaf area needed at least two. [ABSTRACT FROM AUTHOR]

Fertilization is one of the nutrient management efforts that play an important role in improving the productivity of plantation forests. It was conducted to provide adequate nutrients for the plant at the initial growth period when the availability of soil nutrients is very limited. The optimum dose of fertilization for each plant is different depending on its requirement, climate, and soil properties. This study investigated the influence of fertilization on early growth, aboveground biomass, carbon storage, and leaf characteristics in Eucalyptus pellita in the sixth months after field establishment. An experiment comprising four treatments of fertilization, i.e., 0, 75, 133, and 167 kg ha -1 of triple superphosphate 46% P2O5 was set up using randomized complete block design with five replications. Four indicators were selected to evaluate the early growth of E. pellita, namely survival rate, height, the collar of diameter, and crown projection area. Aboveground biomass and carbon storage of E. pellita were estimated in each component, covering stem, bark, branches, and leaves. The leaf characteristics of E. pellita were described by individual leaf area, individual leaf dry weight, specific leaf area, and leaf area index. Results showed that the different treatment of fertilization did not have a meaningful effect on survival rate, individual leaf area, and specific leaf area. The treatments presented a substantial effect on other indicators such as height, diameter, crown projection area, aboveground biomass, carbon storage, individual leaf dry weight, and leaf area index. Despite the fact that the highest mean of height and collar of diameter were observed in the dose of 167 kg ha -1, the greatest average of aboveground biomass and carbon storage were noted in the rate of 133 kg ha -1. Nevertheless, this study did not find a highly different performance of E. pellita between both treatments statistically.

Citrus fruit, one of the most important economic crops, is playing an important role in the industrial development of modern agriculture in rural China. However, the management mode of most orchards in China is currently undeveloped and extensive, particularly with high dependence on labor force, as well as insufficient scientific and technological support. In recent years, the unmanned aerial vehicle (UAV) monitoring technology has become a significant way to quickly extract the structural parameters in the growth of field crops at the park scale, due to its flexibility, low cost, and high resolution imaging. This study aims to construct a monitoring system for the citrus canopy structure and nutrition information using the UAV digital and multi-spectral remote sensing, to get he with the single tree segmentation. The UAV digital images and watershed algorithm were used to segment the structural dataset of citrus canopy, and then the canopy height model of citrus trees was established to extract the plant height using digital surface module. Structural parameters were also calculated, such as the number of citrus trees, and canopy projection area at the park scale. In addition, the UAV multispectral images were used to obtain eight common vegetation indexes, thereby to predict the nitrogen content of canopy in the citrus trees. The whole subset analysis was used to screen the sensitive vegetation index for the nitrogen content of canopy in the citrus trees. The inversion model of canopy nitrogen was constructed using the multiple linear regression. The remote sensing mapping was carried out to estimate the nitrogen content of citrus canopy in park scale. The results showed that: (1)Since the planting density of fruit trees was low in the experimental area, there was a certain distance between trees that can be clearly distinguished. The watershed image processing was selected to segment the single tree of height model for a citrus canopy. The overall identification accuracy, recall rate, and F value of the fruit trees were above 93 %, 95 %, and 94 %, respectively, indicating that the model was well suitable to monitor the number of fruit trees in the park. (2) The canopy structure parameters of individual fruit trees were obtained in the individual tree segmentation. There was a strong correlation between the plant height of citrus trees extracted by the canopy height model and the measured value, where the R² = 0.87, and RMSE = 31.9cm. (3) Using the watershed segmentation, the extracted projection area of crown width per plant achieved a high correlation with the artificial sketching area. The correlation coefficient was more than 0.93 in most cases, except that of orchard A lower than 0.78 in December. Meanwhile, the extraction accuracy of the model depended greatly on the single tree segmentation. (4) In full subset analysis, the sensitive vegetation indexes were selected to determine the nitrogen content of citrus canopy, including the normalized difference vegetation index (NDVI), green normalized difference vegetation index (GNDVI), and simple ratio pigment index(SIPI), where the R² and RMSE of the model were 0.82 and 0.22%, respectively. The data demonstrated that the nitrogen content of most fruit trees in orchard B was in the suitable range, while there was excessive application of nitrogen fertilizer in orchard A. Therefore, the UAV technology can greatly contribute to extract the physical and chemical parameters of citrus canopy, further to improve the level of accurate management of citrus on the large-scale orchard. [ABSTRACT FROM AUTHOR]

This study assessed and mapped the aboveground tree carbon stock using very high-resolution satellite imagery (VHRS)—WorldView-2 in Barkot forest of Uttarakhand, India. The image was pan-sharpened to get the spectrally and spatially good-quality image. High-pass filter technique of pan-sharpening was found to be the best in this study. Object-based image analysis (OBIA) was carried out for image segmentation and classification. Multi-resolution image segmentation yielded 74% accuracy. The segmented image was classified into sal (Shorea robusta), teak (Tectona grandis) and shadow. The classification accuracy was found to be 83%. The relationship between crown projection area (CPA) and carbon was established in the field for both sal and teak trees. Using the relationship between CPA and carbon, the classified CPA map was converted to carbon stock of individual trees. Mean value of carbon stock per tree for sal was found to be 621 kg, whereas for teak it was 703 kg per tree. The study highlighted the utility of OBIA and VHRS imagery for mapping high-resolution carbon stock of forest. [ABSTRACT FROM AUTHOR]

Fertilization is one of the nutrient management efforts that play an important role in improving the productivity of plantation forests. It was conducted to provide adequate nutrients for the plant at the initial growth period when the availability of soil nutrients is very limited. The optimum dose of fertilization for each plant is different depending on its requirement, climate, and soil properties. This study investigated the influence of fertilization on early growth, aboveground biomass, carbon storage, and leaf characteristics in Eucalyptus pellita in the sixth months after field establishment. An experiment comprising four treatments of fertilization, i.e., 0, 75, 133, and 167 kg ha-1 of triple superphosphate 46% P2O5 was set up using randomized complete block design with five replications. Four indicators were selected to evaluate the early growth of E. pellita, namely survival rate, height, the collar of diameter, and crown projection area. Aboveground biomass and carbon storage of E. pellita were estimated in each component, covering stem, bark, branches, and leaves. The leaf characteristics of E. pellita were described by individual leaf area, individual leaf dry weight, specific leaf area, and leaf area index. Results showed that the different treatment of fertilization did not have a meaningful effect on survival rate, individual leaf area, and specific leaf area. The treatments presented a substantial effect on other indicators such as height, diameter, crown projection area, aboveground biomass, carbon storage, individual leaf dry weight, and leaf area index. Despite the fact that the highest mean of height and collar of diameter were observed in the dose of 167 kg ha-1, the greatest average of aboveground biomass and carbon storage were noted in the rate of 133 kg ha-1. Nevertheless, this study did not find a highly different performance of E. pellita between both treatments statistically. [ABSTRACT FROM AUTHOR]

In order to determine the differences in morphometric parameters of young plantations of Acacia magium Willd. in Villa Clara, two sites planted with this species were selected, located in Salaminas at 22° 27' 16.27" north latitude and 79° 49' 7.91" west longitude (Site 1) and in the Sabanas de Manacas Model Forest, in the 22° 39' 25.9'' North latitude and 80°17'43.43'' West longitude (Site 2). Temporary sampling plots were established in both sites and six morphometric relationships were determined from variables measured in all the trees of the plots. The database was processed using the professional package STATGRAPHICS CENTURION, Ver. XV-II 2006. It was found that the growth and morphometric parameters of the evaluated trees were infiuenced by changing the growth regions, reaching the highest values of slenderness, cup percentage and crown index in Site 2; while significantly higher values of cup mantle, cup shape and crown projection area were reached in Site 1. The morphometric parameters evaluated are useful for describing young stands of this species, making management decisions and interpreting their growing conditions. [ABSTRACT FROM AUTHOR]

• Proposing a practical solution for extracting individual tree crown parameters. • Constructing a CW and CPA estimation model considering inter-tree competition. • Considering accessibility of competition factors and their matching with TCRO data. • Verifying the reliability of our model using TLS data of various forest plots. • Evaluating feasibility of the model using CRP data in complex forest environments. Automatic tree crown mapping, crown width (CW) and crown projection area (CPA) extraction are the basis for high-precision estimation of forest productivity and carbon stock. Terrestrial close-range observation (TCRO) technology, mainly including terrestrial laser scanning (TLS) and close-range photogrammetry (CRP), measures individual tree structural parameters by generating detailed three-dimensional (3D) points, making it a potential replacement for labor-intensive manual forest inventories. However, accurate extraction of crown parameters using TCRO in high-density forests remain a challenge due to different degrees of missing crown information caused by occlusion between trees and limitations of computer 3D modeling techniques and segmentation methods. Here, we propose a model for estimating crown parameters using tree spacing, diameter at breast height (DBH) and stand age, which collaboratively considers the advantages of TCRO data and the bioecological mechanisms of inter-tree competition. First, an approach to construct a tree triangulation network with tree position and tree spacing is designed based on the analysis of the bioecological mechanisms of inter-tree competition relationships. Second, a model to quantify inter-tree competition using tree spacing, DBH and stand age is developed to extract CW and CPA. We demonstrate the generality of our model to high-density forests in subtropical China with TLS data. It shows a good performance in Chinese fir, Eucalyptus and Spingbract Chinkapin-dominated plots with estimation accuracy (EA) ≥ 90.22 % and relative root mean square error (rRMSE) ≤ 0.1286 for CW and EA ≥ 84.51 % and rRMSE ≤ 0.1861 for CPA. In addition, the performance in estimating CW (EA = 89.80 %) and CPA (EA = 86.13 %) using CRP point clouds demonstrate the applicability of our model to CRP. The proposed model collaboratively considers inter-tree competition mechanism and TCRO data characteristics, therefore it is interpretable in terms of bioecological principle and universal for different forest environments (e.g., coniferous, broad-leaved and mixed coniferous species). The results show that the method provides an efficient solution for automatic and accurate measurements of the crown parameters in the forest sample plot investigation, which can support the fine forest management and carbon stock estimation. [ABSTRACT FROM AUTHOR]

The continuous expansion of built-up areas in the urban environment at the expense of green spaces brings up numerous environmental problems, for which accurate and efficient solutions should be found. The assessment of ecosystem services developed within the field of landscape ecology is playing an ever more important role in environmental sciences and thus may offer suitable answers. Such assessments can be carried out by developing indicators. Accordingly, in the case of urban trees, an accurate quantitative characterization of their services (such as e.g. carbon sequestration, pollutant removal and microclimate regulation) is also needed. The aim of this study is to establish a generally applicable method based on indicator development, using widely available data. In the case of urban green spaces there are several services for which the development of proper indicators and evaluation methods requires a delineation of tree crowns, or at least the crown projection area. Accordingly, in our work, we map the crown projection area of a large and popular urban park of Szeged, Széchenyi square, using object-based image analysis on UltraCamD digital orthophotos. Following a multiresolution segmentation the classification of the resulting objects was carried out, using the eCognition image analysis software. Besides fulfilling the policy objectives related to the evaluation of urban ecosystem services, the produced crown base can also be used in several other types of urban ecological and urban climatological studies (e.g. urban climate modelling, human-comfort assessment). In this paper the first results are presented.

Sustainable forest management practices and the increased interest of plantation forestry in species mixtures require an understanding of individual-tree growth in complex and diverse forests. Individual-tree growth has been found to be affected by factors such as species identity and size of the target tree as well as of neighboring trees, neighbor density and abiotic factors. However, most of these studies have been conducted in plantations or mixed forests with a very limited number of species. We conducted our study in a subtropical forest in China, which was very species rich and highly heterogeneous with regard to topography (slope inclination and aspect, elevation) and successional status. Prior to our study the forest was subjected to an exceptional snow break event. We asked whether individual-tree basal area increment (BAI) over three growing seasons following the snow break event was related to local biotic and abiotic conditions. We hypothesized that individual-tree BAI is negatively affected by local neighborhood competition, positively affected by local neighborhood diversity, negatively related to slope inclination, and positively related to aspect to south. Individual-tree BAI of four different species was mainly affected by tree size, local neighborhood competition and species identity. Contrary to our expectations, we did not observe significant effects of local neighborhood functional diversity and abiotic conditions. However, we did find a negative effect of plot functional diversity on BAI. This finding may be explained by a negative correlation of plot functional diversity and snow break damage, which was observed in mid- and late-successional stages. The disturbance event did considerably change the competitive local neighborhood interactions by reducing competition, which increased the BAI of target trees in more disturbed/more diverse plots.

The fire-tolerant eucalypt forests of south eastern Australia are assumed to fully recover from even the most intense fires; however, surprisingly, very few studies have quantitatively assessed that recovery. The accurate assessment of horizontal and vertical attributes of tree crowns after fire is essential to understand the fire’s legacy effects on tree growth and on forest structure. In this study, we quantitatively assessed individual tree crowns 8.5 years after a 2009 wildfire that burnt extensive areas of eucalypt forest in temperate Australia. We used airborne LiDAR data validated with field measurements to estimate multiple metrics that quantified the cover, density, and vertical distribution of individual-tree crowns in 51 plots of 0.05 ha in fire-tolerant eucalypt forest across four wildfire severity types (unburnt, low, moderate, high). Significant differences in the field-assessed mean height of fire scarring as a proportion of tree height and in the proportions of trees with epicormic (stem) resprouts were consistent with the gradation in fire severity. Linear mixed-effects models indicated persistent effects of both moderate and high-severity wildfire on tree crown architecture. Trees at high-severity sites had significantly less crown projection area and live crown width as a proportion of total crown width than those at unburnt and low-severity sites. Significant differences in LiDAR -based metrics (crown cover, evenness, leaf area density profiles) indicated that tree crowns at moderate and high-severity sites were comparatively narrow and more evenly distributed down the tree stem. These conical-shaped crowns contrasted sharply with the rounded crowns of trees at unburnt and low-severity sites and likely influenced both tree productivity and the accuracy of biomass allometric equations for nearly a decade after the fire. Our data provide a clear example of the utility of airborne LiDAR data for quantifying the impacts of disturbances at the scale of individual trees. Quantified effects of contrasting fire severities on the structure of resprouter tree crowns provide a strong basis for interpreting post-fire patterns in forest canopies and vegetation profiles in Light Detection and Ranging (LiDAR) and other remotely-sensed data at larger scales.

Many recent studies have shown that the structure, density, and productivity of mixed-species stands can differ from the weighted mean of monospecific stands of the respective species. The tree and stand properties emerging by inter-specific neighborhood should be considered in models for understanding and practical management. A promising approach for this is a more realistic representation of the individual tree allometry in models and management concepts, as tree allometry determines many structural and functional aspects at the tree and stand level. Therefore, this paper is focused on the crown allometry in mixed and mono-specific stands. Firstly, we review species-specific differences in the crown allometry in monospecific stands. Secondly, we show how species-specific differences and complementarities in crown allometry can emerge in mixed-species stands. Thirdly, the consequences of allometric complementarity for the canopy packing density will be analyzed. Fourthly, we trace the crown allometry from the tree level to the stand density and show the relevance for the self-thinning in mixed versus monospecific stands. Fifth, the consequence of the findings for modeling and regulating tree and stand growth will be discussed. The review deals mainly with widespread even-aged, mono-layered stands, but the main results apply for more heterogeneous stands analogously.

Terrestrial laser scanning (TLS) has been successfully used for three-dimensional (3D) data capture in forests for almost two decades. Beyond the plot-based data capturing capabilities of TLS, vehicle-based mobile laser scanning (MLS) systems have the clear advantage of fast and precise corridor-like 3D data capture, thus providing a much larger coverage within shorter acquisition time. This paper compares and discusses advantages and disadvantages of multi-temporal MLS data acquisition compared to established TLS data recording schemes. In this pilot study on integrated TLS and MLS data processing in a forest, it could be shown that existing TLS data evaluation routines can be used for MLS data processing. Methods of automatic laser scanner data processing for forest inventory parameter determination and quantitative structure model (QSM) generation were tested in two sample plots using data from both scanning methods and from different seasons. TLS in a multi-scan configuration delivers very high-density 3D point clouds, which form a valuable basis for generating high-quality QSMs. The pilot study shows that MLS is able to provide high-quality data for an equivalent determination of relevant forest inventory parameters compared to TLS. Parameters such as tree position, diameter at breast height (DBH) or tree height can be determined from MLS data with an accuracy similar to the accuracy of the parameter derived from TLS data. Results for instance in DBH determination by cylinder fitting yielded a standard deviation of 1.1 cm for trees in TLS data and 3.7 cm in MLS data. However, the resolution of MLS scans was found insufficient for successful QSM generation. The registration of MLS data in forests furthermore requires additional effort in considering effects caused by poor GNSS signal.

Crown projection area (CPA) is a critical parameter in assessing inter-tree competition and estimating biomass volume. A multi-layer seeded region growing-based approach to the fully automated assessment of CPA based on 3D-point-clouds derived from terrestrial laser scanning (TLS) is presented. Independently repeated manual CPA-measurements in a subset of the stand serve as the reference and enable quantification of the inter-observer bias. Allometric models are used to predict CPA for the whole stand and are compared to the TLS-based estimates on the single tree- and stand-level. It is shown that for single trees, the deviation between CPA measurements derived from TLS data and manual measurements is on par with the deviations between manual measurements by different observers. The inter-observer bias propagates into the allometric models, resulting in a high uncertainty of the derived estimates at tree-level. Comparing the allometric models to the TLS measurements at stand-level reveals the high influence of crown morphology, which only can be taken into account by the TLS measurements and not by the allometric models.

Knowledge of the quantitative relationship between plant cover and its corresponding biomass for shrubs is not well known, especially for those on the Tibetan Plateau. Based on investigations of 35 sites, 90 plots and 95 standard individuals for two typical shrub species ( Rhododendron nivale Hook. f. and Sophora moorcroftiana (Benth.) Baker) across Tibet, we developed allometric models for biomass estimation from measurements of crown diameter and/or height. We found that the parameters of crown projection area (CPA), height and their product (volume) were all significantly ( p < 0.01) correlated with dry mass of different organs for both species at individual level. The CPA rather than volume best predicted aboveground dry mass. This is because that the bulk density declined significantly with increasing plant height, leading to the inappropriateness for plant height itself being employed as a parameter in biomass estimation, especially for shrubs in smaller size groups. At community level, cover was tightly correlated with the aboveground, belowground and total biomass ( R 2 = 0.97–0.99). Therefore, biomass for the two shrubs can be simply estimated by measuring plant cover, which enables rapid estimation of shrubland carbon stock at large scales by using satellite data and repeated experiments over time. This non-destructive method using cover to estimate shrub biomass can be applied not only in arid ecosystems but also in alpine or subalpine environment. [ABSTRACT FROM AUTHOR]

The paper presents an attempt to apply measurable traits of a tree - crown projection area, crown length, diameter at breast height and tree height for classification of 135-year-old oak ( Quercus L.) trees into Kraft classes. Statistical multivariate analysis was applied to reach the aim. Empirical material was collected on sample plot area of 0.75 ha, located in 135-year-old oak stand. Analysis of dimensional traits of oaks from 135-year-old stand allows quite certain classification of trees into three groups: pre-dominant, dominant and co-dominant and dominated ones. This seems to be quite promising, providing a tool for the approximation of the biosocial position of tree with no need for assessment in forest. Applied analyses do not allow distinguishing trees belonging to II and III Kraft classes. Unless the eye-estimation-based classification is completed, principal component analysis (PCA) method provided simple, provisional solution for grouping trees from 135-year-old stand into three over-mentioned groups. Discriminant analysis gives more precise results compared with PCA. In the analysed stand, the most important traits for the evaluation of biosocial position were diameter at breast height, crown projection area and height. [ABSTRACT FROM AUTHOR]

Qinghai spruce (Picea crassifoliaKom.), the dominant species in Qilian Mountains of Northwest China, has an important role in ecological service function, especially in carbon sequestration. The current work simulated stem volume growth of Qinghai spruce at individual and stand levels using a widespread bio-geochemical cycle (BIOME-BGC) model and considering the crown projection area (CPA). CPA was introduced because photosynthesis was only carried out on the vegetation canopy. The results showed that: (1) the CPA-simulated stem volume of individual Qinghai spruce in the three sites fitted well with the observed stem volume; (2) the introduction of CPA corrected the over-predicted stem volume for relatively younger stands and the under-predicted stem volume for relatively older stands in BIOME-BGC; and (3) meteorological factors may be crucial parameters that influence the model accuracy, aside from CPA. Therefore, CPA should be considered in correcting the carbon simulated by BIOME-BGC, and the meteorological data should be improved to obtain high-accuracy BIOME-BGC outputs. [ABSTRACT FROM PUBLISHER]

Biomass models are key to the correct quantification of aboveground biomass and carbon stocks. Most of the current available sets of biomass models were developed for adult trees although very few have been employed to accurately estimate biomass during the first years of reforestations, despite the increasing number of reforestations over recent years. In this study, species-specific and generalized models for aboveground biomass of single trees have been developed for the main 14 species used in reforestations in Spain. A comparison with the existing biomass models at individual tree level for larger trees of these species was also conducted to confirm the hypothesis that specific models are required for the first years of the reforestation. A new set of biomass models was fitted simultaneously per species, based on three different independent variables – root-collar-diameter, total height and crown projection area- and their combinations. The fitted models provide more accurate and unbiased predictions of aboveground biomass in the first years after reforestation when compared with previously existing models for adult trees. The generalized models can be applied to reforestations when the main species is unknown or for mixed plantations where species are not individualized. The set of models provided can be used in a wide variety of surveys and monitoring conditions depending on the available data, from classical field inventories to more novel approaches such as airborne LiDAR data or aerial photographs. • Species-specific tree biomass models were fitted for those most used in reforestations in Spain. • Generalized models also presented can be used when the species identity are unknown. • Differences with estimations from adult tree biomass models were stated at this stage. • Field data, LIDAR or remote sensing data can be used with these models. • Models developed are key to estimate carbon stocks from afforestation/reforestations. [ABSTRACT FROM AUTHOR]

Highlights: [•] DBH was estimated for Eucalypt species from crown projection area. [•] Average crown projection area per stem within of tree clusters was related to average DBH. [•] Both the single tree and tree cluster models were statistically similar. [•] A combined model to predict average stem DBH yielded a mean error of 13cm. [•] A single model can be used to infer DBH for both single trees and clusters. [Copyright &y& Elsevier]

The amount of growing space occupied by trees of given sizes and species is traditionally assessed on a plot basis, using observations from groups of trees growing within an area of fixed size. Our study combines individual-tree with plot-based observations of upper-canopy trees representing a range of shade tolerance (Fagus grandifolia ≥ Acer saccharum > Betula alleghaniensis ≥ Fraxinus americana) in three young, fully stocked, even-aged northern hardwood stands. The amount of canopy growing space used by a stem of given size was described by the ratios of crown projection area and crown surface area to stem basal area. These variables were related to species, stand, and relative basal area using analysis of covariance. Both ratios were generally highest in the youngest (19 years) stand, intermediate in the mid-aged stand (24 years), and lowest in the oldest stand (29 years). A few differences were detected among species, with shade-tolerants having larger ratios. Allometric models were used in conjunction with plot density data to estimate canopy cover at the stand level. Considerable crown overlap was indicated among upper-canopy trees in all three stands. Estimates from tree-centered plots suggested that crowns occupied 1.81 ± 0.02 times the ground area in the youngest stand and 1.45 ± 0.03 times in the mid-aged and oldest stands; when corrected for sampling bias, these ratios were at least 1.30 and 0.96, respectively. Combining individual-tree with plot-level measurements afforded a comprehensive assessment of trends in growing-space occupancy not possible using either technique alone. [ABSTRACT FROM AUTHOR]

Abstract: Trees are able to respond to their local biotic and abiotic environment with morphological adjustments which improve resource acquisition and, thus, growth. In forests, light is broadly recognised as one of the major factors determining growth, and morphological responses comprise changes in crown architecture and stem stature. On sloping terrain, the interplay of phototropism and gravitropism may further affect morphological growth characteristics. However, different tree species are expected to show species-specific responses. In this study, we analysed three growth characteristics of tree individuals belonging to four species of two functional groups (evergreen: Schima superba, Castanopsis eyrei, deciduous: Quercus serrata var. brevipetiolata, Castanea henryi) in a species-rich Chinese subtropical forest. Crown projection area, relative crown displacement and stem inclination were related to biotic (local species richness, functional richness, competition, stand age) and abiotic (slope aspect and inclination, soil depth) variables in the local neighbourhood of the tree individuals. We hypothesised that (i) there are species-specific differences in the morphological response of crown architecture and stem stature and (ii) that crown size and asymmetry as well as stem inclination are influenced by both, biotic and abiotic factors. In contrast to our expectations we were unable to reveal any species-specific differences in any of the three growth characteristics. The results of mixed effects models showed that crown area was mainly affected by the target tree''s dbh and biotic variables related to neighbours (competition, functional diversity), whereas stem inclination was mainly influenced by slope. Relative crown displacement was influenced by both, biotic and abiotic variables. We conclude that growth responses resulting in crown displacement and stem inclination seem to be an important mechanism to ameliorate foraging for light in our study area, but that these responses appear to be species-independent. The interplay of stem inclination and crown displacement allows for a plastic response of tree individuals in biotically and abiotically heterogeneous environments. Our results indicate that forest management in this region should focus on functionally diverse stands which are promoting crown area positively resulting in increased growth rates of individual trees. [Copyright &y& Elsevier]

Abstract: Since individual tree leaf area is an important measure for productivity as well as for site occupancy, it is of high interest in many studies about forest growth. The exact determination of leaf area is nearly impossible. Thus, a common way to get information about leaf area is to use substitutes. These substitutes are often variables which are collected in a destructive way which is not feasible for long term studies. Therefore, this study aimed at testing the applicability of using substitutes for leaf area which could be collected in a non-destructive way, namely crown surface area and crown projection area. In 8 stands of Norway spruce (Picea abies L. Karst.), divided into three age classes and two thinning treatments, a total of 156 trees were felled in order to test the relationship between leaf area and crown surface area and crown projection area, respectively. Individual tree leaf area of the felled sample trees was estimated by 3P-branch sampling with an accuracy of ±10%. Crown projection area and crown surface area were compared with other, more commonly used, but destructive predictors of leaf area, namely sapwood area at different heights on the bole. Our investigations confirmed findings of several studies that sapwood area is the most precise measure for leaf area because of the high correlation between sapwood area and the leaf area. But behind sapwood area at crown base and sapwood area at three tenth of the tree height the predictive ability of crown surface area was ranked third and even better than that of sapwood area at breast height (R 2 =0.656 compared with 0.600). Within the stands leaf area is proportional to crown surface area. Using the pooled data of all stands a mixed model approach showed that additionally to crown surface area dominant height and diameter at breast height (dbh) improved the leaf area estimates. Thus, taking dominant height and dbh into account, crown surface area can be recommended for estimating the leaf area of individual trees. The resulting model was in line with many other findings on the leaf area and leaf mass relationships with crown size. From the additional influence of dominant height and dbh in the leaf area model we conclude that the used crown model could be improved by estimating the position of the maximum crown width and the crown width at the base of the crown depending on these two variables. [Copyright &y& Elsevier]

We present results of individual-based root system measurement and analysis applied for Larix gmelinii trees growing on the continuous permafrost region of central Siberia. The data of root excavation taken from the three stands were used for the analyses; young (26 years old), mature (105 years old), and uneven-aged over-mature stand (220 years old). In this article, we highlight two topics: (1) factors affecting spatio-temporal pattern of root system development, and (2) interactions between aboveground (i.e., crown) and belowground (i.e., root) competition. For the first topic, the detailed observation of lateral roots was applied to one sample tree of the overmature stand. The tree constructed a superficial (<30 cm in depth) and rather asymmetric root system, and each lateral root expanded mainly into elevated mounds rather than depressed troughs. This indicated that spatial development of an individual root system was largely affected by microtopography (i.e., earth hummocks). For these lateral roots, elongation growth curves were reconstructed using annual-ring data, and annual growth rates and patterns were compared among them. The comparison suggested that temporal root system development is associated with differences in carbon allocation among the lateral roots. For the second topic, we examined relationships between individual crown projection area (CA) and horizontal rooting area (RA) for the sample trees of each stand. RA was almost equal to CA in the young stand, while RA was much larger (three or four times) than CA in the mature and overmature stands. Two measures of stand-level space occupation, crown area index (aboveground: CAI; sum of CAs per unit land area) and rooting area index (belowground: RAI; sum of RAs), were estimated in each stand. The estimates of RAI (1.3–1.8 m2 m−2) exceeded unity in all stands. In contrast, CAI exceeded unity (1.3 m2 m−2) only in the young stand, and was much smaller (<0.3 m2 m−2) in the two older stands. These between-stand differences in RAI–CAI relationships suggest that intertree competition for both aboveground and belowground spaces occurred in the young stand, but only belowground competition still occurred in the two older stands. Based on this finding, we hypothesized that competition below the ground may become predominant as a stand ages in L. gmelinii forests. Methodological limitations of our analysis are also discussed, especially for the analysis using the two indices of space occupation (CAI, RAI). [ABSTRACT FROM AUTHOR]

Abstract: Small volumes of timber are now being produced from Acacia mangium plantations in Indonesia. These trees require pruning and thinning to increase the strength and appearance of the wood. However, cut surfaces from pruning are potential infection courts for the entry of decay-causing fungi like heart rot. This study investigated the effects of pruning on stem form and the incidence of heart rot in an 18-month-old plantation of Acacia mangium in South Sumatra. The objectives were to assess whether pruning is associated with an increase in the incidence of heart rot and whether form pruning compared to lift pruning reduced the incidence of heart rot and improved stem form. Form pruning removed 25% of leaf area by removing large branches and those subtending a narrow angle with the stem up to 3m height, and lift pruning removed 25% of crown length from below. Trees in these treatments were singled before pruning. The third treatment, a control, was not singled and was used to assess base levels of heart rot. No significant difference in diameter increment between the two pruning treatments was found. There was strong evidence that form pruning was associated with better form 18 months after treatment. Trees in this treatment had a reduced number of branches >30mm diameter and improved stem straightness (reduced kink). Lift pruning reduced average branch size but did not improve stem straightness. No heart rot was detected in any treatment. The results showed that form pruning is likely to have positive benefits on stem straightness and is likely to be effective to any selected pruning height. However a subsequent lift pruning is still considered a requirement. While wounds created from pruning and singling are assumed to have a large impact on the incidence of heart rot, this may not be an issue unless there is a sufficient source of fungi present in the environment to invade the wounds. [Copyright &y& Elsevier]

The fire-tolerant eucalypt forests of south eastern Australia are assumed to fully recover from even the most intense fires; however, surprisingly, very few studies have quantitatively assessed that recovery. The accurate assessment of horizontal and vertical attributes of tree crowns after fire is essential to understand the fire's legacy effects on tree growth and on forest structure. In this study, we quantitatively assessed individual tree crowns 8.5 years after a 2009 wildfire that burnt extensive areas of eucalypt forest in temperate Australia. We used airborne LiDAR data validated with field measurements to estimate multiple metrics that quantified the cover, density, and vertical distribution of individual-tree crowns in 51 plots of 0.05 ha in fire-tolerant eucalypt forest across four wildfire severity types (unburnt, low, moderate, high). Significant differences in the field-assessed mean height of fire scarring as a proportion of tree height and in the proportions of trees with epicormic (stem) resprouts were consistent with the gradation in fire severity. Linear mixed-effects models indicated persistent effects of both moderate and high-severity wildfire on tree crown architecture. Trees at high-severity sites had significantly less crown projection area and live crown width as a proportion of total crown width than those at unburnt and low-severity sites. Significant differences in LiDAR -based metrics (crown cover, evenness, leaf area density profiles) indicated that tree crowns at moderate and high-severity sites were comparatively narrow and more evenly distributed down the tree stem. These conical-shaped crowns contrasted sharply with the rounded crowns of trees at unburnt and low-severity sites and likely influenced both tree productivity and the accuracy of biomass allometric equations for nearly a decade after the fire. Our data provide a clear example of the utility of airborne LiDAR data for quantifying the impacts of disturbances at the scale of individual trees. Quantified effects of contrasting fire severities on the structure of resprouter tree crowns provide a strong basis for interpreting post-fire patterns in forest canopies and vegetation profiles in Light Detection and Ranging (LiDAR) and other remotely-sensed data at larger scales. [ABSTRACT FROM AUTHOR]

Many recent studies have shown that the structure, density, and productivity of mixed-species stands can differ from the weighted mean of monospecific stands of the respective species. The tree and stand properties emerging by inter-specific neighborhood should be considered in models for understanding and practical management. A promising approach for this is a more realistic representation of the individual tree allometry in models and management concepts, as tree allometry determines many structural and functional aspects at the tree and stand level. Therefore, this paper is focused on the crown allometry in mixed and mono-specific stands. Firstly, we review species-specific differences in the crown allometry in monospecific stands. Secondly, we show how species-specific differences and complementarities in crown allometry can emerge in mixed-species stands. Thirdly, the consequences of allometric complementarity for the canopy packing density will be analyzed. Fourthly, we trace the crown allometry from the tree level to the stand density and show the relevance for the self-thinning in mixed versus monospecific stands. Fifth, the consequence of the findings for modeling and regulating tree and stand growth will be discussed. The review deals mainly with widespread even-aged, mono-layered stands, but the main results apply for more heterogeneous stands analogously. [ABSTRACT FROM AUTHOR]

Crown projection area (CPA) is a critical parameter in assessing inter-tree competition and estimating biomass volume. A multi-layer seeded region growing-based approach to the fully automated assessment of CPA based on 3D-point-clouds derived from terrestrial laser scanning (TLS) is presented. Independently repeated manual CPA-measurements in a subset of the stand serve as the reference and enable quantification of the inter-observer bias. Allometric models are used to predict CPA for the whole stand and are compared to the TLS-based estimates on the single tree- and stand-level. It is shown that for single trees, the deviation between CPA measurements derived from TLS data and manual measurements is on par with the deviations between manual measurements by different observers. The inter-observer bias propagates into the allometric models, resulting in a high uncertainty of the derived estimates at tree-level. Comparing the allometric models to the TLS measurements at stand-level reveals the high influence of crown morphology, which only can be taken into account by the TLS measurements and not by the allometric models. [ABSTRACT FROM AUTHOR]