Tree Volume Growth Research Articles

A Mathematical Model for Estimating Carbon Storage Dynamics of Forest Communities

Using the JABOWA single-tree growth model, a program was designed to estimate carbon storage dynamics in the aboveground biomass of a mixed forest community. The developed model incorporates the parameters of tree species that are common to the forests of Central Russia: pedunculate oak (Quercus robur L.), silver birch (Betula pendula Roth), common aspen (Populus tremula L.), small-leaved lime (Tilia cordata Mill.), Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), and fir (Abies Mill.). A differential equation for tree diameter at breast height (D) was solved. The results were compared with the forest inventory data. The amount of carbon stored in the aboveground biomass of trees was calculated following the methodology suggested by the Intergovernmental Panel on Climate Change. The dynamics of tree volume were analyzed. An analytical formula was proposed to describe the dependence of tree volume and stored carbon on tree age. The differences in the rates of tree volume growth and carbon accumulation were identified among the species studied. The analytical and numerical results on stored carbon and tree age showed a good agreement for a test plot with the known species composition and tree count, which is located within the forest part of the carbon polygon of Kazan Federal University. The formula offers an accurate estimation and prediction of carbon storage dynamics in mixed forest communities with trees varying in age and, hence, is a valuable tool for managing forestry activities. However, when predicting tree biomass growth and carbon storage dynamics, one should also consider forest site quality classes reflecting the actual growth conditions of trees. Developing a mathematical model based on forest site quality classes as a key variable would help increase the reliability of biomass growth and carbon storage predictions for forest communities. Notably, the obtained model applies to actual forest communities with known species composition and fails to account for natural regeneration. To incorporate this parameter, spatial diffusion models that describe forest regeneration in non-forest areas should be utilized.

Bite Me: Bark Stripping Showed Negligible Effect on Volume Growth of Norway Spruce in Latvia.

Over the past few decades, increasing populations of cervid species in the Baltic region have reduced the quality and vitality of cultivated Norway spruce (Picea abies (L.) Karst.) stands. This study evaluated the effect of bark stripping on the volume growth of spruce trees in Latvia. Data collection took place in two forest stands. In each stand, 20 Norway spruce trees were sampled, 10 with visible bark damage scars and 10 control trees. Stem discs were collected from control trees at specified heights (0 m, 0.5 m, 1 m, 1.3 m, and 2 m, and then at one-metre intervals up to the top) and from damaged trees at additional specific points relative to the damage. Each disc was sanded and scanned; tree ring widths were measured in 16 radial directions using WinDendro 2012a software. Annual volume growth reconstruction was performed for each tree. Changes in relative volume growth were analysed in interaction with scar parameters, tree type (damaged/control), and pre-damage volume using linear regression models. The significance of parameter interactions was assessed using analysis of variance (ANOVA). Pairwise comparisons of estimated marginal means (EMMs) were conducted using Tukey's HSD post hoc test. No significant effect of bark stripping on the total stem volume increment was detected. However, the length of bark stripping scars had a significant impact on relative volume growth in the lower parts of the stems. These findings underscore the importance of further research examining a broader spectrum of cervid damage intensity and the effects of repeated damage on tree survival and growth.

Effect of different irrigation and fertigation schedules on growth and productivity of Red Velox apple in Northwestern Himalayan region

The present study was conducted at the experimental farm of Department of Soil Science and Water Management, Dr. YS Parmar University of Horticulture and Forestry, Nauni, Solan (HP) to study the effect of different irrigation and fertigation schedules on growth and productivity of Red Velox apple in Northwestern Himalayan region. A factorial experiment comprised of sixteen treatment combination of four drip irrigation levels viz. drip irrigation at 100% ETc (I1), drip irrigation at 80% ETc (I2), drip irrigation at 60% ETc (I3), conventional irrigation (I4) and four levels of fertigation viz. absolute control; no application of fertilizer (F0), 100% of adhoc dose of NPK (F1), 75% of adhoc dose of NPK (F2) and 50% of adhoc dose of NPK (F3) were replicated thrice with three plants in each replication. With an increase in the volume of water and an increasing dose of NPK, vegetative growth parameters (tree height, tree spread, trunk girth, tree volume and annual extension growth), leaf nutrient content and yield were noted to be significantly increased. Drip irrigation at 100% ETc (I1) and fertigation at 100% of adhoc dose of NPK (F1) significantly increased the growth, foliage nutrient content and productivity of apple. Interaction I1F1 recorded highest growth parameters, leaf NPK content as well as yield. The results of two years experiment indicated a positive impact of drip irrigation and fertigation schedules on enhanced fertilization effectiveness and improved vegetative growth, leaf nutrient content and yield of apple.

Site quality impacts tree form, heartwood content and veneer production of plantation-grown Pinus patula

Abstract Plantation forest species were introduced into South Africa due to limited availability of native forests for wood-derived products. Currently, the Mexican pine species, Pinus patula, is the most widely planted softwood species in the country. To study the effect of growth environment on wood and processing properties for the species, sample plots were established in a 20-year rotation covering a wide range of soil geologies and altitudes in Mpumalanga, South Africa. Temperature and seasonal rainfall were also determined for the sample plots. Randomly selected sample trees were harvested from the plots and processed at a plywood plant to determine veneer recovery and quality. Trees grown on sites composed of granite soils, with higher annual maximum temperatures and less rainfall, found in the Highveld region, displayed superior tree size, slenderness, and volume growth, compared to trees grown on dolomite and shale soils common to the Lowveld region. Veneer derived from Lowveld trees had more splits which were largely related to defects. Larger trees also had a greater percentage volumetric heartwood and a smaller live crown, compared to smaller trees. Highveld trees had greater net veneer recovery and produced better quality veneer than trees grown on the Lowveld. In the Mpumalanga forestry region, strong co-relatedness exists between soil geology, altitude, and climate. Although tree form and wood properties were found to differ with varying soil geology and altitude, these differences were primarily related to climate rather than soil properties. These findings highlight the pitfalls associated with neglecting either climate or soil properties when analysing site-specific growing conditions on tree growth and form.

Defoliation-Induced Growth Reduction of Pinus sylvestris L. after a Prolonged Outbreak of Diprion pini L.—A Case Study from Eastern Finland

The frequency and intensity of insect outbreaks have increased in boreal forests, along with associated impacts on the growth and economic losses of host trees. In Finland, the common pine sawfly (Diprion pini L.) is a serious pest, causing declines in health and growth responses of Scots pine (Pinus sylvestris L.). We focused on investigating the species’ defoliating impact on tree radial and volume growth and estimated the economic value of the declined growth. Managed P. sylvestris forests in our study area in eastern Finland have suffered from extended defoliation by D. pini for 15 years since 1999 at varying intensity levels. We classified 184 trees into four defoliation classes and compared annual growth, expressed as growth indices between the classes. We modelled tree volume, estimated economic loss, and compared those to a reference period preceding the initial outbreak. We found significant differences in growth indices between the defoliation classes. Growth losses of 4.2%, 20.8%, and 40.4% were obtained for the mild, moderate, and high defoliation classes, with related economic impacts of 51 €, 272 €, and 734 € per ha for 11 years, respectively. Growth was slightly enhanced in the lowest defoliation class. We suggest that growth-related economic loss caused by D. pini may be significant and depend on defoliation intensity and outbreak duration.

A Combination of Biotic and Abiotic Factors and Diversity Determine Productivity in Natural Deciduous Forests

The relative importance of different biotic and abiotic variables for estimating forest productivity remains unclear for many forest ecosystems around the world, and it is hypothesized that forest productivity could also be estimated by local biodiversity factors. Using a large dataset from 258 forest monitoring permanent sample plots distributed across uneven-aged and mixed forests in northern Iran, we tested the relationship between tree species diversity and forest productivity and examined whether several factors (solar radiation, topographic wetness index, wind velocity, seasonal air temperature, basal area, tree density, basal area in largest trees) had an effect on productivity. In our study, productivity was defined as the mean annual increment of the stem volume of a forest stand in m3 ha−1 year−1. Plot estimates of tree volume growth were based on averaged plot measurements of volume increment over a 9-year growing period. We investigated relationships between productivity and tree species diversity using parametric models and two artificial neural network models, namely the multilayer perceptron (MLP) and radial basis function networks. The artificial neural network (ANN) of the MLP type had good ability in prediction and estimation of productivity in our forests. With respect to species richness, Model 4, which had 10 inputs, 6 hidden layers and 1 output, had the highest R2 (0.94) and the lowest RMSE (0.75) and was selected as the best species richness predictor model. With respect to forest productivity, MLP Model 2 with 10 inputs, 12 hidden layers and 1 output had R2 and RMSE of 0.34 and 0.42, respectively, representing the best model. Both of these used a logistic function. According to a sensitivity analysis, diversity had significant and positive effects on productivity in species-rich broadleaved forests (approximately 31%), and the effects of biotic and abiotic factors were also important (29% and 40%, respectively). The artificial neural network based on the MLP was found to be superior for modeling productivity–diversity relationships.

Assessment of the effects of thinnings in scots pine plantations in Mongolia: a comparative analysis of tree growth and crown development based on dominant trees

The post-thinning stand density and spacing in forest plantations influence individual tree growth and crown development, and the changes detected in dominant tree growth are a good indication of the thinning effect. The objective of this study was to determine the effects of different thinning intensities on diameter and height growth in a Scots pine (Pinus sylvestris L.) plantation. The field measurements were carried out between 2016 and 2020 on a Scots pine plantation, growing in Selenge province of northern Mongolia. Following this, experimental thinnings were carried out with different intensities. Thinning treatments comprised thinning with very low, low, medium, and high intensities, as well as an unthinned control stand. Stem analyses were performed to calculate the annual and cumulative diameter, height, and volume growth. For tree crown measurements several parameters were analyzed: crown diameter, crown projection area, and crown index. A total of 300 trees (5 treatments*3 replications*20 dominant trees from each plot) were subjected to the comparative analyses. This study revealed that thinning showed a stronger positive effect on diameter and volume growth of dominant trees in the plantation. Our results showed a gradual increase in diameter, basal area, and volume growth depending on the thinning intensity. An ANOVA test for growth analyses of dominant trees showed a significant difference in diameter (p < 0.0001) and height (p < 0.0001) growth performance following experimental felling with different thinning intensities. Finally we elaborated linear mixed effect models (LMM) for tree growth between 2016 and 2020 of selected dominant trees. With the help of the LMM we analyzed and described the thinning impact on DBH, BA, height, volume and crown diameter. The models confirmed that higher thinning intensity triggered growth of the response variables except for height. A greater height growth was found in very low (10%) and low (15%) intensity treatments. Due to reduction of competition and optimization of the distance between individuals, thinnings contributed to a relatively faster development of the tree crown in radial directions. Based on our analysis results and comparative graphs representing post-thinning dominant tree growth in diameter, height, basal area, and volume, we recommend medium- (30%) and high-intensity (45%) thinnings as at the beginning stage of plantation establishment.

Long-term effects of stand density management and genotype on wood properties of loblolly pine (Pinus taeda L.) in the mid-South USA

Changes in ownership and forest product use patterns have incentivized growing loblolly pine (Pinus taeda L.) for chip-and-saw and sawtimber in shorter rotations in the southeastern United States. These management objectives can be accomplished by relatively low stand densities and moving fast-growing genotypes from the Atlantic Coastal Plain to other regions of the loblolly pine range, but wood quality concerns accompany these silvicultural options. In three trials in the Western Gulf region of the mid-South United States, effects of stand density management options on key wood properties (specific gravity, corewood (juvenile wood) diameter, corewood proportion, latewood proportion, corewood:outerwood (juvenile wood:mature wood) transition age as determined using specific gravity) were tested. At one site, clearwood modulus of elasticity (MOE) and modulus of rupture (MOR) were measured. Genotypes of Atlantic Coastal Plain and Western Gulf origin were also tested at two sites. In a trial in which stand density was managed at diverse levels through sequential thinning, beginning at precommercial size, only a regime that was commercially thinned to half its density two times from 297 TPH at age 7 to 62 TPH by age 41 had significant reductions in MOE, MOR, and specific gravity. Corewood diameter increased with decreasing planting density at two sites at the northwestern edge of the loblolly pine range, but corewood proportion declined with decreasing planting density due to greater diameter growth and earlier transition from corewood to outerwood. Specific gravity differences among planting densities was site-specific, with no differences at the more well-drained site. Latewood proportion, which was greater at higher planting densities, was more strongly correlated with specific gravity differences among planting densities. A planting density between 1075 and 1680 TPH would likely be optimum for these site conditions for balancing tree volume growth with minimizing reductions in specific gravity associated with reduced latewood proportion and larger corewood size. The Atlantic Coastal Plain genotype retained its tendencies to transition to outerwood earlier and have greater latewood proportions relative to a local genotype when planted at these Western Gulf sites, and its specific gravity was similar to that of the local genotype. Together these trials suggest that forest managers have flexibility in managing loblolly pine stand density without altering wood properties. Furthermore, these results provide some evidence that moving genotypes may not carry a risk of reduced wood specific gravity.

Assessments of growth performance, crown structure, stem form and wood property of introduced poplar clones: Results from a long-term field experiment at a lowland site

Climate change brings about more frequent short-term waterlogging leading to unfavorable conditions for tree growth. Poplar is a preferred tree species for fast-growing plantations. Although limited short-term comparative studies exist with poplars that examine clonal variation in growth and physiological responses to waterlogging, a comprehensive assessment on growth performance, crown structure and wood property of poplar clones is lacking from a long-term study. This study compares the clonal variations in survival rate, growth, crown structure, stem form and wood property of poplar clones to better match the genotype with specific site. In line with the result of the preliminary evaluation, 17 poplar clones were harvested to further investigate crown structure, stem form and wood property after 24 growing seasons. A significant difference in tree growth was observed among the clones, ranging from 1.08 to 2.64 m3 for tree volume, whereas male clones generally had a better growth performance than the female. Hierarchical cluster analysis indicated the 17 poplar clones can be classified into three distinct groups in term of mean values of branching angle, branch numbers and branch base diameter. There existed visible differences in breast-height form factor and height-diameter ratio among the poplar clones, and four distinct groups can be divided based on Euclidean distance of stem form indexes. Significant clonal variations in wood basic density (WD) and microfibril angle (MFA) were observed among the sampled clones, and the mean clonal WD and MFA at breast height ranged from 0.325 to 0.390 g/cm3 and 11.8 to 16.7° respectively. Based on the TOPSIS method, a comprehensive assessment of adaptability and prioritization of the 17 clones was made from tree volume growth, stem form, branching traits and wood density, and some superior poplar clones were recommended for future applications in the similar lowland sites.

Vegetative Growth and Foliage Nutrient Content of Super Chief Apple under Different Irrigation and Fertigation Schedules in NW Himalayan Region

ABSTRACT In the scheduling of nutrient supply programs, analysis of plant nutrient status has been found to be useful to prevent the deficiency or toxic effects of nutrients in any horticultural crop. So the present study was framed to assess the foliage nutrient content and vegetative growth under different irrigation and fertigation combination modules. Recently apple (Malus ×domestica) orchards in the state Himachal Pradesh of India have converted from the traditional royal delicious orchard at 6 × 6 m spacing with rainfed/basin irrigation to early spur varieties on dwarfing rootstock with drip irrigation, both with or without fertigation. An experimental field trial was started at the end of 2018 in a ‘Super Chief’/MM106 orchard at an experimental farm of the department of Soil Science & Water Management, Dr. YS Parmar University of Horticulture and Forestry, Nauni, Solan (HP). A factorial experiment with 16 treatment combinations of 4 irrigation levels viz. I1 – drip irrigation at 100% ETc, I2 – drip irrigation at 80% ETc, I3 – drip irrigation at 60% ETc, I4 – conventional irrigation, and four fertigation levels viz. F0 – No fertilizer application (absolute control), F1 – 100% of AD (NPK), F2 – 75% of AD (NPK) and F3 – 50% of AD (NPK) were replicated thrice with 3 plants in each replication. Vegetative growth parameters and leaf nutrient contents were affected by both fertilization and water rate. Irrigation and nutrient levels and their interactions exhibited significant effect on leaf N (3.10%), P (0.28%), K (1.77%), and S (0.44%) contents. Significantly maximum contents were observed in the irrigation level I1 (DI at 100% ETc). Among fertigation level, F1 [100% AD (NPK)] recorded highest contents of leaf N (3.17%), P (0.29%), K (1.80%), S (0.46%). Interaction I1F1 registered maximum leaf N (3.36%), P (0.36%), K (1.92%) and S (0.63%). With an increase in the water volume and an increasing dose of NPK, vegetative growth parameters, i.e., tree height, plant spread, tree volume, trunk girth, and annual extension growth were noted to increase proportionately. Treatment DI at 100% ETc (I1), increased the tree height by 9.41, plant spread (EW by 32.0, NS by 16.3), tree volume by 61.36, trunk girth by 8.05, and annual extension growth by 14.22% over conventional irrigation (I4). Drip fertigated trees with F1 [100% AD (NPK)] reported the highest growth parameters. The results of two years apple trial suggested a positive effect of fertigation on enhanced effectiveness of fertilization and improved foliage nutrient content and vegetative growth.

Growth, Carbon Storage, and Optimal Rotation in Poplar Plantations: A Case Study on Clone and Planting Spacing Effects

Poplar, as the most widely cultivated fast-growing tree species in the middle latitude plain, provides important wood resources and plays an important role in mitigating climate change. In order to understand the response of growth, biomass production, carbon storage to poplar clones, planting spacings, and their interaction, a field trial was established in 2007. In 2018, we destructively harvested 24 sample trees for biomass measurements and stem analyses. Biomass production and carbon storage for the single tree of three clones enhanced as planting spacing increasing at the age of 13, but both the biomass production and carbon storage of clones NL-895 and NL-95 were higher than the clone NL-797 at the spacings of 6 × 6 m and 5 × 5 m. The average carbon concentration of the tested clones was in the order of stem &gt; branches &gt; leaves, and showed significant variation between different components (p &lt; 0.05). Large spacing stimulated more biomass to be partitioned to the canopy. Based on the prediction values of tree volume growth by established Chapman–Richards models, the quantitative maturity ages of stand volume varied among the investigating plantations, ranging from 14 to 17 years old. Our results suggest that the selecting clones NL-895 and NL-95 with 6 × 6 m spacing would be recommended at similar sites for future poplar silviculture of larger diameter timber production, as well as for carbon sequestration.

The extent to which an unforeseen biotic disturbance can challenge timber expectations

Forest pathogens are one of the key drivers of the dynamics and diversity of forested landscapes, contributing to structural and compositional complexity at multiple scales in space and time. Growth and yield models help guide forest management decisions but the roles of abiotic and biotic disturbance agents including pathogens are often overlooked. In our study of mid-rotation spruce plantations in northwest British Columbia (BC), Canada, we examine the influence of tomentosus root disease on the oldest managed stands in a previously unmanaged landscape allowing us to witness pathogen expression in a first rotation setting over the longest duration available. Our 10 one-hectare stem-mapped plots capture the spatial variability of root disease expression and their large size, coupled with their random selection without any prior knowledge of the pathogen, make our study unique. We found tomentosus root disease accounted for nearly 90% of both the number and the volume of spruce trees that died and that the incidence of the disease more than doubled over a 16-year period from stand age ~30–46. The volume growth of trees that were initially healthy but became infected was 17% less than that of the trees that remained healthy, while the volume growth of trees that were infected since plot establishment was 28% less than that of trees that remained healthy. We found a weak relationship between infected stumps from the previous stand and the condition of trees surrounding those stumps at age 30, but more critically we found a similarly weak relationship between infected trees at age 30 and the condition of the neighbouring trees 16 years later. Using the growth and yield model TASS II v2.7.75, we found model projections of spruce volume exceeded measured plot volume by an average of 30.5%. TASS is based on the same foundational tenets that are the dominant paradigm in forestry where the prediction of forest growth is based on the assessment of site index (dominant stand height and age), Eichhorn’s rule (which implies that when the dominant tree height is known, stand yield can be easily estimated now and then projected into the future), and the thinning response hypothesis. Our results reflect the influential role of a forest pathogen that is operating on a different scale and following a different set of rules. This, in combination with the unexpected behaviour of the forest pathogen itself, represents a multifaceted challenge in forecasting forest growth.

Increased Individual Tree Growth Maintains Stand Volume Growth after B-Level Thinning and Crop-Tree Management in Mature Oak Stands

AbstractSix study areas were established in 80–125-year-old upland oak stands on average sites to compare stand and individual tree growth response following two active treatments (B-level thinning, crop tree) with an unmanaged control. Initial stocking of 104 percent was reduced to 62 percent and 60 percent on the B-level and crop-tree-management plots, respectively. Approximately 7,200 board feet per acre (International ¼) were harvested on the actively managed plots with upland oaks accounting for 81 percent of pre- and 86 percent of residual stand. Eleven-year diameter and volume growth of oak sawtimber trees was greater on actively managed plots. Growth response increased with degree of release and was maintained for the length of the study. Because of the increased individual tree growth of oaks in response to release, stand volume growth of oak sawtimber did not differ between treatments. In contrast to an 11-year decline of poletimber stocking on unmanaged plots, poletimber stocking increased on managed plots as diameter growth increased in response to partial release. This may increase difficulty of regenerating oak in the future. For those mature red oak stands where traditional regeneration prescriptions will not be implemented or will be delayed, commercial harvests can be conducted without compromising stand volume growth of oak.

Examining Changes in Stem Taper and Volume Growth with Two-Date 3D Point Clouds

Exact knowledge over tree growth is valuable information for decision makers when considering the purposes of sustainable forest management and planning or optimizing the use of timber, for example. Terrestrial laser scanning (TLS) can be used for measuring tree and forest attributes in very high detail. The study aims at characterizing changes in individual tree attributes (e.g., stem volume growth and taper) during a nine year-long study period in boreal forest conditions. TLS-based three-dimensional (3D) point cloud data were used for identifying and quantifying these changes. The results showed that observing changes in stem volume was possible from TLS point cloud data collected at two different time points. The average volume growth of sample trees was 0.226 m3 during the study period, and the mean relative change in stem volume was 65.0%. In addition, the results of a pairwise Student’s t-test gave strong support (p-value 0.0001) that the used method was able to detect tree growth within the nine-year period between 2008–2017. The findings of this study allow the further development of enhanced methods for TLS-based single tree and forest growth modeling and estimation, which can thus improve the accuracy of forest inventories and offer better tools for future decision-making processes.

Mapping the 3D structure of almond trees using UAV acquired photogrammetric point clouds and object-based image analysis

The geometric features, such as canopy area, tree height and crown volume, of agricultural trees provide useful information to elucidate plantation status and to design input prescription maps adjusted to real crop needs. This work presents an innovative procedure for computing the 3-dimensional (3D) geometric features of almond trees by applying two phases: 1) generation of photogrammetric point clouds with unmanned aerial vehicle (UAV) technology, and 2) analysis of the point clouds using object-based image analysis (OBIA) techniques. To test this approach, a UAV with a visible-RGB (low-cost) sensor was flown over three experimental almond groves at different phenological stages for two years, and the validation field method consisted of registering the height of a total of 325 trees in the two fields. The OBIA algorithm developed in this study achieved successful results: i) the individual and overall similarity measures between manually delineated and automatically detected almond tree crowns were above 0.9, and ii) the validation assessment conducted to estimate tree height from the UAV-derived algorithm produced an R2 = 0.94, an overall root mean square error (RMSE) of 0.39 m. The information derived from the OBIA algorithm was used for generating 3D maps for every tree volume and volume growth, which would be useful to understand the linkages between tree and crop management operations in the context of precision agriculture, with relevant agro-environmental implications. Our findings show that an RGB, low-cost sensor on-board a UAV provided dense 3D point clouds can be used for accurately characterising almond tree architecture.

Tree-level growth and survival following commercial thinning of four major softwood species in North America

Thinning is commonly applied to increase the tree growth in forest stands by improving the availability of water, light, and nutrients. However, thinning also can increase soil evaporation and intensify wind penetration into residual stands, potentially increasing moisture stress and wind damage. To strengthen our understanding of tree-level responses to thinning, we used long-term measurements from three controlled, replicated thinning experiments for four commercially important softwood species in North America, including the shade-intolerant loblolly pine (Pinus taeda L.), moderately shade-tolerant Douglas-fir (Pseudotsuga menziesii Mirbel), and shade-tolerant red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.). The objectives of this study were to assess the long-term (13–24 years) pattern of individual-tree growth and survival after a variety of commercial thinning treatments. Our results showed that on average tree volume growth was 31% higher in thinned stands relative to unthinned stands irrespective of species and tree size. However, the rate of growth decreased over time following thinning for loblolly pine and Douglas-fir, while a curvilinear relationship was observed for red spruce and balsam fir. Tree size was important only for loblolly pine where growth increased linearly with the size of residual trees. Tree survival was also higher in thinned stands than unthinned stands across all species in the long-term, but a significant initial decrease in survival was found in balsam fir and red spruce immediately after thinning due primarily to windthrow and breakage. Stand relative age and total basal area at time of thinning were negatively related with growth for all tree species, which may indicate that the trees examined in this study had reached their maximum growth potential or had a period of suppression prior to thinning. The relatively minor influence (i.e., 5% of total R2) of thinning intensity on growth may suggest that the timing of thinning (i.e., age of trees when thinned) and stand characteristics (species, tree age, and stand basal area) were more important in promoting individual-tree growth. However, a heavier intensity of thinning increased survival of loblolly pine and Douglas-fir trees. Overall, our results indicated that thinning can increase tree growth and survival across species of varying shade tolerance. To ensure the maximum benefits of thinning, the timing and intensity of the treatment needs to be adjusted for species characteristics, stand structure, and tree age.

Afforestation in Bulgaria

The historical development of afforestations in Bulgaria was investigated. Some of the more important decisions and events which determine the correct state policy in the field of afforestations are pointed out. The most significant achievements are in: erosion control, incl. water tank protection from silting up; increasing the tree volume and forest growth; protection of agriculture via forest protection belts; landscape improving. The social importance for more employment and improvement of means of livelihood is mentioned. Proved reasons for decreasing the afforested areas since 1980s are given. The main mistakes and problems are mentioned as well as the changes in the afforestation policy and future challenges.

Outbreaks of Gremmeniella abietina cause considerable decline in stem growth of surviving Scots pine trees

In the early 2000s, an extensive epidemic of the fungus Gremmeniella abietina (Lagerb.) Morelet occurred in Sweden and caused severe damages to coniferous species. This study aimed to evaluate the impacts of this outbreak on the stem growth of the surviving Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.) trees, using the country-wide data on pine and spruce from the Swedish National Forest Inventory and data from stem analyses of pine growth in four infected plots (ntrees=12) in the Bergslagen area of middle Sweden. Analyses of volume dynamics in the four stands indicated a decade-long negative effect of pathogen infections on volume growth of pine trees. Over 2000–2012, the difference between projected (assuming no infection) and observed volume growth was 10–62%, depending on infection-related crown transparency (varying between less than 20% to above 80%). Height growth of pine in affected stands was reduced by 64–85%, although the reduction did not correlate with levels of crown transparency. The average reduction in basal area increment (BAI) in affected areas country-wide, accumulated over 2000–2006, was ∼21% for pine and ∼4% for spruce. The use of regular ring-width chronologies, as compared to volume increment chronologies, resulted in underestimation of volume losses by 25–30%.

Effect of local stand structure on leaf area, growth, and growth efficiency following thinning of white spruce

We examined the influence of stand structure surrounding individual dominant and codominant trees on leaf area, tree growth, and growth efficiency (stem growth per unit leaf area) in young white spruce (Picea glauca (Moench) Voss) plantations. Objectives were to (i) test the hypothesis that individual tree volume increment and growth efficiency increase with increasing growing space, and (ii) determine the relative importance of growth efficiency and leaf area to stem volume increment in young spruce following thinning. Growing space was expressed as area potentially available (APA) to each tree. Relative current annual volume increment (annual increment divided by the mean increment for the 3years immediately preceding thinning) increased linearly with increasing APA 2 and 3years after thinning, supporting our hypothesis that tree volume increment increases with APA. Growth efficiency however, was not related to APA. Leaf area was positively related to APA 3years after thinning, and current annual volume increment was related to leaf area. Leaf area per tree increased from 17.8m2 to 29.8m2 over the 3years (2011–2013) following thinning and was 16.5–18.7m2 for unthinned trees over the same period. Growth efficiency decreased from 1.35 to 0.64dm3m−2 for thinned trees and from 0.74 to 0.55dm3m−2 for unthinned trees from 2010 to 2013. Growth efficiency did not differ between thinned and unthinned trees, but it was significantly lower in year 3 than year 1 after thinning (p=0.0178) and significantly lower than the prethinning growth efficiency (p=0.0034). Our results show that thinning increased individual tree volume increment by increasing leaf area of remaining trees and not by increasing their growth efficiency.

Estimating Tree Growth Using Crown Metrics Derived from LiDAR Data

In order to determine current tree condition and predict future growth using LiDAR data, tree height, diameter at breast height, diameter 4 m above the ground, tree volume, tree volume growth, diameter at breast height growth and diameter growth 4 m above ground for individual trees were estimated from various crown height metrics and measurements obtained using a small footprint airborne laser scanner flown over a planted forest in Japan. Ground-truth values for tree height, diameter at breast height, diameter 4 m above ground, tree volume, and volume and diameter growth were collected. The actual values were compared with the laser-derived crown height metrics, including: percentiles, maximum, mean, coefficient of variation and crown density, all for the first and last crown height laser pulses. The regressions explained 75–79 % of the variability in ground-truth tree height, diameter at breast height, diameter 4 m above ground and tree volume. Cross-validation of the regressions revealed standard deviations of the differences between predicted and ground-truth values of 1.30 m (6.7 %), 5.2 cm (22.2 %), 3.8 cm (18.7 %) and 0.22 m3 (43.3 % of ground-truth mean), respectively. The regressions also explained 69–77 % of the variability in ground-truth averages. Cross-validation of the regressions revealed standard deviations of the differences between predicted and ground-truth values of 0.15 cm yr−1 (43.7 %), 0.1 cm yr−1 (31.0 %) and 0.008 m3 yr−1 (58.5 % of ground-truth mean), respectively. The study confirms that it may be possible to predict individual tree growth based on LiDAR data.