Tree Diameter Research Articles

The Efficacy of Green Organic Fertilizer on the Growth and Health of Mango Tree (Mangifera Indica)

In Malaysia, 98% of garden waste is being dumped in the landfills. Meanwhile, only 2% is being recycled or compost. This is because no specified policy or guidelines focusing on garden waste management, and it often collected separately due to its bulk/large in size caused higher disposal cost. In this study, composting of organic fertilizer (OF) was performed to determine the effectiveness using two types of decomposition medium [leaf mold (LM) and green grass] and to evaluate the growth and health status of the Mango Tree (Mangifera Indica). Six different types of soil samples were collected at two-weeks intervals over a three-months period during the composting process. The 6 of tree plots physical monitoring analysis consists of height and diameter of tree and physicochemical parameters tested included pH, total nitrogen (TN), total phosphorus (TP), potassium (K), and heavy metals was performed. Results showed growth and health for plotted tree sample using dripping of OF is more higher and healthy than others. While, N, P and K analysis contents were obviously responsive to the treatments and followed the same trend in wide areas. The result showed highest levels treated with (LM+OF) by dripping automatic system. While, both plot of (LM+OF) manual and both plot (LM) treatments showed significantly the same effectiveness and came second statistically in this regard. In contrast, the lowest values were generally found in plot (control). It was concluded that OF has better effects on plant growth and soil quality with the N, P, and K concentration content. Our results indicate that the residues from the fermentation of organic fertilizers can be widely used.

On diameter $5$ trees with the maximum number of matchings

A matching in a graph is any set of edges of this graph without common vertices. The number of matchings, also known as the Hosoya index of the graph, is an important parameter, which finds wide applications in mathematical chemistry. Previously, the problem of maximizing the Hosoya index in trees of radius $2$ (that is, diameter $4$) of fixed size was completely solved. This work considers the problem of maximizing the Hosoya index in trees of diameter $5$ on a fixed number $n$ of vertices and solves it completely. It turns out that for any $n$ the extremal tree is unique. Bibliography: 6 titles.

The Use of UAV in Mapping and Inventorying Mangrove Forest for Handling Climate Change

Mangrove forest are known to play a pivotal role in supporting the global carbon cycle by effectively mitigating greenhouse emissions and reducing the impact of climate change. However, the current conditions have increased concerns due to the escalating degradation of these ecosystems for development purposes. An area of particular concern is Tanjung Lalansoi, Osi Island, Eti Village, West Seram District. This region has the potential to harbor mangrove forest to store Biomass and Carbon. To address these environmental challenges, the use of remote sensing technology using Unmanned Aerial Vehicle (UAV) hold great potential due to its advantages. These include its cost-effectiveness and ability to provide spatial and up-todate data with high resolution. Therefore, this study aims to assess the ability of UAV to map mangrove forest, analyze Objectbased UAV imagery (ACUBO), as well as determine the relationship between tree height and diameter in the field and on UAV. Field surveys were carried out to obtain data on mangrove species and other supporting vegetation parameters, such as tree height and diameter. The results were used to perform accuracy tests between objects on UAV and in the field, as well as the calculation of biomass reserve and carbon content in the study area. The results on ACUBO for mangrove species showed an Overall Accuracy of 92.98%, with Producer Accuracy of 78%, 97%, 96.63%, and 85% in B. gymnorrhiza, C. tagal, R. stylosa, and R. apiculta, respectively. Meanwhile, User Accuracy of 88.89%, 97.73%, 73%, and 85.92% was obtained in B. gymnorrhiza, C. tagal, R. stylosa, and R. apiculata, respectively. This study revealed that there was a close relationship between tree height in UAV and the field, as shown in the regression equation Y = 0.0386 + 1.135X with R2 = 0.90. There was also a close association between the diameter in UAV and the field, and this was indicated by the regression equation Y = 4.638 +0.5588 X with R2 = 0.87

The potential of biomass and carbon storage of avicennia alba in the mangrove rehabilitation area of Kedaburapat village, Kepulauan Meranti district

This research was conducted from May – August 2023 in the rehabilitation mangrove area of Kedaburapat Village, Rangsang Pesisir Sub-District, Kepulauan Meranti Regency, Riau Province. This study aims to determine the average of tree diameter, potential biomass and carbon storage of each tree and the relationship between potential biomass and carbon storage with the diameter of the Avicennia alba rehabilitation mangrove trees in Kedaburapat Village. The method used in this study is a survey method and determination of sampling points by purposive sampling. The potential biomass and carbon storage of each tree were calculated using the allometric method. The relationship between average tree diameter and potential biomass and carbon storage was analyzed using simple linear regression. The average diameter at breast height (DBH) of A. alba per tree ranged from 2.81 – 4.03 cm, the average biomass per tree was 7.39 – 12.80 kg, the average carbon storage per tree was 3.47 – 5.00 kg C and tree carbon total per ha was 32.62 – 43.95 ton C/ha. The potential of biomass and carbon storage of each tree has a relatively strong positive relationship with the average tree diameter, with a correlation coefficient (r) of 0.9921. The quality of the waters measured in this study were temperatures ranging from 28-30°C, salinity 25-28‰, and pH 7.5-7.9. Environmental parameters indicate that the condition of the rehabilitation mangrove area in Kedaburapat Village is still good and can support the life of mangrove vegetation.

Screening Tree Species for Carbon Storage Potential through Urban Tree Inventory in Planted Vegetation

Urban tree inventory is a great tool for gathering data that can be used by different end users. This study attempted to chart the species diversity in planted areas and measure their tree diameter at breast height to screen them for the carbon storage potential. A total of 2860 trees belonging to 36 species were recorded in the planted vegetation in parks and avenue plantation. The dominant species were Azadirachta indicia (25.5%), Conocarpus erectus (19.2%), Ficus spp. (15.5%), Tabebuia rosea (9.2%), Peitophorum pterocarpum (9.0%) and the remaining represents (21.6%) of the tree identified in this study. It was found that the highest contribution of carbon sequestration (CO2 equivalent) is dominated by the Ficus spp. (30.3%) with a total of 3399.3 tCO2eq, followed by Azadirachta indicia (25.4%) with a total of 2845.2 tCO2eq and Conocarpus erectus (20.4%) with a total of 2286 tCO2eq. The entire area has the capability to sequester around 11,213.3 tCO2eq and on average of 3.9 ± 0.1 tCO2eq. In accordance with the findings, it is imperative for the preservation of a sustainable environment to have vegetation that has the capacity to store carbon. The study suggests, there is potential to increase carbon sequestration in urban cities through plantation programs on existing and new land uses and along roads.

Relationship Between Tree Height-Diameter at Breast Height (DBH) and Crown Diameter-DBH of Fruit Trees in Bogor Botanical Gardens

Ex-situ conservation of Bogor Botanical Gardens (BBG) represents a collection of predominantly Indonesian species and constitutes an exceptional tropical garden. The gardens’ living collections, which include fruit trees, were mostly native to the forest and uncultivated, preserving their original characteristics. The study’s aim was to examine the relationship between tree height and breast height diameter and breast height diameter and canopy diameter of fruit trees at BBG. Three individuals from each of the fifteen selected fruit species were measured for their diameter breast height (DBH), crown diameter, and tree height. The highest mean of all parameters was for Durio zibethinus, while the lowest mean of all parameters was for Garcinia mangostana. Mostly fruit tree species have a positive and strong correlation. The highest and the lowest relationship between tree height and DBH was for C. burmanii (R2=99.88%) and for C. nucifera (R2=1.21%). The highest and the lowest relationship between crown diameter and DBH was for C. burmanii with linear regression (R2=99.94%) and for A. catechu with logarithmic regression (R2=24.06%). There was a positive relationship between DBH and tree height and between crown diameter and DBH for the growth prediction of fifteen fruit trees in BBG.

Post Debarking Response of <i>Prunus africana</i> (Hook. F) Kalkman (<i>Rosaceae</i>) Trees at Two Exploitation Sites in North Kivu (Eastern Democratic Republic of Congo)

Prunus africana is a species of great economic, medicinal and ecological importance. Due to its multiple uses, unsustainable exploitation methods and low regeneration capacity in tropical rainforests, this species is threatened with extinction. Present and exploited in the eastern part of DR Congo, knowledge of the dynamics of post-bark regeneration of Prunus africana remains fragmentary and poorly known. In North Kivu province, this species thrives in both afromontane forest and lowland tropical rainforest habitats. In order to contribute to the rational and sustainable exploitation of Prunus africana in this province, this paper was carried out with the objective of contributing to the knowledge of the dynamics of the regeneration of post-harvest bark of Prunus africana in two exploitation sites (low and high altitude). To achieve this objective, the inventory was conducted on 16 plots of 25 hectares each, with 8 plots per site. Dendrometric parameters (diameter at breast height (DBH), total tree height) and tree growth and regeneration parameters, i.e., stem bark thickness of the unharvested and harvested portions of the trees (bark reconstitution) were measured. A total of 716 barked stems of Prunus africana in 2016 in 25 hectares constituted the study sample. Results show that sites do not influence diameter at breast height of P. africana trees (p > 0.05) or total tree height. The bark diameter of harvested trees and the bark diameter of unharvested trees varied significantly by site (p 0.05). In contrast, the annual growth rate of bark differed with altitude; the highest rate was observed in trees growing at high altitude (2.97 ± 0.9 mm/yr) compared to 2.23 ± 0.74 mm/yr at low altitude. In view of these results, this study indicates that a half-rotation of 7 years could allow an effective reconstitution of the bark of Prunus africana at the second passage on the remaining side of the same stem.

Remote sensing of subtropical tree diversity: The underappreciated roles of the practical definition of forest canopy and phenological variation

Tree species diversity is vital for maintaining ecosystem functions, yet our ability to map the distribution of tree diversity is limited due to difficulties in traditional field-based approaches. Recent developments in spaceborne remote sensing provide unprecedented opportunities to map and monitor tree diversity more efficiently. Here we built partial least squares regression models using the multispectral surface reflectance acquired by Sentinel-2 satellites and the inventory data from 74 subtropical forest plots to predict canopy tree diversity in a national natural reserve in eastern China. In particular, we evaluated the underappreciated roles of the practical definition of forest canopy and phenological variation in predicting tree diversity by testing three different definitions of canopy trees and comparing models built using satellite imagery of different seasons. Our best models explained 42%–63% variations in observed diversities in cross-validation tests, with higher explanation power for diversity indices that are more sensitive to abundant species. The models built using imageries from early spring and late autumn showed consistently better fits than those built using data from other seasons, highlighting the significant role of transitional phenology in remotely sensing plant diversity. Our results suggested that the cumulative diameter (60%–80%) of the biggest trees is a better way to define the canopy layer than using the subjective fixed-diameter-threshold (5–12 ​cm) or the cumulative basal area (90%–95%) of the biggest trees. Remarkably, these approaches resulted in contrasting diversity maps that call attention to canopy structure in remote sensing of tree diversity. This study demonstrates the potential of mapping and monitoring tree diversity using the Sentinal-2 data in species-rich forests.

Dynamic growth model for oak stands in Moscow, Russia

The most objective information about the state of Moscow’s forests is provided by long-term observation data on permanent trial plots. Such data makes it possible to identify changes in forest stands under the influence of recreationists, environmental pollution, and climate change. Long-term observational data are particularly valuable in modeling forest stand growth and productivity. The goal of the study is to develop a dynamic model of the growth of oak stands in Moscow based on long-term observation data. The modelling data were obtained from 7 plots of the permanent sample plot network established by the Forest Experimental Station of the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy. There are a total of 42 inventories and the number of inventories per plot range from 3 to 9. Inventories were carried out between 1927 and 2009. We used three initial state variables for prediction, as in many studies. Taking into account the peculiarities of the inventory of forest stands in Russia, the mean height, quadratic mean diameter and number of trees per hectare were used as initial variables. All obtained models meet the requirements for forest inventory in Russia in terms of error values of stand attributes. The model in this study provides a simple and reliable system for predicting the growth and yield of Moscow oak stands.

Utilization of iPad Pro LiDAR and Low-Cost GNSS Ublox F9R for Data Collection of Road Assets in the Form of 3D Models

The development of mapping survey equipment technology products is growing very rapidly. These products include Global Navigation Satellite System (GNSS) and Light Detection and Ranging (LiDAR) technology. The current development of GNSS receivers can be seen in terms of accuracy and price. The GNSS receiver has very high accuracy, especially with the integration with the inertial measurement unit (IMU). This integration system can provide benefits such as estimation of GNSS position data and GNSS data stability. One of the GNSS receiver products that has been integrated with IMU, has an accuracy below 1 meter, and at an economical price is the low-cost GNSS receiver U-blox F9R series. This receiver has a positional accuracy of 0.01 + 1 ppm. LiDAR products are commonly used for the manufacture of 3D objects and distance determination on Autonomous Vehicles, however, in 2020 the company Apple inc. has made a smartphone device that is integrated with LiDAR technology. One of the goals of using this integration system is to visualize 2D objects into 3D Augmented Reality (AR). In this study, iPad Pro LiDAR technology was used to create a 3D road model. This activity continues from previous studies that have used the iPad Pro LiDAR for making 3D buildings and measuring tree diameters. In research related to the manufacture of 3D buildings, the iPad Pro LiDAR has been analyzed and it is stated that it has an accuracy of 2 cm. However, this observation using the iPad Pro LiDAR still does not provide actual position information. One way to get the true position value is to use position data from the GNSS receiver. In this study, the GNSS observation method receiver used is Real Time Kinematic Networked Transported of RTCM via Internet Protocol (RTK-NTRIP). This method utilizes the Global System for Mobile Communications (GSM) network to transmit corrections from several nearby Continuously Operating Reference Stations (CORS) in Radio Technical Commission for Maritime Services (RTCM) format to the user’s receiver. This activity aims to create a database of road assets in 3D with real positions by utilizing the integration between GNSS, IMU, and iPad Pro LiDAR. From this study, it was found that the volume measurement data using GNSS data has a value of 4,930 m3. Meanwhile, processing using 3D model data from the iPad Pro 2020 resulted in 4,422 m3. The results of the two data have a volume difference of 0.5 m3 or 10% of the validation data.

Performance of seedling and mixed-species planting test of three species of Rubiaceae treated by different seedling media and mycorrhizae application

Seedling growth in the nursery and early field performance of three fast-growing tree species from the Rubiaceae family, i.e., white jabon (Neolamarckia cadamba), red jabon (Neolamarckia macrophylla, and gempol (Nauclea orientalis), were tested by using different seedling media and arbuscular mycorrhizal fungi (AMF) treatments in the nursery and mixed-species field tests. The experiment design in the nursery and field test was laid out following a split-split plot design of a randomized complete block with four replications. The main factors were tree species, the sub-factors were seedling media, and the sub-sub factors consisted of the AMF inoculation, with a mixed species planting pattern. White jabon had a more dominant growth both at the seedling level in the nursery and at the field test level until the age of 2 years, followed by gempol and red jabon. AMF inoculation in those three species at the seedling level was strongly influenced by the characteristics of the seedling media like media with high fertility levels resulting in a very low percentage of AMF colonization. In the field trial, all tree species and treatments were infected with mycorrhizae with colonization percentages ranging from 27.6% to 57.7%, which was suspected to be an infection from native AMF in the planting site. The AMF application had a significant effect on the percentage of colonization and tree diameter growth of 2-year-olds with a percentage increase of 14.4% and 8.4%, respectively.

ESTIMASI SEKUESTRASI KARBON PADA TANAMAN POKOK HUTAN PRODUKSI DI KABUPATEN TUBAN, JAWA TIMUR

Tuban Regency feels the impact of climate change on various economic supporting sectors. This makes the adaptation efforts in these sectors important as well as climate change mitigation to support the reduction of greenhouse gas emissions, one of which is by maintaining the existence of production forests. This study aims to identify the amount of carbon uptake by the two main plants. The method used is tree diameter data collection without harvesting. The diameter data is used to calculate biomass and carbon sequestration with allometric equations. The results showed that teak had the lowest biomass value produced at the age of 5 years at 94.26 t ha-1, and the highest biomass was recorded at the age of 10 years at 200.33 t ha-1. Meanwhile, mahogany at the age of 5 years, 10 years and 15 years had a total biomass of 40.76 t ha-1, 53.55 t ha-1 and 146.37 t ha-1, respectively. From the biomass value, the total carbon stored in teak aged 5 years, 10 years and 15 years, respectively, was 43.36 t ha-1, 92.15 t ha-1 and 90.05 t ha-1. While the the total carbon stores in mahogany aged 5 years, 10 years and 15 years respectively was 18.75 t ha-1, 24.63 t ha-1 and 67.33 t ha-1. The teak and mahogany production forests in this age group have a total area of ​​more than 280 ha, so that the total carbon sequestration at BKPH Sundulan is 78,471 tons C from teak production forests and 1,835.3 tons C absorbed from mahogany production forests.

Demographic changes in China's forests from 1998 to 2018

BackgroundTree demography is an essential indicator of various forest ecosystem services, and understanding its changes is critical for the sustainable management of forests. During the past four decades, China implemented unprecedented forest restoration projects, which altered tree demography by increasing the number of trees and introducing new species. However, it remains unclear how species composition has changed in China in response to the past forest restoration and demographical processes. MethodsWe applied Forest Stability Index (FSI) and the relative change of FSI (%FSI) to describe the population dynamics of tree species and structure in China since 1998, using field-survey data collected from over 200,000 plot-records from the 6th to 9th National Forest Inventories (NFIs). ResultsThe overall populations of both natural and planted forests have grown rapidly from 1998 to 2018, while the range of changes in the relative tree density was more variable for natural forests (ranging from −8.53% to 42.46%) than for planted forests (ranging from −1.01% to 13.31%). The populations declined only in some of the tree species, including Betula platyphylla, Ulmus pumila, and Robinia pseudoacacia. In contrast, the populations of trees in the largest size-class either remained stable or expanded. ConclusionsTree density of China's forests (both natural and planted forests) generally expanded and the overall populations increased in most size classes, with greater increases occurred in planted forests. In contrasting to the global decline trends of large diameter trees, here we found no apparent decline for trees in the largest size-class in China, highlighting China's success in improving forest health and forest adaptations to climate change. We advocate for more studies to reveal the mechanisms of the changes in tree demography, which will help to improve forest ecosystem services such as the carbon sequestration capacity.

Assessment of Tree Species Diversity, Family Composition and Diameter Size Class of Tree Species in Igbo-Olua Sacred Groove, Ondo State, Nigeria

This study was carried out to assess the tree species diversity, family composition and diameter size distribution of the tree species in Igbo-Olua sacred groove, Ondo state, Nigeria using appropriate standard techniques. A total of 34 tree species distributed in 23 families were recorded. Sterculiaceae family (66) had the highest number of individual stem per ha while Moraceae family had the highest number in terms of tree species per hectare (7). The distribution of the diameter structure is typical of the natural forest type with high number of tree species in the smaller size classes or interval (12.5) and the number of tree species decreases with increasing size class or interval. Diversity measures obtained included Shannon-Weiner index (3.09), Evenness (0.64) and Margalef index (6.36). Awakening the consciousness of people towards the protection of sacred groves has practical implications on their survival. Hence government and other allied institutions should gear efforts towards grove conservation.

Spatial distribution of vegetation diversity, timber production, and carbon storage in secondary tropical rainforest at South Kalimantan, Indonesia

Abstract. Suyanto, Nugroho Y, Harahap MM, Kusumaningrum L, Wirabuana PYAP. 2022. Spatial distribution of vegetation diversity, timber production, and carbon storage in secondary tropical rainforest at South Kalimantan, Indonesia. Biodiversitas 23: 6147-6154. Sustainable management in secondary tropical rainforests requires basic information about stand characteristics, mainly related to productivity and biodiversity. This study aimed to quantify vegetation diversity, timber production, and carbon storage from various sites of secondary forests in South Kalimantan. Forest inventory was conducted using a census method at seven different natural forest management unit compartments. Four parameters were measured from each tree, including the type of species, commercial categories, tree diameter, and tree height. Individual tree volume and biomass were estimated using allometric equations, while carbon storage was determined using a conversion factor from biomass. Three indicators were used to evaluate vegetation diversity: richness, heterogeneity, and evenness. The analysis of correlations was applied to examine the relationship between vegetation diversity and stand productivity with a significant level of 5%. Results found that there were 41 tree species in the study site comprising 20 commercial and 21 non-commercial species. The highest richness (R') was recorded in compartment 18X by approximately 4.0, while the most increased heterogeneity (H') and evenness (E') were observed in compartment 18Y by around 2.4 and 0.7, respectively. The accumulation of timber production varied in each site, with a range of 45.46-68.32 m3 ha-1. The highest carbon storage was noted in compartment 19Y (38.74±1.79 t C ha-1), while the lowest was found in compartment 18W (20.76±0.93 t C ha-1). The relative contribution of commercial species to timber production and carbon storage was substantially higher than non-commercial species at all sites. However, there was not a significant correlation between vegetation diversity and stand productivity (P>0.05). Overall, our study concluded that the secondary tropical forest ecosystems in the site had good vegetation diversity, timber production, and carbon storage.

Effects of two different thinning methods on the diameter and basal area increments of silver lime (Tilia tomentosa Moench) target trees in Fruška Gora (Serbia)

This paper analyses the cumulative effects of selective thinning and thinning from below on diameter and basal area increments of target trees after 25/26 years in 52, 69- and 86-year-old silver lime (Tilia tomentosa Moench) stands. Two target tree collectives were analysed: (1) elite trees selected between 1993–1994 from permanent sampling plots (selective thinning method), and (2) a ‘comparable collective’ of target trees selected in 2019 (25/26 years later) according to the same criteria as the elite trees, in the same stands thinned from below. Elite trees that were selectively thinned had: higher diameter, basal area and volume per tree, higher diameter and basal area increment for a given time period, and lower slenderness coefficients compared to the target trees that were thinned from below at 52 and 69 yr. While diameter increment decreases with age, and differences between elite trees of different ages are clearly delineated, diameter increments of trees thinned from below are not significantly different at 52 and 69 yr. In addition, basal area increment of trees is highest at 69 yr with selective thinning. When thinning from below, there were no significant differences in basal area increments between trees at 69 and 86 yr. Silver lime shows a strong growth response after selective thinning at ages 25/26 and 44 yr. However, our results show that this response is less pronounced when selective thinning begins at 61 yr.

Short-Term Effects of Thinning on Tree Growth and Soil Nutrients in the Middle-Aged Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook.) Plantations

Knowing the effect of thinning on forest ecosystem services is an important aspect of sustainable forest management. This study analyzed the traditional thinning on tree growth and soil nutrients in the Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations. The Chinese fir plantations were 11 years old with different initial densities in Jinji (4000 tree·ha−1), and Yingde (3000 tree·ha−1), Xiaolong (2000 tree·ha−1) forest farms, and 20 years old in Yangmei (2000 tree·ha−1) forest farm. The thinning intensity was 35% in Yangmei and Xiaolong forest farms, and 43% in Jinji and Yingde forest farms. Tree growth was measured as the increment of diameter at breast height and stand volume; soil nutrients were measured as pH, soil carbon and nitrogen contents at 0–10 cm soil. The thinning led to an increase in the diameter of trees in all study plots, with the fastest growth rate in Jinji (22.02%) forest farm. The stand volume growth rate was higher in thinning plots than in control plots, with the highest volume growth rate in Xiaolong (27.8%), due to its higher leaf area index and lower density. There was an increasing pattern of C and N contents in the higher initial density plots after thinning (Jinji and Yingde forest farms). During the extreme drought year in 2021, the thinning mitigated the changes in soil acidity and soil moisture, which indicated that thinning could also increase drought tolerance in the short term. Thinning response studies frequently focus on the long-term effect; our results demonstrate how thinning promotes tree growth in the short term.

The bigger the tree the better the seed – effect of Sessile oak tree diameter on acorn size, insect predation, and germination

Sessile oak is one of the ecologically and economically most important tree species in Europe. Recently, the importance of this species has been particularly highlighted in the context of climate change, where it is expected that these species will play a significant role within their natural range and beyond. To regenerate and expand the range of the sessile oak forests, a large amount of healthy acorns is needed. The acorn production and the acorns themselves are endangered by a large number of abiotic and biotic factors. As oak trees of different sizes do not produce the same amount of seed of the same quality, we investigated how the sessile oak tree diameter affects the acorn size, insect infestation, and germination rate. On the other side, as the acorn size influences the attack rates of the most significant acorn pest – Curculio glandium (Marsham, 1802), and the germination rates of both the damaged and healthy acorns we also investigated how the acorn dimensions influence the insect damage and germination rates, and how the insect damage influences the germination rates. We determined that the oak tree size influences some oak seed characteristics that are important for forest regeneration, while it does not affect others. A greater acorn yield was recorded on the bigger oak trees. The tree dimensions also had a significant influence on the acorn size. Greater average length, as well as greater average acorn diameter, were recorded on bigger trees. Although the tree size affects the acorn size, it does not influence the acorn insect predation rates or its germination rates. These parameters are affected by the acorn size itself. Bigger acorns had a greater germination rate. Insects preferred smaller acorns and had a significantly negative influence on the germination rate.

Growth Dynamics of Young Mixed Norway Spruce and Birch Stands in Finland

Mixed-species forests in Fennoscandia are of increasing interest because they may improve resilience, biodiversity, and productivity. Currently there is scarce knowledge available of the early growth dynamics of mixed spruce–birch stands in even-aged managed production forests with artificial regeneration of spruce. The main objective of our study was to examine the present state and the past growth dynamics of current single-storied, young spruce–birch (Picea abies (L.) Karst., Betula pendula Roth, Betula pubescens Ehrh.) stands (age 17–29 years), where spruce was planted and birch naturally regenerated, and juvenile management practices (early cleaning and precommercial thinning) were carried out. We inventoried ten such stands in Southern Finland, for a total of twenty plots. For 160 spruces and 160 birch trees, we reconstructed the past diameter and height growth through stem analysis. We analyzed mean stand characteristics by tree species, and we modelled the individual tree height and diameter growth using the mixed effects Chapman–Richards model. Spruces had slower initial height growth, but by the age of about 20 years their height growth rate eventually approached and exceeded that of birches regenerated naturally at the time of spruce planting. The diameter growth of planted spruce exceeded that of birches even sooner (at the age of about 10 years). Thus, spruces are not suppressed by birches, and they may coexist in the same canopy layer in managed stands. Contrary to earlier guidelines, due to the fast growth of planted spruces, birch mixture needs to be maintained already in the first juvenile stand management (i.e., early cleaning). The growth dynamics of young, planted spruce, and naturally regenerated birch allow the establishment and management of such mixtures and also maintenance of the mixture in the future until the end of the rotation, thus improving biodiversity in boreal, planted spruce forests.

Growth and productivity of energy plantations of poplars in the Right-Bank Forest Steppe conditions

Purpose. To determine the features of the growth of an energy plantation of poplar variety ‘Robusta’ on leached chernozems in the conditions of the Central Forest Steppe of Ukraine. Methods. Field, laboratory, statistical. Results. One-year lignified cuttings 25 cm long and 0.8–1.0 cm in diameter were used as planting material. The designed layout of planting places: 2.0x0.8 m (more density version) and 2.0x0.9 m (more sparse version). After the first year of cultivation, the studied plots had the same height (1.6 m). During the second growing season, their growth in height was 2.0±0.05 m in the more sparse version, and 2.1±0.05 m in the thicker version. After the first year, the diameter at a height of 1.3 m was greater in the thicker version (0.5 cm versus 0.3 cm), but already in the next year, the trees of the more sparse stand became 2 mm thicker, and this difference persisted in the third year, when the average diameter of the trees of the denser version was 5.8 cm, and of the sparser — 6.2 cm. As a result of the higher diameter of trees of the more sparse version, they had a higher weight of the average tree, but due to the smaller number of trees, their productivity was lower. So, after three years of growing a poplar plantation created by cuttings, one hectare can yield 11.66–14.58 tons of dry biomass, or 207.5–259.5 GJ of energy. A sharp increase in morphometric indicators during the third year of cultivation indicates the feasibility of using a longer period of cultivation of such plantations to obtain the maximum amount of biomass. Conclusions. The study of a three-year energy plantation of the ‘Robusta’ variety, created by one-year lignified cuttings on the leached soils of the Right Bank Forest Steppe, with the placement of planting sites 2.0 x 0.8 m and 2.0 x 0.8 m, showed that after three years of growing a poplar plantation, one hectare can get 11.66–14.58 tons of dry biomass, or 207.5–259.5 GJ of energy. A significant increase in growth indicators and biomass productivity of poplar plantations during the third year of cultivation indicates the feasibility of using a 4–6-year period of cultivation of such plantations to obtain the maximum amount of biomass.