Search Results (32)

Crown defoliation in trees is one of the indicators of forest tree vitality, and a primary criterion for selecting trees for sanitary felling. In Croatia, the selection of trees for sanitary felling includes all dead trees and those with crown defoliation greater than 60% (defoliation class 3a); in the past, the threshold for marking trees for sanitary felling was above 80% (class 3b). The aim of this study was to analyze tree mortality in pedunculate oak (Quercus robur), silver fir (Abies alba), and European beech (Fagus sylvatica), as well as crown regeneration, i.e., the reduction in defoliation. The analysis included a total of 7975 trees, comprising 1182 silver fir, 4221 European beech, and 2572 pedunculate oak trees, covering the period from 1998 to 2023. The mortality rate was 7.2% for silver fir, 2.16% for beech, and 9.6% for oak. The percentage of trees that regenerated their crowns or reduced defoliation to below 60% was 17.01% for fir, 4.33% for beech, and 12.51% for oak. Considering the proportion of silver fir and pedunculate oak trees whose defoliation decreased to below 60%, a defoliation threshold greater than 80% would be a more appropriate criterion for sanitary felling, except for European beech trees, for which there is a minimal difference between the recovery rates in classes 3a and 3b. Full article

Within a dam reservoir landscape in the Western Black Sea Region of Türkiye, a dense young-mature stand composed diversely of oriental beeches, European hornbeams, sessile oaks, and silver lindens was chosen as a study field to analyze canopy parameters and to determine phenological patterns along the altitudinal gradients. Referring to the air-soil temperature and precipitation data, intra-annual eco-physiological characteristics of that stand tree canopies, were aimed to be determined regarding those altitudinal gradients. For each of the 10 altitudinal gradients, the mixed deciduous stand canopy physiological characteristics were analyzed by hemispherical photographing. Canopy parameters were acquired from those digital hemispherical photographs, which were confirmed with secondary LAI data from the LAI-2200C. Leaf Area Index, Light Transmission, Canopy Openness, and Gap Fraction were obtained during a total of 21 study field visits throughout the monitoring year. Beginning from a theoretical leafless stage with 0.51 m² m⁻², average LAI increased to 0.89 m² m⁻² during budburst stage, and then gradually up to 3.60 m² m⁻² during climax leaf period, and then to 1.38 m² m⁻² during senescence period, and gradually down to 0.50 m² m⁻² during the next theoretical leafless stage. However, average LT (64%, 61%, 9%, 36%, 74%), CO (65%, 62%, 9%, 37%, 75%), and GF (18%, 14%, 1%, 8%, 14%) followed opposite patterns. Though no apparent trend was valid for those canopy parameters from the lowest to the highest altitudinal gradient, their obvious intra-annual patterns emerged as compatible with the annual air-soil temperature data course. Full article

Forests in Croatia are characterized by higher levels of biodiversity in species composition. Three significant events occurred in Croatian forests over the past ten years, all of which have a common denominator—sanitary felling. The challenge in the sustainable development of forests started with the ice storm of 2014 that amounted to damage and raised costs in forest stands to EUR 231,180,921. The second challenge was in 2017 when the bark beetle outbreak occurred in the Gorski Kotar region. In December 2017, a windstorm in the same area caused damage to approximately 500,000 m³ of wood stock. The third climate extreme was in the summer of 2023 when three storms with strong winds and heavy rain damaged even-aged forests of common beech and pedunculated oak. The damage was substantial: 3,954,181 m³ of timber was mostly broken and destroyed across 21,888.61 ha of area, and the most damage was in the pedunculate oak forests of Slavonia, i.e., Quercus robur subsp. Slavonica, at 1,939,175 m³. For the main meteorological stations in lowland Croatia, data on precipitation amounts (mm) and wind speeds (m/s) were collected for the period 1981–2023, and the results of our analysis for the last decade are presented. Meteorological drought was analyzed using the rain anomaly index RAI. Data regarding open space fires in the Mediterranean karst area of Croatia were collected from the Croatian Firefighting Association, and the calculation of the burned area index (BAI) was determined. Throughout the entire area of Gorski Kotar County, a sample of permanent plots was set and used to assess the extent of forest damage from the ice storm in 2014 and for the establishment of permanent monitoring of the recovery of trees and forests damaged by the ice storm. The monitoring of bark beetles in the Gorski Kotar region started in 1995 and is still in progress. The aftermath of bark beetle outbreaks in two uneven-aged silver fir stands was studied after a bark beetle outbreak and a sanitary felling of 4655.34 m³. In the area of lowland Croatia, a statistically significant and positive correlation was found between sanitary fellings, maximum wind speeds, and rain anomaly indices in even-aged forests. In conclusion, sustainable development will be at risk due to difficult recovery, rising costs, and overall climate change in the years to come. Full article

Changing environmental conditions, disturbances, and escalating demands for forest ecosystem services require foresters to restore present forestlands with new forest generations that will exhibit ecological integrity, diversity, high adaptive capacity, and the ability to provide essential ecosystem services. Establishing such forests requires careful consideration of the forest landscape and site dynamics. In pursuit of these requirements, we developed a novel framework that enables the restoration of forest sites and promotes the desired features of the forest complex at the same time. This framework was designed with the methods of system engineering and was organized in the same way as the forest planning process. It was tested in the habitat type of Illyrian Fagus sylvatica forests belonging to the Natura 2000 network. The environmental, vegetation, and site conditions were investigated via field inspections, available forest management plans, and simple GIS analyses. Additionally, we established a seminatural stand composed of European beech, sessile oak, sycamore maple, silver fir, and some wild fruit tree species. The survival of planted species was assessed using census and simple random sampling, the performance of provenances by Student’s test, while microhabitat factors were explored by a one-way ANOVA. The survival rate of key species was estimated to be 55.6%, while that of fruit species was estimated to be 94.5%. Our framework demonstrated satisfactory performance and contained sufficient benchmarks to facilitate consistent decision-making. In the discussion, we elucidate the framework’s primary features and attributes of the mixed stand, where we also expose some open issues to be addressed in the future. Full article

The task of tree species classification through deep learning has been challenging for the forestry community, and the lack of standardized datasets has hindered further progress. Our work presents a solution in the form of a large bark image dataset called CentralBark, which enhances the deep learning-based tree species classification. Additionally, we have laid out an efficient and repeatable data collection protocol to assist future works in an organized manner. The dataset contains images of 25 central hardwood and Appalachian region tree species, with over 19,000 images of varying diameters, light, and moisture conditions. We tested 25 species: elm, oak, American basswood, American beech, American elm, American sycamore, bitternut hickory, black cherry, black locust, black oak, black walnut, eastern cottonwood, hackberry, honey locust, northern red oak, Ohio buckeye, Osage-orange, pignut hickory, sassafras, shagbark hickory silver maple, slippery elm, sugar maple, sweetgum, white ash, white oak, and yellow poplar. Our experiment involved testing three different models to assess the feasibility of species classification using unaltered and uncropped images during the species-classification training process. We achieved an overall accuracy of 83.21% using the EfficientNet-b3 model, which was the best of the three models (EfficientNet-b3, ResNet-50, and MobileNet-V3-small), and an average accuracy of 80.23%. Full article

Tree branches from forest tree harvesting for the timber industry are an important energy feedstock. Solid biofuel in the form of wood chips, produced from branches, is an excellent renewable energy source for generating heat and electricity. However, the properties of wood chips as a solid biofuel produced from forest tree branches can vary greatly depending on the species from which they have been produced. Therefore, this study aimed to assess the thermophysical properties and elemental composition of fresh branches harvested from nine tree species (pedunculate oak, silver birch, European ash, common aspen, grey alder, Norway maple, Scots pine, European larch and Norway spruce) over three consecutive years (2020–2022). The branches of the tree species most commonly found in Polish forests (Scots pine) were characterized by the highest heating value (an average of 20.74 GJ Mg⁻¹ DM), the highest carbon content (an average of 55.03% DM), the lowest ash (an average of 0.60% DM) and nitrogen contents (an average of 0.32% DM), and low sulfur (an average of 0.017% DM) and chlorine contents (an average of 0.014% DM). A cluster analysis showed that the branches of all three coniferous tree species (Scots pine, Norway spruce and European larch) formed one common cluster, indicating similar properties. The branches of the European ash were characterized by the lowest wood moisture content (an average of 37.19% DM) and thus the highest lower heating value (an average of 10.50 GJ Mg⁻¹). During the three years of the study, the chlorine and ash contents of the branches of the tree species under study exhibited the highest variability. Full article

Forests of the Carpathians are of increasing research interest, as they cover a large area (>9 Mha) within European forests and are influenced by diverse environmental conditions and contrasting historical developments. We reviewed 251 papers dealing with Carpathian forests, their history, and future perspectives. Over 70% of articles and reviews appeared in the last ten years, and 80% refer to the Western and Eastern Carpathians, while the Serbian Carpathians remain a gap in this research field. Forest expansion and species changes have occurred since Holocene deglaciation, influenced by timber use, settlements, cropland development, and, since the Bronze Age, pasture activities. At higher elevations, early conifer successors have been increasingly replaced by Norway spruce (Picea abies), silver fir (Abies alba), European beech (Fagus sylvatica), and hornbeam (Carpinus betulus), while oaks have been present in the Carpathian foothills throughout the whole of history. In the 19th and 20th centuries, Norway spruce afforestation was favored, and timber use peaked. Recent transitions from agriculture to forest land use have led to a further increase in forest cover (+1 to +14% in different countries), though past forest management practices and recent environmental changes have impaired forest vitality in many regions; climate warming already causes shifts in treelines and species distributions, and it triggers pest outbreaks and diseases and affects tree–water relations. The risk of forest damage is the highest in monodominant Norway spruce forests, which often experience dieback after cascade disturbances. European beech forests are more resilient unless affected by summer droughts. In the future, increasing dominance of broadleaves within Carpathian forests and forest management based on a mix of intensive management and ecological silviculture are expected. Maintenance and promotion of silver fir and mixed European beech forests should be encouraged with respect to forest stability, biodiversity, and economic sustainability. As supported by the Carpathian Convention and related institutions and initiatives, connectivity, management, and stakeholder cooperation across administrative borders will be crucial for the future adaptive potential of Carpathian forests. Full article

Silky Oak or Silver Oak (Grevillea robusta A.Cunn. ex R.Br.) is classified as a high-value economic wood in Thailand, it is also considered to be a plant that can grow rapidly, and it has the potential to efficiently reduce greenhouse gases emitted into the atmosphere. This research aimed to study and develop an allometric equation to evaluate the biomass of F1 Silky Oak, which was imported to Thailand from Australia, and grown in Thailand’s economic woods in Silky Oak sites in Pak Chong District, Nakhon Ratchasima Province. The sample group consisted of trees of different ages (i.e., of 2 years, 3–4 years, and 7 years). An allometric equation was used to determine the tree biomass, based on mathematical models that describe the relationship between tree biomass and diameter at breast height (DBH). It was developed in the form of a quadratic equation by multiplying the square DBH by the total height (DBH² × Ht). Subsequently, the equation was separated into different components, which corresponded with different parts of the tree (i.e., stem, branches, leaves, and roots). The following equations were obtained for the stem: Ws = 0.0721 (D²H) 0.8297 R² = 0.998. The following equations were obtained for the branches: Wb = 0.0772 (D²H) 0.7027 R² = 0.977. The following equations were obtained for the leaves, Wl = 0.2085 (D²H) 0.4313 R² = 0.990. The following equations were obtained for the roots: Wr = 0.3337 (D²H) 0.4886 R² = 0.957. The results of a laboratory elemental analysis of the carbon sequestration in the biomass, using a CHN elemental analyzer, showed that the mean percentage of carbon content in the stems, branches, leaves, and roots was 45.805. Applying the developed allometric equation for evaluating carbon sequestration, using the survey data from the sample sites of Silky Oak, it was found that the amount of carbon sequestration for the aboveground biomass in three sites was 130.63 tCO₂eq. When the amount was converted into carbon dioxide, which was absorbed in the three sites, we obtained a value of 478.99 tCO₂eq. The results of the application of the allometric equation showed that there was substantial carbon sequestration potential in the surveyed sites, emphasizing the role of Silky Oak plantations for climate change mitigation and sustainable land management. This study advances our understanding of Silky Oak growth and carbon storage dynamics, offering valuable tools for biomass estimation and promoting environmentally beneficial land use practices. Full article

Monitoring tree phenology is important for understanding ecosystem functioning and for assessing ecosystem responses to climate change. Satellite imagery offers open-access global coverage but is restricted to forest-level analyses, due to its coarse spatial resolution. Unmanned aerial vehicle (UAV) imagery can monitor phenology at the individual tree level by utilizing a centimeter-scale resolution. Two research objectives were identified for this study: (1) to derive phenological metrics at the individual tree level, using various vegetation indices (VIs); and (2) to assess the accuracy of automatic crown delineation in a diverse ecosystem. To achieve this, fourteen multi-spectral UAV flights were performed, and the ability of the normalized difference vegetation index (NDVI), enhanced vegetation index 2 (EVI2), optimized soil-adjusted vegetation index (OSAVI), and chlorophyll index red-edge (CI_re) to model seasonal phenology was assessed. A double logistic model was fitted on the VI observations for each individual tree, to derive the start of season (SOS) and end of season (EOS). Individual tree crowns were delineated automatically using marker-controlled watershed segmentation (MCWS), and the treetops were identified using a local maximum filter (LMF). Overall, the automatic segmentation performed well (F-score: 0.79, IoU: 0.58), with higher accuracies in single-species areas, while it underperformed in complex mixed forest structures. All VIs captured a strong seasonal signal for the deciduous trees and derived SOS and EOS estimates consistent with literature and ground observations. General phenological patterns included an early silver birch SOS, a quick beech budburst, and large within-species phenology variations for oak trees. Seasonal VI variation for coniferous evergreen trees was limited, and the resulting phenology estimates proved unreliable. In conclusion, these findings emphasize the capabilities of UAV imagery for individual tree crown phenology monitoring. However, they also show the difficulty of monitoring evergreen phenology with the commonly-used VIs and stress the need for further investigations. Full article

In forestry research, for forest inventories or other applications which require accurate 3D information on the forest structure, a Terrestrial Laser Scanner (TLS) is an efficient tool for vegetation structure estimation. Light Detection and Ranging (LiDAR) can even provide high-resolution information in tree canopies due to its high penetration capability. Depending on the forest plot size, tree density, and structure, multiple TLS scans are acquired to cover the forest plot in all directions to avoid any voids in the dataset that are generated. However, while increasing the number of scans, we often tend to increase the data redundancy as we keep acquiring data for the same region from multiple scan positions. In this research, an extensive qualitative analysis was carried out to examine the capability and efficiency of TLS to generate canopy top points in six different scanning combinations. A total of nine scans were acquired for each forest plot, and from these nine scans, we made six different combinations to evaluate the 3D vegetation structure derived from each scan combination, such as Center Scans (CS), Four Corners Scans (FCS), Four Corners with Center Scans (FCwCS), Four Sides Center Scans (FSCS), Four Sides Center with Center Scans (FSCwCS), and All Nine Scans (ANS). We considered eight forest plots with dimensions of 25 m × 25 m, of which four plots were of medium tree density, and the other four had a high tree density. The forest plots are located in central Slovakia; European beech was the dominant tree species with a mixture of European oak, Silver fir, Norway spruce, and European hornbeam. Altogether, 487 trees were considered for this research. The quantification of tree canopy top points obtained from a TLS point cloud is very crucial as the point cloud is used to derive the Digital Surface Model (DSM) and Canopy Height Model (CHM). We also performed a statistical evaluation by calculating the differences in the canopy top points between ANS and the five other combinations and found that the most significantly different combination was FSCwCS respective to ANS. The Root Mean Squared Error (RMSE) of the deviations in tree canopy top points obtained for plots TLS_Plot1 and TLS_Plot2 ranged from 0.89 m to 14.98 m and 0.61 m to 7.78 m, respectively. The relative Root Mean Squared Error (rRMSE) obtained for plots TLS_Plot1 and TLS_Plot2 ranged from 0.15% to 2.48% and 0.096% to 1.22%, respectively. Full article

The main goal of our study was to determine whether biosynthesized silver nanoparticles (SNPs) could be used as a novel antibacterial material in order to control soft rot in vegetables. Exudates from oak fruit were used in the green synthesis of SNPs. Postharvest soft rot disease in vegetables has resulted in significant crop losses all over the globe. Because managing Pectobacterium carotovorum subsp. carotovorum (Pcc), the causal agent of soft rot disease, is difficult due to its wide host range, developing innovative disease-management methods that do not involve the use of hazardous chemicals is a top priority for maintaining sustainable agriculture. The current research has found that silver nanoparticles (SNPs) have a detrimental effect on the progression of Pcc and soft rot disease in in vitro conditions. At SNPs’ sub-MIC, the greatest levels of inhibition against tissue maceration were 22, 19.8, 21.5, and 18.5 percent in potato, zucchini, carrot, and eggplant, respectively. SNP treatment of tubers and fruits had a noteworthy suppressive impact on soft rot disease symptoms as compared to controls. SNPs may be able to replace chemical pesticides in the management and prevention of soft rot disease in vegetables in postharvest settings, according to this study. Full article

Massive propagation of cork oak (Quercus suber) individuals tolerant to Phytophthora cinnamomi (Pc) is probably the most important challenge for cork production. Screening for resistance to Pc of ca. 200 seedlings obtained from a single cork oak tree that has survived the epidemic was performed by soil infestation. Twenty months after Pc inoculation, 33 seedlings survived from Pc infection and the four most vigorous seedlings were selected. The plants were forced to produce new shoots under controlled climatic conditions, and the new shoots were used to establish the plants in vitro by axillary budding. High axillary shoot proliferation rates were achieved by culturing the new shoots on Lloyd and McCown (WPM) medium, followed by subculturing for 2 weeks on 0.22 µM benzyladenine (BA) and for 2 weeks further on 0.04 µM BA. Addition of 20 µM silver thiosulphate (STS) increased the proliferation rates and improved the appearance and development of shoots. Rooting rates of 80–100% were obtained by culturing the shoots for 24 or 48 h on Gresshoff and Doy medium with ⅓ macronutrients plus 122.5 µM indole-3-butyric acid and subsequent transfer to root expression medium containing 20 µM STS. The results of this study optimize the micropropagation of a relevant and recalcitrant tree species in forestry. Full article

Altitudinal distributions, population structures and seasonal dynamics of tick fauna at three localities in Continental Croatia (Medvednica and Papuk) and an alpine biogeographic region (Gorski Kotar) were studied. Sampling of questing ticks was performed twice a year (spring and autumn, from 2019 to 2021) at different altitudes (200, 400, 600, 800 and 1000 m above sea level) using the flagging method. In total, 2942 ticks (53.9% larvae, 40.1% nymphs, 6.0% adults) were sampled and 2937 (99.83%) were determined as Ixodes ricinus, 4 (0.14%) as Haemaphysalis concinna and 1 (0.03%) as Ixodes frontalis. Ixodes ricinus was the only species found at all altitudes and sampling sites. The highest tick abundance was recorded at higher altitudes (800–1000 m asl.) on Medvednica and in Gorski Kotar within mixed forests of European beech and European silver fir, while on Papuk most of the ticks were sampled at lower altitudes (200 m asl.) in Sessile oak forest. From 27 pools containing 305 ticks, 1 (3.7%) was positive for Borrelia burgdorferi sensu lato infection. Borrelia burgdorferi s.l. was detected in 20% (1/5) of the pools containing nymphs and adults collected in Gorski Kotar (600 and 800 m asl.). Sequencing of the ospA gene and phylogenetic analysis revealed the presence of the Borrelia burgdorferi sensu stricto genotype. Full article

Several techniques can be used for the detection and analysis of odors. Among them, electronic noses emerged as a rapid and non-invasive diagnostic tool with various applications ranging from the food industry to medical diagnosis or forestry and agriculture. The concept of an electronic nose consists of using an array of nonspecific gas sensors equipped with machine learning pattern recognition algorithms. A few devices based on MOX (metal-oxide) commercially available sensors (Figaro Inc., Osaka, Japan) have been constructed in our laboratory. The operation of developed devices consisted of measuring sensors’ conductivity, carried out as a response to changing operation conditions by moving sensors from clean air to the vicinity of the sample where volatile organic components are present. Additionally, the sensors’ operation in various working temperatures was exploited. Our goal was to develop an inexpensive and effective tool for the early detection of tree diseases caused by pathogenic oomycetes such as fungi. The devices were tested, both on pure cultures of cultivated organisms, and in interaction with infected plants. Distinguishing between the pathogenic oomycetes Phytophthora plurivora and Pythium intermedium, and the fungi Fusarium oxysporum and Rhizoctonia solani, by detecting the odors of their volatile secondary metabolites has been reported. Information about which pathogen we are dealing with in forest nurseries allows us to design an appropriate plant protection strategy (e.g., selecting appropriate pesticides). Experiments aiming to detect the fungal infection of tree seeds during storage were also performed on English oak (Quercus robur) acorns and silver fir (Abies alba) seeds. Additionally, studies of ash (Fraxinus excelsior) dieback caused by Hymenoscyphus fraxineus pathogenic fungi using a PEN3 electronic nose device (portable electronic nose, Airsense Analytics GmbH, Schwerin, Germany) were performed by measuring infected roots and soil. Full article

In this work, new treatments based on multi-walled carbon nanotubes (MWCNTs), MWCNTs decorated with zinc oxide (ZnO), MWCNTs decorated with hydroxyapatite (HAp) and MWCNTs decorated with silver (Ag) nanoparticles dispersed in PHBHV solution are proposed for improving sound oak wood properties. We hypothesize that the solutions containing decorated MWCNTs will be more efficient as wood consolidants, not only because of the improved mechanical properties of the treated wood but also because of the hydrophobic layer created on the wood surface. In order to test these hypotheses, the treatments’ potential was investigated by a number of complex methods, such as colorimetric parameter measurements, water absorption tests, mechanical tests, artificial aging and antifungal tests. The data confirm that the treated wood materials have moderate stability, and the color differences are not perceived with the naked eye. A significant improvement of the treated samples was observed by water absorption, humidity and mechanical tests compared to untreated wood. The best results were obtained for samples treated by brushing with solutions based on decorated CNTs, which confirms that a uniform and thicker layer is needed on the surface to ensure better protection. The wood behavior with accelerated aging revealed that the control sample degraded faster compared to the other treated samples. Antifungal tests showed that higher growth inhibition was obtained for samples treated with 0.2% MWCNTs_ZnO + PHBHV. Considering all of the obtained results, it can be concluded that the most effective treatment was MWCNTs_ZnO + PHBHV at a nanocomposite concentration of 0.2%, applied by brushing. Thus, wood protection against mold and fungi will be achieved, simultaneously ensuring improved mechanical strength and water barrier properties and therefore maintaining the structural integrity of sound oak wood over time. Full article