Effect of weather cycles on cone harvesting for six coniferous species in Czech forest management

Aims: The study was conducted to analyze the wood density for three conifer tree species (Juniperus recurva, Picea spinulosa, and Abies densa) which are widely used in Bhutan for house construction, incense making and firewood purposes. The wood density for these species is exhibited according to physiographic regions of the country (West, West-Central, East, and East-Central). Study Design: This study investigates the wood density of Juniperus recurva, Abies densa, and Picea spinulosa across Bhutan's physiographic zones. A total of 32 trees per species were sampled, with eight trees selected per zone. Due to its limited distribution, Picea spinulosa was sampled from only three zones. Sampling was stratified across different physiological conditions, with trees classified into eight diameter classes and four crown categories. Destructive randomized branch sampling (RBS) was employed, wherein trees were felled to extract stem disc samples at four positions along the main bole. Standard measurements of tree height, stump height, and basal diameter were recorded. Samples were dried in an oven at 80°C until a constant dry weight was achieved. Wood density was determined using the ratio of dry mass to green volume, with the latter measured via the water displacement method. This methodological approach ensures accurate wood property quantification, providing valuable insights into species-specific density variations. Place and Duration of Study: The study was conducted across Bhutan’s four physiographic zones, covering a range of environmental conditions to ensure comprehensive regional representation. Field sampling took place over multiple locations where Juniperus recurva, Abies densa, and Picea spinulosa are naturally distributed. Methodology: This study was conducted across four physiographic zones of Bhutan—western, west-central, east-central, and eastern—at elevations ranging from 2800 to 5000 meters above sea level to capture regional variations in wood density. Sample collection focused on three conifer species: Juniperus recurva, Picea spinulosa, and Abies densa. A total of 96 trees (32 per species) were sampled, with trees categorized into eight diameter classes and four crown classifications to ensure a representative dataset. Destructive randomized branch sampling (RBS) was employed, involving tree felling and extraction of stem disc samples from different height strata of the main bole. Fresh samples were labeled, cleaned, and transported to the laboratory for analysis following standardized protocols. In the laboratory, the green volume of each wood sample was determined using the water displacement method, while the dry mass was recorded after oven-drying the samples at 80°C until a constant weight was achieved. Basic wood density was calculated as the ratio of dry mass (g) to green volume (cm³). The density values were analyzed across different physiographic zones to identify regional variations. Additionally, the results were compared with the Global Wood Density Database to assess differences between Bhutanese conifers and global averages. The findings provide baseline wood density values for these species, supporting sustainable forestry practices and contributing to ecological and climate-related research. Results: The analysis revealed significant variation in wood density across the different physiographic zones and conifer species. Abies densa exhibited the highest average wood density across all zones, with values ranging from 0.46 to 0.56 g/cm³. Picea spinulosa showed intermediate density values, ranging from 0.40 to 0.48 g/cm³, while Juniperus recurva had the lowest average density, between 0.34 and 0.42 g/cm³. Wood density generally increased with elevation, with the highest densities found in the eastern and west-central zones, which have higher altitudes and more challenging environmental conditions. When grouped by diameter classes, the data revealed that larger trees typically had higher wood densities than smaller trees within each species. Crown classification also played a role, with trees exhibiting a fuller canopy tending to have slightly higher density values than those with less developed crowns. The results also showed a notable difference between Bhutanese conifers and the global wood density averages, with Abies densa and Picea spinulosa having slightly higher densities compared to global values for similar species, while Juniperus recurva was comparable. These findings suggest that local environmental conditions in Bhutan, including altitude and climatic factors, contribute to variations in wood density, which could inform forest management and conservation strategies Conclusion: This study highlights the significant variation in wood density among Bhutanese conifers, with species such as Abies densa showing higher densities compared to Picea spinulosa and Juniperus recurva. Elevation and crown classification were key factors influencing wood density, with higher altitudes and fuller crowns generally associated with increased density. These findings contribute valuable insights into the wood properties of Bhutanese conifers, providing essential data for forest management and conservation strategies, as well as offering a comparative perspective against global wood density norms.

Species identification in Quebec, Canada, is usually performed with photo-interpretation at the stand level, and often results in a lack of precision which affects forest management. Very high spatial resolution imagery, such as WorldView-3 and Light Detection and Ranging have the potential to overcome this issue. The main objective of this study is to map 11 tree species at the tree level using an object-based approach. For modeling, 240 variables were derived from WorldView-3 with pixel-based and arithmetic feature calculation techniques. A global approach (11 species) was compared to a hierarchical approach at two levels: (1) tree type (broadleaf/conifer) and (2) individual broadleaf (five) and conifer (six) species. Five different model techniques were compared: support vector machine, classification and regression tree, random forest (RF), k-nearest neighbors, and linear discriminant analysis. Each model was assessed using 16-band or first 8-band derived variables, with the results indicating higher precision for the RF technique. Higher accuracies were found using 16-band instead of 8-band derived variables for the global approach (overall accuracy (OA): 75% vs. 71%, Kappa index of agreement (KIA): 0.72 vs. 0.67) and tree type level (OA: 99% vs. 97%, KIA: 0.97 vs. 0.95). For broadleaf individual species, higher accuracy was found using first 8-band derived variables (OA: 70% vs. 68%, KIA: 0.63 vs. 0.60). No distinction was found for individual conifer species (OA: 94%, KIA: 0.93). This paper demonstrates that a hierarchical classification approach gives better results for conifer species and that using an 8-band WorldView-3 instead of a 16-band is sufficient.

Fires cause significant changes to forest structure, disrupt ecological connections, and affect recovery processes. This study aimed to assess the extent of damage to tree stands and compare the resistance of coniferous and deciduous species to fire. The impact of these phenomena on various tree species and the functioning of forest ecosystems in northeastern Ukraine, which experienced large-scale fires between 2022 and 2024, was analysed. The analysis included an examination of damage to the bark, trunk, root system, and tree crowns, as well as an assessment of natural succession processes. Coniferous species, such as Pinus sylvestris L., were found to be the most vulnerable: approximately 60% of trees were either completely destroyed or severely damaged, and 70% of root systems lost their ability to recover. The crowns were destroyed in 80% of cases, leading to a reduction in tree stand density. In contrast, deciduous species such as oak and maple demonstrated greater fire resistance, with only 20-30% of trees sustaining severe damage, most of which successfully regenerated through regrowth. Mosses and lichens, which play a crucial role in soil stabilisation, were among the most affected, with their populations declining by more than 40%. This disruption in natural succession processes negatively impacted forest regeneration. Fires also increased forest fragmentation, underscoring the importance of creating ecological corridors and enhancing connectivity between forested areas to facilitate natural recovery. It is recommended to develop adaptive forest management strategies that consider the increasing frequency of fires, driven by both natural factors (such as climate change) and anthropogenic influences. The spread of fires caused by military activities is particularly relevant to the northeastern region of Ukraine. Determining tactical and strategic approaches for managing such areas requires consideration not only of the specific dynamics and patterns governing forest ecosystems but also of security-related factors. Military actions act as an additional powerful force driving environmental transformation and pollution. Addressing these challenges should form an integral part of programme documents concerning the post-war restoration of Ukraine’s natural complexes

Abstract. Forest plantations have been widely used as an effective measure for increasing soil carbon (C), and nitrogen (N) stocks and soil enzyme activities play a key role in soil C and N losses during decomposition of soil organic matter. However, few studies have been carried out to elucidate the mechanisms behind the differences in soil C and N cycling by different tree species in response to climate warming. Here, we measured the responses of soil's extracellular enzyme activity (EEA) to a gradient of temperatures using incubation methods in 78-year-old forest plantations with different tree species. Based on a soil enzyme kinetics model, we established a new statistical model to investigate the effects of temperature and tree species on soil EEA. In addition, we established a tree species–enzyme–C∕N model to investigate how temperature and tree species influence soil C∕N contents over time without considering plant C inputs. These extracellular enzymes included C acquisition enzymes (β-glucosidase, BG), N acquisition enzymes (N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP) and phosphorus acquisition enzymes (acid phosphatases). The results showed that incubation temperature and tree species significantly influenced all soil EEA and Eucalyptus had 1.01–2.86 times higher soil EEA than coniferous tree species. Modeling showed that Eucalyptus had larger soil C losses but had 0.99–2.38 times longer soil C residence time than the coniferous tree species over time. The differences in the residual soil C and N contents between Eucalyptus and coniferous tree species, as well as between slash pine (Pinus elliottii Engelm. var. elliottii) and hoop pine (Araucaria cunninghamii Ait.), increase with time. On the other hand, the modeling results help explain why exotic slash pine can grow faster, as it has 1.22–1.38 times longer residual soil N residence time for LAP, which mediate soil N cycling in the long term, than native coniferous tree species like hoop pine and kauri pine (Agathis robusta C. Moore). Our results will be helpful for understanding the mechanisms of soil C and N cycling by different tree species, which will have implications for forest management.

Successful regeneration following harvesting or natural disturbance is a fundamental prerequisite for sustainable forest management. However, some regenerating stands have poor juvenile growth rates, which compromise sustainable management objectives. In particular, the presence of some ericaceous species that proliferate after forest disturbance, such as Kalmia angustifolia, can slow succession of boreal stands to the point that ecosystem retrogression is induced. We used data from a silvicultural field trial established in central Newfoundland to evaluate how various combinations of silvicultural treatments (trench scarification, herbicide application, fertilization at planting) influenced growth of three conifer species planted on a Kalmia-dominated cutover. Ground-level diameter (GLD), height, diameter at breast height (DBH), and percent Kalmia cover were assessed at the end of 15 growing seasons after planting. We detected several interactions between silvicultural treatments and planted conifer species. Globally, height and estimates of foliar biomass of all conifer species responded positively to scarification. Fifteen-year height in both scarified and unscarified treatments was in the order Picea mariana < Pinus banksiana < Larix laricina. Black spruce and jack pine height increased when Kalmia was controlled with herbicide, but height of tamarack was not. The use of herbicide significantly increased 15-year GLD and volume index of all three conifer species, but only black spruce responded positively to fertilization at planting. Our results confirm that species-specific responses to silvicultural treatments are to be expected when managing Kalmia-dominated sites. Although chemical vegetation management has great silvicultural potential, our results suggest that mechanical site preparation can also be effective in promoting early conifer seedling growth that leads to rapid canopy closure. It is anticipated that canopy closure will lead to exclusion of Kalmia later in the rotation through natural successional pathways. Key words: Kalmia angustifolia, vegetation management, scarification, herbicide, fertilizer, black spruce, jack pine, tamarack

Accurate detection and segmentation of individual trees from unmanned aerial vehicle images is critical for forestry resource surveys and accurate forest management. Deep learning methods have been used for studies of individual tree crown segmentation, classification, and number of trees in mixed coniferous and broad-leaved forests, but the accuracy needs to be improved. Therefore, this study uses BlendMask, a simpler and more efficient algorithm that combines Mask R-CNN and Yolact algorithms to effectively combine instance-level information with semantic information at a finer granularity level, greatly improving crown segmentation accuracy and classification results. Three coniferous species and five broad-leaved species unmanned aerial vehicle images collected from the Jing Yue multispecies ecological forestry site in Changping District, Beijing, were used as the dataset, and the results were compared with Yolact and Mask R-CNN. The results show that the method described in this work has the highest Kappa coefficient (0.89) and overall accuracy (92.14%) in the test set. For segmentation accuracy, coniferous species’ producer’s accuracy was 0.91 to 0.95, whereas that of broad-leaved species was 0.89 to 0.92. For species classification, the F1-score and mean average precision for coniferous species were greater than 91%, whereas those for broad-leaved species were 77.64% to 85.63%. The accuracy of extracting stand density in low and medium canopy density stands was 0.9909 and 0.9422, respectively, whereas that in high canopy density stands was 0.8913. This study shows that the BlendMask model has a good effect in studying the classification of multiple tree species, the segmentation of individual tree crowns, and the statistics of the number of trees in complex forest areas. Compared with broad-leaved forests and high canopy density stands, this model is more suitable for coniferous forest and medium and low canopy density stand scenarios. This study provides an important tool for obtaining more accurate species classification, canopy segmentation, and resource inventory results in complex forest areas.

In an effort to ameliorate the impacts of climate change, forest managers in Central Europe increasingly turn to conifer species that produce higher yields and are better adapted to projected future climatic conditions. Though small mammals are an important component of the forest ecosystem, the impacts of enriching native broadleaf forests with conifers on small mammal communities are not well understood. We conducted mark–recapture surveys of small mammals to ascertain differences in their community structure among stands of two conifers (native Norway spruce Picea abies and non-native Douglas fir Pseudotsuga menziesii) and the dominant broadleaf in the region, European beech (Fagus sylvatica). After estimating the density of two common species, the yellow-necked mouse Apodemus flavicollis and bank vole Clethrionomys glareolus, we found that the population density of each is positively related to the proportion of beech and negatively to the proportion of conifers in each stand, though these effects of stand composition are smaller than the positive effect of herb cover. Increasing Norway spruce proportion reduced monthly survival of small mammals, while Douglas fir proportion had a positive effect on survival. We conclude that the two conifer species have similar impacts on small mammal density, though overall small mammal survival was significantly lower on plots with Norway spruce. This suggests that increasing the proportion of Douglas fir at the expense of Norway spruce may be possible without significantly changing local patterns of small mammal population density, but further research is necessary to elucidate the exact impacts of these two conifer species on small mammal demography and behavior.

Few studies have focused on the effects of long-term forest plantations on the soil profile of carbon (C) and nitrogen (N) stocks. In this study, we selected 78-year-old tree plantations that included three coniferous tree species (i.e., slash pine, hoop pine and kauri pine) and a Eucalyptus species in subtropical Australia. We measured soil extractable organic C (EOC) and N (EON) contents and total C and N stocks under different tree species on the forest floor and along a soil profile to 100cm depth. The results showed that Eucalyptus had significantly higher soil EOC contents (3.3Mgha-1) than the other tree species (EOC of 1.9-2.3Mgha-1) and had significantly higher EON (156kgha-1) contents than slash pine (107kgha-1). Eucalyptus had significantly higher soil C (58.9Mgha-1) and N (2.03Mgha-1) stocks than the other tree species (22.3-27.6MgCha-1 and 0.71-1.23MgNha-1) at 0-100cm depth. There were no differences in soil C stocks at the 0-100cm depth among the coniferous tree species. Forest floor C stocks had stronger effects on mineral soil total N stocks than fine root biomass, whereas fine root biomass exerted stronger effects on soil total C stocks at the 0-100cm depth than forest floor C and N stocks. Our results addressed large differences in soil C and N stocks under different tree species, which can provide useful information for local forest management practices in this region.

Soil fungal composition under decomposing deadwood is largely affected by tree bark density rather than soil properties

Urban heat islands (UHIs) and global warming will unavoidably have a negative impact on human health in urban areas, making urban forests much more susceptible to the risk of heat waves than forests. It is pivotal for urban forest management to understand tree species’ adaptation mechanisms by focusing on the species-dependent variability of polyamines (PAs), significant players in the amelioration of biotic and abiotic stress in plants, to mitigate the negative effects of UHIs and global warming on human health. Based on this background, the content of major polyamines (PAs) (putrescine, spermidine, and spermine) and total phenolics and the corresponding antioxidant capacities were determined and analyzed in the 24 most prevalent deciduous and coniferous tree species found in urban areas, namely Futoški Park in Novi Sad (Serbia). High-performance liquid chromatography (HPLC) coupled with fluorometric detection (HPLC-FD) was used to separate and quantify major PAs from tree species. Results showed a species-specific level variation in polyamines, total phenolic, and antioxidant capacity in coniferous and deciduous woody plant species in inspected urban areas. In terms of total PA content, the most notable deciduous tree species were Betula pendula, Junglans regia, and Quercus rubra, while the coniferous tree species Thuja occidentalis, Taxodium distichum, Pinus nigra, and Abies concolor stand out. The most dominant foliar PA in most of the inspected species was putrescine (ranging from 527.67 to 10,049.3 nmol g−1 DW), followed by spermidine (from 250.56 to 2015.92 nmol g−1 DW) and spermine (from 168.8 to 718.41 nmol g−1 DW). Furthermore, significant intra-genus variability in terms of PA content was recorded within the genera Pinus, Thuja, and Picea. This study demonstrated that the PA and phenolic compounds, in combination with antioxidant assays, can serve as reliable and trustworthy criteria and descriptors for the selection of adaptable tree species in the context of urban climate–smart forestry.

Background and AimsConifers are key components of many temperate and boreal forests and are important for forestry, but species differences in stem growth responses to climate are still poorly understood and may hinder effective management of these forests in a warmer and drier future.MethodsWe studied 19 Northern Hemisphere conifer species planted in a 50-year-old common garden experiment in the Netherlands to (1) assess the effect of temporal dynamics in climate on stem growth, (2) test for a possible positive relationship between the growth potential and climatic growth sensitivity across species, and (3) evaluate the extent to which stem growth is controlled by phylogeny.Key resultsEighty-nine per cent of the species showed a significant reduction in stem growth to summer drought, 37 % responded negatively to spring frost and 32 % responded positively to higher winter temperatures. Species differed largely in their growth sensitivity to climatic variation and showed, for example, a four-fold difference in growth reduction to summer drought. Remarkably, we did not find a positive relationship between productivity and climatic sensitivity, but instead observed that some species combined a low growth sensitivity to summer drought with high growth potential. Both growth sensitivity to climate and growth potential were partly phylogenetically controlled.ConclusionsA warmer and drier future climate is likely to reduce the productivity of most conifer species. We did not find a relationship between growth potential and growth sensitivity to climate; instead, some species combined high growth potential with low sensitivity to summer drought. This may help forest managers to select productive species that are able to cope with a warmer and drier future.

Research Highlights: We investigated the competitive interactions among three tree species (interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce (Picea glauca [Moench] Voss × Picea engelmannii Engelm.), and lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Englem.)) in multi-aged stands in central British Columbia, Canada. Background and Objectives: Understanding competitive interactions among tree species in mixed-species stands is fundamental to supporting silvicultural decision-making in such stands. Using the periodic annual basal area increment for single trees as our dependent variable, we investigated whether neighboring trees competed with subject trees independently of species identity. We also examined the differences in single-tree basal area growth among the three conifer species over time under different levels of competition. Materials and Methods: We developed several spatially explicit, single-tree basal area growth models for interior Douglas-fir, interior spruce, and lodgepole pine using data from 16 plots in two blocks of a long-term study (five measurements over a 21-year period) on the response to pre-commercial thinning. We compared these equations to assess whether intraspecific or interspecific competition predominated. We also examined the differences in basal area growth among the three conifer species over time under different levels of competition. Results: We found asymmetrical relationships between the conifer trees and their neighbors for all species, indicating that the main driver limiting growth in these stands is aboveground competition for light. There was evidence of higher intraspecific competition for small (<10.0 cm DBH) interior Douglas-fir in one block. However, there was no general pattern among larger subject trees with respect to the identity of neighborhood competitive effects and the equivalence of neighbors. We observed a higher level of basal area growth over time for interior Douglas-fir than for lodgepole pine and interior spruce, irrespective of the competition intensity and, not surprisingly, the growth rate declined with increasing competition levels for the three species. Conclusions: Our results provide an understanding of how interior Douglas-fir stands will develop over time and information on species interactions that could help forest managers explore different silvicultural options and their effects on individual tree growth in these complex stands.

Flowering, the beginning of the reproductive growth, is a significant stage in the growth and development of plants. Conifers are economically and ecologically important, characterized by straight trunks and a good wood quality and, thus, conifer plantations are widely distributed around the world. In addition, conifer species have a good tolerance to biotic and abiotic stress, and a stronger survival ability. Seeds of some conifer species, such as Pinus koraiensis, are rich in vitamins, amino acids, mineral elements and other nutrients, which are used for food and medicine. Although conifers are the largest (giant sequoia) and oldest living plants (bristlecone pine), their growth cycle is relatively long, and the seed yield is unstable. In the present work, we reviewed selected literature and provide a comprehensive overview on the most influential factors and on the methods and techniques that can be adopted in order to improve flowering and seed production in conifers species. The review revealed that flowering and seed yields in conifers are affected by a variety of factors, such as pollen, temperature, light, water availability, nutrients, etc., and a number of management techniques, including topping off, pruning, fertilization, hormone treatment, supplementary pollination, etc. has been developed for improving cone yields. Furthermore, several flowering-related genes (FT, Flowering locus T and MADS-box, MCMI, AGAMOUS, DEFICIENCES and SRF) that play a crucial role in flowering in coniferous trees were identified. The results of this study can be useful for forest managers and for enhancing seed yields in conifer plantations for commercial use.

Drivers of forest regeneration patterns in drought prone mixed-species forests in the Northern Calcareous Alps

BackgroundClimate warming increases fire activity for many regions around the world, prompting concern over the long-term persistence of conifer species that regenerate poorly from seed after high-severity fire. However, substantive regeneration of non-serotinous conifer species within a large high-severity patch, a process we refer to as conditional pyriscence, is possible if the fire occurs in the window following seed maturation but before cone opening, the enclosed seeds can withstand the heat range of the fire, and the non-serotinous cone crop is sufficient. To define this temporal window, we collected closed cones from June to September over two seasons, examining seed maturation as a function of the heat sum for four non-serotinous California conifer species: ponderosa pine (Pinus ponderosa), Sierra lodgepole pine (Pinus contorta var. murrayana), incense cedar (Calocedrus decurrens), and Douglas-fir (Pseudotsuga menziesii). Additionally, we examined seed survival based on viability testing in closed cones following heat treatments ranging from ~ 20 to 600 °C. Finally, we overlayed the period of viability with the timing of fires for northern California to identify the proportion of fires that may be conducive to conditional pyriscence.ResultsThe accumulated heat sum was positively associated with seed maturity; the proportion of seeds that were viable varied by species but generally ranged from late-July (10%) to mid-September (90%) with heat sums ranging from 1285 to 2081 °C, respectively. Higher cone heat exposure was negatively associated with seed survival and some withstood temperatures as high as 400 °C for 150 s. Seeds of the smaller cone species tended to have lower survivability to heat treatments than the larger cone species. The period of availability of mature seeds overlapped with 60% of the area burned during wildfires for northern California.ConclusionsWe identify circumstances suitable for conditional pyriscence following high-severity fires for four non-serotinous conifers in northern California. The temporal window that permits conditional pyriscence for these species may provide one explanation as to why some large high severity patches can result in substantive seedling regeneration. Inclusion of this information has potential to improve post-fire regeneration modeling and can aid forest management decision-making in fire-prone ecosystems containing non-serotinous conifers.