Korean Pine Trees Research Articles

Pesticide residues and risk assessment of trunk-injected pesticides in pine nut (Pinus koraiensis) seeds

Pine nuts, the edible seeds of pines (Family: Pinaceae, Pinus spp.), are popular worldwide, particularly those from the Korean pine tree (Pinus koraiensis), which is economically significant and widely exported. The spread of pine wilt disease (PWD) caused by pinewood nematodes (PWNs) has necessitated the use of trunk injections of pesticides in Korea, raising concerns about pesticide residues in edible pine nuts. This study investigated the concentration of pesticide residues in pine nuts from trunk-injected trees and assessed their potential health risks to consumers. After Korean pine tree was trunk-injected with pesticide, the pine nuts were subsequently harvested and analyzed for pesticide residues using LC‒MS/MS. Short- and long-term risk assessments of trunk-injected pesticides in pine nuts were conducted. Abamectin and emamectin benzoate were not detected, while acetamiprid and sulfoxaflor were detected, but their levels were below the maximum residue limits (MRLs) set by Korea, the EU, and the US. The short-term and long-term risk assessments indicated negligible health risks for consumers from these residues. Despite the low risk, we recommend continued monitoring of pesticide residues in pine nuts intended for sale to ensure consumer safety.

Transcriptome Analysis Provides Insights into Korean Pine Tree Aging and Response to Shading

Age controls a tree’s responses to environmental cues and shading influences tree growth and physiology. These are basic principles of “Afforestation under canopy”, an approach that is widely used in the regeneration of Korean pine forests. Studying the underlying mechanism helps us to understand tree adaptation and utilize it in forest management. In this study, we investigated the transcriptomic changes in the uppermost main stems of the Korean pine tree (Pinus koraiensis, Sieb. et Zucc.) at different ages (5, 7, 10, 14, and 17 years) and in different growth conditions (open-grown and shade-grown trees) using RNA-Seq. In total, 434,005,837 reads were produced and assembled into 111,786 unigenes. After pairwise comparisons, 568 differentially expressed unigenes (DEUs) were identified. The greatest number of DEUs was identified in the comparison between 5-year-old open-grown trees and 17-year-old shade-grown trees, while no DEUs were identified in 15 pairwise comparisons. Among these 568 DEUs, 45 were assigned to gene ontology (GO) terms associated with response to environmental changes, including “response to stress” (26) and “response to light and temperature” (19); 12 were assigned to GO terms associated with sexual reproduction, such as “sexual reproduction”, “specification of floral organ identity”, “pollen tube guidance”, and “fruit ripening”; 15 were heat shock protein genes and showed decreased expression patterns with age; and one, annotated as Pinus tabuliformis DEFICIENS-AGAMOUS-LIKE 1, showed an increased expression pattern with age, independent of the reproductive state or growth conditions of Korean pine trees. Altogether, these findings not only demonstrate the molecular aspects of the developmental and physiological effects of age and shading on Korean pine trees, but also improve our understanding of the basic principles of “Afforestation under canopy”.

Neighborhood Tree Position and Size Had Hierarchical Effects on Korean Pine Growth at Different Opening Degree Levels

Certain fluctuations were found when using the opening degree index to evaluate the effects of the adjacent broadleaved trees on the under-canopy target Korean pine (Pinus koraiensis Sieb. et Zucc.) trees in a mixed forest of planted Korean trees and natural broadleaved trees. The fluctuations were probably caused by the different positions and sizes of the adjacent broadleaved trees over the target Korean pine trees. For the purpose of clarifying this issue, the effect of the position and size (marked by height and diameter) of the neighborhood broadleaved trees on the height and diameter growth of Korean pine trees under the canopy in a secondary forest at different opening degree levels was studied. Generally, the mean DBH (diameter at breast height) and mean height of P. koraiensis trees under the canopy were higher when the adjacent broadleaved trees were located on the north or east sides of the target P. koraiensis trees than when they were located on the south or west sides. This was the case at all opening degree levels except the 0.5 opening degree level, where no significant difference was observed among the growth indexes of Korean pine trees based on the different positions of neighborhood trees. The mean DBH and height of P. koraiensis trees under the canopy decreased with the increase in the DBH and height of the adjacent broadleaved trees at all orientations and at all opening degree levels, but only those of the Korean pine trees with adjacent broadleaved trees on the south side in the 12.6–13.5 m height range and those with adjacent broadleaved trees on most sides in the 18.6–21.0 cm and 13.6–14.5 m height ranges at opening degree levels of K = 2.0, 1.5, and 1.0 reached a significant level of difference; whereas those of most Korean pine trees with adjacent broadleaved trees on the south and west sides in the height range of 11.6–12.5 m and DBH ranges of 13.6–16 cm and 16.1–18.5 cm, as well as the ones with adjacent broadleaved trees on most sides in the DBH range of 18.6–21.0 cm and the height range of 13.6–14.5 m at the opening degree level of K = 0.5, reached a significant level of difference, with a few exceptions. In conclusion, the broadleaved trees with a large diameter, great height, and a south or west orientation of the target P. koraiensis trees had a negative impact on their growth, but influence intensities changed at different opening degree levels.

Spatial Distribution of Pinus koraiensis Trees and Community-Level Spatial Associations in Broad-Leaved Korean Pine Mixed Forests in Northeastern China.

Investigating the spatial distributions and associations of tree populations provides better insights into the dynamics and processes that shape the forest community. Korean pine (Pinus koraiensis) is one of the most important tree species in broad-leaved Korean pine mixed forests (BKMFs), and little is known about the spatial point patterns of and associations between Korean pine and community-level woody species groups such as coniferous and deciduous trees in different developmental stages. This study investigated the spatial patterns of Korean pine (KP) trees and then analyzed how the spatial associations between KP trees and other tree species at the community level vary in different BKMFs. Extensive data collected from five relatively large sample plots, covering a substantial area within the natural distribution range of KP in northeastern China, were utilized. Uni- and bivariate pair correlation functions and mark correlation functions were applied to analyze spatial distribution patterns and spatial associations. The DBH (diameter at breast height) histogram of KP trees in northeastern China revealed that the regeneration process was very poor in the Changbai Mountain (CBS) plot, while the other four plots exhibited moderate or expanding population structures. KP trees were significantly aggregated at scales up to 10 m under the HPP null model, and the aggregation scales decreased with the increase in size classes. Positive or negative spatial associations were observed among different life stages of KP trees in different plots. The life history stages of the coniferous tree group showed positive spatial associations with KP saplings and juvenile trees at small scales, and spatial independence or negative correlations with larger KP trees at greater scales. All broad-leaved tree groups (canopy, middle, and understory layers) exhibited only slightly positive associations with KP trees at small scales, and dominant negative associations were observed at most scales. Our results demonstrate that mature KP trees have strong importance in the spatial patterns of KP populations, and site heterogeneity, limited seed dispersal, and interspecific competition characterize the spatial patterns of KP trees and community-level spatial associations with respect to KP trees, which can serve as a theoretical basis for the management and restoration of BKMFs in northeastern China.

Physiological and Biochemical Traits of Needles Imply That Understory Light Conditions in the Growing Season May Be Favorable to Pinus koraiensis Trees

Light is often considered the primary factor leading to the regeneration failure of Korean pines (Pinus koraiensis) under the forest canopy. However, studies on the effect of light on Korean pines mainly focus on the use of an artificial sunshade net to control shade; field studies on the canopy are extremely scarce, and the current experimental results are contradictory. For a deeper understanding of the relationship between light conditions and understory Korean pine trees, the conditions of low, middle, high and full light (control) under the forest were tested at 18 years of age. The photosynthetic pigments, chlorophyll fluorescence, non-structural carbohydrate metabolism, antioxidant enzyme activity, and nutrient concentrations of current-year needles from Korean pine trees were measured. From June to September, light intensity and quality decreased under full light, but following leaf fall, understory light conditions improved slightly. As the light conditions improved, the photosynthetic pigments in the needles decreased, but Car/Chl were highest in the needles under full light. All light conditions had a positive correlation with glucose concentrations and Rubisco activity. Full-light needles had the highest APX activity, DPPH scavenging capacity, and proline concentration, as well as higher NPQ and lower Fv/Fm readings. This indicated that full-light Korean pine trees were stressed and inhibited photosynthesis to some extent, while the understory light environment may alleviate stress. The conservative strategy of storing more starch and using less glucose in understory Korean pine trees may be one of the reasons for the observed differences in growth rates among Korean pine trees under varying light conditions. Overall, this study implies that understory light during the growing season is not always unfavorable to 18-year-old Korean pine trees; this means that 18-year-old Korean pine trees still have shade tolerance to some extent and are capable of living under a canopy of deciduous trees.

Effects of Competition on the Vertical Distribution of Foliage Biomass within the Crowns of Planted Korean Pine Trees in Northeast China

The characteristics and distribution of foliage biomass are important aspects of the crown structures of trees. In this study, we developed a foliage biomass distribution model at the branch level and annual shoot level (i.e., all branches on an annual increment of the main tree bole) using a sample of 51 Korean pine trees that were destructively sampled in Liaoning Province, northeast China. A variety of independent variables, including branches, trees, and forest competition, were used as explanatory variables in the model development. Our results indicated that foliage biomass at the branch level increased with an increasing relative distance from the tree tip into the crown. The peak of the foliage biomass distribution shifted to the tree tip with increasing tree age. A power function, including branch diameter and competition variables, showed excellent performance in modeling branch foliage at the branch level. The final model, which included branch diameter, competition variables, and relative distance to branch base for the relative foliage density, showed best performance. The trees that showed advantageous growth ability also had a larger amount of foliage biomass.

Competition intensity affects growing season nutrient dynamics in Korean pine trees and their microhabitat soil in mixed forest

Exploring the response mechanisms of the understorey replanted target trees to competitive pressure from upper neighbouring trees in mixed forests is the scientific basis for growth promotion of the target trees. Taking a mixed forest of artificial planted Korean pine trees (target species) and natural broadleaved trees as the studying case, six competition intensity gradients to Korean pine trees were established according to the Hegyi competition index and the responses of growth, hormones and nutrition status of the target Korean pine trees to different competition intensities were analysed. Competition intensities had significant effect on the growth of Korean pine trees, and the more significant the competition intensity was, the more pronounced the inhibition effect. When the Hegyi competition index was greater than 15, the neighbourhood trees had a significant inhibition effect on the growth of Korean pine trees. With the increase of the competition intensity, the content of gibberellin and indoleacetic acid in Korean pine trees decreased; the content of abscisic acid increased; the moisture content of needles, the soluble sugar content and C/N ratio of needles and roots decreased; the chlorophyll, P and K and starch content, and total non-structure carbohydrates (NSC) of needles and roots increased at first and then decreased; the P and K content and C/N ratio in Korean pine microhabitat soil decreased. Excessive adjacent tree competition reducing the living space, the endogenous hormone content, nutrient content, and NSC of the target Korean pine trees, resulting in the growth of the target trees and subsequent nutrient synthesis to be inhibited. Appropriate adjacent tree competition increased the target tree chlorophyll, NSC, and nutrient content and had no excessive inhibitory effect on the growth of the target Korean pine trees. There was certain trait correlationship between Korean pine needles and fine roots, but there was an endostatin equilibrium mechanism for changes in the surrounding soil of the target trees. The above results indicated that competition intensity of the upper neighbourhood trees significantly influenced the growth and internal nutrient situation of the replanted target trees and their microhabitat soil conditions. In this case, when the Hegyi competition index of neighbouring trees in the surrounding area of the understorey planted target Korean pine trees was greater than 15, the growth space of target trees should be regulated to ensure their healthy development.

Modeling Primary Branch Diameter and Length for Planted Pinus koraiensis by Incorporating Neighbor Competition in Northeast China

Korean pine (Pinus koraiensis Sieb. et Zucc.) is the most important forest vegetation in northeast China. The timber quality of this tree species is largely driven by branch growth and distribution within the crown. Thus, developing branch diameter and length models, especially those that include competition indices, is essential. A total of 48 Korean pine trees were selected to conduct destructive measurements of branch characteristics. This was carried out on all live branches, and a branch diameter and length model was developed. Various indices, including the absolute depth into the branch base (DINC) from tree tip, were used. The equation with the largest Radj2 and smallest root mean square error (RMSE) values was selected as the best model. Each parameter from the best model was reparameterized to the tree variables and competition indices. Finally, the branch diameter model that included diameter at the breast height (DBH), tree height (HT), and the crown length index (CLI), and the branch length model that included DBH and HT exhibited the best performance. The Radj2 and RMSE values were 0.42 and 4 mm, respectively, for the branch diameter model, and 0.77 and 63 cm, respectively, for the branch length model. Branch diameter and length increased as DBH increased and decreased as HT increased. Furthermore, branch diameter decreased as the CLI increased.

Droplet deposition and pest control efficacy on pine trees from aerial application.

Aerial application, a spraying method with aircraft as the application platform, is one of the most important methods of pest control in pine forests. This work aimed to investigate the movement and distribution patterns of droplets and the pest control effectiveness of helicopter spraying on Masson pine (MP) and Korean pine (KP) trees. In particular, three nozzle types (CP02, CP03 and CP04) were evaluated and compared at the same spray volume rate (15 L ha-1 ) in both wind tunnel and field trials. The CP04 nozzle with a larger orifice size showed significantly better deposition and penetration, but the precision of flight operation parameters must be strictly controlled when using this type of nozzle. The majority (≥48%) of the droplets produced by the three nozzle types were concentrated in the range of <200 μm, and the spray performance of each nozzle type was more stable in the range 201-300 μm. The final pest correction control rate (CR) of MP was in the range 59.24-95.74% and that of KP was 45.41-54.39% by helicopter spraying. This study confirmed that it is necessary to select the appropriate nozzle type and ensure accurate flight parameters for aerial application in mountain pine forests. Meanwhile, it also confirms the importance of the timing of operation which can lead to incorrect implementation, resulting in poor control effectiveness. © 2022 Society of Chemical Industry.

Moisture history in the Northeast China since 1750s reconstructed from tree-ring cellulose oxygen isotope

Northeast China has suffered many serious droughts, with loss of agricultural production. A lack of long-term monitoring data has hindered our understanding of drought characteristics and mechanisms. The moisture-related history of the region was investigated by constructing a tree-ring cellulose δ18O chronology for the period 1752–2015 using samples collected from four Korean pine (Pinus koraiensis) trees in eastern NE China. Results indicate that tree-ring δ18O values are significantly correlated with summer (June–September) precipitation, relative humidity, and drought severity. The tree-ring δ18O chronology accounts for 50.7% of the observed variance in summer relative humidity and was used to reconstruct regional relative humidity levels back to 1752. Compared with previous reconstructions of drought-related changes in NE China, the reconstruction reveals more high- and low-frequency variability, with two drought periods during the 1750s–1820s and 1960s–2015, and a wet period during 1820–1960. Regional drying trends is mainly influenced by a weakened East Asia summer monsoon (EASM), with both drought periods being concurrent with high temperatures and a weak EASM. Together with the global warming trend, the increasing temperature and associated precipitation reduction in NE China indicates increasing likelihood of drought for the region in future.

Differences in growth pattern and response to climate warming between Larix olgensis and Pinus koraiensis in Northeast China are related to their distinctions in xylem hydraulics

Tree-ring analysis provides an effective way to detect complex responses of trees to climate warming and has been extensively used in ecological studies; however, there is often a lack of simultaneous physiological investigations explaining the observed patterns. Here, we paralleled dendroclimatic analyses with hydraulics measurements in co-occurring Larix olgensis and Pinus koraiensis trees along an elevational gradient (low, middle and high) in Northeast China. We aimed to detect potential differences in patterns of growth and responses to climate warming between the two conifer species considering their distinctions in life history strategy and key functional traits and to provide a mechanistic explanation for such differences. Our tree-ring analyses showed that L. olgensis trees exhibited a linear increase in basal area increment at the initial part of lifetime while Korean pine trees usually have a long slow growth period up to several decades at the juvenile stage. Consistent with their contrasts in growth rate, the larch species showed significantly higher hydraulic conductivity and functional traits favoring more efficient carbon gain at the shoot level compared to sympatric Korean pine trees. Results of the dendroclimatological analyses indicate that temperature rather than precipitation is the controlling factor for growth in both species under the current climate regime. Radial growth of both species overall accelerated accompanying the rapid warming since 1990s except a significant decrease in growth for Korean pine trees at the low elevation site, which is likely due to stronger competitions from co-occurring broadleaf trees in the mixed forest environments. In the larch species, the substantially lower degree of response in growth at the low elevation site compared to trees at higher elevations suggests that the drying effect of warming at the low elevation may have to a certain degree offset the beneficial effects of warming on growth of larch trees.

Direct in vitro organogenesis from sprouted seeds of a highly economical and ecological valued tree, Korean pine

Korean pine (Pinus koraiensis Sieb. et Zucc.) is a critical coniferous species ecologically. In addition, its fruits have numerous nutraceutical properties and its wood is high quality timber. However, this plant has a low propagation rate and is under risk of extinction. To accelerate breeding of the excellent seedlings and selection from Korean pine, determining methods to increase the number of Korean pine trees successfully is imperative. In this present study, using sprouted seeds as the initial explants, the de novo organogenesis system for this coniferous species has been successfully developed. After 30 days of incubation on Gupta and Durzan (DCR) medium containing 2 mg L−1 kinetin (KT) and 0.5 mg L−1 thidiazuron (TDZ), 92.67% of explants produced direct buds with an average of about 15 buds per explant. We confirmed the organogenic regeneration pattern by a scanning electron microscopy (SEM). For bud elongation after 60 days of culture, we obtained the highest mean length of 34.99 mm on DCR basal media supplemented with 6-benzyladenine (6-BA, 0.2 mg L−1), 1-naphthaleneacetic acid (NAA, 0.1 mg L−1), and activated charcoal (AC, 1 g L−1). The highest rooting rates of 20.74 and 21.48% were obtained within two months of culturing on 1/2 DCR medium (halved major elements) supplemented with 0.05 mg·L−1 NAA and 0.5 or 1 mg ·L−1 indole-3-butyric acid (IBA), respectively. Rooted shoots showed a survival rate of 90.28% after acclimatization in the substrate consisting of perlite, peat, and vermiculite (1:1:1). This protocol is a successful and efficient biotechnological approach to the micropropagation of Korean pine, and the results will be helpful to the clonal propagation and conservation of Korean pine.

Optimization of maturation process for somatic embryo production and cryopreservation of embryogenic tissue in Pinus koraiensis

Korean pine broadleaf mixed forests are important for maintaining biodiversity in Northeast China. Excessive harvesting of the Korean pine tree has led to it being listed as an endangered species in China. Somatic embryogenesis technology has the potential to accelerate breeding by improving seedling quality to meet future wood harvesting needs. In addition, rare and valuable germplasm resources can be maintained through the use of cryopreservation. Here, we described the utilization of somatic embryogenesis in Korean pine, with a focus on maturation and cryopreservation. Embryogenic tissues (ETs) were induced from immature seeds collected from open-pollinated sources of Korean pine (28 families). Highest induction percentage of ET reached 22%. The proliferation ability of ET in different cell lines differed. Increasing ABA(up to 80 µM L− 1), gellan gum (up to 12 g L− 1) and sucrose (0.2 m L− 1) concentrations in maturation medium improved the yield of cotyledonary somatic embryo (SE). Maximum yield of cotyledonary SEs (160 SEs g− 1 fresh mass) was obtained following ET dispersion on filter paper discs at low density (50 mg fresh mass). Both the germination percentage of SEs and survival percentage of regenerated plants were about 50%. Moreover, ET began to lose their potential for somatic embryogenesis after 6 months of subculture. ET cultures were cryopreserved, and culture recovery (133 SEs g− 1 fresh mass) was demonstrated after thawing. In this paper we report a significantly improved procedure for generating Korean pine SEs, leading to a high yield of cotyledonary SEs. A cryopreservation protocol for the ET of Korean pine was also established. The present work reports a significantly improved procedure for generating somatic embryos and cryopreservation of embryogenic tissue in Korean pine.

Microfibril Angle Characteristics of Korean Pine Trees from Depending on Provinces

This study investigated the characteristics of microfibril angle(MFA) in order to see if there was any difference in pine tree lumber quality among the three mountain areas surrounding the Taebaek Mountains in Korea – Yeongdong (Goseong-gun), Yeongseo (Hongcheon-gun) and Yeongnam (Bonghwa-gun). Pine trees of each mountain area were divided into earlywood and latewood in relation to heartwood part (1959 ~ 1961, 3 annual rings) and sapwood part (2002 ~ 2004, 3annual rings), and measured at tangential section. The microfibril angle showed significant differences between mountain areas. In general, Goseong Mountain was found to have 37.35°, followed by Hongcheon Mountain 32.42° and Bonghwa Mountain 25.75°, in order. The sapwood part had larger angle than heartwood part; and earlywood, than latewood. Variation within a single annual ring tended to be smaller from earlywood toward latewood.

Relationship between tree ring δ13C and net primary productivity of Pinus koraiensis in Changbai Mountain, China

Carbon isotope in tree ring is an effective indicator of climate and environmental change. However, few studies have analyzed the indication effect of tree ring carbon isotope on net primary productivity (NPP) of forests. Based on meteorological factors of growing seasons, we analyzed the variation trend and the relationship between the tree ring δ13C chronosequence of Korean pine (Pinus koraiensis) and net primary productivity (NPP) of Korean pine in Changbai Mountain. We found that before 1970, the change of Korean pine tree ring δ13C and NPP was synchronous, with a highly significant linear positive correlation between them, indicating that tree ring δ13C recorded the impacts of climate change on NPP. After 1970, tree ring δ13C was negatively correlated with NPP but not statistically significant, meaning that other environmental factors such as severe droughts reduced the sensitivity of tree ring δ13C to climate change and the recording of NPP by tree ring δ13C. The δ13C of the current year was also correlated with the corresponding NPP in the following year, which indicated that the current year's environmental conditions were of great significance to the growth of Korean pine in the following year. This study showed that tree ring δ13C was a good indicator of the NPP of Korean pine in Changbai Mountain and that tree ring δ13C had the potential to reconstruct long-term changes of forest NPP in the history.

The interaction between nonstructural carbohydrate reserves and xylem hydraulics in Korean pine trees across an altitudinal gradient.

Nonstructural carbohydrates (NSC) have been proposed to play an important role in maintaining the hydraulic integrity of trees, particularly in environments with high risks of embolism formation, but knowledge about the interaction between NSC reserves and xylem hydraulics is still very limited. We studied the variation of NSC reserves and hydraulic traits in Pinus koraiensis Sieb. et Zucc. (Korean pine) in March and June across a relatively large altitudinal gradient in Changbai Mountain of Northeast China. One of the major aims was to investigate the potential role NSC plays in maintaining hydraulic integrity of overwintering stems in facing freezing-induced embolism. Consistent with our hypotheses, substantial variations in both NSC contents and hydraulic traits were observed across altitudes and between the two seasons. In March, when relatively high degrees of winter embolism exist, the percentage loss of conductivity (PLC) showed an exponential increase with altitude. Most notably, positive correlations between branch and trunk soluble sugar content and PLC (P = 0.053 and 0.006) were observed across altitudes during this period. These correlations could indicate that more soluble sugars are required for maintaining stem hydraulic integrity over the winter by resisting or refilling freezing-induced embolism in harsher environments, although more work is needed to establish a direct causal relationship between NSC dynamics and xylem hydraulics. If the correlation is indeed directly associated with varying demands for maintaining hydraulic integrity across environmental gradients, greater carbon demands may compromise tree growth under conditions of higher risk of winter embolism leading to a trade-off between competitiveness and stress resistance, which may be at least partially responsible for the lower dominance of Korean pine trees at higher altitudes.

Modelling conifer crown profiles as nonlinear conditional quantiles: An example with planted Korean pine in northeast China

With few exceptions crown profile models for coniferous trees have conventionally been estimated within the least squares framework that is confined to describing the central trend of whorl radius along the stem. This article introduces a new approach of modelling the outer profiles of conifer tree crowns as nonlinear conditional quantiles using plantation grown Korean pine in northeast China as an example. The approach was demonstrated with two nonlinear model forms using data from detailed measurements of 83 sample trees with a total number of 1415 whorls and 5123 live branches. One model was based on a segmented polynomial function and the other was a modified variable-exponent function. For each model form, 11 nonlinear quantile curves were estimated using the branch radius data by taking 11 values of q, representing the qth quantile, from 0.5 to 0.95 with an even interval of 0.05 plus one extreme value of 0.99. Parameter estimates for a given value of q were obtained through repeated fitting by leaving one tree out each time in a simple form of jackknife model averaging. To select the best q values for delineating the outer or outmost contours of the exterior edges of tree crowns, three fix-effects (marginal) models of the same nonlinear form was fitted iteratively to the entire, about one-half and one-quarter of the whorl radius data after removing non-positive residuals at each iteration. Based on graphical evaluations and comparisons of benchmarking statistics, the 0.90th and 0.95th nonlinear quantiles were chosen for depicting the outer and outmost crown profiles of Korean pine trees for both model forms. The variable-exponent model appeared to be superior to the segmented polynomial model not only in delineating the outer crown profiles but also in estimating the largest crown radius of individual trees. In comparison to the marginal models or to the more traditional least squares regression, the new approach enables more accurate depictions of the outer or outmost crown profiles without subjective data selection and thus any loss of information. It also has the potential to profile the inner part of individual tree crowns through a family of nonlinear conditional quantial curves, therefore providing a greater insight into the crown structure than the conventional methods.

Responses of bark beetle (Coleoptera: Curculionidae: Scolytinae) community structure to green-tree retention in pine tree forest from Korea

This study was aimed to investigate the response of bark beetle community structure to green-tree retention in a Korean pine tree forest between 2013 and 2015. Five types of retention methods were evaluated to investigate the retention effect on insect community structure at various sites in Keunjeogol, Samcheok, and Gangwon-do. Lindgren funnel traps were installed to collect insects from July to August, over a 3-year period. Overall, 690 individuals and 29 species of Scolytinae were collected, with populations of insects appearing to gradually increase by each year of the study. Results of the insect community analysis showed that most survey sites presented a higher diversity than the control site annually except in 2015. This study can be used as a baseline dataset for the long-term study of early changes in insect community in response to green-tree retention in forests.

Branch quantity distribution simulation for Pinus koraiensis plantation in Heilongjiang Pro-vince, China.

Based on the measurement of 955 branch samples of 65 Korean pine (Pinus koraiensis) trees in 12 plots from Mengjiagang forest farm, Heilongjiang Province, and by using Poisson model and negative binomial model, the second-order branch count models for Korean pine were developed in this paper. AIC, Pseudo-R2, RMSE and Vuong test were selected to compare the goodness-of-fit statistics of the models. The results indicated that the first-order branch count in a whorl was 3 to 5, with mean value of 4, and the first-order branch count in a whorl for Korean pine plantation associated with its own characteristics. The second-order branch count of the first-order standard branch had a large discrete degree. All subset regression techniques were used to develop the second-order branch count model. The negative binomial regression model E(Y)=exp(β0+β1lnRDINC+β2RDINC2+β3HT/DBH+β4CL+β5DBH) was selected as the optimal second-order branch count model (β represented the parameter, RDINC represented the relative depth into crown from tree apex, HT represented the total tree height, DBH represented the tree diameter at breast height, CL represented the crown length). Pseudo-R2 of the optimal model was 0.79, the mean error was close to 0 and the mean absolute error was less than 7. For the developed model, the parameter values of lnRDINC, CL and DBH were negative, and the parameter values of RDINC2 and HT/DBH were positive. With the increase of RDINC, the number of second-order branch had a peak value in the tree crown. On the whole, the precision of the second-order branch count model for Korean pine plantation was 96.4%, which would be suitable for predicting the second-order branch count for the study area and provide a theoretic basis for branch photosynthesis and biomass research.

Relationships between tree-ring cell features of Pinus koraiensis and climate factors in the Changbai Mountains, Northeastern China

Anatomical characteristics have been proven useful for extracting climatic signals. To examine the climatic signals recorded by tree-ring cell features in the Changbai Mountains, we measured cell number and cell lumen diameter, in addition to ring widths, of Korean pine (Pinus koraiensis) tree rings at sites of varied elevation, and we developed chronologies of cell number (CN), mean lumen diameter (MLD), maximum lumen diameter (MAXLD) and tree-ring width (TRW). The chronologies were correlated with climatic factors monthly mean temperature and the sum of precipitation. As shown by our analysis, the cell parameter chronologies were suitable for dendroclimatology studies. CN and TRW shared relatively similar climatic signals which differed from MLD and MAXLD, and growth-climate relationships were elevation-dependent, as shown by the following findings: (1) at each elevation, MLD and MAXLD recorded different monthly climatic signals from those recorded by TRW for the same climatic factors; and (2) MLD and MAXLD recorded climatic factors that were absent from TRW at lower and middle elevations. Cell lumen diameter proved to be an effective archive for improving the climate reconstruction for this study area.