Zelkova Serrata Research Articles

A Study on Health Diagnosis of Zelkova serrata (Thunb.) Makino Using Hyperspectral Technique

Background and objective: Health diagnosis is essential for large, old trees that are designated and protected by the Act on the Preservation and Utilization of Natural Heritage and the Forest Protection Act. However, in the field, the overall health of trees is diagnosed by measuring the photosynthetic efficiency (PE) of some leaves. Therefore, this study aimed to examine the possibility of using hyper-spectral technology to replace the PE measurement as an approach for diagnosing the health of Zelkova serrata (Thunb.) Makino, which has a high rate of natural monument designation among South Korea’s natural heritage.Methods: The PE and hyper-spectral values were acquired from Zelkova leaves, and a Monte Carlo simulation was performed based on the spectral bands used to calculate vegetation indices (VI) in previous studies to select bands that have a high correlation with the PE. The explanatory power of these values on tree health was verified through a regression analysis of the VI and PE calculated from the selected bands, and the results of the study are as follows.Results: First, a variance analysis of the PE and VI of leaves found that there were differences depending on direction, and that the hyper-spectral values of leaves collected from the west were the most effective in measuring tree health. Second, it was found that it was effective to use 520 and 570 nm in the green region, 684 nm in the red region, 860 and 890 nm in the NIR region, 500 nm in the carotenoid region, and 531 nm in the xanthophyll region to derive the VI that replace PE metrics from the hyper-spectral values of leaves collected from the west. Third, PRI showed a very high effect with an explanatory power of 73.2% for the maximum quantum yield (Fv/Fm) regression equation. In other words, it was found that PRI can be used as an index derived from hyperspectral values to diagnose and record the healthy parts of Zelkova tree.Conclusion: By expanding the scope of this study to include Pinus densiflora and Ginkgo biloba, it is expected that if the utility and field applicability of this approach for diagnosing the health of large old trees are generally verified, it can be used for regular surveys of such trees designated as natural monuments in the future. Furthermore, it is expected that it can be expanded to diagnose park trees, street trees and the like, in addition to large, old trees.

Comparative Temporal Infrared Thermography of Arboricultural Materials for Sun‐Induced Trunk Injury Prevention in Broad‐Leaved Woody Plants

ABSTRACTUsing an infrared (IR) thermal camera, we evaluated the efficacy of six arboricultural materials for preventing sunscald and frost crack. The trunks of adult Yoshino cherry (Prunus × yedoensis) and Japanese zelkova (Zelkova serrata) were treated with (i–iii) three paint types (white water paint [P–W], white latex paint [P–L], and quicklime [P–Q]), (iv and v) two band wrap types [brown tree wrap (B–B) and white tree wrap (B–W)], and (vi) a wound paste: thiophanate‐methyl paste (TP) in the shape of a band 10 cm thick. Outdoor IR thermographs were captured four times a day at 3 h intervals (09:00 a.m., 12:00 p.m., 03:00 p.m. and 06:00 p.m.) over four consecutive days in late October 2019. Bark temperatures recorded for P–W, P–L, P–Q and B–W treatments were consistently lower than those for untreated trunks. The mean temperature difference between B–W and untreated bark (up to 4.57°C) remained pronounced between 09:00 a.m. and 06:00 p.m. for both tree species each day. Conversely, no significant differences in bark temperatures were observed under B–B and TP treatments compared with untreated bark (p = 0.01). Elevated bark temperature was observed on the south side compared with the other three cardinal directions; however, temperatures were similar in all directions at 06:00 p.m. These findings suggest that white tree wrapping may provide a viable approach to prevent sun‐induced trunk injuries, leveraging the light reflectivity of the white colour and thermal insulation properties of the wrapping material.

Differences of stomatal ozone uptake in leaves of mature trees and seedlings of Zelkova serrata

Ozone uptake through the stomata in tree leaves is an important process for improving air quality by urban trees. Stomatal conductance (gs) is a key determinant of stomatal ozone uptake. The parameterization of gs models for estimating stomatal ozone uptake of trees has mainly been carried out using gs data measured in seedling leaves although the leaf traits may differ between mature trees and seedlings. In the present study, we compared stomatal ozone uptake estimated by gs models parameterised with data from mature trees and seedlings of Zelkova serrata. We measured gs in leaves of mature trees and seedlings of Z. serrata using a leaf porometer for 3–4 growing seasons. The Jarvis-type gs model was parameterised with data from mature trees and seedlings, separately. The maximum gs, and the functions of the seedling gs estimation model regarding the response to air temperature, vapour pressure deficit and atmospheric ozone concentration were the factors inducing lower stomatal ozone uptake. In contrast, the function of the seedling gs estimation model regarding the response to irradiance resulted in a higher estimated stomatal ozone uptake. The estimated stomatal ozone uptake for one growing season (April–September) by the seedling gs estimation model was 27% lower than that by the mature tree gs estimation model. These results indicate that leaf gas exchange traits of Z. serrata were different between mature trees and seedlings, and that estimating ozone uptake in mature tree leaves using a model based on seedling gs measurements results in an underestimation.

Dry Deposition in Urban Green Spaces: Insights from Beijing and Shanghai

Urbanization and industrialization have escalated air pollution into a critical global issue, particularly in urban areas. Urban green infrastructures (GIs), such as parks and street trees, play a vital role in mitigating air pollution through dry deposition, the process by which air pollutants are removed by deposition onto plant surfaces or through plant uptake. However, existing studies on the dry-deposition capacity of urban green spaces are limited in their ability to reflect variations at the tree-species level, hindering comprehensive evaluations and effective management strategies. This study aims to quantitatively assess the dry-deposition capacity of the urban green spaces of Beijing and Shanghai for six major air pollutants in using an improved dry-deposition model and tree-species-specific data. Results showed that Shanghai’s urban green spaces had a monthly average dry-deposition rate of 5.5 × 10−6 s m−1, slightly higher than Beijing’s rate of 5.3 × 10−6 s m−1. Significant seasonal variations were observed, with summer showing the highest deposition rates due to favorable meteorological conditions. Broad-leaved species such as Zelkova serrata in Beijing and Photinia serratifolia in Shanghai exhibited superior dry-deposition capacities compared to coniferous species. Temperature significantly influenced dry-deposition rates for gaseous pollutants, while particulate-matter deposition was primarily affected by pollutant concentrations. This study provides critical insights into the air = purification functions of urban green spaces and underscores the importance of species selection and strategic green-space planning in urban air-quality management, informing the development of optimized urban-greening strategies for improved air quality and public health.

Comparison of biogenic volatile organic compounds emissions from representative urban tree species in South Korea and evaluation of standard emission rate models

Although trees generally help alleviate global warming, they generate biogenic volatile organic compounds (BVOCs) that may contribute to air pollution and exacerbate climate change. To estimate BVOCs emission rates, several models have been widely used to calculate the standard emission rate (ERs) that takes temperature and light intensity into account. In this study, the effects of temperature and light intensity on the isoprene and monoterpene emissions from various tree species were investigated. Four broad-leaved trees (Platanus occidentalis, Quercus mongolica, Zelkova serrata, and Acer palmatum) and three coniferous trees (Pinus densiflora, Metasequoia glyptostroboides, and Pinus koraiensis) were investigated in August 2022 for the comparison by the species. Emissions from Pinus densiflora were also measured in May for comparison with different climate conditions. Platanus occidentalis revealed the highest emission of isoprene, followed by Quercus mongolica, Zelkova serrata, and Acer palmatum. It was found that the isoprene emissions from Zelkova serrata and Quercus mongolica had a stronger correlation with light intensity than those from Platanus occidentalis. In contrast, the isoprene emissions from Platanus occidentalis exhibited the strongest correlation with temperature compared to other trees concerned. The monoterpene emission from Metasequoia glyptostroboides showed the highest correlation with light intensity (r2 = 0.662). Among the monoterpenes, α-pinene was the most affected by light intensity. Pinus densiflora was affected more by light intensity in May. The ERs estimation using the G93 model confirmed this pattern. Therefore, this study suggests that both light and temperature be taken into account in order to obtain more reliable ERs data of monoterpenes.

Feasibility of constructed soils for tree planting – A pilot study in New York City

Constructed soils are soils that are created with a mixture of various materials. An innovative soil exchange program - the Clean Soil Bank (CSB) in New York City allows recycling of clean glacial outwash sediments excavated from depth at construction sites. One previous study showed that soils constructed from CSB sediment and compost can effectively support crop growth in community gardens, but no research has been conducted on its potential usage as a medium for tree growth. Moreover, biochar has been used to improve soil quality, but its efficacy for street trees incorporated into constructed soils has largely not been quantified in the field. The objective of this project was to evaluate the feasibility of using soils constructed from the CSB and compost for tree planting and to investigate the impact of biochar on tree performance. Thirty-six trees of two species (Maackia amurensis and Zelkova serrata) were planted in 2019, on the sidewalks of a residential-business neighborhood in Bronx, New York. Each tree pit contains one of three soil types: type A - existing and purchased topsoil mixed with 33% compost and biochar, type B - CSB sediment mixed with 33% compost, and type C - CSB sediment mixed with 33% compost and biochar. Soil samples were collected in 2019 (before planting) and in 2021. Tree health assessments were conducted in September 2020 and July 2021 using a protocol developed by the USDA Forest Service. Other tree health parameters collected include diameter at breast height (DBH), crown diameter, tree height, photosynthetic capacity, and foliar chemistry. Significant differences in bulk density, water holding capacity, and K, Fe, and Zn concentrations were found among the three soil types. However, comparison of tree performance and foliar chemistry showed no systematic differences among the three soil types. The results indicate that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. No evidence was found that biochar provides additional benefits to street tree performance. Considering the abundant availability of glacial outwash sediment at low cost to the city, as well as access to locally produced compost, constructed soils can be a reliable source of material for urban forestry programs.

Urban roadside greenery as a carbon sink: Systematic assessment considering understory shrubs and soil respiration

Roadside greenery is an efficient strategy for maximizing ecosystem services, including carbon sequestration in urban settings. However, the quantification of carbon sequestration is not comprehensive because understory shrubs and soil respiration have not been thoroughly considered. We developed an integrated methodology that combined field measurements and greenhouse incubation to comprehensively assess carbon sequestration in roadside greenery systems. The system was defined as an 8 m long section comprising a single tree (Zelkova serrata), 79 shrubs (Euonymus japonicus), and soil. Annual carbon uptake by a tree was estimated using an allometric equation derived from an official government report. For shrubs, carbon uptake was measured in the field by monitoring CO2 concentration change in the chamber enclosing the leaves and stems. Annual carbon uptake by shrubs was estimated by using the regression equation among carbon uptake, air temperature, and photosynthetically active radiation. We also estimated shrub root respiration by combining net primary production (NPP) from the greenhouse incubation and measured pruning effect in the field. This enabled us to differentiate heterotrophic respiration from the total soil respiration. The overall methodology accurately assessed net ecosystem production (NEP) from the roadside greenery system, which is 0.528 kg C m−2 yr−1. If this figure is extended to all roads in the target city, it can offset daily carbon emitted from the total registered passenger vehicles in the target city. Considering that shrubs sequester an amount equivalent to 29.3 % of the carbon sequestered by tree species, the current greenhouse gas inventory should include shrubs as an important carbon sink. As we also revealed that roadside soil has high carbon vulnerability, proper soil management is needed to enhance NEP. Our systematic approach evaluating the carbon balance within the roadside greenery system can be applied to other cities, contributing to enhance global understanding of urban carbon cycle.

Agroforestry system construction in eastern coastal China: Insights from soil–plant interactions

AbstractAgroforestry, as a phytoremediation measure, shows great potential for mitigating land degradation by constructing multidimensional and efficient agroforestry composite systems through regulating the microenvironment of agroforestry sites and improving soil properties. However, the effects of different agroforestry composite management modes on saline soils and the interactions between soil–plant systems under salt stress conditions in coastal areas remain largely unexplored. In this study, two salt‐tolerant tree species (Sapium sebiferum (Linn.) Roxb and Zelkova serrata (Thunb.) Makino) and four crop species (Medicago sativa, Sesbania cannabina, Sorghum bicolour, and Avena sativa) were selected for intercropping in eight composite patterns via field experiments, with dynamics of soil physicochemical properties and crop photosynthesis observed. The results showed that treatments intercropped with M. sativa had the highest soil bulk density range (1.41–1.48 g cm−3). The dynamics of topsoil (0–10 cm) chemical properties showed similar change patterns among treatments, whereas those of the 10–40 cm soil chemical properties (especially soil pH, soil organic matter [SOM], and total nitrogen [TN]) showed heterogeneity. Moreover, planting S. sebiferum (L.) Roxb under the same crop conditions increased tree height growth rate and survival rate by 75%–114% and 14%–33%, respectively, relative to planting Z. serrata (T.) Makino. Furthermore, a significant negative correlation was observed between soil moisture with crop intercellular CO2 concentration (λ = −0.77), while significant positive correlations were found between crop net photosynthetic rate (Pn) with soil TN (λ = 0.71), as well as SOM with atmospheric CO2 content (λ = 0.72). Structural equation modeling showed significant direct effects between tree height growth rate with soil TN and SOM. Soil moisture (λ = 0.47) and tree height growth rate (λ = 0.53) were dominant drivers of crop Pn. Our findings provide useful information for the prevention of coastal saline soil degradation and sustainable development of agroforestry.

Functionalized Carbon Quantum Dots Derived from Zelkova serrata Plant Leaves for the Detection of Normetanephrine in Geriatric Plasma Samples and ROS-Induced Antibacterial Applications Using a Plausible Mechanistic Approach

Functionalized Carbon Quantum Dots Derived from Zelkova serrata Plant Leaves for the Detection of Normetanephrine in Geriatric Plasma Samples and ROS-Induced Antibacterial Applications Using a Plausible Mechanistic Approach

Effects of Elevation, Stand Density, and Inter-Tree Competition on Tree Sizes, Vulnerability, and Health of Planted <i>Zelkova serrata</i> and <i>Quercus glauca</i> in Reforestation

Effects of Elevation, Stand Density, and Inter-Tree Competition on Tree Sizes, Vulnerability, and Health of Planted <i>Zelkova serrata</i> and <i>Quercus glauca</i> in Reforestation

나무의 사계절 이미지를 모티브로 한 헤어아트 디자인 연구

People have pursued healing for healthy lives. As the most common way of healing, nature has often been chosen. Therefore, many diverse nature-themed works have been found in daily lives. Among such naturerelated elements, a tree is commonly used, and it is also frequently found in hair art. Even though hairstyles created based on the formative beauty or symbolic meaning of a tree are commonly observed, it is very difficult to find hair art works which give psychological inspiration. Under these circumstances, this study attempted to suggest new hairstyles by analyzing the seasonal images of trees. To analyze hair art works with the seasonal images of the natural monument ‘Zelkova serrata’ in Danjeon-ri, Jangseong-gun as motives, the different images of the tree in spring, summer, fall and winter were examined. In addition, the diverse colors and shapes of leaves and branches were expressed with hairpieces. In other words, human emotions which can be felt through such colors and shapes of the tree were expressed, using hairpieces. This kind of expression targeted to heal human body and mind by stimulating people’s vision and emotions differed from conventional hair art. In addition, it unveiled the excellence of Korean cultural heritage by creating hair art based on the natural monument. It is anticipated that there would be further studies on more diverse images of trees and that such hair art created based on natural monuments would enhance the value of Korean cultural heritage.

Characteristics of BVOCs emitted from representative tree species in South Korea according to environmental influences

This study was conducted to understand emission characteristics of biogenic volatile organic compounds (BVOCs) emitted from representative tree species planted in South Korea. For broad-leaved species, isoprene emission was found to be significantly different depending on environmental factors (temperature and photosynthetically active radiation (PAR)) except for Chionanthus retusus. On the other hand, for monoterpenes, except for Acer palmatum and Zelkova serrata, significant results were not obtained in emission change according to environmental factors. In the case of conifers, there were significant differences according to environmental factors in tree species excluding Chamaecyparis obtusa. Monoterpenes known to be affected only by temperature were also affected by PAR. Standard emission rate (under standard environmental conditions, 30 °C, 1000 μmol m−2 s−1) of isoprene was the highest for genus Quercus, a forest species (3174 to 11,914 ngC gdw−1 h−1). For monoterpenes, Pinus thunbergii, a forest species, had the highest emission rate (3524 ngC gdw−1 h−1), followed by Metasequoia glyptostroboides, an urban forest species (2087 ngC gdw−1 h−1). Composition ratios of monoterpenes showed a clear difference between broad-leaved species and conifers. In the case of conifers, α-pinene and d-limonene were dominant monoterpenes, whereas ratios of these two compounds were very small in broad-leaved species.

Photosynthetic responses of large old Zelkova serrata (Thunb.) Makino trees to different growth environments

Large old trees, which provide ecosystem services and serve as a historical and cultural heritage, are exposed to various environmental threats, such as habitat fragmentation and climate change, necessitating diagnosis of tangible and intangible stresses and their effects on tree growth for effective management. This study investigated the photosynthetic characteristics of 25 large old Zelkova serrata (Thunb.) Makino trees in Chungcheong Province, Korea, and identified the physical environmental factors affecting their physiological responses. Maximum assimilation rate (Amax) was the highest in July (summer), transpiration rate (E) and stomatal conductance (gs) increased from May (spring) to September (fall), and water use efficiency (WUE) was the highest in May (spring) and decreased until September (fall). Amax decreased as tree height increased. Ambient CO2 and vapor pressure deficit (VPD) were negatively correlated with photosynthetic parameters throughout the growth season and in July (summer) and September (fall), respectively. Physical environmental factors exhibited complex effect on physiological activities, which increased with wide growth space and decreased with deep soil covering and high impervious ground surface ratio. Physiological responses differed with surface types within the growth space, with bare land showing higher mean Amax, E, and gs than areas with mulching material or concrete. This study quantitatively determined the physiological activities of large old Z. serrata and proposes appropriate management measures for ensuring their healthy growth in abiotic stress environment.

Conservation Treatment of Wooden Artifacts Excavated at the Bongseon-ri Site in Seocheon, Korea

Nine wooden artifacts excavated from the Bongseon-ri site in Seocheon were deteriorated and frail. Therefore, to prevent deformation and damage, conservation treatment was performed through dimensional stabilization. As a result of tree species analysis before conservation treatment, it was identified as 3 Hardpine, 2 <i>Alnus Japonica</i>, 2 <i>Castanea</i> spp., 1 Cerris Section, and 1 <i>Zelkova serrata</i>. For the conservation treatment, wooden artifacts were impregnated with PEG#3,350 in water solution with 40% concentration and performed by freeze-drying. Artifacts that have been preserved were judged to be living tools such as farming and containers compared to those of other historical sites.

Relationship between the amount of black carbon particles deposited on the leaf surface and leaf surface traits in nine urban greening tree species

To select urban greening tree species suitable for the purification of the atmosphere polluted by black carbon (BC) particles, it is necessary to clarify the determinants of the amount of BC particles deposited on the tree leaves. In the present study, we investigated the relationship between the amount of BC particles that were deposited from the atmosphere and firmly adhered to the leaf epicuticular wax, and leaf surface traits in seedlings of nine tree species grown for two years under natural conditions (Fuchu, Tokyo, Japan). There was a significant interspecific difference in the maximum amount of BC particles deposited on the leaf surface, and the order was as follows: Ilex rotunda > Cornus florida > Osmanthus fragrans > Cornus kousa > Quercus glauca ≒ Quercus myrsinifolia > Magnolia kobus ≒ Zelkova serrata ≒ Styrax japonicus. In the nine tree species, significant highly positive correlations were observed between the amount of BC particles deposited on the leaf surface, and the hydrophobicity of leaf epicuticular wax determined by its chemical composition. Therefore, we concluded that the hydrophobicity of leaf epicuticular wax is an important determinant of the amount of BC particles deposited on the leaf surface of urban greening tree species.

Unique characteristics of residual stress distribution of large-diameter keyaki (Zelkova serrata) logs and examination of their measurement method

Large-diameter keyaki (Zelkova serrata Makino) logs have long been used in Japan as high-quality material especially for traditional construction and furniture. However, unlike other major wood species in Japan, keyaki has been practically considered as a wood species of high difficulty when processing. Keyaki frequently shows processing defects due to sawing, such as warping, cracking, and so forth, which often reduces the production yield of logs. Furthermore, there are drastic differences in those behaviors between individual logs, so causing unexpected processing defects. A scientific approach is required to improve this situation, but data on the material characteristics of keyaki were scarce. This study aimed to characterize the radial pattern of the residual stress as one of the processing-related characteristics. The measurement method was also examined. This study used diametral planks obtained from large-diameter keyaki logs to measure released strain of residual stress from pith to the bark sides. The results showed the distribution of released strain often showed peculiar zig-zag patterns characterized with localized residual stress, unlike the smooth bell curve pattern seen in typical logs of other species. Because of the unique characteristics, some practical points related to the measuring methodology were investigated. The extent of influence of this residual stress in the longitudinal direction was limited to within 30 cm from the site of measurement of the strain. In addition, the length of log necessary to measure the released strain without being affected by crosscutting was more than four times the log diameter—greater than the diameter ratio theorized by previous studies.

Optimization of weathered coal biodegradation by Penicillium aculeatum 13-2-1 and UV-visible spectral characteristics of active degraded products

Weathered coal is widely distributed in many provinces in China. It has great potential utilization values as soil ameliorant in sustainable agriculture. To find the optimal condition for the biodegradation of weathered coal and obtain the spectral characteristics of active degraded products of coal, the bioactivation of humic acid in weathered coal is essential. In this study, a fungal strain (Penicillium aculeatum 13-2-1) capable of degrading weathered coal was isolated from the rhizosphere of Zelkova serrata. The experimental results using classical one factor at a time method showed that weathered coal of 1.0 g, inoculum of 150 µL, and sodium nitrate of 0.10 g in 100 mL broth were the optimal conditions for the biodegradation of coal, respectively. The variance analysis of orthogonal tests illustrated that the three factors had little effects on biodegradation of weathered coal, but the weathered coal significantly negatively affected the contents of soluble humic acids in liquid coal products. Different diluted solutions of liquid coal products for all orthogonal combinations promoted the growth of the seeds of Brassica napus L., especially on radicles. The UV-visible spectra of the liquid coal products for all combinations presented the differential absorbance closely associated with the quantity of sodium nitrate in medium.

Arbuscular Mycorrhizal Fungi Alleviate Salt Stress Damage by Coordinating Nitrogen Utilization in Leaves of Different Species

With the intensification of coastal erosion, damage to coastal shelterbelts has gradually increased. Arbuscular mycorrhizal fungi (AMF) can improve the salinity tolerance and productivity of plants in saline–alkali soils using various strategies including nutrient uptake, osmotic regulation, soil shaping, etc. Thus, the application of AMF to alleviate the impacts of salinization for these shelterbelts has become a research hotspot. For this study, we investigated the effects of inoculation with different AMF strains on the growth and nitrogen (N) utilization of Gleditsia sinensis Lam. and Zelkova serrata (Thunb.) Makino leaves under different salt concentrations. As the salt concentration increased, the growth rates and leaf areas of the autoclaved AMF inoculant (CK) treatment exhibited a decreasing trend for both G. sinensis and Z. serrata, while Funneliformis mosseae (FM) and Corymbiglomus tortuosum (CT) treatments weakened this trend. Between them, on average, FM increased the G. sinensis height growth rate by 396.9%, ground diameter growth rate by 99.0%, and Z. serrata leaf area by 29.1%. At a salt concentration of 150 mM, the chlorophyll content and nitrate reductase activities of leaves under the FM treatment for both tree species were significantly higher than for CK, with an average increase in chlorophyll content of 106.1% and nitrate reductase activities by 74.6%. Moreover, the AMF inoculation significantly reduced the leaf N content and photosynthetic N-use efficiency of G. sinensis in contrast to Z. serrata. Further, in contrast to G. sinensis, the photosynthetic N-use efficiency was significantly positively correlated with the growth rate and leaf area of Z. serrata. Meanwhile, the nitrate reductase activity contributed most to the growth rate and leaf area of Z. serrata. Our results suggest that the issues with coastal shelterbelts might be effectively alleviated through appropriate AMF–plant combinations, which is of great significance for the optimization of forestry production.

Tree ring oxygen isotope dating of wood recovered from a canal in the ancient capital of Japan

Trees growing in the lowlands of Japan are not climatically stressed; consequently, ring-width patterns are weakly correlated between different trees. Therefore, dendrochronological studies in Japan based on ring widths rely largely on climatically stressed conifers growing in mountainous regions and/or at higher latitudes. In contrast, oxygen isotope ratios (δ18O) are well-matched between trees, irrespective of climatic stress, indicating that the huge amounts of wood excavated in Japan could potentially be dated. Here, we tested oxygen isotope dating using unearthed stumps (Abies sp., Quercus sp., and Zelkova serrata) from Japan, which historical documents and archaeological evidence suggest date from 708 to 715 CE. A new 2470-year master chronology based on Japanese cypress samples (mainly Chamaecyparis obtusa) was developed, and our dating method was evaluated using modern samples collected from several species (Tsuga, Picea, Taxus, Pinus, and Quercus) across Japan and Korea. Our chronology was then used to date stumps recovered from the bank of a canal, which was constructed when Nara became the new capital city of Japan (Heijō-kyō in Japanese). Even though the samples had only 30–60 rings and comprised multiple species, including broad-leaf trees, their tree ring δ18O patterns were successfully cross-matched. The resulting site chronology was robustly dated against the master chronology, indicating that the felling dates of the stumps ranged from winter 697/8 to 709/10 CE. Overall, the dates are consistent with previous findings, but our study provides exact calendar dating related to the construction of the new capital, and demonstrates that oxygen isotope dendrochronology works well in Japan.

Seasonal variations in accumulated particulate matter on leaves of four major tree species in Korea

Tree planting is a countermeasure used to mitigate the effects of the high concentrations of atmospheric particulate matter (PM), because trees have a strong ability to adsorb PM. However, owing to the limited information on PM accumulation on leaves throughout the year, guidelines for the implementation of urban forests cannot be provided. Therefore, in this study, we measured PM accumulation in leaves to compare the PM-reducing ability of four common species (Metasequoia glyptostroboides, Prunus yedoensis, Spirea prunifolia f. simpliciflora, and Zelkova serrata) during one growing season. We collected leaves almost every two weeks from 7 May to 23 October 2019, in Seoul Forest Park. We then measured the PM quantities on the leaves before and after rainfall (28 mm/h) to determine the amount of PM that washed off. We found that the average PM10 (PM <10 µm in diameter) accumulation on the leaves of S. prunifolia f. simpliciflora, Z. serrata, M. glyptostroboides, and P. yedoensis during one growing season was 68.1, 58.3, 43.5, and 28.2 mg/m2, respectively. The average PM2.5 (PM <3 µm) accumulation on the leaves of S. prunifolia f. simpliciflora, Z. serrata, M. glyptostroboides, and P. yedoensis was 18.2, 11.6, 7.8, and 6.5 mg/m2, respectively. However, the accumulation of both PM10 and PM2.5 on the leaves of the four species fluctuated during the sampling period. The average ratio of PM2.5 to PM10 accumulation in the leaves of S. prunifolia f. simpliciflora and P. yedoensis was significantl higher than that of Z. serrata and M. glyptostroboides; however, this ratio fluctuated throughout the sampling period. Rainfall considerably reduced the levels of PM10 on the leaves of P. yedoensis and PM2.5 on the leaves of M. glyptostroboides. We found no significant removal of PM from the leaves of other species. These results indicated that the PM-reducing ability of trees varies between species and over time. Therefore, urban forests should be managed with a high diversity of tree species.