Cryptomeria Research Articles

Developing simple DNA extraction and PCR-RFLP for MALE STERILITY 4 (MS4) gene in Cryptomeria japonica D. Don: toward an environmentally friendly protocol

Developing simple DNA extraction and PCR-RFLP for MALE STERILITY 4 (MS4) gene in Cryptomeria japonica D. Don: toward an environmentally friendly protocol

A chromosome-level genome assembly of a model conifer plant, the Japanese cedar, Cryptomeria japonica D. Don.

The Japanese cedar (Cryptomeria japonica D. Don) is one of the most important Japanese forest trees, occupying approximately 44% of artificial forests and planted in East Asia, the Azores Archipelago, and certain islands in the Indian Ocean. Although the huge genome of the species (ca. 9 Gbp) with abundant repeat elements may have represented an obstacle for genetic analysis, this species is easily propagated by cutting, flowered by gibberellic acid, transformed by Agrobacterium, and edited by CRISPR/Cas9. These characteristics of C. japonica recommend it as a model conifer species for which reference genome sequences are necessary. Herein, we report the first chromosome-level assembly of C. japonica (2n = 22) using third-generation selfed progeny (estimated homozygosity rate = 0.96). Young leaf tissue was used to extract high molecular weight DNA (> 50kb) for HiFi PacBio long-read sequencing and to construct an Hi-C/Omni-C library for Illumina short-read sequencing. The 29× and 26× genome coverage of HiFi and Illumina reads, respectively, for de novo assembly yielded 2,651 contigs (9.1 Gbp, N50 contig size 12.0 Mbp). Hi-C analysis mapped 97% of the nucleotides on 11 chromosomes. The assembly was verified through comparison with a consensus linkage map comprising 7,781 markers. BUSCO analysis identified ∼ 91% conserved genes. Annotations of genes and comparisons of repeat elements with other Cupressaceae and Pinaceae species provide a fundamental resource for conifer research.

Within-Site Variations in Soil Physicochemical Properties Explained the Spatiality and Cohabitation of Arbuscular Mycorrhizal Fungi in the Roots of Cryptomeria Japonica

Arbuscular mycorrhizal fungi (AMF) live in a community in the roots of host plants. Still, the patterns and factors that drive their spatiality and cohabitation remain uncovered, particularly that of trees in planted forests, which we aimed to clarify in Cryptomeria japonica, a major plantation tree in Japan. We analyzed 65 paired root and soil samples of Cryptomeria japonica trees collected from 11 microsite (MS) plots at two environmentally different forest sites in central Japan and measured soil pH, total phosphorus (TP), C, N, and the carbon-to-nitrogen ratio. Root AMF communities were recovered using Illumina’s next-generation amplicon sequencing targeting the small subunit of ribosomal DNA. We detected more than 500 AMF OTUs at each site but only three belonging to Dominikia, Rhizophagus, and Sclerocystis were dominant in the roots of C. japonica, detected each at an average relative abundance higher than 20%. Two showed negatively correlated spatial distributions and different associations with soil pH. Similarly, the physicochemical properties at MSs significantly determined the AMF assemblages in the roots of C. japonica. Dominikia, Rhizophagus, and Sclerocystis coexist in the roots of C. japonica where soil physicochemical properties, particularly pH, determine their spatial dynamic, turnovers, and cohabitation patterns. These findings highlight the importance of simultaneous colonization of plants by multiple AMF.

Forest types matter for the community and co-occurrence network patterns of soil bacteria, fungi, and nematodes

Tree growth influences the biological, physical, and chemical properties of the soil through the input of different types of litter and various root exudates. However, our understanding of tree-mediated effects on the composition and diversity of soil biota remains limited. This study aimed to determine the effects of physically neighboring forest types (i.e., an artificial Japanese cedar (Cryptomeria japonica) plantation vs. a broadleaf (Quercus serrata) secondary forest) on individual bacterial, fungal, and nematode communities and the associations among these inter-kingdoms. Bacterial, fungal, and nematode aggregates were estimated using MiSeq high-throughput sequencing system. The amplicon sequence variant richness of fungi and nematodes was significantly greater in the cedar plantation than in the broadleaf forest, and the three soil biota community structures were significantly clustered among the forest types. Environmental factors such as soil pH, C, N, and C/N ratio significantly influenced the three soil biota community structures. The bacterial–fungal–nematode co-occurrence network of the broadleaf forest had more nodes and edges than that of the cedar plantation. Moreover, Ascomycota and Basidiomycota fungi mainly co-occurred with fungivorous nematodes in the cedar and broadleaf forests, respectively. Our results suggested that unique soil biota communities and characteristic co-occurrence network patterns were established among the tripartite inter-kingdom relationships between adjacent forest types.

Genome editing efficiency improvement in Japanese Cedar (<i>Cryptomeria japonica </i>D. Don) by Cas9 codon optimization

Genome editing efficiency improvement in Japanese Cedar (<i>Cryptomeria japonica </i>D. Don) by Cas9 codon optimization

A Case of the Anti-aquaporine-4 Antibody-negative Neuromyelitis Optica Spectrum Disorders Associated with Atopic Disease with High Concentration of Anti-IgE Autoantibody and HyperIgEemia

We report a 70-year-old male patient with the sero-negative neuromyelitis optica spectrum disorders (NMOSD) associated with atopic disease (AD). He was diagnosed with allergic rhinitis at the age of 20. When he was 61 years old, he subacutely developed orthostatic hypotension, bilateral optic neuritis, quadriparesis, urinary retention, and constipation. The laboratory results revealed allergen-specific IgE positivity for cryptomeria japonica and hinoki, hyperIgEemia, and Th (helper T cell) 1 dominance. The serological tests for autoantibodies revealed negative anti-aquaporine 4 antibody, and high concentration of anti-IgE autoantibody (anti-IgE AAb). Cerebrospinal fluid was negative for anti-myelin-oligodendrocyte glycoprotein antibody and glial fibrillary acidic protein antibody. Fluid-attenuated inversion recovery on brain magnetic resonance imaging (MRI) showed high signal intensities in bilateral cerebral deep white matter. T2 weighted image on spine MRI showed longitudinally extensive high signal intensities in the spinal cord, specifically involving C1 vertebral level to conus medullaris. Intravenous methylprednisolone (IVMP) and plasma exchange resulted in partial improvement. Following the onset of NMOSD, he had relapse of NMOSD four times. In each episode, IVMP was to be partially effective with anti-IgE AAb reduction. Anti-IgE AAb may be a reasonable clinical indicator of increased disease activity in the sero-negative NMOSD associated with AD.

Retrospective Observational Study on Telemedicine in Sublingual Immunotherapy for Patients with Japanese Cedar Pollinosis and House Dust Mite Allergic Rhinitis.

Introduction: In Japan, telemedicine has gradually expanded due to deregulation in response to the COVID-19 pandemic. However, its current status remains unclear, as it is primarily provided by general practitioners. This study aims to examine the use of telemedicine in sublingual immunotherapy (SLIT) for patients with Japanese cedar pollen allergy and/or house dust mite allergic rhinitis. Methods: We conducted a retrospective analysis of medical record data from seven otorhinolaryngology clinics and performed an exploratory evaluation between a group that combined telemedicine and in-person visits during the initial 6 months of SLIT and another group with only in-person visits. Results: Following propensity score matching, 51 and 82 patients were eligible for the telemedicine and in-person groups, respectively, with 33 cases in both groups. Both groups had similar characteristics after matching. No significant difference was found in the withdrawal rate at 6 months from the start of SLIT (6.1% and 9.1% in each group; p = 1.00), side effects, or treatment efficacy between the two groups. The average copayment for patients tended to be significantly higher in the telemedicine group after one, three, and 6 months following SLIT initiation. Discussion: The situation of patients who receive an appropriate combination of telemedicine and in-person visits is not significantly different from patients who receive in-person visits alone. This study may help indicate the actual status of telemedicine in Japan. Further investigation at more facilities is necessary in the future to dispel concerns in the practice setting.

Cell Extracts Derived from Cypress and Cedar Show Antiviral Activity against Enveloped Viruses.

The antiviral efficacy of cell-extracts (CEs) derived from cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl., C. obtusa) and cedar (Cryptomeria japonica (Thunb. ex. L.) D.Don, C. japonica) was assessed using phi6 and MS2 bacteriophages, which are widely accepted surrogate models for enveloped and non-enveloped viruses, in order to verify their potential use as antiviral agents. Our results indicate that CEs derived from C. obtusa are dominantly composed of terpinen-4-ol (18.0%), α-terpinyl acetate (10.1%), bornyl acetate (9.7%), limonene (7.1%), and γ-terpinene (6.7%), while CEs derived from C. japonica are dominantly composed of terpinen-4-ol (48.0%) and α-pinene (15.9%), which exhibited robust antiviral activity against phi6 bacteriophage. Both CEs successfully inactivated the phi6 bacteriophage below the detection limit (10 PFU/mL) within a short exposure time of 30 s (log reduction value, LRV > 4). Through exposure experiments utilizing CEs with content ratios prepared via 2-fold serial dilutions (ranging from 3.13% to 100%), we demonstrated that the antiviral effect could be sustained up to a concentration of 25% (C. obtusa LRV = 3.8, C. japonica LRV > 4.3 at a 25% CE content ratio for each species). However, CEs with content ratios below 12.5% did not produce a significant reduction in bacteriophage concentration and consequently lost their antiviral effects. Conversely, both CEs did not exhibit antiviral activity against MS2 bacteriophage, a non-enveloped virus. Our findings reveal for the first time the potential of CEs derived from C. obtusa and C. japonica for use as antiviral agents specifically targeting enveloped viruses.

Energy transfer during tree movement for different wind conditions and forest configurations

Catastrophic winds from tropical cyclones and storms cause tree failure in forests, leading to economic and environmental losses. Tree failure, especially uprooting, results from energy transfer from winds to the roots through the tree stem. However, we do not fully understand how trees in forests respond to winds under different weather conditions and whether the responses remain unchanged with the configurations of the forest. In this study, we established two Cryptomeria japonica plots, namely P-100 as a control (3000 stem ha−1), and P-50, which was thinned to halve the control stand density (1500 stem ha−1) in November 2017, in Kasumigaura City, Japan. Two kinds of sensors were installed on the tree stems in the plots and data was collected over the following 2 years. Strain gauge transducers at the stem base were used to calculate turning moments. Inertial measurement unit (IMU) sensors at 6 m height provided the x, y, and z coordinates of the tree motion. At the end of the observation period, we conducted tree-pulling experiments to calculate the maximum turning moments the trees could resist. During the observation period, the trees experienced winds from typhoons, including super typhoon Trami in 2018, causing some tree failure in the thinned plot (P-50). Based on this damage incident, we selected four different forest configurations and 18 windy conditions (7 typhoons and 11 weather conditions in which a maximum wind speed of more than 7 m s−1 was observed). We found two dominant movement frequencies, one at between 0.2 – 0.5 Hz and one at between 2.0 – 2.3 Hz. The higher movement frequency appeared at the lower wind speeds and the lower movement frequency appeared at the higher wind speeds. The transition wind speeds from the higher to the lower movement frequency were found between 1.79 and 7.44 m s–1 in the P-100 unthinned plot and between 1.57 and 5.63 m s–1 in the P-50 thinned plot. In addition, we determined that the resistance to the damage over a 10-min period during typhoon Trami, based on the tree that uprooted, was only 48 % of the maximum tree resistance estimated from the tree-pulling experiments. Our study describing tree dynamic responses to winds under different forest configurations and wind conditions could provide alternative methods for modifying the forest environment, especially through forest management activities such as thinning and harvesting, in order to mitigate wind damage risk in the future.

Effects of Wood Drying Temperatures on the Reduction in Mechanical Properties of Japanese Cedar (Cryptomeria japonica D. Don) Perpendicular to Grain

Wood drying is often accompanied by changes in mechanical properties due to external thermal energy. This study examined the influences of drying temperature on the mechanical properties of Japanese cedar based on the partial compression properties and bending properties. Two types of longitudinal specimens with quarter grain on both lateral surfaces were prepared under green conditions, followed by subsequent drying under each drying temperature (20 °C, 40 °C, 60 °C, 80 °C, and 100 °C). Then, the partial compression and bending tests were performed using the respective specimens. Young’s modulus perpendicular to grain, yield stress, and compressive strength obtained by the partial compressive test were highest for wood dried at 20 °C. It was considered that the decrease in mechanical properties was attributed to the thermal influences during drying at 100 °C and other factors such as compressive residual stress and cell walls collapsing at lower temperatures. The strain energy suggested that the effects of drying temperature became apparent, especially in the plastic region during loading in the direction perpendicular to the wood fiber. Bending properties showed little influence on drying temperatures compared to the partial compressive properties, whereas the fractures found under the loading point of the wood dried at 100 °C suggested a reduction in resistance to shear forces.

Different patterns of fine-root exudation rates along soil depth of Pinus densiflora, Chamaecyparis obtusa, and Cryptomeria japonica in coniferous forests

Tree fine-root exudation and organic carbon compounds in the soil affect physiological functions through degradation by microorganisms around the roots and the enhancement of allelopathic effects on invasion attempts by other plant species. However, the underlying mechanism of fine-root action in vertically heterogeneous resource-distribution patterns along the soil profile is little known. Here, we quantified root exudation and its morphological and chemical traits in the soil layers down to 100-cm depth for three conifer species, Pinus densiflora (ectomycorrhiza), Chamaecyparis obtusa, and Cryptomeria japonica (arbuscular mycorrhiza), in a cool temperate Japanese forest. By using glass filter-trap method, root exudation rates in all three species varied with soil depth in a species dependent pattern. Specifically, the root exudation rate of P. densiflora was significantly higher in the middle soil layer, and lower in the topsoil layer, whereas the exudation rates significantly decreased in C. japonica and did not vary in C. obtusa along soil depth. Exudation strongly correlated with variation in root traits in C. obtusa and C. japonica but not in P. densiflora. These findings suggest that differences in exudation patterns among tree species are likely compensated for by structural modifications in fine roots in response to soil depth. In addition, the traits with mycorrhizal types might be related to adequate root exudation and enhanced soil-nutrient acquisition. Distinct differences among species in exudation, associated with vertical root distribution, will increase our understanding of root survival strategies for nutrient acquisition and carbon sequestration in forest tree species.

Plasticity of leaf functional traits and growth responses to disturbance among cutting cultivars of Cryptomeria japonica in southern Japan

ABSTRACT Cryptomeria japonica (Thunb. ex L. f.) D. Don is the most major plantation species in Japan, and cultivars have been developed and planted under variable environmental conditions across the country. Productivity of clonal plantations is influenced by the ability of the genotype to acclimate to edaphic- and geographic-scale variation in environmental conditions and disturbance regimes. Because all individuals are genetically identical in a clonal plantation, the trait differences among individuals represent phenotypic plasticity. Here, we investigated how phenotypic plasticity and response to disturbance vary among cutting cultivars of C. japonica. We compared tree height, leaf morphology, nitrogen content, and frequency/intensity of growth-release observed in tree rings after thinning and disturbance among six cutting cultivars in 45-year-old provenance trials in south-western Japan. Nitrogen use efficiency was higher in the site where maximum tree height (H max) was taller, while shoot mass per area (SMA) was larger in the site where H max was shorter. Cultivars that grew well had high leaf nitrogen content (N G) and showed more efficient nitrogen use with high nitrogen-resorption efficiency (NRE). Yabukuguri, an intermediate-growth cultivar, was characterized by large SMA and greater plasticity in SMA and tree height in response to topographical and regional variation, as well as greater intensity of growth-release in tree-ring series indicating growth resilience following disturbance. Our results provide guidelines for selecting cultivars with high acclimation potential and resilience to environmental perturbation, which is important for sustaining plantation forests in uncertain environmental conditions expected by future climate change.

Ubiquity of methanogenic archaea in the trunk of coniferous and broadleaved tree species in a mountain forest.

Wetwood of living trees is a habitat of methanogenic archaea, but the ubiquity of methanogenic archaea in the trunk of various trees has not been revealed. The present study analysed methanogenic archaeal communities inside coniferous and broadleaved trees in a cold temperate mountain forest by culture-dependent or independent techniques. Heartwood and sapwood segments were obtained from the trunk of seven tree species, Cryptomeria japonica, Quercus crispula, Fraxinus mandshurica, Acer pictum, Aesculus turbinata, Magnolia obovata, and Populus tremula. Amplicon sequencing analysis of 16S rRNA genes showed that Methanobacteriaceae predominated the archaeal communities and Methanomassiliicoccaceae also inhabited some trees. Real-time PCR analysis detected methanogenic archaeal mcrA genes from all the tree species, with a maximum of 107copiesg-1 dry wood. Digital PCR analysis also detected mcrA genes derived from Methanobacterium spp. and Methanobrevibacter spp. from several samples, with a maximum of 105 and 104copiesg-1 dry wood. The enumeration by the most probable number method demonstrated the inhabitation of viable methanogenic archaea inside the trees; 106cellsg-1 dry wood was enumerated from a heartwood sample of C. japonica. Methanogenic archaea related to Methanobacterium beijingense were cultivated from a heartwood sample of Q. crispula and F. mandshurica. The present study demonstrated that the inside of various trees is a common habitat for methanogenic archaeal communities and a potential source of methane in forest ecosystems.

Impact of wheat sensitization on wheeze and T2 phenotypes in general population of children

BackgroundThe association between sensitization to specific aeroallergens and outcomes in patients with asthma is well-researched; however, the association between childhood-onset wheeze/asthma and sensitization to various aeroallergens and food allergens in the general pediatric population remains poorly understood. ObjectiveThe association between sensitization to common aeroallergens and food allergens with wheeze and type 2 (T2) inflammation in the general pediatric population was investigated. MethodsSpecific IgEs against nine aeroallergens and four food allergens were measured in the prospective Hokkaido birth cohort of 428 school-age children (approximately 10 years of age). Wheeze and other allergic symptoms were assessed using the International Study of Asthma and Allergies in Childhood questionnaire. Blood eosinophil count and fractional exhaled nitric oxide level were assessed as T2 biomarkers. The Isle of Wight (IOW) birth cohort in UK was used for replication analysis (n=1032). ResultsThe prevalence of sensitization to at least one aeroallergen and food allergen was 70.5% and 22.3%, respectively. A significant association between wheeze and sensitization to aeroallergens such as ragweed, Japanese cedar, mugwort, and pet dander, were found. However, the association between wheeze and wheat sensitization was highly significant (Hokkaido birth cohort, odds ratio [OR]: 4.67; 95% confidence interval [CI]: 1.98–11.01; IOW birth cohort, OR: 4.01, 95% CI: 1.78–9.07). Sensitization to most aeroallergens, though not any food allergens, was associated with the T2high phenotype. ConclusionSensitization to wheat may be an important risk factor for wheeze/asthma development, especially the pathogenesis of T2-non/low asthma, independent of aeroallergens, in the general pediatric population.

Effect of low vacuum medium temperature drying on reduction of residual stress and correction of warp of Japanese cedar timber

Cryptomeria japonica (Japanese cedar) in Japan plantations are aging, and the main supply of timber in the market is shifting from small- and medium-diameter to large-diameter logs. The effective utilization of these logs has become an important issue in the timber industry. When producing timber-without-pith from large-diameter logs, an unavoidable warp occurs because of the release of residual stress within the logs. Utilizing high-temperature drying with a load on these timbers has achieved significant drying effects, and the residual stress-induced warp was corrected. However, high-temperature drying has drawbacks, such as high energy consumption and the potential for thermal degradation. We applied low-vacuum-medium-temperature drying (LVMT-drying, 10 days, 40 kPa, 80/55 °C (DB/WB)—90/65 °C (DB/WB)) with load (650 kgf/m2) to the stacked timber sawn from large-diameter logs to address these questions. When LVMT-drying was successful, residual stresses in timber-with-pith were reduced to nearly zero, and warps in timber-without-pith were reduced to less than 8 mm, i.e., below the Japan Agriculture Standard "Level 1" for 4000 mm timber, and the acceptance rate for "Level 1" increased from 45% (green timber) to 85% (treated timber) in the most successful sample. LVMT-drying is a practical drying method for timber from large-diameter logs because it is effective in reducing residual stress and correcting warps while shortening the treatment period and avoiding thermal degradation.

Estimating the Single Shear Strength Performance of Joints Using Screws and Nails with Decayed Wood

To enable the long-term use of existing wooden structures, appropriately evaluating the extent of damage of the biodeterioration of structural performance, including members and joint systems, is necessary. To give one example, accurately estimating the single shear strength performance of nail and screw joints with decay is crucial. Therefore, this study proposes a method to model this by dividing wood into multiple layers with different strength performance, considering the grade of deterioration in a cross-section of decayed wood. The model was used to differentiate the sound layer and three decayed layers (multilayer) according to the extent of the damage. The estimated values, which were produced using the proposed model, were compared to the single shear strength of screw and nail joints with decay using two species of wood, namely Abies sachalinensis (Todomatsu) and Cryptomeria japonica (Sugi). The results point to a good fit between the average value of the experimental results and the estimated values of the proposed model. Compared with the existing (single-layer) model, the proposed model improved the accuracy of estimating the strength of wood undergoing early deterioration and therefore was considered usable.

Sequential Separation of Essential Oil Components during Hydrodistillation of Fresh Foliage from Azorean Cryptomeria japonica (Cupressaceae): Effects on Antibacterial, Antifungal, and Free Radical Scavenging Activities.

Cryptomeria japonica wood industry generates large amounts of foliage biomass residues. Due to the increasing applications and markets for essential oils (EOs), fresh Azorean C. japonica foliage (Az-CJF) residues are used for local EO production. Hydrodistillation (HD), a common process for obtaining EOs, also provides the possibility to fractionate them. Thus, this study evaluated the in vitro antimicrobial and antioxidant activities of six Az-CJF EO fractions (Frs. 1-6), collected at sequential HD timeframes (HDTs: 0-2, 2-10, 10-30, 30-60, 60-120, and 120-240 min), in comparison to the crude EO, obtained from a non-fractionated HD (0-240 min HDT). Antimicrobial activities were assessed via disc diffusion method against seven bacteria (foodborne and/or human pathogens) and two Penicillium spp. (phytopathogenic fungi), and antioxidant activity was estimated using DPPH and ABTS assays. Concerning the antibacterial activity, all the EO samples were effective only toward Gram-positive bacteria. Fractions 1-3 (<30 min HDT) were the most active, with growth inhibition zones (GIZ) of 7.0-23.3 mm (1.4-2.2 times higher than those of the crude EO), being Bacillus spp. (B. licheniformis and B. subtilis) the most sensitive, followed by Staphylococcus aureus and Micrococcus luteus. Regarding the antifungal activity, Frs. 1-3 also displayed the best activities, but only against P. italicum (GIZ around 9.0 mm), while the crude EO showed no antifungal activity. Overall, the best antimicrobial properties of Frs. 1-3 could be attributed, at least in part, to their highest content in α-pinene and bornyl acetate. On the other hand, Frs. 4-6 (>30 min HDT) exhibited the strongest antioxidant activities (EC50 values: 1.5-2.3 and 1.0-1.7 mg mL-1 for DPPH and ABTS, respectively), being at least 1.3-fold higher than those of the crude EO. The presence of nezukol, elemol, and eudesmol isomers could strongly contribute to the best free radical scavenging properties of Frs. 4-6. In conclusion, HD was found to be an efficient process for obtaining new Az-CJF EO fractions with variable and enhanced bioactivities due to their differential composition, as assessed using GC-MS. Hence, these findings could contribute to increasing the commercial potential of the C. japonica EO industry, namely, the Fr2 and Fr6, which presented the most significant activities and can have potential applications in the food, medical, and agriculture sectors.

Vertical gradient of needle ozone uptake within the canopy of Cryptomeria japonica

Leaf ozone uptake through the stomata is an important index for the ozone risk assessments on trees. Stomatal conductance (gs) and ozone concentration ([O3]), determinants of the leaf ozone uptake, are known to show vertical gradients within a tree canopy. However, less is known about the within-canopy vertical gradient of leaf ozone uptake. This study was aimed to elucidate how the vertical gradient of [O3] and gs affect needle ozone uptake within a canopy of mature Cryptomeria japonica trees in a suburban forest at Tokyo, Japan. For this purpose, a multilayer gas exchange model was applied to estimate the vertical gradient of needle gs and the accumulated ozone uptake during the study period (POD1, Phytotoxic Ozone Dose above a threshold of 1 nmol m−2 s−1). In addition, we also tested several scenarios of vertical gradient of [O3] within the canopy for sensitivity analysis. The POD1 was declined from the top to the bottom of the canopy. This tendency strongly depended on the vertical gradient of gs and was hardly affected by the changes in simulated vertical reductions of the [O3]. We further assessed the photosynthesis of sunlit needles (needles absorbing both direct and diffuse light) and shaded needles (needles only absorbing diffuse light). The photosynthesis of shaded needles in the upper half of the canopy made a great contribution to the entire canopy photosynthesis. In addition, given that their POD1 was lower than that of sunlit needles, ozone may affect sunlit and shaded needles differently. We concluded that these considerations should be incorporated into modeling of the calculation of ozone uptake for mature trees to make accurate predictions of the ozone effects on trees at the canopy scale.

Downward migration of 137Cs promotes self-cleaning of forest ecosystem by reducing root uptake of Japanese cedar in Fukushima

Approximately 70 % of the area highly 137Cs-contaminated by the Fukushima Daiichi Nuclear Power Plant accident is forested. Decontamination works in most of these forests have not progressed, and the forestry industry remains stagnant. Although the long-term dynamics of 137Cs in the forest ecosystem will be controlled by the amount of 137Cs absorbed by roots in the future, temporal changes in 137Cs of tree roots have rarely been reported. In the present study, we monitored the depth distribution of 137Cs in the soil and absorptive very fine (VF) roots of 0.5 mm or less in a Japanese cedar forest from 2011 to 2023. As a result, the 137Cs inventory in the mineral soil increased over time due to the migration from the forest canopy and litter layers, whereas that in the VF roots tended to decrease since 2020, although there was a large variation. Temporal decrease in the exchangeable 137Cs fraction with fixation and temporal increase in VF root biomass with their growth were not clearly observed, the 137Cs concentration in the VF roots at 0–2 cm decreased with the decrease in 137Cs concentration in the litter layers. Although the 137Cs concentration in the VF roots below 2 cm tended to increase with increasing 137Cs concentration in the soil at the same depth, the downward migration of 137Cs within the soil can reduce the amount of 137Cs absorbed by roots because the VF root biomass decreases exponentially with depth. In other words, 137Cs can be removed from the long-term active cycles of forest ecosystems as they migrate deeper into the soil. This natural migration process can be regarded as a “self-cleaning” of the forest ecosystem, the green and sustainable remediation using such self-cleaning should be actively adopted for the future forest management.

Genotypic variations appear in fine root morphological traits of Cryptomeria japonica trees grown in a common garden

AbstractFine root morphological traits regulate the belowground resource acquisition strategies of trees. Therefore, investigating genotypic variations isolated from environmental variations within tree species helps in understanding how genotypic backgrounds affect intragenerational tree acclimation to the growing environment. Thus, this study aimed to clarify the effects of genotypic variations on the fine root morphology of three types of Japanese cedar (Cryptomeria japonica), which were derived from different provenances but were grown in a common garden. In the three geographically different provenances of C. japonica stands (Yanase, Yoshino, and Yaku), fine root morphological traits, such as root length and diameter and specific root length (SRL), were measured for each root up to the 4th branching order. Yaku cedar exhibited root traits distinct from the other provenances, such as growing longer and thinner roots in 1st root order to enhance root surface area. In addition, the SRL patterns with root orders and higher root tissue density suggested a resource conservation strategy. Yanase cedar demonstrated a significantly higher root branching ratio and specific root tips than the other provenances, indicating a strategy for investing resources in absorptive roots. Although Yoshino cedar had traits similar to those of Yanase cedar or intermediate between Yanase and Yaku cedars, high aboveground production may be achieved through nutrient acquisition with root exudates instead of absorptive root growth. Genotypic variations appeared in fine root morphological traits of C. japonica trees, even when grown in the same environments, implying distinct resource acquisition strategies characterized by each provenance.