Ozone (O sub(3)) pollution and soil infertility may negatively affect boreal forests across the Northern Hemisphere. Impacts to economically and ecologically important larches (Larix sp., Pinacaeae) ...are particularly concerning. Using a free air O sub(3) enrichment (FACE) system, we investigated the effect of 2-year elevated O sub(3) exposure ( approximately 66 nmol mol super(-1)) on Japanese larch (L. kaempferi) and its hybrid larch F sub(1) (L. gmelinii var. japonica L. kaempferi) planted directly into either fertile brown forest soil (BF) or BF mixed with infertile volcanic ash soil (VA). Overall, photosynthetic pigmentation and the growth performance of the stem and crown were reduced in both taxa exposed to elevated O sub(3). Furthermore, hybrid larch, in both O sub(3) treatments, performed better than Japanese larch. This finding contradicts findings of prior experiments with potential experimental artifacts of O sub(3) exposure facilities and root restrictions. Elevated O sub(3) also disproportionately inhibited stem diameter growth and caused an imbalance in chlorophylls a/b and chlorophyll/carotenoid ratios. Hybrid and Japanese larches grown in BF and VA had a significantly lower drop of stem diameter over the run of stem height (from base to top) when exposed to elevated O sub(3), compared to ambient O sub(3). This finding indicates altered stem shape under elevated O sub(3). Among 11 response variables, there were no significant interactions between O sub(3) treatment and taxa. There was also no significant interaction of soil condition and taxa, suggesting that the two larches shared a similar response to O sub(3) and soil type. Understanding the performance of hybrid larch in relation to its parent species has ramifications for breeding success in a soil-degraded and O sub(3)-polluted environment.
The frequency and severity of drought are expected to increase due to climate change; therefore, drought tolerance of tree species should be considered before planting for maximal survival in the ...field. In this study, we examined the response of drought stress in two of the most popular plantation species: Sargent cherry (Prunus sargentii) and Japanese larch (Larix kaempferi) based on the morphological and physiological characteristics. These plantation species are widely planted in central and northern Asia, especially in Japan and Korea, and also widely used for plantation purpose in northern Europe. Three different irrigation regimes of control (CT; 100% precipitation (P)), light drought (LD; 40% reduction of P), and heavy drought (HD; 80% reduction of P) were applied at the experimental site of Mt. Jiri, the Republic of Korea. For morphological responses, both species experienced a significant decrease in leaf size in drought conditions; however, Sargent cherry and Japanese larch experienced reduced leaf width and length, respectively. On the other hand, leaf mass area (LMA, g cm−2) increased and branch growth decreased in both species under drought conditions. As physiological responses, drought stress significantly decreased maximum photosynthesis rate (Amax) and electron transfer rate (Jmax) for both species, while stomatal conductance (Gs) at Amax significantly decreased only in Sargent cherry. Drought significantly reduced predawn (ΨPD), midday leaf water potential (ΨMD), and transpiration in Sargent cherry but not in Japanese larch. In mid-summer, carbon isotopic composition (δ13C) significantly decreased in Sargent cherry but only showed a reduction tendency in Japanese larch. However, the changes of δ13C were not significant in early summer or mid-fall. In the present study, both species showed isohydric and anisohydric characteristics, but Sargent cherry showed greater anisohydric behavior with a steeper slope (Y = 2.132X) and Japanese larch showed more isohydric behavior with a shallower slope (Y = 1.722X). Our results highlight that both species altered their morphological and physiological responses under drought stress; however, the Japanese larch showed greater resistance and resilience in morphological and physiological responses, and in plant-water relations. Therefore, Japanese larch would be more beneficial for plantations in water deficit regions than Sargent cherry.
Cross-laminated timber (CLT) fails in the outermost tensile lamina under bending loads, or rolling shear failure occurs in the Minoir direction lamina. This study investigated the effect of lamina ...width (90 mm, 120 mm), modulus of elasticity (MOE), and placement of major direction lamina on the shear strength of Larix kaempferi Carr CLT. The shear test was conducted using the short span bending test. Results showed that the specimen with 90 mm width of lamina underwent rolling shear failure at the minor direction lamina. The specimen with 120 mm width of lamina had suppressed rolling shear failure and failed at the outermost tensile lamina, which resulted in 52% higher shear strength compared to the 90 mm width specimen. CLT with high MOE placed in the outermost tensile lamina had increased shear strength. The specimen with four laminas in the major direction had both the highest strength and the lowest reliability due to the high standard deviation. This suggested that the width of the larch lamina and the MOE affect the strength of CLT. The CLT strength obtained using the FEA and the theoretical analysis were compared with the measured strength values.
Elevated CO sub( 2 ) concentration affected biomass partitioning in above-ground biomass, but size and number of water-conducting cells were unchanged in Larix kaempferi, Kalopanax septemlobus and ...Betula platyphylla. Using a Free-Air CO sub(2) Enrichment (FACE) system, we studied the effect of elevated CO sub(2) on the growth, leaf gas exchange and xylem anatomy of a conifer, Larix kaempferi, and two angiospermous tree species, Kalopanax septemlobus and Betula platyphylla. Two-year-old seedlings were grown at control sites (ambient; 370 ppm) and FACE sites (elevated; 500 ppm) for 5 years. We measured the lumen area and number of water-conducting cells, as well as biomass and leaf gas exchange, and visualized the functional region of water transport using a dye injection experiment. Elevated CO sub(2) did not induce any significant changes in growth or in leaf gas exchange or lumen area of earlywood tracheids in L. kaempferi relative to ambient CO sub(2). In two other tree species, elevated CO sub(2) was found to enhance tree height and total leaf area (LA), with no change in stomatal conductance. In K. septemlobus, there were no changes in lumen area or number of earlywood vessels, or in the functional region of water transport. B. platyphylla also underwent no changes in lumen area or number of vessels, although there was a yearly variation in the size of the vessels. Our results show that 5 years of CO sub(2) exposure did not notably affect the anatomical features of water-conducting cells. This finding suggests that, under elevated CO sub(2), trees respond to changes in water balance due to changes in LA by extending the hydraulically active area of xylem.
Among various factors related to the forest carbon pool, the tree stand age, which interacts with soil organic matter, decomposition rates, and microbial activity, is essential and cannot be ...disregarded. However, knowledge about how tree phases influence soil carbon sinks is not adequate. This study sampled Larix kaempferi (Japanese larch) plantations with different tree stand ages to investigate the temporal dynamics of soil carbon sink in the forest. Physiochemical analyses and high-throughput sequencing results further revealed the interactions of tree stands and their related rhizosphere microbiome. It was found that microbial composition and metabolic activity were significantly affected by different tree ages, whose structures gradually diversified and became more stable from young to mature forests. Many keystone taxa from the phyla Chloroflexi, Proteobacteria, Acidobacteriota, and Nitrospirota were found to be associated with carbon transformation processes. Interestingly, the carbon resource utilization strategies of microbial groups related to tree ages also differed, with near-mature forest soils showing better labile carbon degradation capacity, and mature forests possessing higher degradation potential of recalcitrant carbon. Age-altered tree growth and physiology were found to interact with its rhizosphere microbiome, which is the driving factor in the formation and stability of forest soil carbon. This study highlighted that the tree age-associated soil microbiomes, which provided insights into their effects on soil carbon transformation, were significant in enhancing the knowledge of carbon sequestration in L. kaempferi plantations.
Background and aims
While the coupled effects of root exudates and microbial feedbacks on soil processes are well-recognized, we still lack an understanding of differences in root exudate fluxes and ...the associated ecological consequences among tree growth forms.
Methods
Two deciduous tree species (i.e.,
Cercidiphyllum japonicum
and
Larix kaempferi
) and two evergreen tree species (i.e.,
Pinus armandi
and
Pinus tabulaeformis
) were selected to perform an in-situ collection of root exudates during the growing season in 2016. The net N mineralization rates and associated microbial enzyme activities were measured in rhizosphere and bulk soils to evaluate rhizosphere effects. Moreover, we compiled the dataset related to root exudation and their associated biological traits and the soil chemical properties for 21 tree species from temperate forests.
Results
The root exudation rates and the annual root exudate carbon (C) fluxes of two deciduous tree species were significantly higher than those of the two evergreen tree species. Correspondingly, the rhizosphere effects of deciduous tree species on the microbial biomass, enzyme activity and net N mineralization rate were approximately 1.9, 1.6 and 2.4 times greater than those of the evergreen tree species, respectively. Rhizosphere effects were positively correlated with the root exudation rate. The compiled dataset also suggest that deciduous tree species tend to have higher exudation rates than evergreen tree species in temperate forests.
Conclusions
Collectively, these results suggest that the two tree growth forms exhibit different patterns in root exudate inputs and associated rhizosphere microbial processes. Generally, deciduous tree species tend to exude more C into the soil and consequently induce greater microbial feedback on soil N transformations during the growing season in temperate regions, implying that deciduous tree species induced a greater effect on the C and nutrient cycling in rhizosphere soil than evergreen tree species.
Efficient asexual reproduction techniques are crucial for the expansion of larch; however, the process of adventitious roots (ARs) regeneration has hindered its development. Through comprehensive ...root development proteomics and transcriptomics analysis, we have identified key epigenetic modifying enzymes involved in the organogenesis of
Larix kaempferi
. Subsequently, we cloned the enhancer of zeste homolog CURLY LEAF (CLF) from
L. kaempferi
and performed molecular modeling. The molecular docking results between LkCLF and the histone H3 lysine 27 trimethylation (H3K27me3) inhibitor GSK126 revealed the affinity value is –9 kcal/mol, indicating strong binding interaction between the two. Adding inhibitor GSK126 to the ARs induction medium, morphologically clear primordia appeared between 20 and 25 days after cutting, which was 7–10 d earlier than in the control group, accompanied by an 18.17% increase in rooting rate. Besides, western blot analysis demonstrated the effective inhibition of H3K27me3 levels in stem bases treated with GSK126. Real-time quantitative reverse transcription polymerase chain reaction results showed a significantly elevated expression of
BABY BOOM2
compared with 0 μM GSK126 or dimethyl sulfoxide treated groups. Our findings suggest that treating stem bases with 0.01 μM GSK126 during early-stage AR regeneration expedites the developmental process and enhances the rooting rate. This study lays the foundation for a deeper understanding of the roles by H3K27me3 and polycomb repressive complex 2 in the AR regeneration of larch cuttings.
Key message
The inhibitor GSK126 effectively reduces H3K27me3 levels and enhances the expression of
LkBBM2
, thereby expediting the AR regeneration process and improving rooting rate in
Larix. kaempferi.
Climate change profoundly affects plant viability and forest dynamics, creating uncertainty in future forest management. Post-planting, high-intensity sapling mortality may require costly replanting, ...disrupting plans, and risking forest management goals. Therefore, this study focused on high-intensity sapling mortality (mortality rates exceeding 30 %) in Larix kaempferi, Abies sachalinensis, and Picea glehnii planted in northern Japan attributed to summer drought. Utilizing a dataset spanning approximately three decades, the correlation between high-intensity mortality occurrence and climatic stress was explored employing a Bayesian approach. Additionally, the probability of high-intensity mortality occurrence by the end of this century was predicted based on two representative climate scenarios (RCP2.6 and RCP8.5). The predictive accuracy of high-intensity mortality occurrence probabilities exceeded 70 % after comprehensive consideration of climatic stress factors, thereby accentuating the robustness of the proposed model. These encompass the antecedent precipitation index (API), which serves as a soil drought indicator; 30-day mean daily maximum temperature (MaxTMP̅); 30-day mean daily total solar radiation (TSR̅); and day of year (DOY). All sapling species manifested a pronounced negative correlation between API and the probability of high-intensity mortality occurrence, whereas TSR̅ exhibited a positive impact on this probability. Additionally, MaxTMP̅ positively influenced this probability for L. kaempferi and A. sachalinensis. Delving into interspecific differentials, API exhibited the most pronounced impact on P. glehnii in comparison to the other two tree species, whereas TSR̅ exerted a substantial influence on A. sachalinensis and P. glehnii. The susceptibility to MaxTMP̅ was hierarchically ordered as L. kaempferi >A. sachalinensis >P. glehnii. DOY, used to assess phenological effects like leaf morphology, negatively affected the probability of high-intensity mortality occurrence exclusively for L. kaempferi. The median probability of high-intensity mortality occurrence in Hokkaido, calculated from the estimated probabilities across all regions of Hokkaido (encompassing non-forested areas but excluding remote islands), at a 1 km resolution, was 0.37 for L. kaempferi, 0.57 for A. sachalinensis, and 0.41 for P. glehnii under RCP2.6 by the century’s end. These probabilities have decreased in comparison to those observed in 2018–2022. In stark contrast, under RCP8.5, the probabilities soared to 0.91, 0.87, and 0.56, representing an increase of 2.12 times for L. kaempferi, 1.36 times for A. sachalinensis, and 1.14 times for P. glehnii in comparison to 2018–2022. Even the least affected species, P. glehnii, witnessed a increase in mortality probability. This study underscores the importance of forest management and adaptation to climate change.
•High-intensity mortality occurrence has sharply increased in recent years.•Climate stress and the day of year explain over 70 % of high-intensity mortality.•RCP8.5 leads to fir and larch mortality, mainly due to maximum temperatures.•Spruce is susceptible to drought stress, but was less affected by climate change.•Offers insights for forest management practices amidst climate change.
The present study conducted a stem analysis to trace growth information of Japanese larch (Larix kaempferi) and predict the future changes in growth volume. For this purpose, six L. kaempferi trees ...over 47 years old were cut at 1-2 m intervals from a height of 0.2 m, and circular plates of 5 cm thickness were collected for stem analysis. The analysis indicated that approximately 1-8 years are required to grow up to chest height. The annual height and diameter growth increased rapidly until the trees are 15 years old and gradually decreased after 20 years. The volume of 30-year-old trees in Oegam-ri forests, which were well-managed after artificial reforestation, was 0.4837 m 3 , whereas that in unmanaged Singi-ri forests was 0.1956 m 3 . Although the volume of individual trees differed greatly depending on the forest management status, it was found that the volume increased by 1.67-1.76, 2.49, and 3.49 times at 40, 50, and 60 years age, respectively, compared to the legal harvesting age 30. Therefore, factors such as the carbon dioxide reduction effect, forest management benefits, and the condition of trees at the site should be considered before harvesting trees.
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