Larix Kaempferi Research Articles

Forecasting Spring Flight of Ips subelongatus (Coleoptera: Curculionidae: Scolytinae) in Japanese larch Larix kaempferi (Pinales: Pinaceae) Forests in the Republic of Korea.

Ips subelongatus is a species of bark beetle experiencing population outbreaks in Korea. In this study, a predictive model and empirical prediction were used to forecast the spring flight of these beetles in Japanese larch forests. The number of beetles caught in pheromone traps was investigated in larch forests thinned in 2009, 2010, 2012, or 2013. Data from the sites thinned in 2009, 2010, or 2012 were used in the predictive model based on a degree-day model that was validated using data from the site thinned in 2013. The lower threshold temperature for flight (LTF) and a thermal sum for the spring flight of I. subelongatus were estimated. The empirical prediction that beetles initiate their flight when daily maximum temperatures reach 16 or 20°C was tested using daily maximum temperature and the beetles caught. The LTF was estimated as 5.97°C, with 42.95 degree-days required for initiation of spring flight. The median flight dates were estimated with a discrepancy from 1 to 3 d by the predictive model. Using the empirical prediction, differences between the day when daily maximum temperature reached 16 or 20°C and flight peak days ranged from 4 to 45 d. These results demonstrate that the predictive model is more suitable than the empirical prediction for predicting the spring flight of I. subelongatus. Overwintering I. subelongatus adults seem to need to gain a determined thermal sum before initiating spring flight rather than merely waiting for the daily maximum temperature to exceed a critical temperature.

Salt Stress Reduced the Seedling Growth of Two Larch Species Under Elevated Ozone

The effect of elevated ozone (O3) and soil salinization with alkaline salts in northeastern (NE) China is a serious concern in the success of the national replanting project. As the areas planted exceed 4 million hectares in China, we must consider the future afforestation after thinning and harvest at some parts of them. Here, we investigated the effects of O3 and salt stress on seedlings of Dahurian larch (Larix gmelinii var. japonica; DL) and Japanese larch (L. kaempferi; JL). The two species of seedlings were exposed to elevated O3 [approximately 70 nmol mol-1] and ambient control [approximately 40 nmol mol-1] for one growing season in an open top chamber (OTC) system that simulated the salinity in NE China [alkaline salt, NaHCO3 : NaCl = 9:1, 20mM Na+]. The seedlings under salt free treatment received tap water. Effects of O3 on the growth of both larches were not significant, although the LMA of JL was reduced more than that of DL seedlings. Further, the combined effects of O3 and salt stress were not significant. This may be attributable to the stronger effects of salt stresses on both larch seedlings. Salt stress decreased the total dry mass in both larch species by more than 10%. DL seedlings showed specific salt tolerance in absorption of some mineral nutrients. Although salt stress reduced Ca and Mg content in needles, we found the degree of reduction was lower in DL than JL, with specific salt tolerance of mineral homeostasis in DL seedlings. Our results indicated that DL seedlings may be future candidate afforestation species even in saline soil and O3 levels less than 70 nmol mol-1.

Visual grading criteria for Japanese larch (Larix kaempferi) structural timber from Spain

Larch wood is structurally classified in many countries as one of conifers with the highest load-bearing capacity (strength class of C30). The Spanish visual classification regulation only assigns a strength class to 4 pine woods: Laricio pine (Pinus nigra Arn. var. Salzmannii), Silvestre pine (Pinus sylvestris L.), Radiata pine (Pinus radiata D. Don), and Pinaster pine (Pinus pinaster Ait.). This work adds to the number of structurally characterised species by creating a visual classification table for Japanese larch wood (Larix kaempferi (Lamb.) Carr.) which differentiates between 2 visual classes, MEG-1 and MEG-2. Characteristic strength values were calculated for each class (fk,MEG-1 = 31.80 MPa, fk,MEG-2 = 24.55 MPa), mean module of elasticity (E0,mean,MEG-1 = 13,082 MPA, E0,mean,MEG-2 = 12,320 MPA) and density (ρk,MEG-1 = 456.6 kg m−3, ρk,MEG-2 = 469.1 kg m−3), before finally assigning a strength class of C30 to visual class MEG-1, and a strength class of C24 to visual class MEG-2.

Relationship between the composition and distribution of nutritional substances, secondary metabolites, and internal secretory structures in the bark tissues of Larix gmelinii var. japonica, L. kaempferi, and their F1 hybrid and susceptibility to vole herbivory

ABSTRACTWe investigated the quantitative composition and distribution of nutritional substances (soluble sugars, starch, and protein), secondary metabolites (terpenoids and phenolic compounds), and the length, area, and density of internal secretory structures (resin ducts and cavities) in the rhytidome (outer bark) and secondary phloem (inner bark) of Kuril larch (Larix gmelinii var. japonica), Japanese larch (L. kaempferi), and their F1 hybrid (L. gmelinii var. japonica × L. kaempferi) in order to clarify the relationship of these parameters to susceptibility to red-backed voles’ herbivory in Hokkaido, Japan. The amounts of most nutritional substances in each of both bark tissues were not significantly different among the three larch taxa. The amounts of carane-type monoterpenoid and labdane-type diterpenoid in both bark tissues of L. gmelinii var. japonica and the F1 hybrid were significantly higher than those of L. kaempferi. The amounts of phenolic compounds in both bark tissues of L. gmelinii var. japonica were significantly lower than those of L. kaempferi. The quantitative composition of most secondary metabolites in both bark tissues of the the F1 hybrid were between L. gmelinii var. japonica and L. kaempferi. The area and density of the resin ducts and cavities, which were containing terpenoids, in both bark tissues of L. gmelinii var. japonica and the F1 hybrid were significantly larger and higher than those of L. kaempferi. These results suggest that L. gmelinii var. japonica and the F1 hybrid utilize some predominant constitutive mono- and diterpenoids as chemical defensive substances in the bark tissues against the voles.

A GH3-like gene, LaGH3, isolated from hybrid larch (Larix leptolepis × Larix olgensis) is regulated by auxin and abscisic acid during somatic embryogenesis

A Gretchen Hagen 3-like gene, LaGH3 from hybrid larch (Larix leptolepis × Larix olgensis), was identified, and the effects of abscisic acid (ABA) and indole-3-acetic acid (IAA) on its transcriptional levels and expression patterns during somatic embryogenesis were analyzed. A full-length cDNA sequence of a Gretchen Hagen 3 (GH3) gene was isolated from hybrid larch (Larix leptolepis × Larix olgensis) and designated LaGH3. The cDNA was 2053 bp in length and contained an 1848-bp open-reading frame encoding a predicted protein of 615 amino acids, characterized by four conserved motifs of the GH3 protein family: P-loop, α5, α6, and β8–β9. The 5′-flanking promoter region of LaGH3 was cloned using an improved TAIL-PCR technique. In this region, we identified several auxin- and abscisic acid (ABA)-inducible elements. Expression analysis showed that LaGH3 was induced by indole-3-acetic acid and that its transcript accumulation was inhibited by ABA. Further experiments demonstrated that ABA was the main factor in LaGH3 downregulation during the early stage of somatic embryogenesis, although the absence of auxin decreased LaGH3 expression slightly. LaGH3 transcripts gradually increased and peaked at 28 days with the rapid development of somatic embryos and then declined as the somatic embryos matured. We suggest that the level of LaGH3 transcripts partly represents the dynamics of endogenous auxin during somatic embryo development in larch. Taken together, our results provide evidence that GH3 genes play important roles in the crosstalk between auxin and ABA by maintaining auxin homeostasis during somatic embryo development.

Over-Expression of LaMIR166a Promotes Organs Development in Nicotiana benthamiana

Most studies related to the functions of miR165/166 have used Arabidopsis as the experimental material. However, Nicotiana benthamiana Domin is a more ideal research material as its typical stem structure. Additionally, most of the relevant research has focused on the functions of HD-ZIP III genes. As an upstream regulatory factor, the function of miR165/166 needs to be defined more directly. So far, the function of miR165/166 in N. benthamiana has not yet been examined. The Agrobacterium-mediated genetic transformation method was used to transform LaMIR166a from Larix leptolepis overexpression vector into N. benthamiana leaves, and three transgenic lines were obtained after molecular detection. Observation on the one-month seedlings revealed that overexpression of LaMIR166a markedly enhanced the biomass accumulation of N. benthamiana plants. Additionally, growth parameters including root length and basal diameter, lateral root density, stem ground diameter and stem internode length of transgenic plants were significantly higher than in wild type (WT) plants. Microscopic observation of stem slices and root squashes showed that overexpression of LaMIR166a significantly promoted xylem formation and development, and the growth of root hairs, which showed a bent phenotype. The results of the present study suggest that up-regulation of miR166a promotes the growth and development of N. benthamiana plants.

Effects of Radial Growth Rate on Wood and Lumber Properties of 67-Year-Old Japanese Larch (Larix Kaempferi) Trees Planted in Tochigi, Japan

The wood and lumber properties were examined for 67-yr-old Japanese larch (Larix kaempferi) trees with different radial growth rates planted in Tochigi Prefecture, Japan. The trees were categorized into slow-, medium-, and fast-growing groups based on the stem diameter. No significant difference in stresswave velocity of stems, which is closely related with Young’s modulus of wood, was found among three radial growth categories (stem diameter classes). The boundary between juvenile wood (JW) and mature wood (MW) determined by latewood tracheid length (TL) existed about the 20th annual ring from the pith in all sample trees. Significant differences between JW and MW were found in most of examined wood and lumber properties. It was found that trees with fast growth do not always cause lower grade lumberproperties.

Comparative transcriptome analyses reveal candidate genes regulating wood quality in Japanese larch (Larix kaempferi)

We studied the molecular mechanism of the quality traits of wood formation in larch. We used the immature latewood cells of two Japanese larch (Larix kaempferi) clones with significant differences in density and in microfibrillar angle (MFA) as materials to analyze their gene expression profiles. A total of 1735 differentially expressed genes were detected in immature latewood cells of the two clones, among which, 971 were up-regulated and 764 were down-regulated. Digital gene expression profiling analysis revealed that genes encoding transcription factor members NAC66 and R2R3-MYB4, microtubule-associated protein, actin-related protein, cell wall protein members, arabinogalactan protein, Fasciclin-like arabinogalactan protein and glycine-rich protein, and several cell-wall-synthesis genes affected wood density and MFA by regulating latewood formation at transcriptional level. Our study results represent a basis for selection of quality traits and genetic improvement of larch wood.

Cell cytotoxity and anti-glycation activity of taxifolin-rich extract from Japanese larch, Larix kaempferi

The larches, the Larix genus of plants are known as a natural source of taxifolin (dihydroquercetin), and extracts of its taxifolin rich xylem are used in dietary supplements to maintain health. In the present study, to assess biological activities of a methanol extract of the Japanese larch, Larix kaempferi (LK-ME), the effects of LK-ME on cell viability, inflammatory cytokine expression, and glycation were investigated. The effects of taxifolin which is known to be a main compound of LK-ME, and its related flavonoids, quercetin and luteolin were also examined. The results show that taxifolin exhibits lower growth inhibition activity and lesser induction activity of inflammatory cytokines in a human monocyte derived cell line, THP-1 cells, while in vitro anti-glycation activities of taxifolin were inhibiting at comparable levels to those of quercetin and luteolin. The growth inhibition and the cytokine induction activities, and the anti-glycation effects of LK-ME are assumed to have properties similar to taxifolin. The results of high performance liquid chromatography (HPLC) analysis indicated that taxifolin was detected as the main peak of LK-ME at the absorbance of 280 nm, and the concentration of taxifolin was measured as 3.12 mg/ml. The actual concentration of taxifolin in LK-ME is lower than the concentration estimated from the IC50 values calculated by the results of glycation assays, suggesting that other compounds contained in LK-ME are involved in the anti-glycation activity.

Effect of Organic Solvent Extractives on Korean Softwoods Classification Using Near-infrared Spectroscopy

This study analyzed the effect of organic solvent extractives on the classification of wood species via near-infrared spectroscopy (NIR). In our previous research, five species of Korean softwood were classified into three groups (i.e., Cryptomeria japonica (cedar)/Chamaecyparis obtuse (cypress), Pinus densiflora (red pine)/Pinus koraiensis (Korean pine), and Larix kaempferi (Larch)) using an NIR-based principal component analysis method. Similar tendencies of extractive distribution were observed among the three groups in that study. Therefore, in this study, we qualitatively analyzed extractives extracted by an organic solvent and analyzed the NIR spectra in terms of the extractives’ chemical structure and band assignment to determine their effect in more detail. Cedar/cypress showed a similar NIR spectra patterns by removing the extractives at 1695, 1724, and 2291 nm. D-pinitol, which was detected in cedar, contributed to that wavelength. Red pine/Korean pine showed spectra changes at 1616, 1695, 1681, 1705, 1724, 1731, 1765, 1780, and 2300 nm. Diterpenoids and fatty acid, which have a carboxylic group and an aliphatic double bond, contributed to that wavelength. Larch showed a catechin peak in gas chromatography and mass spectroscopy analysis, but it exhibited very small NIR spectra changes. The aromatic bond in larch seemed to have low sensitivity because of the 1st overtone of the O-H bond of the sawdust cellulose. The three groups sorted via NIR spectroscopy in the previous research showed quite different compositions of extractives, in accordance with the NIR band assignment. Thus, organic solvent extractives are expected to affect the classification of wood species using NIR spectroscopy.

Differences in root exudate inputs and rhizosphere effects on soil N transformation between deciduous and evergreen trees

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. 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. 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. 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.

Full-diallel-based analysis of genetic parameters for growth traits in Japanese larch (Larix kaempferi)

Genetic parameters were estimated for tree height (H), diameter at breast height (DBH), and volume from a progeny trial conducted in Japanese larch (Larix kaempferi) in Liaoning, China. A 12 × 12 full-diallel mating design with selfing was adopted, and data were collected in 2005 and 2014 at 20 and 29 years after planting. Based on an analysis of 55 of 144 potential crosses, general combining ability (GCA) and specific combining ability (SCA) were statistically significant for these traits. Variance was larger in SCA than in GCA in 2005, and the ratio of SCA to GCA was lower in 2014. Estimates of narrow-sense heritability were low to moderate, ranging from 0.10 for DBH to 0.14 for H, in 2005 and decreased in all traits except H as the trees aged. The reciprocal effect was not significant. Selfed progeny did not show severe inbreeding depression for survival or growth. The results of this study will facilitate the development of breeding and deployment strategies to increase the efficiency of genetic improvement in Japanese larch.

Functional characterization of LkERF-B2 for improved salt tolerance ability in Arabidopsis thaliana.

The ethylene response factors have been reported to play critical roles in developmental and environmental responses in plants. In the present study, an ERF transcription factor gene was aimed to be identified from Larix kaempferi. Molecular characteristics and function of this gene were further explored. The result showed that a 1344bp ERF transcription factor gene containing initiation and termination codon was obtained by RT-PCR and named LkERF-B2. LkERF-B2 gene encoded 447 amino acids containing a typical AP2/ERF domain. Alignment of predicted amino acid sequence of LkERF-B2 in various plant species showed that this ERF transcription factor was highly homologous (79.0%) with that of Picea sitchensi. To elucidate the function of LkERF-B2, LkERF-B2 overexpression vector was successfully constructed and transformed to Arabidopsis thaliana via dip flower. Compared with control plant, LkERF-B2 overexpressed transgenic A. thaliana showed a significantly higher survival rate under cold, heat, NaCl and drought stresses. NaCl stress analysis revealed that control and transgenic Arabidopsis were both flowering earlier under 100 and 150mM/L NaCl treatment. While under 200-300mM/L NaCl treatment, the growth of control plant was significantly inhibited compared with transgenic A. thaliana. Salt injury rate and salt injury index of transgenic Arabidopsis were lower than those of the control. Further investigation showed that transgenic Arabidopsis exhibited much higher content of chloroplast pigments under different NaCl concentration. Meanwhile, the activity of SOD and POD was also enhanced in transgenic A. thaliana. These results suggested that LkERF-B2 was a key transcription factor and could lead to enhanced salt stress tolerance.

Analytical models of the mechanical properties of Japanese larch (Larix kaempferi (Lamb.) Carr.) based on non-destructive testing and visual grading parameters

ABSTRACT Increasing concern about the rapid proliferation of fungi attacking stands of radiata pine in the north of the Iberian Peninsula has led to a search for alternative conifer species that would be able to replace the affected trees. In this context one of the candidate species is the Japanese larch, a species that has not been structurally characterised within Spanish standards. This study describes several analytical models which make it possible to estimate the strength and rigidity variables of this species, using a combination of non-destructive testing techniques and visual grading parameters. Models were obtained by multiple regressions to estimate the global elasticity modulus (MOEG) and the local elasticity modulus (MOE), including and excluding correction for moisture content. The modulus of rupture (MOR) was also calculated while including and excluding correction for size. When the analytical models were subjected to the relevant corrections they were all less accurate. Estimation of the MOEG (r 2 = 0.66) was slightly more accurate than estimation of the MOE (r 2 = 0.56), and it was far more accurate than estimation of the MOR (r 2 = 0.44).

Evaluating maximum stand density and size–density relationships based on the Competition Density Rule in Korean pines and Japanese larch

Understanding the relationship between size and density is an important issue for stand density management in terms of self-thinning in even-aged stands. This study was conducted to determine the maximum stand density and evaluate the size–density relationship based on the Competition Density Rule (C-D rule) for Korean red pine, Korean white pine, and Japanese larch in Korea. The study area covered permanently monitored plots of even-aged plantations established for investigating and modeling long-term growth changes through silviculture. Data were applied using the first inventory within the permanent plots before implementing artificial thinning according to research design. To predict the maximum stem number by species, the C-D rule was applied, and the three-parameter method was shown to be better than the four-parameter method. According to the results based on the C-D rule with three parameters, stand density index by species was 1041 trees (Korean red pine, Pinus densiflora), 1089 trees (Korean white pine, P. koraiensis), and 1005 trees (Japanese larch, Larix kaempferi) in 25 cm of quadratic mean diameter. In the relationship between the maximum stem number and quadratic mean diameter with log–log scale, the intercept for Korean red pine, Korean white pine, and Japanese larch was 10.317, 10.901, and 11.331, and the slope by species was −1.047, −1.214, and −1.373, respectively. To analyze the size–density relationship, the sample plots were classified based on relative spacing and relative density. In regression analysis with log–log scale using the censored sample plot data, maximum size–density relationship was explained the most with quadratic mean diameter rather than mean stem volume and dominant height.

Community reestablishment and poor body conditions of small mammal assemblages in subtropical afforested ecosystems

Afforestation is one of the high-efficiency practices for the restoration of degraded forest ecosystems and has been increasingly used worldwide. It is crucial to determine the restoration status of wildlife in afforested forests to effectively monitor biodiversity conservation and the self-sustainability of forest ecosystems, as well as to effectively guide the implementation of afforestation projects in the future. China has the largest area of man-made forests around the world, but the effects of the restoration efforts on the faunal diversity in artificial woodlands are unclear. Here, we evaluated the effects of afforestation practices on small mammals in two types of planted forests: Japanese larch (Larix kaempferi, an introduced species) and China Armand pine (Pinus armandii, a native species) plantations, and two reference forests: young- and old-growth forests, at the community, population, and individual levels. The diversity of small mammals did not differ significantly among the four forest types and the population densities of small mammals in two plantations were between the young- and old-growth forests. Collectively, our findings indicated that small mammal assemblages had reestablished in afforested forests. Four body condition indices were measured in the Chinese white-bellied rat (Niviventer confucianus), a predominant species, and differences were found between afforested and reference forests. Chinese white-bellied rats had the lowest body masses and highest endoparasite loads in the Japanese larch planted forest, while body length or carcass mass did not differ among the four forest types. In comparison, study rats had slightly lower body masses and lower endoparasite loads in the China Armand pine planted forest than reference forests. These findings indicated that small mammals inhabiting both types of afforested forests had poor body conditions but these trends were worse in the Japanese larch planted forest, i.e., the introduced species. Given that afforestation is a widespread practice for global forest landscape restoration, we propose two suggestions to guide afforestation efforts and the subsequent management thereof: (1) native species rather than exotic species are preferable for use in afforestation projects, and (2) wildlife diversity in afforested forests should be considered when monitoring the restoration and management of degraded forest ecosystems.

Can needle nitrogen content explain the interspecific difference in ozone sensitivities of photosynthesis between Japanese larch (Larix kaempferi) and Sakhalin fir (Abies sachalinensis)?

Although deciduous and evergreen conifers are expected to utilize needle nitrogen differently, their interspecific differences in the ozone sensitivity remain unclear. We compared the growth and physiological responses to elevated O3 concentrations in deciduous Japanese larch (Larix kaempferi) and evergreen Sakhalin fir (Abies sachalinensis) seedlings. Seedlings of both species were exposed to 62.5 ± 1.95 nmol(O3) mol-1 during the day time in open-top chambers. Elevated O3 had no effect on height or diameter growth in either of the species but suppressed photosynthetic parameters. A decline in photosynthetic nitrogen-use efficiency was observed in both species. However, needle N content in larch was decreased by O3, whereas it was not decreased in fir. Needle N responses to O3 were different between larch and fir seedlings, indicating that the O3 sensitivity of photosynthesis could vary depending on needle N dynamics. We also observed a higher correlation between photosynthesis and needle N even under O3 exposure, particularly in the mass-based relationship with higher accuracy. The result indicated that mass-based needle N could explain difference in O3 sensitivity of photosynthesis between the different leaf habits in larch and fir seedlings.

Stability of B-type natriuretic peptide (BNP) stored under different conditions when measured with the lumipulse assay

The larches, the Larix genus of plants are known as a natural source of taxifolin (dihydroquercetin), and extracts of its taxifolin rich xylem are used in dietary supplements to maintain health. In the present study, to assess biological activities of a methanol extract of the Japanese larch, Larix kaempferi (LK-ME), the effects of LK-ME on cell viability, inflammatory cytokine expression, and glycation were investigated. The effects of taxifolin which is known to be a main compound of LK-ME, and its related flavonoids, quercetin and luteolin were also examined. The results show that taxifolin exhibits lower growth inhibition activity and lesser induction activity of inflammatory cytokines in a human monocyte derived cell line, THP-1 cells, while in vitro anti-glycation activities of taxifolin were inhibiting at comparable levels to those of quercetin and luteolin. The growth inhibition and the cytokine induction activities, and the anti-glycation effects of LK-ME are assumed to have properties similar to taxifolin. The results of high performance liquid chromatography (HPLC) analysis indicated that taxifolin was detected as the main peak of LK-ME at the absorbance of 280 nm, and the concentration of taxifolin was measured as 3.12 mg/ml. The actual concentration of taxifolin in LK-ME is lower than the concentration estimated from the IC50 values calculated by the results of glycation assays, suggesting that other compounds contained in LK-ME are involved in the anti-glycation activity.

Enhanced understory carbon flux components and robustness of net CO2 exchange after thinning in a larch forest in central Japan

Thinning is a necessary procedure for the sustainable management of plantation forests. Thinning has a remarkable influence on forest carbon balance; however, there are limited studies showing the integrated assessment of the effects of thinning on several understory carbon flux components using long-term monitoring data. We measured understory flux components using automated chambers continuously over 12 years to understand the effects of forest thinning conducted in May 2014 and March 2015 and to elucidate the effect of short-term climate change on understory carbon balance in a Japanese larch (Larix kaempferi Sarg.) forest in central Japan. Although thinning (39% decrease in tree stems) increased the mean annual soil moisture by 16.5% and growing season soil temperature by 2.4%, large inter-annual variations in precipitation and soil temperature largely masked the effects of thinning on both soil respiration (Rs) and soil heterotrophic respiration (Rh). Annual mean soil temperature was positively related to all annual efflux components. Thinning also increased the understory photosynthetic photon flux density (PPFDu) by 63.1% during the growing season (May to October). In post-thinning years, the average three-year understory photosynthesis (GPPu), understory plant respiration (Rp), and total understory respiration (Ru) increased significantly by 59.5%, 99.7%, and 26.9%, respectively. The net understory CO2 exchange (NUE = Ru − GPPu) changed significantly only in 2015 (13.8%). A marginally significant change in NUE based on the three-year average in post-thinning years was also detected (14.4%). Our results indicated each flux component (especially GPPu, Rp, and Ru) changed dramatically after thinning. In contrast, the NUE of this forest was relatively more robust than other enhanced understory flux components. However, the marginally significant increase of NUE (3-year average in post-thinning years) implied a slight increase in NUE after thinning.

First Report of Damping-Off Caused by Dactylonectria pauciseptatum in Larch (Larix kaempferi) in Korea

First Report of Damping-Off Caused by Dactylonectria pauciseptatum in Larch (Larix kaempferi) in Korea