Density effects on the conifer mortality in declining spruce-fir forest in northern Japan: Implication of bark beetle attack to, cause spruce decline

We examined mortality patterns of two conifer species in relation to tree abundance and species composition in a declining spruce-fir forest in Akan National park, Hokkaido, northern Japan. The data taken from eleven 58 m × 58 m square study plots showed that percentage basal area (BA) of dead trees of canopy trees during the last decade was 49% forPicea jezoensis (Sieb. et Zucc.) Carr and 30% forAbies sachalinensis (Fr. Schm.) Masters. InP. jezoensis, percentage basal area (BA) of dead trees was positively related to both BA of its own species and proportion of it to BA of all species, whereas it was not significantly related to both of these variables inA. sachalinensis. Multiple logistic regression with dbh as a confounding factor also indicated that, inP. jezoensis, the proportion of dead stems was positively affected by the stem density of conspecific trees, whereas it was negatively affected by the stem density of the other species in each study plot. However, inA. sachalinensis, the proportion of dead stems was significantly related to neither of these factors. The different mortality pattern between two conifer species suggests that the spruce bark beetle,Ips typographus (L.), which is a serious pest of spruce, may have caused theP. jezoensis decline. Instead of wind-throw or thinning that usually initiate this bark beetle attack, some unknown factors seemed to predispose the trees to insect attack. These unknown factors may also explain the high mortality ofA. sachalinensis in this forest. This research was supported by FFPRI Project, Ministry of Agriculture, Forestry and Fishery.     

Phosphate buffer–extractable organic nitrogen as an index of soil‐N availability for sorghum and pearl millet

The availability of soil nitrogen (N) is usually quantified by the amount of mineralized N as determined after several weeks of soil incubation. Various alternative methods using chemical solvents have been developed to extract the available organic N, which is easily mineralized. We compared one such solution, neutral phosphate buffer (NPB), with conventional incubation and 0.01 M–CaCl₂ extraction, as measures of soil N available to two major cereal crops of the semiarid tropics, based on the total N uptake by plants in a pot experiment. Mineralized N had the highest correlation with N uptake by pearl millet (Pennisetum glaucum L., r = 0.979***) and sorghum (Sorghum bicolor [L.] Moench, r = 0.978***). NPB‐extractable N was also highly correlated with N uptake (pearl millet, r = 0.876***; sorghum, r = 0.872***). Only one major peak was detected when NPB extracts were analyzed using size‐exclusion high‐performance liquid chromatography, regardless of soil properties. In addition, the organic N extracted with NPB was characterized by determining the content of peptidoglycan, the main component of bacterial cell walls. Although the characteristics of NPB‐extractable organic N are still unclear, it offers a promising quick assay of available N.     

Clone identification in Japanese flowering cherry (Prunus subgenus Cerasus) cultivars using nuclear SSR markers

Numerous cultivars of Japanese flowering cherry (Prunus subgenus Cerasus) are recognized, but in many cases they are difficult to distinguish morphologically. Therefore, we evaluated the clonal status of 215 designated cultivars using 17 SSR markers. More than half the cultivars were morphologically distinct and had unique genotypes. However, 22 cultivars were found to consist of multiple clones, which probably originate from the chance seedlings, suggesting that their unique characteristics have not been maintained through propagation by grafting alone. We also identified 23 groups consisting of two or more cultivars with identical genotypes. Most members of these groups were putatively synonymously related and morphologically identical. However, some of them were probably derived from bud sport mutants and had distinct morphologies. SSR marker analysis provided useful insights into the clonal status of the examined Japanese flowering cherry cultivars and proved to be a useful tool for cultivar characterization.     

Development of an air-injection press for preventing blowout of particleboard IV: effects of air-injection conditions on board performance and formaldehyde emission

An air-injection press, which has holes punched in the heating plates, injects high-pressure air through the holes of one plate into particleboard and discharges the air through the other plate during press heating. The press can manufacture particleboard from high-moisture particles by controlling blowout of the boards. In this study, the optimum diameter and spacing of the air-injection holes and the effects of pre- and post-pressing were investigated. An optimum hole diameter was not found for the modulus of rupture and thickness swelling for a spacing of either 25 or 50 mm. In terms of internal bond strength, the optimum diameter of the holes arranged at a spacing of 25 mm was 1 mm, but the internal bond strength was not changed by the diameter of holes spaced 50 mm apart. Air injection under all hole conditions reduced the formaldehyde emission from the board. Pre-pressing was tested for further increase in the modulus of rupture and internal bond strength, but was found to have no effect. More efficient use of the air-injection press was achieved by injecting air from the early stages of pressing.     

Performance of particleboard manufactured using air-injection press I: effects of air-injection press on preventing blowout of board manufactured from low-moisture particles

An air-injection press (AIP) was developed to prevent accidental blowouts of boards during production. In this study, the effects of the AIP on preventing blowouts were investigated by artificially creating a blowout-prone condition, and the press was shown to be effective in preventing blowouts. The modulus of rupture of the boards was almost constant irrespective of pressing time. Longer pressing time resulted in higher internal bond strength when pressed at 170 °C. The thickness swelling of the boards pressed at 170 or 190 °C was almost uniform irrespective of pressing time, and the manufactured boards showed performance similar to those manufactured with an ordinary press. The AIP prevented blowouts sufficiently even when the pressure of the injected air was reduced, and this reduction did not adversely decrease the performance of the boards. Air injection reduced formaldehyde emissions from the board.     

Tolerance to low temperatures of Toxocara cati larvae in chicken muscle tissue

Infectivity of Toxocara cati larvae in muscle tissue of chickens after storage at 4°C and -25°C was assessed in a mouse bioassay to provide information on the risk of meat-borne toxocarosis. Muscle tissue samples of 30-day old T. cati infections were stored at 4°C for 14 and 28 days and at -25°C for 12, 24 and 48h, whereafter, larvae were released by digestion. For each experimental group, the released larvae were inoculated in six mice. After 15 days, mice were euthanized and larval burden was assessed by digestion. In the control group (no storage of the infected chicken meat), 47.9% of the inoculated larvae established in mice, whereas storage of meat at 4°C for 14 days or 28 days reduced the recovery to 24.1% or 3.3%, respectively. Muscle larvae exposed to -25°C for 12, 24 or 48h did not establish in the mice. The observation that larvae retain infective after refrigeration at exposure in 4°C for 28 days, emphasize the zoonotic potential of poultry meat as a causative agent of human toxocarosis.     

Effective pollination period in durian (Durio zibethinus Murr.) and the factors regulating it

The effective pollination period (EPP) of durian was determined by both delayed and bud pollination, during which reproductive factors affecting the EPP, e.g., stigma receptivity, pollen tube growth in the style, and ovule longevity were studied histologically. This study was conducted in three distinct locations in Thailand, namely, the Chantaburi Horticultural Research Center and two private orchards in Chantaburi and Trat provinces. Results from artificial pollination revealed that at anthesis, the durian flower is receptive and has a high fruit set ratio. A mean fruit set of 50% was obtained at anthesis in the private orchard in Chantaburi province. However, the EPP of durian was found to be very short, lasting for only one night; the fruit set from pollination on the morning after anthesis ranged from 0% to 3.4%. No fruit set occurred following pollination 24 or more hours after anthesis. When compared with the flowers of other fruit species, the durian flower has a unique feature in that it blooms overnight; the following morning, there is abscission of all parts of the flower, except the gynoecium. Thus, EPP appears to be synchronized with flower longevity. On the other hand, the durian flower was receptive several hours before anthesis. The results of chemical tests, including the hydrogen peroxide test and Perex-Test^®, for the evaluation of stigma receptivity appeared to be in agreement with the EPP. However, fluorescent microscopy revealed that pollen could germinate even in the stigmas pollinated 48 h after anthesis, but the number of pollen tubes at the top of the style rapidly decreased from 34.6 (at anthesis) to 0.5 (48 h after anthesis). A correlation test demonstrated a higher correlation coefficient between the fruit set and the number of pollen than that between the fruit set and the result of Perex-Test^®. This indicated that pollen tube penetration or elongation in the style was inhibited, probably due to the deterioration of nutritional support from the pistil to the pollen tubes; this can be a limiting factor of the EPP in durian.     

Effects of correcting missing daily feed intake values on the genetic parameters and estimated breeding values for feeding traits in pigs

Daily feed intake (DFI) is an important consideration for improving feed efficiency, but measurements using electronic feeder systems contain many missing and incorrect values. Therefore, we evaluated three methods for correcting missing DFI data (quadratic, orthogonal polynomial, and locally weighted (Loess) regression equations) and assessed the effects of these missing values on the genetic parameters and the estimated breeding values (EBV) for feeding traits. DFI records were obtained from 1622 Duroc pigs, comprising 902 individuals without missing DFI and 720 individuals with missing DFI. The Loess equation was the most suitable method for correcting the missing DFI values in 5–50% randomly deleted datasets among the three equations. Both variance components and heritability for the average DFI (ADFI) did not change because of the missing DFI proportion and Loess correction. In terms of rank correlation and information criteria, Loess correction improved the accuracy of EBV for ADFI compared to randomly deleted cases. These findings indicate that the Loess equation is useful for correcting missing DFI values for individual pigs and that the correction of missing DFI values could be effective for the estimation of breeding values and genetic improvement using EBV for feeding traits.