Short communication: Initial Growth of Japanese Cedar and Hinoki Cypress Saplings Using Biodegradable Nonwoven Fabric Pot during 2 Years after Planting
Authors: Fumiaki Kitahara, Atsushi Sakai, Reiji Yoneda
Vol. No. Page：Vol. 102 No. 4, pp. 263-269 (2020)
The authors and their institution have requested to withdraw the above short communication. Editorial board of the Journal of the Japanese Forest Society have thought about the their request, and we retracted the above short communication.
We investigated the systems used to supply fuel chips to 10 small gasification combined heat and power (CHP) plants, to assess the dried fuel chip supply system in Japan. The supply systems could be categorized into six patterns based on where and by whom artificial drying was conducted, which was the main drying method in the surveyed cases. In all six patterns, the CHP operators were the main agents in drying. They purchased undried chips or produced and dried chips themselves. Intermediate companies, such as chip producers or distributors, made limited contributions to drying, but there was no well-developed dried fuel chip supply system. The main reason for the limited contribution of intermediate companies was the current chip price usually does not cover the cost of drying, and the companies want adequate pricing. To enable this, the CHP operators would need to generate revenue through the sale of heat from the CHP facility, which is currently used for drying. We recognized new approaches, such as a dried chip distribution system developed by a CHP facility vendor or a chip-drying business that uses the surplus heat to dry chips. These new activities could provide dried chips in areas where intermediate companies cannot.
Wilting has been observed in clean Larch softwood cuttings after sticking. We examined the effects of the following on the wilting of cuttings in 15 nurseries: (1) rainfall for stock plants, (2) number of days since sticking, and (3) temperature, relative humidity (RH), humidity deficit, and light intensity on the propagation bed. Time-lapse photography was used for visual assessments of wilting. According to the ordered logistic regression model, the rainfall for stock plants, number of days since sticking, and temperature were significant factors associated with the degree of wilting. Seventy-two-hours precipitation before harvesting the cuttings was significantly positively associated with the intensity of wilting during 10 days after sticking. Also, the degree of wilting was extraordinarily high on the third day after sticking, but it gradually decreased with the passage of days. As a result of estimating the relationship between the degree of wilting and environmental conditions of the propagation bed by Bayesian models, high wilting would occur at a temperature of ＞29.9 ℃, RH ＜73％, and humidity deficit ＞9.2 g/m3.
Factors affecting the growth and survival of planted seedlings were essential information for the establishment of methods to change a coniferous plantation into conifer-broadleaved mixed forest. To reveal these factors, three deciduous trees (Castanea crenata, Cerasus jamasakura, and Quercus serrata) were planted in the different densities (1,000, 1,500, or 2,000 seedlings per ha) and methods (single tree mixed planting or single planting) in the small-scale clear-cut Hinoki cypress plantations in Hyogo Prefecture, and the growth and survival of the planted seedlings were analyzed. The canopy openness and the previous year's diameter at ground height (DGH) had a positive effect on the growth of three deciduous trees, but the soil water content had a negative effect on three deciduous trees. In terms of the survival rate, the previous year's DGH had a positive effect on three deciduous trees, and the canopy openness had a positive effect on C. crenata, and a negative effect on C. jamasakura and Q. serrata. In the single planting plot of Q. serrata, there was a large difference in the stand basal area after five years of planting among sites with different topography. In the mixed planting plot, the difference was not as large as in the single planting plot of Q. serrata, and the higher the planting density, the larger the stand basal area after five years of planting. It was suggested that the low growth and survival of seedlings could be avoided by planting multiple tree species with different response to environment, and that planting 2,000 seedlings per ha, which was the highest density among tested, was the optimal from the viewpoint of resultant stand basal area after five years of planting.
Although line-thinning is recommended for coastal forest, no study has examined the effects of line-thinning on a densely planted coastal forest. To examine the effect of the first line-thinning, we established line- and zigzag-thinning plots and un-thinned plots in a coastal Larix gmelinii var. japonica stand in Hokkaido, in 2014. During line-thinning, one line was thinned and two lines were preserved. We measured the diameter at breast height and tree height of living trees in the plots in 2014 just before thinning, and in 2017 and 2020. Hemispherical photographs were taken in 2015 and 2020 to evaluate canopy gap closure. Wind speed was measured in the gap in two thinned plots and under the canopy in the control plot. The thinning effects of line- and zigzag-thinning were the same for improved diameter growth. Although the canopy remained open in the line-thinning plots after 6 years, a thinning effect was observed only for the first 3 years. No strong winds were observed in the gaps in either line- or zigzag-thinning plots. These results imply that more trees should be removed if we expect a persistent thinning effect. However, there is no concern about wind damage when thinning a young coastal stand.
To improve the performance of pinewood nematode-resistance of seedlings obtained from the nematode-resistant seed orchards, it is important to examine the relative implications of several factors affecting the performance that previous studies have highlighted. We evaluated the resistance of seedlings collected from 64 mother trees of 22 nematode-resistant Japanese red pine (Pinus densiflora) clones planted at six nematode-resistant seed orchards, which are different ages and consisted of different clones. After the nematode-inoculation tests, the soundness rate of two-year-old seedlings exhibited highly positive correlation with the resistance ranking of the mother clone in most of orchards in two times of the trial. Paternity analyses for the seedlings based on eight nuclear microsatellite markers showed that seedlings collected in the orchards younger than ten years old had higher percentages of external paternity and lower sound tree rates. Generalized linear mixed models showed that the resistance rankings of both the mother clone and the assigned paternal parent had large positive effects on the soundness rate of seedlings, and the proportion of internal paternity, which increased with the orchard age, also had significant positive effects. These results indicate that, to improve the level of the resistance of seedlings, it is effective to (1) change the clones into those with genetically higher resistance and (2) collect seeds at more than fifteen years old or regenerate orchards partially.
A lack of exposure to nature is considered to be detrimental to people's physical and mental health and has been a growing concern in recent years. The global COVID-19 pandemic, which began in 2020, may have changed people's lifestyles and affected their level of interest in experiencing nature. In this study, the effects of these changes to experiencing nature were discussed. We analyzed the changes in Google search volumes from 2016 to 2020 in Japan, and found that searches of keywords related to experiencing nature decreased during the period when a state of emergency was announced in Japan. However, after the declaration of state of emergency was lifted, the search volume of keywords related to experiencing nature remained the same or was higher than before. The results show that in the short term, people's interest in experiencing nature decreased, most likely because they refrained from traveling in order to prevent the spread of COVID-19. However, the long-term interest in experiencing nature, which remained the same or was at a higher level than in previous years, suggests that people's interest has increased since experiencing nature is a good way to avoid the risk of infection from the virus.
We attempted to select heterozygous plus-trees to study a male sterility gene in the Japanese hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.), which is one of the primary tree species that cause pollinosis. Hence, we produced self-pollinated families derived from eight plus-trees. We observed pollen dispersal at the age of 8 years and pollen cell at the age of 9 years. Male sterile trees were found in two self-pollinated families of “Tanzawa 6” and “Tanzawa 7,” at proportions of 22.2％ and 25.0％, respectively. This indicated that these two clones have a male-sterile gene in heterozygotes. All the confirmed male-sterile individuals had no transition from the pollen mother cell stage to the next stage of pollen development. Two self-pollinated male sterile trees in “Tanzawa 7” exhibited normal seed germination, which indicated that they were not female-sterile. These results suggested that these trees are useful for male sterile breeding in Japanese hinoki cypress. However, the seed germination rate and early growth of self-pollinated individuals were inferior to those of other cross-pollinated individuals. Because of the possibility that selfing could also affect pollen cell development, it is essential to perform additional observation using backcross families.