We measured the growth and mass increment of 2-year-old containerized Japanese cypress (Chamaecyparis obtusa) seedlings for 2 years after planting and compared them with those of bare-root seedlings. We also clarified the influence of nursery application of slow-release fertilizer, which is eluted over long periods, on the initial growth of planted-out C. obtusa seedlings. We grew containerized seedlings for 1 year in multi-cavity containers with slow-release fertilizer with a 700-day elution period. At planting, the containerized seedlings were smaller in root collar diameter (hereafter, diameter) and taller, with a greater height-to-diameter ratio, than bare-root seedlings. Height and diameter 2 years after planting were bigger, and growth of both parameters during the first 2 years was higher, in the containerized seedlings. The height-to-diameter ratio of the containerized seedlings dropped rapidly in the first year. Increases in the leaf, stem, branch, and root mass were steeper in the containerized seedlings, but there was no difference in the top-root ratio between the two types of seedlings. The relative height and diameter growth rate of the containerized seedlings was superior in the first year, but this superiority became less clear in the second year. Slow-release fertilizer use in nurseries therefore improves the initial growth of C. obtusa seedlings, although its influence decreases with time.
Seeking measures to address pollinosis caused by pollen from the Japanese cypress, we searched for a sterile staminate individual. We discovered an individual with staminate flowers that did not release pollen, in a Japanese cypress forest in Kanagawa Prefecture. To check whether pollen is released, after bagging the branch with staminate flowers and pouring water in, we found that the microsporangia did not open and no pollen was released at all, even after the typical release period. An optical microscope revealed particles larger and smaller than normal pollen inside the microsporangia. An electron microscope revealed orbicules inside the microsporangia on the pollen surface, similar to normal pollen, although normal pollen was not found. When investigating seed fertility, cones were found to be small in size and abnormally shaped. The rooting rate of cuttings was 70%, and clonal growth succeeded. No pollen was released from the staminate flowers of the cloned tree, showing that sterility traits were reproducible in the cloned individual. There were 22 chromosomes for both the selected individual and normal individual. From observation of the pollen tetrad period, it was hypothesized that the staminate sterility traits were caused by unequal division at the time of meiosis. Based on the condition of staminate flowers and cones, it was concluded that sterility had been confirmed in both the staminate and pistillate flowers.
Forest dynamics can be documented in detail by repeatedly measuring permanent plots. The Japanese National Forest Inventory (NFI) aims to estimate forest resources and dynamics over large regions. NFI plots were established on a 4-km national grid and were expected to be re-measured every 5 years. In private forests of the Toyama Prefecture, a plot was established during the first NFI in each of the 101 grid points (1999－2003) . To clarify data availability for analyzing forest dynamics at a prefecture level, this study examined whether these 101 plots had been re-measured until the third NFI (2009－2013) . Twelve plots were abandoned because of difficulty in accessibility; thus, the third NFI measurement was not performed. During the second or third NFI measurement, locations of 11 plots could not be found; thus, alternative new plots were established at different locations. Plot shapes were converted from square to circle at a single location in 20 plots. Data from these transformed plots can sometimes be regarded as equivalent to data from re-measuring plots. Only 58 plots were re-measured; therefore, data were flawed regarding analysis of forest dynamics. Provisions for future NFI measurement to enhance data continuity and availability were discussed.
To ensure the quality of seeds produced from a seed orchard composed of Hinoki (Chamaecyparis obtusa) with few male flowers, pollen contamination from outside the orchard must be reduced. We established two seasonal plastic-house seed orchards (SPH seed orchard) and an outdoor seed orchard, and compared pollen contamination rates. An alternative method to reduce pollen contamination is polycrossing. In this study, progeny from polycrossed C. obtusa, in which three mixtures from three paternal donors were crossed with each of three maternal parents, were analyzed to detect departures from equal paternal contribution. In the results of this study, SPH seed orchards were effective to reduce pollen contamination rate. However, the SPH seed orchard that had its plastic cover removed earliest resulted in high contamination rates and low seed germination rates. On the other hand, there was no pollen contamination in seedlings produced from polycrossed female strobili covered by nonwoven bags. In addition, the clone with the lowest pollen germination rate did not show low paternal contribution in the polycrossing. Therefore, polycrossing using nonwoven bags was more effective in reducing pollen contamination than SPH seed orchards to produce seeds of C. obtusa with few male flowers.
Conditions of regeneration in gaps formed because of mass mortality of oak trees were compared inside and outside a deer-proof fence to clarify how sika deer (Cervus nippon) affect the regeneration. Fourteen species, including Zanthoxylum ailanthoides, Mallotus japonicus, Quercus glauca, and Padus grayana, regenerated and reached a height of ≥1.3 m inside the fence. Conversely, only two species-Triadica sebifera and Symplocos prunifolia-that were little consumed by deer regenerated to a height of ≥1.3 m outside the fence. Among the saplings that grew to heights of <1.3 m, 34 species, including Rubus microphyllus and Carpinus tschonoskii, were found inside the fence, whereas seven species were found outside; all saplings outside the fence were <10 cm tall. New seedlings and sprouts were also found outside the fence. These results suggested that only a small number of specific species might regenerate under the pressure of deer foraging after the mass mortality of oak trees.
Edited and published by : The Japanese Forest Society Produced and listed by : Center for Academic Publications Japan/Shobi printing Co., Ltd. (Vol.96 No.2-) Center for Academic Publications Japan/Fukasawa Ltd. (Vol.91 No.3-Vol.96 No.1) Center for Academic Publications Japan/Daishowa Printing Co., Ltd(Vol.88 No.1-Vol.91 No.2)