Periodical stirring is supposed to be an effective method for enhancing transpiration drying of wood chips. An experiment to evaluate the effect of periodical stirring was conducted using container boxes filled with wood chips to a depth of 60 cm. The experiment was carried out at three sites, an outdoor site without shelter from the rain, an indoor site, and a greenhouse site, for 98 days. The enhancement of transpiration drying attributable to weekly stirring of chips was highly significant; chips at the outdoor site that had been stirred exhibited a higher drying rate than the indoor chips that had not been stirred and the indoor chips that had been stirred exhibited a higher drying rate than the greenhouse chips that had not been stirred. Significant transpiration drying was observed up to 10 cm depth despite the lack of stirring. It seems that transpiration drying occurred mainly during the time of stirring because a direct exchange of water content between wet and dry chips was not observed and the drying rate of the stirred chips regardless of depth was observed to be higher than that of non-stirred chips that were deeper than 5 cm. The effect of stirring was estimated to be equivalent to that of a wind blowing with a velocity of 2.8 to 4.6 m/s.

View full abstract

The effects of forest type, topography, and understory vegetation on infiltration rates were investigated in the Tokoro and Abashiri River watersheds, in eastern Hokkaido. This study was performed in order to develop measures for soil and water conservation. Infiltration rates were lower on skidding roads and at felling sites where skidders worked, and were higher in hardwood or mixed natural forests than in plantations of the conifers Abies sachalinensis and Larix kaempferi, which are common in Hokkaido. A higher coverage of understory vegetation resulted in a higher infiltration rate, suggesting that vegetation root growth may increase soil porosity. To promote soil porosity, in the interests of soil and water conservation, mechanized operations by skidders should be minimized and stand density should be controlled to facilitate invasion by hardwood or understory vegetation.

View full abstract

We estimated genetic parameters for basal bending due to snow pressure damage in sugi (Cryptomeria japonica). Using 19 factorial mating designs in 13 progeny trials, we analyzed 160 snow-resistant trees and 23 plus trees. Because the plus trees could be considered to be resistant against snow pressure, they were used as materials together with snow-resistant trees in this study. We measured basal bending at the age 10 of the trials. The results showed that the ratio of additive genetic variance to the total genetic variance was high. Therefore, we concluded that additive genetic variance can be used effectively in the genetic improvement program to reduce basal bending by providing open-pollinated seeds from seed orchards. The mean heritability was 0.11 (range, 0∼0.27). The genetic parameters calculated in this study were estimated from snow-resistant populations. Thus, the parameters should be used (e.g., to estimate the genetic gain) for finding effective and efficient ways to breed against basal bending.

View full abstract

We investigated the germination traits of Fraxnus lanuginosa fruits which were collected in Yamagata Prefecture, in the northern part of Honshu, Japan. While fruits set at 5°C were in quiescence showing negligible germination, more than 90% of germinations were obtained from fruits set at temperatures above 10°C. These results indicate that fruits of F. lanuginousa do not acquire dormancy. Since removal of the pericarp from the seed significantly enhanced the germination rate, intact fruit shows delayed germination due to pericarp. Further experiments on pericarp revealed that germination delay was caused by the hardness of the pericarp which mechanically inhibits the inner embryo from growing. Moist chilling treatment for three months improved germination rate which suggests that cold moist conditions under snow cover during the winter season remove the mechanical inhibition and fruits will germinate simultaneously at the beginning of the following spring. The above result was opposite that in a previous paper using the fruits from Hokkaido showing dormancy; thus geographical variation in germination/dormancy traits might exist in F. lanuginousa fruits.

View full abstract

To determine the invasion and growth processes of natural broadleaved trees in a conifer plantation, and to examine the influence of forest operations on these processes, we investigated the species composition, the number of annual rings at 0.3 m from the ground and annual diameter increments of natural broadleaved trees in an 80-year-old Abies sachalinensis plantation in Hokkaido, northern Japan. Species number and the density of broadleaved trees increased after thinning. The frequency of the number of annual rings at 0.3 m from the ground was apparently high in years following thinnings, except for the first thinning. Therefore, plantation thinning induced natural invasion of broadleaved trees. Furthermore, the diameter increments of many broadleaved trees apparently increased after thinning. Thinning positively influenced the growth of broadleaved trees in the plantation. Mean annual diameter increments differed between late-successional and gap-phase species. The mean diameter increment and increases in the increment after a thinning were larger in gap-phase species than in late-successional species. Additionally, the individual ratio and frequency of apparent increases in diameter increments after thinning were larger in older broadleaved trees. Consequently, we conclude that age and ecological characteristics of broadleaved trees in an Abies sachalinensis plantation influence their growth and the influence of thinning on growth.

View full abstract

An identification of nematode-resistant Japanese black pine (Pinus thunbergii Parl.) clones was developed using SNP (single nucleotide polymorphism) analysis. On the basis of EST (Expressed Sequence Tag) sequence data of maritime pine (Pinus pinaster Ait.), two PCR primer pairs were designed to amplify the two regions in the nuclear DNA. The sequences of all 16 clones were directly determined from the PCR products which were amplified with those primer pairs. As a result, a total of 20 SNP sites were recognized in the two regions. As all 16 clones could be distinguished completely with 9 informative SNPs among 20 SNPs, SNP types of all clones were determined in these sites by using a fluorescence-based primer extension method. A combined system with a multiplex PCR using two primer pairs and a multiplex typing of the nine SNPs was constructed for an efficient analysis. The high reproducibility of this system was confirmed as a result of repeat tests using plural ramets of the clones. The SNP system will make it possible to establish a highly reliable management of nematode-resistant clones.

View full abstract

At the ninth meeting of the Conference of the Parties (COP), scheduled for May 2008 in Bonn, Germany, an in-depth review of the expanded programme of work on forest biological diversity is planned. Historically, forest, as a thematic topic, has been one of the central issues for the Convention. The aim of the in-depth review of the expanded programme of work on forest biological diversity is to promote the further implementation of the programme as opposed to reviewing the programme itself. Procedures for the review are outlined in two decisions, one of which applies to the Convention as a whole (annex to decision VIII/15) and one of which is specific to the expanded programme of work on forest biological diversity (annex to decision VIII/19). The review aims to identify the barriers and priorities relevant to implementation. Japan officially expressed its intention to host COP 10 in 2010. In fulfilling such a leading role, it is necessary to understand the underpinning history and background of the process.

View full abstract

We examined the species composition of soil seed banks (to 5 cm depth), using germination tests, for the Ooyamazawa riparian forest in the Chichibu Mountains. The canopy of this forest is dominated by Fraxinus platypoda. The dominant species in the soil seed bank were Hydrangea macrophylla var. acuminata, Euptelea polyandra and Betula grossa, which existed in the above-ground vegetation, and Buddleja japonica, which was not present in the above-ground vegetation. Of the buried viable seeds, there were few Fraxinus platypoda and a few zoochorous seed plants, such as Actinidia arguta and Rubus phoenicolasius. However, there were many species found in both the buried viable seeds and the current above-ground vegetation. In riparian forests, there are frequent disturbances such as flushing. It is assumed that old seed banks which included zoochorous seeds were lost in the riparian forest, while anemochorous and/or barochorous seeds were provided by parent plants near the riparian forest.

View full abstract