The Japanese Forestry Society Congress Database

Show abstractHide abstract

The normal growth of many tree species depends on colonization by ectomycorrhizal (ECM) fungi, which improve nutrient absorption from soils. In the early stages of primary succession, available nutrients such as nitrogen are quite limited. Thus, ECM fungi strongly influence the survival and growth of host plants in these severe environments. On the south-east side of Mt. Fuji, the vegetation is patchily distributed, like vegetation islands in a sea of volcanic desert, and at elevations from 1,500 to 1,600 m the total vegetation coverage is only 5-6%, indicating an early stage of primary succession. At this site, Salix reinii, an alpine dwarf willow, is distributed in some vegetation patches and is virtually the exclusive ECM host, contributing over 99% of the total ECM hosts. In the present study, we studied ECM colonization on current-year seedlings of pioneer tree species, including Salix reinii, Betula ermanii and Larix kaempferi, and also studied the growth and nutrient content of them. Ectomycorrhizae were almost absent on S. reinii seedlings that were transplanted on bare ground and in willow-absent vegetation patches. On the other hand, seedlings that were transplanted beside mature willows extensively formed ectomycorrhizae, and the growth of them was considerably enhanced. By molecular analyses, the most fungal constituents on these ECM root tips were identified as the species colonizing mature willows, such as Inocybe lacera, Laccaria spp. and Scleroderma bovista. Seedlings of L. kaempferi and B. ermanii also formed ectomycorrhizae beside the mature willows, but not without mature willows. These results indicate that existing mature willows act as ECM inocula for pioneer seedlings and enhance the survival and growth of them, leading the vegetation succession.

View full abstract

Santalum boninense Tuyama is a semi-parasitic shrub. The species is an endangered and endemic species in the Ogasawara (Bonin) Islands. Total number of trees is estimated less than two hundred fifty. For conservation of this species, the real genet number must be estimated, but not the ramet number. It is said that the fruiting scarcely occurs and it is difficult to produce the next generation in nature.The purpose of this study is 1) to clarify distribution of S. boninense and 2) to examine the genetic structure. Six populations were found in the Ogasawara Islands. Three populations are in Chichi Island with 8 to 50 ramets each. The other three are in Haha Islands with 8 to 50 ramets. Haha Island populations have taller trees in the mean than Chichi Island ones. ITS1 has 376bp in the length while ITS2 has 358bp. There are no variations in 71 shrubs in 6 populations in ITS1 and ITS2. The spacer regeon of psbM-trnD in Chloroplast DNA genome consists of 1001bp. The spacer regeon of trnR-trnN in chloroplast DNA is composed of 630bp. No sequence variations were founded in these spacers. No DNA sequence variations in S. boninensis show low gene diversity of this species. The shrubs within a population may composed of one or a few genets. Low or no genetic variation is often related to poor fluiting rate due to imbreeding depression. The rare fluiting of S. boninense may be explained by the low genetic diversity and frequent clonal growth.

View full abstract

Microsatellites, comprising tandemly repeated short nucleotide sequences, are ubiquitous in eukaryotic genomes. The tendency of microsatellites to be codominant and highly polymorphic is a major factor responsible for their popularity as genetic markers for ecological and evolutionary studies.In this study, the high mutation of a microsatellie was shown in leaves collected from different parts from one indvidual of Robinia pseudoacacia, suggesting that it should be checked the mutation carefully before using this kind of markers to investigate individual genotypes and paternity analysis.

View full abstract

A small population of Picea glehnii isolatedly distributing at Mt. Hyachine in Tohoku area suffered considerable losses from mudflow in 1948. At non-mudflow place 78 individuals with DBH>20cm and 62 ones with 20cm>DBH>5cm survive now, while about 130 young trees with DBH>5cm grow at the post-mudflow place. Analysis on genetic diversity of these populations were carried out using microsatellite markers. The population which holds the biggest genetic diversity is the individuals with DBH>20cm at non-mudflow place. In comparison with this population, the population with 20cm>DBH>5cm at non-mudflow place keep 79.2% of allelic numbers and 95.1% of gene diversity, and the population with DBH>5cm at post-mudflow place holds 89.6% of allelic numbers and 90.3% of gene diversity. In both places in non-mudflow and post-mudflow, young generation trees have relatively low level of genetic diversity.

View full abstract

Register with J-STAGE for free!