Macrofungal Flora on the Volcano Usu, Deforested by 2000 Eruptions

Article

Mycorrhizal associations in woody plant species at the Mt. Usu volcano, Japan.

We investigated the association between ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi and pioneer woody plant species in areas devastated by the eruption of Mt. Usu, Japan, in 2000. We observed eight woody plant species at the research site, most of which were associated with ECM and/or AM fungi. In particular, dominant woody plant species Populus maximowiczii, Salix hultenii var. angustifolia and Salix sachalinensis were consistently associated with ECM fungi and erratically associated with AM fungi. We found one to six morphotypes in the roots of each ECM host and, on average, two in the roots of each seedling, indicating low ECM fungal diversity. ECM colonization ranged from 17 to 42% of root tips. Using morphotyping and molecular analyses, 15 ECM fungi were identified. ECM fungi differed greatly between hosts. However, Laccaria amethystea, Hebeloma mesophaeum, Thelephora terrestris and other Thelephoraceae had high relative colonization, constituting the majority of the ECM colonization in the roots of each plant species. These ECM fungi may be important for the establishment of pioneer woody plant species and further revegetation at Mt. Usu volcano

The Study on Mycorrhizal Status of Current-Year Acer mono Seedlings

We investigated mycorrhizal status of current-year Acer mono seedlings at different regenerated sites. The arbuscular mycorrhizae (AM) formation degree, spore density, available phosphorus (AP) and total nitrogen (TN) contents of samples were tested. Our results indicated that current-year A. mono seedlings may not be obligatory mycorrhizal species since AM colonization was not found in some of the seedlings in the bare sites. The spore density in the soils can play an important role in AM formation since it has significantly positive correlations with the frequency of vesicles and hyphae. AP and TN contents in the soil also have close relationships with the frequency of hyphae in roots

Morphological Characteristics of Ectomycorrhizas Found in Willow and Poplar Seedlings Established in the Area Devastated by the Volcanic Eruption of Mt.Usu,Hokkaido,Japan in 2000

Article

Damage to Abies koreana seeds by soil-borne fungi on Mount Halla, Korea

Abies koreana Wilson is an endemic tree species that is facing critical population declines in Korea. To identify factors affecting the natural regeneration of A. koreana, we examined the role of seed pathogens in the overwintering survival of seeds in natural seedbeds on Mount Halla, Korea. In September 2003, seeds of A. koreana were placed on seedbeds in the following three types of sites: Sasa dominated, shaded by rocks, or forest floor; seeds were then recovered from beneath the snow cover in April 2004 and were analyzed for the occurrence of harmful microfungi. Racodium therryanum Thuem. was the fungus most often isolated from retrieved seeds and was also the most detrimental of the eight fungal species tested in a pathogenicity trial. In vitro, R. therryanum caused a total loss of germination ability in A. koreana seeds at 0 °C after 100 days. The infection rate of R. therryanum was negatively correlated with the seed germination rate. The infection rate of R. therryanum was highest on the forest floor and increased with the duration of snow cover. The occurrence of R. therryanum was temporally restricted to the period of snow cover and spatially to the thick A0 soil layer on the forest floor. This study suggests that R. therryanum may be a significant factor inhibiting the natural regeneration of A. koreana at the seed stage. Abies koreana Wilson est une espèce d’arbre indigène dont la population décline de façon inquiétante en Corée. Dans le but d’identifier les facteurs qui affectent la régénération naturelle d’A. koreana, nous avons étudié le rôle des pathogènes qui affectent les graines dans la survie des semences après qu’elles aient passé l’hiver dans des lits de germination naturels sur le mont Halla, en Corée. En septembre 2003, des graines d’A. koreana ont été placées sur des lits de germination dans les trois types suivants de sites : dominé par Sasa, à l’ombre de rochers ou sur le parterre forestier. Les graines ont ensuite été récupérées sous le couvert de neige en avril 2004 et examinées pour détecter la présence de champignons microscopiques nocifs. Racodium therryanum Thuem. est le champignon qui a été le plus souvent isolé des graines récupérées et ce champignon était également le plus nuisible des huit champignons testés dans un test de pathogénicité. In vitro, R. therryanum a causé la perte totale du pouvoir de germination des graines d’A. koreana après 100 jours à 0 °C. Le taux d’infection par R. therryanum était négativement corrélé au taux de germination des graines. Le taux d’infection par R. therryanum était le plus élevé sur le parterre forestier et augmentait avec la durée du couvert de neige. L’occurrence de R. therryanum était restreinte dans le temps à la période durant laquelle il y avait un couvert de neige et dans l’espace à l’épais horizon A0 du sol sur le parterre forestier. Cette étude indique que R. therryanum peut être un facteur significatif en inhibant la régénération d’A. koreana dès le stade de la semence

Vegetation and Colonization Status of Mycorrhizal and Endophytic Fungi in Plant Species on Acidic Barren at Crater Basin of Volcano Esan in Hokkaido, Japan

We investigated the colonization status of mycorrhizal and endophytic fungi in roots of plants established on an acidic barren at volcano Esan, Hokkaido, Japan. In total, 87 individuals of 21 plant taxa were investigated in four different vegetation sites and the surrounding area. Ericaceous plants such as Empetrum nigrum var. japonicum, Ledum palustre var. diversipilosum, Vaccinium vitis-idaea var. minus and Loiseleuria procumbens were the main colonizers at the study sites and dominated under even the most severe conditions of low soil moisture and nutrient content. They were associated with ericoid mycorrhizal (ERM) fungi at all vegetation sites and erratically with dark septate endophytic (DSE) fungi. They commonly associated together with arbuscular mycorrhizal (AM) fungi only at sites where Sasa senanensis dominated. Among the ericaceous plants, only Enkianthus campanulatus associated with AM and DSE fungi and had no associations with ERM fungi. Other herbaceous and woody plants associated commonly with AM or erratically with DSE fungi, except for Carex sp. and Polygonum spp. which erratically associated with AM and DSE fungi. Mycorrhizal associations were common in representative vegetation on the crater basin of Mt. Esan. In particular, ERM associations might play a significant role in invasion and establishment of ericaceous plants, and also in the development of plant communities in the harsh environment at Mt. Esan

An Unknown Non-denitrifier Bacterium Isolated from Soil Actively Reduces Nitrous Oxide under High pH Conditions

A nitrous oxide (N2O)-consuming bacterium isolated from farmland soil actively consumed N2O under high pH conditions. An acetylene inhibition assay did not show the denitrification of N-2 to N2O by this bacterium. When N2O was injected as the only nitrogen source, this bacterium did not assimilate NN2O. A polymerise chain reaction demonstrated that this bacterium did not have the typical nosZ gene. This bacterium belonged to Chitinophagaceae, but did not belong to known families that include bacteria with the atypical nosZ. This is the first study to show that a non-denitrifier actively reduces N2O, even under high pH conditions

Scarification with surface soil replacement can promote understory reinitiation as well as the growth of a secondary birch stand

Soil scarification using heavy machinery has been widely used in the assisted natural regeneration of stands with a dense dwarf-bamboo understory in northern Japan. After scarification, birch forests have a high probability of growing, but dwarf-bamboos also recolonize the understory, resulting in the development of single-layered stands with lower levels of transition to the late-successional stage. In this study, we examined the long-term effects of an improved soil scarification practice called replacement treatment, in which the removed surface soil is returned to the scarified area. A previous study showed that the replacement treatment had a positive effect on the initial establishment and growth of birches. The site was remeasured at approximately 20 years of age, and the replaced stand, when compared with the standard scarification stand, had DBH and height values that were 1.5 times greater and stand volume that was 3 times greater. The difference in terms of height growth between the two stands widened especially during the first ten years. Additionally, in the replacement treatment stand the number of initiated saplings had more than doubled (> 100 thousand stems/ ha) and consisted of a diverse range of tree species. We have concluded that the soil replacement treatment is a suitable alternative practice that (1) significantly promotes the growth of birches and (2) promotes the reinitiation of tall-tree species in the understory and the development of the later successional stage