Miyakejima Island Research Articles

Effects of skeleton-type erosion control greening materials on preventing soil erosion and vegetation recovery on Miyakejima island

Effects of skeleton-type erosion control greening materials on preventing soil erosion and vegetation recovery on Miyakejima island

Hundreds of billions of silent outbreaks: A historic outbreak record of the gall midge Schizomyia castanopsisae (Diptera: Cecidomyiidae) on the Izu Islands, Tokyo, Japan, and its potential mechanism

AbstractHerbivore outbreaks cause serious damage to forest trees. In recent decades, outbreaks of the gall midge Schizomyia castanopsisae (Diptera: Cecidomyiidae) inducing inflorescence galls on Castanopsis sieboldii (Fagaceae) occurred in the Izu Islands, Tokyo, Japan. We investigated the gall density on the islands and estimated the larval population on Miyakejima Island. We also surveyed seasonal changes in larval age structure, presence of natural enemies, larval cold tolerance, and thermal effects on the adult emergence. In addition, we conducted molecular phylogenetic analyses of S. castanopsisae populations among different localities. The gall density was particularly high in southern parts (from Miyakejima to Aogashima) of the Izu Islands. The gall midge seemed to have been expanding its range toward northern parts in recent years. On Miyakejima, the larval population was estimated to be approximately 158 and 36 bn in 2017 and 2018, respectively. Parasitoids were not found in the dissection of galls. A cold temperature treatment did not affect the percentage of adult emergence. Developmental zero and thermal constant during the period from larval departure to adult emergence were estimated to be 4.7°C and 588.2°C‐days in males and 7.4°C and 476.2°C‐days in females, and the adults were predicted to emerge in April. Populations in Kyushu were genetically distinct from those in Okinawajima and the Izu Islands, but a common haplotype was found between the latter two localities. These imply that S. castanopsisae on the Izu Islands may be a recent invasion, and the absence of natural enemies causes its outbreaks.

Photosynthetic Properties of Co-Occurring Pioneer Species on Volcanically Devastated Sites in Miyake-jima Island, Japan.

Pioneer species differing in their inherent ecological characteristics (e.g., N-fixing ability, photosynthetic pathway) can have a large impact on local ecosystems in the early stages of volcanic succession. However, it remains unclear as to how these pioneer species adapt to the extreme environment of volcanically devastated sites in terms of ecophysiological leaf traits. In this study, we compared the leaf traits (including morphological, physiological) of three co-occurring pioneer species, including a C4 non-N-fixing grass, a C3 N-fixing tree, and a C3 non-N-fixing herb from a newly created (18 years after eruption) volcanically devastated site in Miyake-jima, Japan. Our results showed that three pioneer species have different sets of leaf traits that are associated with their ecophysiological growth advantages, respectively. Miscanthus condensatus shows the highest light-saturated photosynthetic rate (Amax). The higher Amax were partially the result of higher water use efficiency (WUE) and photosynthetic N-use efficiency (PNUE). The PNUE in M. condensatus appears to be high, even for a C4 grass. Alnus sieboldiana rely on its N-fixing ability, has a higher leaf N content (Narea) that compensates for its photosynthetic machinery (Rubisco), and further ensures its photosynthetic capacity. Fallopia japonica var. hachidyoensis has a higher leaf mass per area (LMA), chlorophyll content (Chl), and maximum quantum yield of PSII (Fv/Fm), demonstrating its higher light capturing ability. These results make it possible to predict certain ecological processes that take place in the early stages of volcanic succession resulting from ecological characteristics and from some key leaf traits of pioneer species. It also provides a theoretical basis for species selection and species combination for volcanic ecological restoration.

Changes in Soil Physical and Chemical Properties during Vegetation Succession on Miyake-jima Island

The bare lands formed after volcanic eruptions provide an excellent opportunity to study the interactions between vegetation succession and soil formation. To explore the changes in soil physicochemical properties in the vegetation succession processes and the relationship between them, soil physicochemical properties of different volcanic ash accumulation on Miyake-jima Island were studied at different vegetation succession stages. The results showed that soil bulk density gradually decreased and that soil porosity, soil water content (SWC), pH, cation exchange capacity (CEC), soil total organic carbon (TOC), and total nitrogen (TN) increased significantly with vegetation succession. The physicochemical properties changes in the soil surface horizon were most obvious, and the deep soil accumulated a large amount of relatively stable soil carbon and nitrogen. The forest land formed a thicker organic matter horizon, accumulating more carbon and nitrogen than grassland, and the soil quality index (SQI) was higher than that of grassland and shrubland. In conclusion, our research indicates the significant change in soil physicochemical properties and the improvement in soil quality in the vegetation succession processes, emphasizing a significant relationship between vegetation succession and soil development in bare land.

Hydrothermal and Magmatic System of a Volcanic Island Inferred From Magnetotellurics, Seismicity, Self‐potential, and Thermal Image: An Example of Miyakejima (Japan)

AbstractPhreatic and phreatomagmatic eruptions represent some of the greatest hazards occurring on volcanoes. They result from complex interactions at a depth between rock, water, and magmatic fluids. Understanding and assessing such processes remain a challenging task, notably because a large‐scale characterization of volcanic edifices is often lacking. Here we focused on Miyakejima Island, an inhabited 8‐km‐wide stratovolcano with regular phreatomagmatic activity. We imaged its plumbing system through a combination of four geophysical techniques: magnetotellurics, seismicity, self‐potential, and thermal image. We thus propose the first comprehensive interpretation of the volcanic island in terms of rock properties, temperature, fluid content, and fluid flow. We identify a shallow aquifer lying above a clay cap (<1 km depth) and reveal its relation with magmatic‐tectonic features and past eruptive activity. At greater depths (2–4.5 km), we infer a seismogenic resistive region interpreted as a magmatic gas‐rich reservoir (≥370°C). From this reservoir, gases rise through a fractured conduit before being released in the fumarolic area at ∼180°C. During their ascent, these hot fluids cross a ∼1.2‐km‐long liquid‐dominated zone causing local steam explosions. Such magmatic‐hydrothermal interaction elucidates (i) the origin of the long‐period seismic events and (ii) the mixing mechanism between magmatic and hydrothermal fluids, which was previously observed in the geochemical signature of fumaroles. Our results demonstrate that combining multidisciplinary large‐scale methods is a relevant approach to better understand volcanic systems, with implications for monitoring strategies.

Photosynthetic Properties of Miscanthus condensatus at Volcanically Devastated Sites on Miyake-jima Island.

How photosynthetic-related leaf traits of non-nitrogen (N)-fixing pioneer species respond to extreme habitat conditions of primary succession is still not well-elucidated, especially in volcanically N-deplete habitats. The effect of N-deplete soil on photosynthetic-related leaf traits can provide a basis for predicting how plants adjust their strategies to adapt to such habitats. To examine the responses of leaf traits to extreme conditions, we investigated Miscanthus condensatus (a non-N-fixing C4 pioneer grass) which grows on a volcanically devastated area on Miyake-jima Island, Japan, in which the volcanic ash has been deposited for 17–18 years since the 2000-year eruption. Leaf N content (Narea), light-saturated photosynthetic rate (Amax), and photosynthetic N use efficiency (PNUE) in three contrasting study sites: bare land (BL), shrub land gap (SLG), and shrub land under canopy (SLUC) were determined. Results indicated that compared to previous studies and internal comparison of Miyake Island, M. condensatus in BL was able to maintain a relatively high Amax, Narea and PNUE. The higher Amax was in part a result of the higher PNUE. This is a characteristic necessary for its successful growth in N-deplete soils. These results suggest that M. condensatus has photosynthetic-related advantages for adaptation to volcanically N-deplete habitats.

Hyperxiphia hirashimai, comb. n. (Hymenoptera, Xiphydriidae) from southern Japan: remarkable sexual dimorphism revealed by DNA barcodes and new distribution records.

Based on a study of the type material, Genaxiphia hirashimai Okutani, 1965, a southern Japanese xiphydriid showing remarkable sexual dimorphism, is newly combined with the genus Hyperxiphia Maa, 1949. The previously unknown female is described, and the male is redescribed with additional material. The sexes are associated by examination of specimens of both sexes that apparently emerged from the same piece of branch and by a molecular analysis using mitochondrial COI sequences. Hyperxiphia hirashimai, originally described from Amami-oshima Island, is newly recorded from Miyake-jima Island, southwestern Shikoku, southern Kyushu, Yakushima, Kuroshima and Okinawa-jima Islands.

Larvae and juveniles of two Brotula species (Ophidiiformes: Ophidiidae) collected from the Northwest Pacific Ocean

Larva and juveniles belonging to two ophidiid species of the genus Brotula Cuvier 1829, Brotula sp. 1 [3 specimens, 14.2, 50.7, and 55.7 mm in standard length (SL)] and Brotula sp. 2 (1 specimen, 47.8 mm SL), were collected from the Northwest Pacific Ocean off the Okinawa, Izu (Aoga-shima Island and Miyake-jima Island), and Ogasawara Islands, Japan. Although the counts and proportions of both species agree with the documented ranges of Brotula multibarbata Temminck and Schlegel 1846 known from Japan, the larva and juveniles are clearly different from each other by the following combination of characters: counts of dorsal-fin rays [Brotula sp. 1, 122–126 (about 130 in the larva) vs. Brotula sp. 2, 118], anal-fin rays [94–101 (106) vs. 85], caudal-fin rays (11 vs. 9), and vertebrae (14 + 45–46 = 59–60 vs. 16 + 42 = 58); position of dorsal-fin origin [above or posterior to pectoral-fin base (above 6th vertebra) vs. anterior to pectoral-fin base (above 3rd vertebra)]; predorsal length (56.5–59.8% vs. 51.0% of preanal-fin length); blackish spots behind eye (present vs. absent); brown spots on body and vertical fins (present vs. absent); size of pectoral fin [small, not reaching anus (13.5–13.7% of SL) vs. large, reaching anus (28.3% of SL)]; and length between dorsal- and anal-fin origins (22.7–24.6% vs. 31.3% of SL). The occurrence of the larva and juveniles suggests that “B. multibarbata” known from Japan represents two species: Brotula sp. 1 and Brotula sp. 2 are probably B. multibarbata and Brotula formosae Jordan and Evermann 1902, respectively; the former is currently regarded as the senior synonym of the latter. In addition, this study describes for the first time the living coloration of Brotula larva.

Relationship between Vegetation Structure and Avian Communities on Miyakejima Island, Japan, 13 Years after a Major Volcanic Eruption1

Volcanic eruptions can have significant impacts on plant and animal communities. Thus, it is important to understand the recovery process following these eruptions, particularly on isolated islands, in order to assist with biodiversity management and conservation. We studied relationships between vegetation structure and avian species composition on Miyakejima Island, Japan, where a volcanic eruption in 2000 destroyed almost half of the vegetated land. Bird species and nine vegetation variables were surveyed at 24 sampling sites from 2011 to 2014. The results showed that avian species composition mainly varied along two vegetation variables, namely plant species richness and total basal area of all tree species. Bird species were classified into four groups, that is, grassland species, widely distributed species, developing-forest species, and developed-forest species. Developed-forest species were only recorded at the sites where vegetation height was more than 10 m. The relationship between developed-forest bird abundance and vegetation height was similar to that between total basal area of all tree species and vegetation height. The restoration of mature evergreen forest is essential to conserve avian diversity on the island, and natural seed dispersal by birds plays an important role in supporting forest restoration after a major disturbance.

Effects of Sulfur Dioxide on Fractional Exhaled Nitric Oxide Concentration in the Child Residents of Miyakejima Island

The island of Miyakejima in Japan is subject to ongoing emissions of volcanic gases, including high concentrations of sulfur dioxide (SO2). Annual health checkups on the island, therefore, include the examination of respiratory system parameters. Here, we aimed to investigate the relationship between SO2 exposure and fractional exhaled nitric oxide (FeNO) concentration among children who received health checkups from 2008 to 2014. The subjects were 83 and 31 second-year junior high school students aged 13–14 years who resided on Miyakejima island and an SO2-free reference island, respectively. SO2 concentration in the air was measured at 6 fixed-point monitoring stations. FeNO was examined according to the American Thoracic Society guideline and European Respiratory Society recommendations for standardized procedures. Average concentrations of SO2 on Miyakejima over a period of 3 months prior to each health checkup from 2008 to 2014 were 22.2, 20.6, 8.9, 10.5, 10.7, 4.4 and 8.0 ppb, respectively. Among the Miyakejima students, geometric mean (GM) FeNO concentrations measured at each health checkup from 2008 to 2014 were 28.2, 18.2, 23.6, 35.5, 36.9, 28.1, and 32.1 ppb. The GM FeNO concentration measured from all Miyakejima students across the study period was 28.3ppb. No clear dose-response relationship was observed. The GM FeNO concentration among the students from the reference island was 27.7ppb in 2017. No significant difference was observed between the two populations, even when the data was stratified by sex and sensitivity. There was no clear significant difference in GM of FeNO concentration between Miyakejima and control students, when the average concentration of SO2 over a period of 3 months was 22ppb or less.

Characteristics of an atypical large-meander path of the Kuroshio current south of Japan formed in September 2017

Since September 2017, the Kuroshio has taken a large-meander (LM) path in the region south of Japan. We examined characteristics of the 2017–present LM path in comparison with previous LM paths, using tide gauge, altimetric sea surface height, and bottom pressure data. The 2017–present LM path was formed from a path passing through a channel south of Hachijo-jima Island, while a typical LM path originated from a path through a channel north of Miyake-jima Island. The meander trough of this atypical path was found to be shifted far to the east and to vary on a timescale of months. These characteristics are different from those of a typical LM path but they are similar to those of the 1981–1984 LM path. Therefore, we identified two types of LM path; a stable and unstable LM paths. The 2017–present unstable type large meander has a zonal scale greater than that of the 2004–2005 stable type large meander and protrudes from the eastern boundary of the Shikoku Basin, i.e., Izu-Ogasawara Ridge. No significant bottom pressure depression was observed, associated with the formation of the 2017–present LM path, indicating that baroclinic instability was not important in the formation of this LM path. Due to no significant bottom steering, even during the 2017–present LM period, a mesoscale current path disturbance occurred southeast of Kyushu, propagated eastward, and amplified the offshore displacement of the Kuroshio.

Soil Net Nitrogen Mineralization at Different Ecosystem Development Stages after the Year 2000 Eruption on Miyakejima Island

Soil nitrogen (N) mineralization is a central process in the N cycle in terrestrial ecosystems. Previously many studies were conducted on soil N mineralization in terrestrial ecosystems, but those studies remain unclear due to large spatial and temporal variations. In present study soil N mineralization rates were measured in situ by using a resin core technique. The study reports the relationship of these rates with environmental factors at ten sites with various vegetation and soil properties which formed after the latest eruption in year 2000 on a volcanic island, Miyakejima. Miyakejima has diverse ecosystems, from grasslands with little soil organic matter to mature forests. With little damage from the year 2000 eruption, it is suitable for exploration of spatial and temporal variations in soil N mineralization. Annual soil N mineralization rates ranged from 0.9 to 52.5 kg N ha-1 yr-1 and were higher in the presence of the N-fixing vegetation Alnus sieboldiana. Present study data along with other data obtained from insitu observation suggested that soil C/N ratio can be a good indicator of annual soil N mineralization rate, like many previous studies pointed out; however, the relationship between the rate and soil C/N ratio was complicated due to some factors, such as existence of N-fixing vegetation and high sulfur dioxide gas exposure.

Influence of sulfur dioxide on the respiratory system of Miyakejima adult residents 6 years after returning to the island.

Mount Oyama, on the Japanese island of Miyakejima, began erupting in June 2000, necessitating the evacuation of 3,000 island residents. Volcanic gas emissions, primarily consisting of sulfur dioxide (SO2), gradually decreased and residents returned to the island after the evacuation order was lifted in February 2005. To assess the exposure-effect and exposure-response relationships between SO2 exposure and effects on respiratory system in adult Miyakejima residents. Health checkups focusing on pulmonary function and respiratory/irritative symptoms were conducted six times every November from 2006 to 2011. The study population comprised 168 subjects who underwent all health checkups. SO2 concentrations were measured at six fixed monitoring stations in inhabitable areas. Based on the annual mean SO2 concentration, inhabitable areas were classified into three categories; namely, lower (L), higher (H-1), and highest (H-2) areas. Average SO2 concentrations (ppb) during 3 months prior to each health checkup dropped from 11.3 to 3.29, 32.2 to 13.4 and 75.1 to 12.6 from 2006 to 2010/2011 in L, H-1, and H-2. No significant declines in pulmonary function were observed in all areas. However, prevalence of subjective symptoms such as "Cough," "Irritation and/or pain in throat," "Irritation, runny nose, and/or nasal sniffles," and "Irritation and/or pain in the eyes," dependently increased on SO2 concentration. Odds ratios were statistically significant at approximately 70 ppb of SO2 or above. Adult residents of Miyakejima island showed no deterioration in pulmonary function at SO2 levels, but complained of respiratory/irritative symptoms in an SO2 concentration-dependent manner.

The characterization of Herbaspirillum- like strains isolated from recent volcanic deposits in Miyake-jima Island(The annal Meeting of the Society in 2007)

The characterization of Herbaspirillum- like strains isolated from recent volcanic deposits in Miyake-jima Island(The annal Meeting of the Society in 2007)

三宅島2000年噴火後の植生変化( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島2000年噴火後の植生変化( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

植物の繁殖に関わる生物間相互作用 : ヤブツバキとメジロが三宅島の森林生態系回復に果たす役割( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

植物の繁殖に関わる生物間相互作用 : ヤブツバキとメジロが三宅島の森林生態系回復に果たす役割( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島2000年噴火後の生態系の回復過程から学ぶ( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島2000年噴火後の生態系の回復過程から学ぶ( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

初成土壌環境における微生物 : 三宅島土壌生態系再生のメカニズムを探る( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

初成土壌環境における微生物 : 三宅島土壌生態系再生のメカニズムを探る( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島の火山灰堆積地における発達程度の異なる植生が炭素蓄積量と土壌構造発達に与える影響( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島の火山灰堆積地における発達程度の異なる植生が炭素蓄積量と土壌構造発達に与える影響( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島2000年噴火後の植生の退行・回復にともなう鳥類群集の変化( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)

三宅島2000年噴火後の植生の退行・回復にともなう鳥類群集の変化( 三宅島2000年噴火後の生態系の回復過程-巨大噴火に対する陸上生態系の応答-)