Mitsuru Hirota - Academia.edu (original) (raw)

Papers by Mitsuru Hirota

Forests, 2022

Understory trees occupy a spatially heterogeneous light environment owing to light interception b... more Understory trees occupy a spatially heterogeneous light environment owing to light interception by patchily distributed canopy leaves. We examined the spatial distribution of canopy leaves and the spatial structure of the understory tree community (height < 5 m) and their relationships in a beech forest in Nagano, Japan. We measured the canopy leaf area index (LAI) at 10 m intervals (n = 81) in a permanent research plot (1 ha). We established a circular subplot centered on each LAI measurement point, and determined the species composition and the aboveground net primary production of wood (ANPPW) of the understory tree community by using tree size data from an open database in the Monitoring Sites 1000 project. There was a significant negative correlation between canopy LAI and the ANPPW of understory trees and a significant positive correlation between the ANPPW of understory and understory tree density. The dominant species of understory trees differed between subplots with hig...

available online at www.jpe.oxfordjournals.org Altitudinal variation of ecosystem CO2 fluxes in a... more available online at www.jpe.oxfordjournals.org Altitudinal variation of ecosystem CO2 fluxes in an alpine grassland

Aims Recent studies have recognized the alpine grasslands on the Qing-hai–Tibetan plateau as a si... more Aims Recent studies have recognized the alpine grasslands on the Qing-hai–Tibetan plateau as a significant sink for atmospheric CO2. The carbon-sink strength may differ among grassland ecosystems at var-ious altitudes because of contrasting biotic and physical environ-ments. This study aims (i) to clarify the altitudinal pattern of ecosystem CO2 fluxes, including gross primary production (GPP), daytime ecosystem respiration (Redaytime) and net ecosystem produc-tion (NEP), during the period with peak above-ground biomass; and (ii) to elucidate the effects of biotic and abiotic factors on the altitudinal variation of ecosystem CO2 fluxes. Methods Ecosystem CO2 fluxes and abiotic and biotic environmental factors were measured in an alpine grassland at four altitudes from 3600 to 4200 m along a slope of the Qilian Mountains on the northwestern Qinghai–Tibetan Plateau during the growing season of 2007. We used a closed-chamber method combined with shade screens and an opaque cloth to mea...

available online at www.jpe.oxfordjournals.org Characterization of CO2 flux in three Kobresiamead... more available online at www.jpe.oxfordjournals.org Characterization of CO2 flux in three Kobresiameadows differing in dominant species

Journal of Plant Research, 2021

The American Journal of Gastroenterology, 2013

Journal of Ecosystem & Ecography, 2018

Soil nitrogen (N) mineralization is a central process in the N cycle in terrestrial ecosystems. P... more 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 dat...

The American Journal of Gastroenterology, 2014

Journal of Plant Research, 2021

Forest understory plays an important role in the gross primary production (GPP) of some forest ec... more Forest understory plays an important role in the gross primary production (GPP) of some forest ecosystems. However, differences in understory GPP caused by obviously different overstory canopy structure have not been taken into consideration in previous studies, thus potentially over- or underestimating understory GPP. To estimate the understory GPP more accurately, we separated a forest into "canopy area", with closed-overstory canopy, and "gap area", with open-overstory canopy. The study was conducted in a mature deciduous forest dominated by beech and with an understory dominated by dwarf bamboo, Sasa senanensis. We measured S. senanensis GPP at the community scale (GPPSasa-community) using a static chamber system that covered the aboveground part of the plants and then upscaled it to the ecosystem scale (GPPSasa-ecosystem) by considering the proportions of canopy and gap areas within the forest. GPPSasa-community was 192 g C m-2 year-1 in the canopy area and 699 g C m-2 year-1 in the gap area. The large difference likely occurred because the photosynthetic ability and biomass of the S. senanensis community differed strongly between the two areas. The seasonal dynamics of GPPSasa-community also differed between the areas. The 10-day cumulative GPPSasa-community peaked from July to August in the gap area, whereas there was no clear peak of GPPSasa-community in the canopy area. Multiple linear regressions showed that light intensity and biomass were significant predictors of GPPSasa-community in the canopy area, whereas air temperature and biomass were significant predictors of GPPSasa-community in the gap area. GPPSasa-ecosystem during growing season in 2019 was 3.74 t C ha-1 year-1, which contributed between 16.37 and 19.85% of the entire forest ecosystem GPP. This study highlights the need to consider differences in overstory structure for the accurate estimation of understory GPP.

Forests, 2020

Quantification of leaf area index (LAI) is essential for understanding forest productivity and th... more Quantification of leaf area index (LAI) is essential for understanding forest productivity and the atmosphere–vegetation interface, where the majority of gas and energy exchange occurs. LAI is one of the most difficult plant variables to adequately quantify, owing to large spatial and temporal variability, and few studies have examined the horizontal and vertical distribution of LAI in forest ecosystems. In this study, we demonstrated the LAI distribution in each layer from the understory to canopy using multiple-point measurements (121 points) and examined the relationships among layers in a cool-temperate deciduous forest. LAI at each point, and the spatial distribution of LAI in each layer, varied within the forest. The spatial distribution of LAI in the upper layer was more heterogeneous than that of LAI at the scale of the entire forest. Significant negative correlations were observed between the upper- and lower-layer LAI. Our results indicate that the understory compensates f...

Plants, 2020

How photosynthetic-related leaf traits of non-nitrogen (N)-fixing pioneer species respond to extr... more 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 ...

SIL Proceedings, 1922-2010, 2009

Eeologieal restoration projeets are beeoming more eommon globally, and there is an urgent need fo... more Eeologieal restoration projeets are beeoming more eommon globally, and there is an urgent need for strategies to monitor and assess these projeets. Salt marsh eeosystems in eoastal zones are transitional boundaries between terrestrial and aquatie eeosystems, and they reeeive substantial amounts of anthropogenie nutrients sueh as nitrogen. Beeause nitrogen over-enriehment of saline waters has beeome more widespread on a global seale, an understanding of the nitrogen dynamies of salt marshes is erueial for restoration management of eoastal zones. We are seeking to better understand the nitrogen dynamies of these zones and the levels of emission of nitrous oxide (N20) produeed in nitrogen eycles. lnereased androgenie N20 emissions ean result from sueh events as inereased produetion and use o f nitrogen fertilizers or the eonversion of forests to agrieultural land (SMITH 1997). Nitrous oxide is reeognized as a potent greenhouse gas and a possible intermediate in the destruetion of the stratospherie ozone layer. The atmospherie eoneentration of N20 is eurrently about 31 O ppbv and is inereasing at a rate of 0.6-0.9 ppbv y(PRINN et al. 1990). Although atmospherie N20 eoneentration is lower than that of earbon dioxide (C02) and methane (CH4), N20 is eonsidered to eontribute to future global climate ehange beeause of its long residenee time (130-150 y) and high energy absorption eapaeity per moleeule (K.HALIL & RASMUSSEN 1992). Therefore, N20 emission has attraeted a great deal of attention. Restoration of a wetland was eompleted in February 2006 at Lake Shinji, a lagoon on the eoast of southwestern Honshu, Japan. Our aim was to demonstrate the effeet of eeologieal sueeession on nitrogen dynarnies at the restored site; therefore monitoring nitrogen behavior in the first year after restoration was important. Here we report the nitrogen dynamies, and espeeially the dynarnies of N20 emission, during this establishment year.

Ecological Research, 2019

Limnology, 2003

... 1992), microclimate con-trol in the chamber is crucial for gas exchange measure-ments, especi... more ... 1992), microclimate con-trol in the chamber is crucial for gas exchange measure-ments, especially when convective gas transport dominates (Chanton and Dacey 1991; Brix et al. 1996). Recently, micrometeorological measurements based on the eddy covariance technique ...

Journal of Geography (Chigaku Zasshi), 2013

Limnology, 2015

ABSTRACT Aquatic humic substances (AHSs) are major constituents of dissolved organic matter (DOM)... more ABSTRACT Aquatic humic substances (AHSs) are major constituents of dissolved organic matter (DOM) in freshwater bodies. We performed quantitative analyses of AHSs in Japanese lake and wetland waters, focusing mainly on clear waters with low carbon contents, by using a resin isolation technique based on the carbon concentration in the AHSs of each sample. The proportion of AHS to DOM in the clear waters ranged from 38.4 to 64.1 %; these proportions are lower than those widely assumed for freshwater of 20–80 %. Moreover, the proportions of AHSs in DOM were not constant, so regression analysis cannot be used to predict the AHS concentration from the DOM concentration. Thus, AHS and DOM concentrations must be determined separately for each water sample.

Limnology, 2009

Abstract We examined the effects of tidal fluctuations on CO 2 and CH 4 fluxes from sediment or s... more Abstract We examined the effects of tidal fluctuations on CO 2 and CH 4 fluxes from sediment or soil to the atmosphere in the littoral zone of a brackish-water lake during the growing seasons in 2004 and 2005. The dominant plants at the study site formed three ...

Ecological Research Monographs, 2012

Journal of Geography (Chigaku Zasshi), 2013

Forests, 2022

Understory trees occupy a spatially heterogeneous light environment owing to light interception b... more Understory trees occupy a spatially heterogeneous light environment owing to light interception by patchily distributed canopy leaves. We examined the spatial distribution of canopy leaves and the spatial structure of the understory tree community (height < 5 m) and their relationships in a beech forest in Nagano, Japan. We measured the canopy leaf area index (LAI) at 10 m intervals (n = 81) in a permanent research plot (1 ha). We established a circular subplot centered on each LAI measurement point, and determined the species composition and the aboveground net primary production of wood (ANPPW) of the understory tree community by using tree size data from an open database in the Monitoring Sites 1000 project. There was a significant negative correlation between canopy LAI and the ANPPW of understory trees and a significant positive correlation between the ANPPW of understory and understory tree density. The dominant species of understory trees differed between subplots with hig...

available online at www.jpe.oxfordjournals.org Altitudinal variation of ecosystem CO2 fluxes in a... more available online at www.jpe.oxfordjournals.org Altitudinal variation of ecosystem CO2 fluxes in an alpine grassland

Aims Recent studies have recognized the alpine grasslands on the Qing-hai–Tibetan plateau as a si... more Aims Recent studies have recognized the alpine grasslands on the Qing-hai–Tibetan plateau as a significant sink for atmospheric CO2. The carbon-sink strength may differ among grassland ecosystems at var-ious altitudes because of contrasting biotic and physical environ-ments. This study aims (i) to clarify the altitudinal pattern of ecosystem CO2 fluxes, including gross primary production (GPP), daytime ecosystem respiration (Redaytime) and net ecosystem produc-tion (NEP), during the period with peak above-ground biomass; and (ii) to elucidate the effects of biotic and abiotic factors on the altitudinal variation of ecosystem CO2 fluxes. Methods Ecosystem CO2 fluxes and abiotic and biotic environmental factors were measured in an alpine grassland at four altitudes from 3600 to 4200 m along a slope of the Qilian Mountains on the northwestern Qinghai–Tibetan Plateau during the growing season of 2007. We used a closed-chamber method combined with shade screens and an opaque cloth to mea...

available online at www.jpe.oxfordjournals.org Characterization of CO2 flux in three Kobresiamead... more available online at www.jpe.oxfordjournals.org Characterization of CO2 flux in three Kobresiameadows differing in dominant species

Journal of Plant Research, 2021

The American Journal of Gastroenterology, 2013

Journal of Ecosystem & Ecography, 2018

Soil nitrogen (N) mineralization is a central process in the N cycle in terrestrial ecosystems. P... more 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 dat...

The American Journal of Gastroenterology, 2014

Journal of Plant Research, 2021

Forest understory plays an important role in the gross primary production (GPP) of some forest ec... more Forest understory plays an important role in the gross primary production (GPP) of some forest ecosystems. However, differences in understory GPP caused by obviously different overstory canopy structure have not been taken into consideration in previous studies, thus potentially over- or underestimating understory GPP. To estimate the understory GPP more accurately, we separated a forest into "canopy area", with closed-overstory canopy, and "gap area", with open-overstory canopy. The study was conducted in a mature deciduous forest dominated by beech and with an understory dominated by dwarf bamboo, Sasa senanensis. We measured S. senanensis GPP at the community scale (GPPSasa-community) using a static chamber system that covered the aboveground part of the plants and then upscaled it to the ecosystem scale (GPPSasa-ecosystem) by considering the proportions of canopy and gap areas within the forest. GPPSasa-community was 192 g C m-2 year-1 in the canopy area and 699 g C m-2 year-1 in the gap area. The large difference likely occurred because the photosynthetic ability and biomass of the S. senanensis community differed strongly between the two areas. The seasonal dynamics of GPPSasa-community also differed between the areas. The 10-day cumulative GPPSasa-community peaked from July to August in the gap area, whereas there was no clear peak of GPPSasa-community in the canopy area. Multiple linear regressions showed that light intensity and biomass were significant predictors of GPPSasa-community in the canopy area, whereas air temperature and biomass were significant predictors of GPPSasa-community in the gap area. GPPSasa-ecosystem during growing season in 2019 was 3.74 t C ha-1 year-1, which contributed between 16.37 and 19.85% of the entire forest ecosystem GPP. This study highlights the need to consider differences in overstory structure for the accurate estimation of understory GPP.

Forests, 2020

Quantification of leaf area index (LAI) is essential for understanding forest productivity and th... more Quantification of leaf area index (LAI) is essential for understanding forest productivity and the atmosphere–vegetation interface, where the majority of gas and energy exchange occurs. LAI is one of the most difficult plant variables to adequately quantify, owing to large spatial and temporal variability, and few studies have examined the horizontal and vertical distribution of LAI in forest ecosystems. In this study, we demonstrated the LAI distribution in each layer from the understory to canopy using multiple-point measurements (121 points) and examined the relationships among layers in a cool-temperate deciduous forest. LAI at each point, and the spatial distribution of LAI in each layer, varied within the forest. The spatial distribution of LAI in the upper layer was more heterogeneous than that of LAI at the scale of the entire forest. Significant negative correlations were observed between the upper- and lower-layer LAI. Our results indicate that the understory compensates f...

Plants, 2020

How photosynthetic-related leaf traits of non-nitrogen (N)-fixing pioneer species respond to extr... more 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 ...

SIL Proceedings, 1922-2010, 2009

Eeologieal restoration projeets are beeoming more eommon globally, and there is an urgent need fo... more Eeologieal restoration projeets are beeoming more eommon globally, and there is an urgent need for strategies to monitor and assess these projeets. Salt marsh eeosystems in eoastal zones are transitional boundaries between terrestrial and aquatie eeosystems, and they reeeive substantial amounts of anthropogenie nutrients sueh as nitrogen. Beeause nitrogen over-enriehment of saline waters has beeome more widespread on a global seale, an understanding of the nitrogen dynamies of salt marshes is erueial for restoration management of eoastal zones. We are seeking to better understand the nitrogen dynamies of these zones and the levels of emission of nitrous oxide (N20) produeed in nitrogen eycles. lnereased androgenie N20 emissions ean result from sueh events as inereased produetion and use o f nitrogen fertilizers or the eonversion of forests to agrieultural land (SMITH 1997). Nitrous oxide is reeognized as a potent greenhouse gas and a possible intermediate in the destruetion of the stratospherie ozone layer. The atmospherie eoneentration of N20 is eurrently about 31 O ppbv and is inereasing at a rate of 0.6-0.9 ppbv y(PRINN et al. 1990). Although atmospherie N20 eoneentration is lower than that of earbon dioxide (C02) and methane (CH4), N20 is eonsidered to eontribute to future global climate ehange beeause of its long residenee time (130-150 y) and high energy absorption eapaeity per moleeule (K.HALIL & RASMUSSEN 1992). Therefore, N20 emission has attraeted a great deal of attention. Restoration of a wetland was eompleted in February 2006 at Lake Shinji, a lagoon on the eoast of southwestern Honshu, Japan. Our aim was to demonstrate the effeet of eeologieal sueeession on nitrogen dynarnies at the restored site; therefore monitoring nitrogen behavior in the first year after restoration was important. Here we report the nitrogen dynamies, and espeeially the dynarnies of N20 emission, during this establishment year.

Ecological Research, 2019

Limnology, 2003

... 1992), microclimate con-trol in the chamber is crucial for gas exchange measure-ments, especi... more ... 1992), microclimate con-trol in the chamber is crucial for gas exchange measure-ments, especially when convective gas transport dominates (Chanton and Dacey 1991; Brix et al. 1996). Recently, micrometeorological measurements based on the eddy covariance technique ...

Journal of Geography (Chigaku Zasshi), 2013

Limnology, 2015

ABSTRACT Aquatic humic substances (AHSs) are major constituents of dissolved organic matter (DOM)... more ABSTRACT Aquatic humic substances (AHSs) are major constituents of dissolved organic matter (DOM) in freshwater bodies. We performed quantitative analyses of AHSs in Japanese lake and wetland waters, focusing mainly on clear waters with low carbon contents, by using a resin isolation technique based on the carbon concentration in the AHSs of each sample. The proportion of AHS to DOM in the clear waters ranged from 38.4 to 64.1 %; these proportions are lower than those widely assumed for freshwater of 20–80 %. Moreover, the proportions of AHSs in DOM were not constant, so regression analysis cannot be used to predict the AHS concentration from the DOM concentration. Thus, AHS and DOM concentrations must be determined separately for each water sample.

Limnology, 2009

Abstract We examined the effects of tidal fluctuations on CO 2 and CH 4 fluxes from sediment or s... more Abstract We examined the effects of tidal fluctuations on CO 2 and CH 4 fluxes from sediment or soil to the atmosphere in the littoral zone of a brackish-water lake during the growing seasons in 2004 and 2005. The dominant plants at the study site formed three ...

Ecological Research Monographs, 2012

Journal of Geography (Chigaku Zasshi), 2013