Yoshiko Kosugi
Kyoto University, Graduate School of Agriculture, Faculty Member
Research Interests:
Winter leaf reddening is a phenomenon that evergreen species’ leaf color changes into red resulting from the accumulation of red pigments before or during winter, which persists for several months before dissipating with springtime... more
Winter leaf reddening is a phenomenon that evergreen species’ leaf color changes into red resulting from the accumulation of red pigments before or during winter, which persists for several months before dissipating with springtime warming. Among the many hypotheses about the winter leaf reddening, photoprotection is currently the favored hypothesis. Several studies focused on leaf reddening in angiosperms species. Yet, little researches concerned about leaf reddening in gymnosperms species. In gymnosperms, a kind of xanthophyll pigment rhodoxanthin was reported to play an important role. However, the xanthophyll cycle is the main protection mechanism of plants to deal with excessive light energy.
Research Interests:
Research Interests:
Soils play important roles as CH 4 sources and sinks. CH 4 is produced in anoxic environments, including submerged soils, by methanogenic bacteria. On the contrary, CH 4 is oxidized by methanotrophic bacteria in upland soils. In general,... more
Soils play important roles as CH 4 sources and sinks. CH 4 is produced in anoxic environments, including submerged soils, by methanogenic bacteria. On the contrary, CH 4 is oxidized by methanotrophic bacteria in upland soils. In general, forest soils are recognized as the efficient sinks for atmospheric CH 4, because of their CH 4 oxidation capacity in water-unsaturated soil (Le Mer and Roger, 2001). However, we hypothesized that forest ecosystems, especially in wet warm climates such as Asian monsoon climate, are not always CH 4 sink. In this study, we examined the CH 4 dynamics in a temperate Asian monsoon forest (Kiryu Experimental Watershed: 35 N, 136E), which included wet areas along riparian zones within the watershed. In order to reveal the spatio-temporal variations of CH 4 fluxes, we combined multi-point plot-scale CH 4 flux measurements using chamber methods and ecosystem-scale CH 4 flux measurements using a micrometeorological method, relaxed eddy accumulation (REA) metho...
Research Interests:
Hyperdiverse tropical rainforests, such as the aseasonal forests in Southeast Asia, are supported by high annual rainfall. Its canopy is dominated by the species-rich tree family of Dipterocarpaceae (Asian dipterocarps), which has both... more
Hyperdiverse tropical rainforests, such as the aseasonal forests in Southeast Asia, are supported by high annual rainfall. Its canopy is dominated by the species-rich tree family of Dipterocarpaceae (Asian dipterocarps), which has both ecological (e.g., supports flora and fauna) and economical (e.g., timber production) importance. Recent ecological studies suggested that rare irregular drought events may be an environmental stress and signal for the tropical trees. We assembled the genome of a widespread but near threatened dipterocarp, Shorea leprosula, and analyzed the transcriptome sequences of ten dipterocarp species representing seven genera. Comparative genomic and molecular dating analyses suggested a whole-genome duplication close to the Cretaceous-Paleogene extinction event followed by the diversification of major dipterocarp lineages (i.e. Dipterocarpoideae). Interestingly, the retained duplicated genes were enriched for genes upregulated by no-irrigation treatment. These ...
Research Interests:
Research Interests:
The development of new methods for estimating precise forest structure parameters is essential for the quantitative evaluation of forest resources. Conventional use of satellite image data, increasing use of terrestrial laser scanning... more
The development of new methods for estimating precise forest structure parameters is essential for the quantitative evaluation of forest resources. Conventional use of satellite image data, increasing use of terrestrial laser scanning (TLS), and emerging trends in the use of unmanned aerial systems (UASs) highlight the importance of modern technologies in the realm of forest observation. Each technology has different advantages, and this work seeks to incorporate multiple satellite, TLS- and UAS-based remote sensing data sets to improve the ability to estimate forest structure parameters. In this paper, two regression analysis approaches are considered for the estimation: random forest regression (RFR) and support vector regression (SVR). To collect the dependent variable, in situ measurements of individual tree parameters (tree height and diameter at breast height (DBH)) were taken in a Japanese cypress forest using the nondestructive TLS method, which scans the forest to obtain de...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT Biogenic volatile organic compounds (BVOCs) play important roles in biosphere‒atmosphere interactions and communications among organisms, although little is known about the characteristics of BVOCs in the pedosphere and... more
ABSTRACT Biogenic volatile organic compounds (BVOCs) play important roles in biosphere‒atmosphere interactions and communications among organisms, although little is known about the characteristics of BVOCs in the pedosphere and particularly emissions from fine roots. We evaluated the effects of cutting the fine roots of two tree species on BVOC emissions during sampling and compared the BVOC and CO2 emission rates in the roots of 15 tree species in forests in Japan and Taiwan. The BVOC emission rate in Pinus densiflora roots increased as the number of cross-sections increased. When the cross-section of a P. densiflora root was outside the sample bag, the BVOC emission rate was not affected by application of a cutting treatment. The mean BVOC emission rates in the fine roots of each of 15 tree species ranged from 0 to 0.38 nmol g−1s−1 for monoterpenes and 0 to 0.10 nmol g−1s−1 for a sesquiterpene (longifolene). The monoterpene emission rates in fine roots were very high for some gymnosperm and ectomycorrhizal species (Pinus densiflora 0.38 ± 0.31 nmol g−1s−1 and Abies firma 0.19 ± 0.08 nmol g−1s−1). The longifolene emission rates in fine roots were highest for one gymnosperm and arbuscular mycorrhizal species (Chamaecyparis pisifera 0.10 ± 0.10 nmol g−1s−1). The proportional carbon ratio of BVOCs to CO2 in emissions from fine roots ranged from 0 to 67% among the 15 tree species. Distinct patterns in the exact BVOC compounds and their emission rates indicated species-specific carbon availability in fine roots.
Research Interests:
Abstract Season-long methane ( CH 4 ) exchange was observed in a rice paddy field in central Japan (Kanto Region) using the eddy covariance technique to clarify the variations in environmental controls on CH 4 exchange in different stages... more
Abstract Season-long methane ( CH 4 ) exchange was observed in a rice paddy field in central Japan (Kanto Region) using the eddy covariance technique to clarify the variations in environmental controls on CH 4 exchange in different stages of cultivation. Before heading of rice plant, the CH 4 emission depended on wind speed and soil temperature. The soil temperature dependence can be due to an increase in CH 4 production, higher molecular diffusion, and higher conductance within rice plant at higher soil temperature. An occurrence of ebullitive emission was also suggested from the wind speed dependence. After heading was completed, relative humidity and water temperature influenced CH 4 emission. The amplitude of the diurnal variation in emission increased from 0.03 μ mol m − 2 s − 1 in the late pre-heading stage to 0.13 μ mol m − 2 s − 1 in the post-heading stage. Induced convective throughflow within the rice aerenchyma after the change in plant structure was attributable to this variation in environmental controls after the heading. After drainage, CH 4 emission was confined to short periods after strong rain events. The water level controlled the timing of emission, most likely by influencing the diffusion efficiency from the anoxic soil to the atmosphere and CH 4 oxidation in the surface oxic zone. The variation in the dominant transport pathway needs to be accounted for in terrestrial ecosystem models to accurately predict CH 4 emission from rice paddies.
Research Interests:
Research Interests:
Soil respiration (Rs) plays a key role in the carbon balance of forest ecosystems. There is growing evidence that Rs is strongly correlated with canopy photosynthesis; however, how Rs is linked to aboveground attributes at various... more
Soil respiration (Rs) plays a key role in the carbon balance of forest ecosystems. There is growing evidence that Rs is strongly correlated with canopy photosynthesis; however, how Rs is linked to aboveground attributes at various phenological stages, on the seasonal and diurnal scale, remains unclear. Using an automated closed dynamic chamber system, we assessed the seasonal and diurnal patterns of Rs in a temperate evergreen coniferous forest from 2005 to 2010. High-frequency Rs rates followed seasonal soil temperature patterns but the relationship showed strong hysteresis. Predictions of Rs based on a temperature-response model underestimated the observed values from June to July and overestimated those from August to September and from January to April. The observed Rs was higher in early summer than in late summer and autumn despite similar soil temperatures. At a diurnal scale, the Rs pattern showed a hysteresis loop with the soil temperature trend during the seasons of high b...
Research Interests: Soil, Biology, Medicine, Multidisciplinary, Automation, and 3 moreTemperature, PLoS one, and Seasons
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We examined the effects of Asian monsoon rainfall on CH4 absorption of water-unsaturated forest soil. We conducted a 1-year continuous measurement of soil CH4 and CO2 fluxes with automated chamber systems in three plots with different... more
We examined the effects of Asian monsoon rainfall on CH4 absorption of water-unsaturated forest soil. We conducted a 1-year continuous measurement of soil CH4 and CO2 fluxes with automated chamber systems in three plots with different soil characteristics and water content to investigate how temporal variations in CH4 fluxes vary with the soil environment. CH4 absorption was reduced by the ‘Baiu’ summer rainfall event and peaked during the subsequent hot, dry period. Although CH4 absorption and CO2 emission typically increased as soil temperature increased, the temperature dependence of CH4 varied more than that of CO2, possibly due to the changing balance of activities between methanotrophs and methanogens occurring over a wide temperature range, which was strongly affected by soil water content. In short time intervals (30 min), the responses of CH4 and CO2 fluxes to rainfall were different for each plot. In a dry soil plot with a thick humus layer, both fluxes decreased abruptly ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We analyzed 29 years of acorn production by five species of California oaks (genus Quercus ) to test the hypothesis that trees produce large seed crops prior to wet years, conditions facilitating seedling germination and survival. The... more
We analyzed 29 years of acorn production by five species of California oaks (genus Quercus ) to test the hypothesis that trees produce large seed crops prior to wet years, conditions facilitating seedling germination and survival. The mean crop of three of the species correlated positively and nontrivially with the following year’s rainfall, but none was statistically significant. Including the acorn crop 1 and 2 years earlier yielded several significant relationships between the acorn crop and future rainfall, but none held up when applied to a second, independent site. Across individuals, acorn production by 7% of trees correlated significantly with subsequent rainfall. Although these trees differed from other trees in several characters, differences were not sufficient to discriminate between trees that correlated significantly with subsequent rainfall from those that did not. We conclude that acorn production by California oaks does not forecast wet years and does not support th...