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      • KCI등재

        Can we estimate forest gross primary production from leaf lifespan? A test in a young Fagus crenata forest

        Kohei Koyama,Kihachiro Kikuzawa 한국생태학회 2010 Journal of Ecology and Environment Vol.33 No.3

        It has been well established that leaf longevity is linked to the carbon economy of plants. We used this relationship to predict leaf lifetime carbon gains from leaf lifespan, and estimated the gross primary production (GPP) of a young deciduous forest of Japanese beech (Fagus crenata) located in central Japan. The light-saturated photosynthetic rates of the leaves were measured repeatedly during the growing season. We used the leaf lifespan to calculate the conversion coefficient from the light-saturated photosynthetic rate into the realized leaf lifetime carbon gain under field conditions. The leaf turnover rate was estimated using litter traps. GPP was estimated as the product of lifetime carbon gain per unit of leaf mass, and the annual leaf turnover rate. The GPP of the forest in 2007 was estimated to be 1.2 × 10³ g C m⁻² y⁻¹, which was within the range of previously reported GPP values of beech forests in Japan, and was close to the GPP of a European beech forest, as estimated by eddy flux measurements.

      • SCOPUSKCI등재

        Intraspecific Variation in Leaf Life Span for the Semi-evergreen Liana Akebia trifoliata is Caused by Both Seasonal and Aseasonal Factors in a Temperate Forest

        Kohei, Koyama,Kikuzawa, Kihachiro The Ecological Society of Korea 2008 Journal of Ecology and Environment Vol.31 No.3

        We investigated the leaf demography of a temperate woody liana, Akebia trifoliata, in a temperate forest in Japan, Akebia is semi-evergreen: some leaves are shed before winter, while others remain through the winter. Previous studies of semi-evergreen species found that variation in leaf life span was caused by variation in the timing of leaf emergence, Leaves that appeared just before winter over-wintered, while leaves appearing earlier were shed, However, it is unclear whether leaves of the same cohort (i.e., leaves that appear at the same time within a single site) show variation in life span under the effect of strong seasonality. To separate variation in life span among the leaves in each cohort from variation among cohorts, we propose a new method - the single leaf diagram, which shows the emergence and death of each leaf. Using single leaf diagrams, our study revealed that Akebia leaves within a cohort showed substantial variation in life span, with some over-wintering and some not. In addition, leaves on small ramets in the understory showed great variation in life span, while leaves on large ramets, which typically reach higher positions in the forest canopy, have shorter lives, As a result, small ramets were semi-evergreen, whereas large ramets were deciduous, The longer lives of leaves on small ramets can be interpreted as a shade-adaptive strategy in understory plants.

      • KCI등재

        Intraspecific Variation in Leaf Life Span for the Semi-evergreen Liana Akebia trifoliata is Caused by Both Seasonal and Aseasonal Factors in a Temperate Forest

        Koyama, Kohei,Kihachiro Kikuzawa 한국생태학회 2008 Journal of Ecology and Environment Vol.31 No.3

        We investigated the leaf demography of a temperate woody liana, Akebia trifoliata, in a temperate forest in Japan. Akebia is semi-evergreen: some leaves are shed before winter, while others remain through the winter. Previous studies of semi-evergreen species found that variation in leaf life span was caused by variation in the timing of leaf emergence. Leaves that appeared just before winter over-wintered, while leaves appearing earlier were shed. However, it is unclear whether leaves of the same cohort (i.e., leaves that appear at the same time within a single site) show variation in life span under the effect of strong seasonality. To separate variation in life span among the leaves in each cohort from variation among cohorts, we propose a new method - the single leaf diagram, which shows the emergence and death of each leaf. Using single leaf diagrams, our study revealed that Akebia leaves within a cohort showed substantial variation in life span, with some over-wintering and some not. In addition, leaves on small ramets in the understory showed great variation in life span, while leaves on large ramets, which typically reach higher positions in the forest canopy, have shorter lives. As a result, small ramets were semi-evergreen, whereas large ramets were deciduous. The longer lives of leaves on small ramets can be interpreted as a shade-adaptive strategy in understory plants. We investigated the leaf demography of a temperate woody liana, Akebia trifoliata, in a temperate forest in Japan. Akebia is semi-evergreen: some leaves are shed before winter, while others remain through the winter. Previous studies of semi-evergreen species found that variation in leaf life span was caused by variation in the timing of leaf emergence. Leaves that appeared just before winter over-wintered, while leaves appearing earlier were shed. However, it is unclear whether leaves of the same cohort (i.e., leaves that appear at the same time within a single site) show variation in life span under the effect of strong seasonality. To separate variation in life span among the leaves in each cohort from variation among cohorts, we propose a new method - the single leaf diagram, which shows the emergence and death of each leaf. Using single leaf diagrams, our study revealed that Akebia leaves within a cohort showed substantial variation in life span, with some over-wintering and some not. In addition, leaves on small ramets in the understory showed great variation in life span, while leaves on large ramets, which typically reach higher positions in the forest canopy, have shorter lives. As a result, small ramets were semi-evergreen, whereas large ramets were deciduous. The longer lives of leaves on small ramets can be interpreted as a shade-adaptive strategy in understory plants.

      • KCI등재

        Pre-dispersal Seed Predation by a Granivorous Bird, the Masked Grosbeak (Eophona personata), in Two Bird-dispersed Ulmaceae Species

        Tetsuro Yoshikawa,Kihachiro Kikuzawa 한국생태학회 2009 Journal of Ecology and Environment Vol.32 No.3

        Pre-dispersal seed predation by a granivorous bird, the masked grosbeak(Eophona personata, Fringillidae), was investigated in two bird-dispersed trees, Celtis sinensis and Aphananthe aspera(Ulmaceae). The objectives of this study were to 1)measure direct damage of predation by grosbeaks on plant crops, 2) reveal the temporal pattern of predation within each tree species and its causal factors, and 3) test whether foraging grosbeaks hinder foraging of frugivorous birds, thereby indirectly impacting the reproduction of both tree species. A substantial amount of fruit and seed crop was consumed by grosbeaks(24.3% in Celtis;55.5% in Aphananthe), and only 17.7%(Celtis) and 16.7%(Aphananthe) were removed by frugivorous birds. At the study site, the grosbeak population size fluctuated greatly during the fruiting seasons of both plant species. As for Celtis, predated seed density also fluctuated temporally, and the local population size of grosbeaks was responsible for predated seed density. In Aphananthe, predation was not fully explained by grosbeak populations or plant phenology, but its peak coincided with that of grosbeak population. These results suggest that pre-dispersal seed predation by granivorous birds can have large negative impacts on the bird-dispersed plants. Changes in local population size of granivorous birds can influence predatation and can affect reproductive success of the bird-dispersed plants available to the birds.

      • SCOPUSKCI등재

        Pre-dispersal Seed Predation by a Granivorous Bird, the Masked Grosbeak (Eophona personata), in Two Bird-dispersed Ulmaceae Species

        Yoshikawa, Tetsuro,Kikuzawa, Kihachiro The Ecological Society of Korea 2009 Journal of Ecology and Environment Vol.32 No.3

        Pre-dispersal seed predation by a granivorous bird, the masked grosbeak (Eophona personata, Fringillidae), was investigated in two bird-dispersed trees, Celtis sinensis and Aphananthe aspera (Ulmaceae). The objectives of this study were to 1) measure direct damage of predation by grosbeaks on plant crops, 2) reveal the temporal pattern of predation within each tree species and its causal factors, and 3) test whether foraging grosbeaks hinder foraging of frugivorous birds, thereby indirectly impacting the reproduction of both tree species. A substantial amount of fruit and seed crop was consumed by grosbeaks (24.3% in Celtis; 55.5% in Aphananthe), and only 17.7% (Celtis) and 16.7% (Aphananthe) were removed by frugivorous birds. At the study site, the grosbeak population size fluctuated greatly during the fruiting seasons of both plant species. As for Celtis, predated seed density also fluctuated temporally, and the local population size of grosbeaks was responsible for predated seed density. In Aphananthe, predation was not fully explained by grosbeak populations or plant phenology, but its peak coincided with that of grosbeak population. These results suggest that predispersal seed predation by granivorous birds can have large negative impacts on the bird-dispersed plants. Changes in local population size of granivorous birds can influence predatation and can affect reproductive success of the bird-dispersed plants available to the birds.

      • SCOPUSKCI등재

        Can we estimate forest gross primary production from leaf lifespan? A test in a young Fagus crenata forest

        Koyama, Kohei,Kikuzawa, Kihachiro The Ecological Society of Korea 2010 Journal of Ecology and Environment Vol.33 No.3

        It has been well established that leaf longevity is linked to the carbon economy of plants. We used this relationship to predict leaf lifetime carbon gains from leaf lifespan, and estimated the gross primary production (GPP) of a young deciduous forest of Japanese beech (Fagus crenata) located in central Japan. The light-saturated photosynthetic rates of the leaves were measured repeatedly during the growing season. We used the leaf lifespan to calculate the conversion coefficient from the light-saturated photosynthetic rate into the realized leaf lifetime carbon gain under field conditions. The leaf turnover rate was estimated using litter traps. GPP was estimated as the product of lifetime carbon gain per unit of leaf mass, and the annual leaf turnover rate. The GPP of the forest in 2007 was estimated to be $1.2{\times}10^3gCm^{-2}y^{-1}$, which was within the range of previously reported GPP values of beech forests in Japan, and was close to the GPP of a European beech forest, as estimated by eddy flux measurements.

      • SCOPUSKCI등재

        Distribution of Aucuba japonica in two contrasting geobotanical regions of Japan: An analysis of adaptation mode

        Ali, Md. Sohrab,Kikuzawa, Kihachiro The Ecological Society of Korea 2013 Journal of Ecology and Environment Vol.36 No.3

        Two varieties of Aucuba japonica differ in ways that can be considered adaptive to differing geo-climatic conditions in their respective distribution ranges. Irrespective of growth stage, the mean leaf size of A. japonica var. japonica was significantly larger than A. japonica var. borealis. Smaller leaf size and ultimately smaller stature of A. japonica var. borealis are an advantage under the higher snow load and lower temperatures in the forests along the East Sea where the variety grows. Snow load also acted as an important driving force for structural modifications of A. japonica var. borealis from cellular level in leaves to the organization of branch extension growth. Global warming by changing snowfall patterns in Japan may lead to range shifts in the two varieties of A. japonica.

      • KCI등재

        Distribution of Aucuba japonica in two contrasting geobotanical regions of Japan: An analysis of adaptation mode

        Md. Sohrab Ali,Kihachiro Kikuzawa 한국생태학회 2013 Journal of Ecology and Environment Vol.36 No.3

        Two varieties of Aucuba japonica differ in ways that can be considered adaptive to differing geo-climatic conditions in their respective distribution ranges. Irrespective of growth stage, the mean leaf size of A. japonica var. japonica was significantly larger than A. japonica var. borealis. Smaller leaf size and ultimately smaller stature of A. japonica var. borealis are an advantage under the higher snow load and lower temperatures in the forests along the East Sea where the variety grows. Snow load also acted as an important driving force for structural modifications of A. japonica var. borealis from cellular level in leaves to the organization of branch extension growth. Global warming by changing snowfall patterns in Japan may lead to range shifts in the two varieties of A. japonica.

      • KCI등재

        Responses of different phytoelements to habitat light level and their dynamic convergence towards crown development of Aucuba japonica Thunb. var. japonica

        Md. Sohrab Ali,Kihachiro Kikuzawa 한국생태학회 2012 Journal of Ecology and Environment Vol.35 No.3

        We analyzed crown development in Aucuba japonica Thunb. var. japonica resulting from the responses of phytoelements to habitat light conditions over a long period of time. Over the years, the degree of extension unit (EU) dimorphism and the degree of anisophylly were higher under shaded conditions than in brighter conditions. An overall temporally increasing pattern in the degree of EU dimorphism was found while no clear-cut trend was found in the case of anisophylly. EU length and number of leaves per EU co-varied in a spatio-temporal context. The number of terminal buds and their sizes acted as the key initiators of morphological differences of phytoelements which were further amplified following bud break. Leaf area density was displayed mostly in the apex peripheral layer of the crown and the apex layer received most of the incident light. There was a tradeoff between annual leaf production and mean leaf size. Depending on the heterogeneity of irradiance level within a crown, correlative growth inhibition caused higher EU mortality at brighter sites. Due to high mortality, shorter EUs had a mere role in the construction of structural framework of the crown except for the formation of some gaps. There was a strong convergence of EU dimorphism, anisophylly, EU extension growth and variations in leaf size towards formation of functional crown to reduce potential self-shading. Depending on the irradiance level, Aucuba japonica Thunb. var. japonica showed two different modes of crown expansion. At the brighter sites, individual crown expansion was progressive while at the darker sites, individual crown expanded in a diminishing manner and maintained a stable size. A plant’s “growth diminishing phase” appeared earlier at shaded sites than brighter sites.

      • SCOPUSKCI등재

        Responses of different phytoelements to habitat light level and their dynamic convergence towards crown development of Aucuba japonica Thunb. var. japonica

        Ali, Md. Sohrab,Kikuzawa, Kihachiro The Ecological Society of Korea 2012 Journal of Ecology and Environment Vol.35 No.3

        We analyzed crown development in Aucuba japonica Thunb. var. japonica resulting from the responses of phytoelements to habitat light conditions over a long period of time. Over the years, the degree of extension unit (EU) dimorphism and the degree of anisophylly were higher under shaded conditions than in brighter conditions. An overall temporally increasing pattern in the degree of EU dimorphism was found while no clear-cut trend was found in the case of anisophylly. EU length and number of leaves per EU co-varied in a spatio-temporal context. The number of terminal buds and their sizes acted as the key initiators of morphological differences of phytoelements which were further amplified following bud break. Leaf area density was displayed mostly in the apex peripheral layer of the crown and the apex layer received most of the incident light. There was a tradeoff between annual leaf production and mean leaf size. Depending on the heterogeneity of irradiance level within a crown, correlative growth inhibition caused higher EU mortality at brighter sites. Due to high mortality, shorter EUs had a mere role in the construction of structural framework of the crown except for the formation of some gaps. There was a strong convergence of EU dimorphism, anisophylly, EU extension growth and variations in leaf size towards formation of functional crown to reduce potential self-shading. Depending on the irradiance level, Aucuba japonica Thunb. var. japonica showed two different modes of crown expansion. At the brighter sites, individual crown expansion was progressive while at the darker sites, individual crown expanded in a diminishing manner and maintained a stable size. A plant's "growth diminishing phase" appeared earlier at shaded sites than brighter sites.

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