Theoretical and empirical methods were applied to the analysis of branch growth and crown form in... more Theoretical and empirical methods were applied to the analysis of branch growth and crown form in old trees of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii). Conventional use of allometric models proved insufficient in explaining the variability found in the relationship between branch diameter and length. In order to infer the potential pattern of branch growth, a maximum relationship was empirically estimated by selecting maximum points in an incremental fashion. This relationship asymptoted to infinity, suggesting that factors such as damage and die-back may modify the branch diameter–length relationship before an asymptotic maximum length is reached. The difference between the observed branch length and the estimated maximum branch length was found to be a good measure of the degree of branch damage. The degree of damage increased with increasing branch diameter, suggesting that large diameter branches have experienced more extensive damage and/or die...
To integrate human-disturbed hillslopes with the regional landscape, natural forest restoration h... more To integrate human-disturbed hillslopes with the regional landscape, natural forest restoration has become an important objective of hillslope re-vegetation in Japan. At Kobe Municipal Sports Park (KMSP), seedlings of native species were planted in 1980 to restore semi-natural secondary forest (satoyama) in an urban setting. Here, we present 21 years of stand dynamics based on vegetation surveys conducted in 1992, 2000, and 2013 in two research plots (control and managed) at KMSP in relation to a reference forest to evaluate management effects and restoration success. Total basal area continued to increase in both the plots, but diameter-growth decreased in the control plot, whereas it continued to increase in the managed plot, which had been thinned by volunteers. In the control plot, which was planted at higher initial density than the managed plot, Quercus phillyraeoides (evergreen, mid-canopy tree) dominated the single-layered canopy and vertical development was delayed. In the ...
With increasing height within the crowns of tall trees, leaves tend to become smaller and thicker... more With increasing height within the crowns of tall trees, leaves tend to become smaller and thicker and shoots shorter. In tall trees, the vertical variation in leaf/shoot morphology is largely driven by water status. Morphological changes associated with increasing height in the crown present static constraints on photosynthesis, such as decreasing light intercepting area relative to leaf mass and decreasing
Very fine roots (<0.5 mm in diameter) of forest trees may serve as better indicators of ro... more Very fine roots (<0.5 mm in diameter) of forest trees may serve as better indicators of root function than the traditional category of <2 mm, but how these roots will exhibit the plasticity of species-specific traits in response to heterogeneous soil nutrients is unknown. Here, we examined the vertical distribution of biomass and morphological and physiological traits of fine roots across three narrow diameter classes (Quercus serrata and Ilex pedunculosa at five soil depths down to 50 cm in a broad-leaved temperate forest. In both species, biomass and the allocation of very fine roots were higher in the surface soil but lower below 10-cm soil depth compared to values for larger roots (0.5–2.0 mm). When we applied these diameter classes, only very fine roots of Q. serrata exhibited significant changes in specific root length (SRL; m g−1) and root nitrogen (N) concentrations with soil depth, whereas the N concentrations only changed significantly in I. pedunculosa. The SRL and root N concentrations of larger roots in the two species did not significantly differ among soil depths. Thus, very fine roots may exhibit species-specific traits and change their potential for nutrient and water uptake in response to soil depth by plasticity in root biomass, the length, and the N in response to available resources.
Theoretical and empirical methods were applied to the analysis of branch growth and crown form in... more Theoretical and empirical methods were applied to the analysis of branch growth and crown form in old trees of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii). Conventional use of allometric models proved insufficient in explaining the variability found in the relationship between branch diameter and length. In order to infer the potential pattern of branch growth, a maximum relationship was empirically estimated by selecting maximum points in an incremental fashion. This relationship asymptoted to infinity, suggesting that factors such as damage and die-back may modify the branch diameter–length relationship before an asymptotic maximum length is reached. The difference between the observed branch length and the estimated maximum branch length was found to be a good measure of the degree of branch damage. The degree of damage increased with increasing branch diameter, suggesting that large diameter branches have experienced more extensive damage and/or die...
To integrate human-disturbed hillslopes with the regional landscape, natural forest restoration h... more To integrate human-disturbed hillslopes with the regional landscape, natural forest restoration has become an important objective of hillslope re-vegetation in Japan. At Kobe Municipal Sports Park (KMSP), seedlings of native species were planted in 1980 to restore semi-natural secondary forest (satoyama) in an urban setting. Here, we present 21 years of stand dynamics based on vegetation surveys conducted in 1992, 2000, and 2013 in two research plots (control and managed) at KMSP in relation to a reference forest to evaluate management effects and restoration success. Total basal area continued to increase in both the plots, but diameter-growth decreased in the control plot, whereas it continued to increase in the managed plot, which had been thinned by volunteers. In the control plot, which was planted at higher initial density than the managed plot, Quercus phillyraeoides (evergreen, mid-canopy tree) dominated the single-layered canopy and vertical development was delayed. In the ...
With increasing height within the crowns of tall trees, leaves tend to become smaller and thicker... more With increasing height within the crowns of tall trees, leaves tend to become smaller and thicker and shoots shorter. In tall trees, the vertical variation in leaf/shoot morphology is largely driven by water status. Morphological changes associated with increasing height in the crown present static constraints on photosynthesis, such as decreasing light intercepting area relative to leaf mass and decreasing
Very fine roots (<0.5 mm in diameter) of forest trees may serve as better indicators of ro... more Very fine roots (<0.5 mm in diameter) of forest trees may serve as better indicators of root function than the traditional category of <2 mm, but how these roots will exhibit the plasticity of species-specific traits in response to heterogeneous soil nutrients is unknown. Here, we examined the vertical distribution of biomass and morphological and physiological traits of fine roots across three narrow diameter classes (Quercus serrata and Ilex pedunculosa at five soil depths down to 50 cm in a broad-leaved temperate forest. In both species, biomass and the allocation of very fine roots were higher in the surface soil but lower below 10-cm soil depth compared to values for larger roots (0.5–2.0 mm). When we applied these diameter classes, only very fine roots of Q. serrata exhibited significant changes in specific root length (SRL; m g−1) and root nitrogen (N) concentrations with soil depth, whereas the N concentrations only changed significantly in I. pedunculosa. The SRL and root N concentrations of larger roots in the two species did not significantly differ among soil depths. Thus, very fine roots may exhibit species-specific traits and change their potential for nutrient and water uptake in response to soil depth by plasticity in root biomass, the length, and the N in response to available resources.
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Papers by Hiroaki Ishii