Kazuharu Ogawa

Self-thinning and size variation in a sugi (Cryptomeria japonica D. Don) plantation

Density and stem volume in a sugi (Cryptomeria japonica D. Don) plantation were monitored for 15 years from 1983 to 1997. The tree density decreased year after year from 5002 to 3108 ha � 1 . The time-trajectory of mean stem volume and density provided evidence in favor of the � 3/2 power law of self-thinning. The skewness of the frequency distribution of stem volume showed positive values, which means that the distribution is more or less L-shaped, and the skewness decreased with time, which indicates that smaller trees died as the stand grew. This trend is consistent with the asymmetric or one-sided competition hypothesis that self-thinning is driven by competition for light. Dead trees tended to distribute randomly with the stand growth. The relationship between standard deviation of stem volume and mean stem volume was formulated by a power function, whose exponent was significantly less than unity. This shows that coefficient of variation, ranging from 61.7 to 82.5%, decreased with increasing mean stem volume. That is, the relative size variation becomes small with stand growth. # 2002 Elsevier Science B.V. All rights reserved.

Self-thinning exponents based on the allometric model in Chinese pine (Pinus tabulaeformis Carr.) and Prince Rupprecht's larch (Larix principis-rupprechtii Mayr) stands

Abstract The allometric power relationships of mean tree height H(∝vθ) and stem volume packing d(∝vδ) to mean stem volume v were investigated in 182 Chinese pine (Pinus tabulaeformis Carr.) stands and 56 Prince Rupprechts larch (Larix principis-rupprechtii Mayr) stands. According to Wellers allometric model, the slope of the self-thinning boundary line, i.e. −1/[1−(θ+δ)], was calculated from the exponents of the allometric power relationships. The resulting slope was −1.79 for the larch and −1.72 for the pine. The self-thinning boundary lines corresponded well with the combinations of mean stem volume and density in the nine densest stands of pine and larch. The steeper slope for larch was attributed to allocation of more resources to height growth and to greater stem volume in space already occupied in the larch than in the pine, resulting in higher exponent values of θ and δ in the larch than in the pine.

Time trajectories of mass and density in a Chamaecyparis obtusa seedling population

Abstract In an overcrowded population of tree seedlings of hinoki (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.), the allometric power relation existed between mean dry weights of seedling parts, such as stems, leaves and roots and whole seedlings during the course of self-thinning. The allometric exponent was significantly less than unity in the leaves, higher than unity in the stems and not significantly different from unity in the roots. Therefore, the leaf weight ratio decreased from 0.56 to 0.46 and the stem weight ratio increased from 0.24 to 0.34 with increasing whole seedling dry weight, and the root weight ratio showed an almost constant value of 0.20. The time trajectory of mean whole seedling dry weight and density was formulated. The value of the self-thinning exponent was 1.54 at the final phase of stand development. By combining the allometric power relation and the time trajectory of mean whole seedling dry weight and density, the time trajectories of mean dry weights of seedling parts and density were mathematically derived. The self-thinning exponent in the stems (=1.91) was higher than that in the whole seedlings, while the self-thinning exponent in the leaves (=1.39) was lower than that in the whole seedlings. The self-thinning exponent in the roots (=1.43) almost equalled that in the whole seedlings. In addition, the time-trajectory of the mean dry weight of the tops (=stems+leaves) and density was fitted by the equation with the same value of self-thinning exponent as the whole seedlings.

Interception of photosynthetic photon flux density in a mangrove stand of Kandelia candel (L.) Druce

The canopy structure and interception of photosynthetic photon flux density (PPFD) in a 10-year-old Kandelia candel (L.) Druce stand were investigated before and after artificial defoliation. Leaf and wood areas for different layers were measured through area-weight relationships of subsamples. PPFD was measured at specified heights before and after leaf clipping. The leaf area index (LAI) and wood area index (WAI) were 4.501m2m−2 and 1.412m2m−2, respectively. There was a strong linear relationship between the cumulative wood area (C) and leaf area (F) densities from the top down to a given depth of the canopy, C = aF (r2 = 0.950), with a proportional constant a of 0.096 ± 0.008 (mean ± SE). The PPFD relative to that above the canopy (relative PPFD; IR) at a given depth of the canopy was assumed to be given by the equation IR = e−(KCC+KFF) = e−KF, where the apparent light extinction coefficient K (= KF + aKC, where KF and KC are respectively the light extinction coefficient of leaves and woody organs) was calculated to be 0.502 ± 0.041 (mean ± SE) m−2 m2 before leaf clipping. After leaf clipping,

Tree Size Dependence of Litter Production, and Above-ground Net Production in a Young Hinoki (Chamaecyparis obtusa) Stand

I_{R_C } = e^{ - K_C C}

Size dependence of leaf area and the mass of component organs during a course of self-thinning in a hinoki (Chamaecyparis obtusa) seedling population

is satisfied. As a result, the value of KC was estimated to be 0.785 ± 0.046 (mean ± SE) m−2 m2. The light extinction coefficient of leaves KF was calculated to be 0.427 m−2 m2 using the indirect method, KF = K − aKC, and 0.432 ± 0.026 (mean ± SE) m−2 m2 using the direct method,

Interactive effect of CO2 enrichment and temperature on the photosynthesis of field-grown hinoki cypress (Chamaecyparis obtusa) branches

I_R /I_{R_C } = e^{ - K_F F}

In situ CO2 gas-exchange in fruits of a tropical tree, Durio zibethinus Murray

. Of the total PPFD intercepted by the canopy, the fraction KF/K due to leaves alone was estimated to be 85.0%–86.1% and the rest was contributed by woody organs.

Morphological and phenological characteristics of leaf development ofDurio zibethinus Murray (Bombacaceae)

The study was carried out in a 9-year-old hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.), stand over a span of three years from July 1992 to June 1995, primarily to predict litter production from exteral tree dimensions by combining open-top clothtrap and clipping methods. Litter production was virtually concentrated in October and November. Stem cross-sectional area at the crown base was proved to be the reliable predictor of litter production, and that single regression model was evolved irrespective of year. The regression model had proportional constants of 2.696 × 10−2 and 3.540 × 10−2 kg cm−2 year−1 for leaf litter and total litter production, respectively. Utilizing the model, leaf litter production of the stand was assessed to be 5.04, 5.12, and 4.99, and total litter production to be 6.48, 6.58, and 6.40 Mg ha−1 year−1 for the first, second and third year, respectively. Biomass increment was 6.67, 7.80, and 7.70, tree mortality was 0.15, 0.13, and 0.41, and insect grazing was 0.09, 0.05, and 0.002 Mg ha−1 year−1 for the first, second and third year, respectively. Above-groud net production was therefore 13.39, 14.55, and 14.51, Mg ha−1 year−1, and biomass accumulation ratio (biomass/net production) was 1.86, 2.21, and 2.76 year for the first, second and third year, respectively. Considering data from earlier studies and the results of this study, biomass accumulation ratio,BAR (year), of hinoki stands was best related to above-ground biomass,y (Mg ha−1), using the power function:BAR=0.112y0.936. Excluding seedling stands, leaf efficiency (above-ground net production per unit leaf mass) of hinoki stands was 0.91±0.02 (SE) Mg Mg−1 year−1, irrespective of stand biomass or age.

Mathematical consideration of the pipe model theory in woody plant species

The allometric equation, y = gxh, was applied monthly to the relationships between two different dimensions of tree seedlings of hinoki cypress (Chamaecyparis obtusa) during a course of self-thinning from April 1990 to March 1991 to detect differences in biomass allocation among individuals. As the h-value in the allometry of crown length and seedling height was greater than unity for all seasons, crown ratio became greater as seedling height increased. Leaf weight ratio increased with increasing seedling size because the h-value in the allometry of leaf dry weight and whole seedling dry weight was greater than unity in every month. Therefore, smaller seedlings are disadvantageous to photosynthetic production by leaves. In contrast, the leaf area ratio was constant irrespective of seedling size because the h-value in the allometry of leaf area and whole seedling dry weight was nearly equal to unity in most seasons. In addition, because the h-value in the allometry of leaf area and leaf dry weight was less than unity in all seasons, specific leaf area decreased with an increase in leaf dry weight, indicating that smaller seedlings adapt to low light environments by possessing shade leaves. Root weight ratio decreased with increasing seedling size because the h-value in the allometry of root dry weight and whole seedling dry weight was less than unity in most seasons.