Rempei Suwa

Mixed-power scaling of whole-plant respiration from seedlings to giant trees

The scaling of respiratory metabolism with body mass is one of the most pervasive phenomena in biology. Using a single allometric equation to characterize empirical scaling relationships and to evaluate alternative hypotheses about mechanisms has been controversial. We developed a method to directly measure respiration of 271 whole plants, spanning nine orders of magnitude in body mass, from small seedlings to large trees, and from tropical to boreal ecosystems. Our measurements include the roots, which have often been ignored. Rather than a single power-law relationship, our data are fit by a biphasic, mixed-power function. The allometric exponent varies continuously from 1 in the smallest plants to 3/4 in larger saplings and trees. Therefore, our findings support the recent findings of Reich et al. [Reich PB, Tjoelker MG, Machado JL, Oleksyn J (2006) Universal scaling of respiratory metabolism, size, and nitrogen in plants. Nature 439:457–461] and West, Brown, and Enquist [West GB, Brown JH, Enquist BJ (1997) A general model for the origin of allometric scaling laws in biology. Science 276:122 -126.]. The transition from linear to 3/4-power scaling may indicate fundamental physical and physiological constraints on the allocation of plant biomass between photosynthetic and nonphotosynthetic organs over the course of ontogenetic plant growth.

Allometric relationships for estimating the aboveground phytomass and leaf area of mangrove Kandelia candel (L.) Druce trees in the Manko Wetland, Okinawa Island, Japan

Allometric relationships for estimating the phytomass of aboveground organs (stem, branches, leaves and their sum) and the leaf area in the mangrove Kandelia candel (L.) Druce were investigated. The variable D0.12H (D0.1 stem diameter at a height of H/10, H tree height) showed better accuracy of estimation than D2 (D, DBH) or D2H. A moderate relationship was found when the branch weight, leaf weight and leaf area were plotted against DB2 (DB stem diameter at a height of clear bole length). A strong linear relationship was found between leaf area and leaf weight (R2=0.979). The aboveground weight (wT) showed a strong relationship when plotted against D0.12H (R2=0.958), but very weak relationships were obtained against D2 (R2=0.300) and D2H (R2=0.316). The wT also showed a proportional relationship (R2=0.978) to D0.12H with a proportional constant of 0.04117 kg cm−2 m−1 (R2=0.978). Taking into account the allometric relationships of the weight of aboveground organs or leaf area per tree to different dimensions, such as D2, D2H, DB2 and D0.12H, a standard procedure for estimating the biomass and leaf area index in the K. candel stand, including the shorter trees, is proposed.

The self-thinning process in mangrove Kandelia obovata stands

The self-thinning process was monitored in crowded Kandelia obovata Sheue, Liu & Yong stands over four years. The frequency distribution of tree phytomass was an L-shape, which was kept over the experimental period. Spearman’s rank correlation coefficient for phytomass decreased as the time span of the comparison became longer, a result which indicates that the rank of phytomass changes as stands grow. Death of trees resulted from one-sided competition, i.e., death occurred in lower-rank trees. Surviving trees continued to grow. Whatever the current spatial distribution of the trees, death occurred randomly and the spatial distribution gradually became close to random as stands grew. The self-thinning exponent was 1.46, which can be regarded as evidence in favor of the 3/2 power law of self-thinning. Relative growth rate, RGR, decreased in proportion to decreasing relative mortality rate, RMR, with a proportionality constant of 1.57, which was not significantly different from the slope of the self-thinning exponent. This experimental result probably justifies the assumption that the ratio of RGR to RMR in the mean phytomass-density trajectory for any self-thinning population with different densities becomes constant as the growth stage progresses.

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,

Distribution and stem growth patterns of mangrove species along the Nakara River in Iriomote Island, Southwestern Japan.

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

Canopy photosynthesis in a mangrove considering vertical changes in light-extinction coefficients for leaves and woody organs

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,

Overview of Forest Carbon Stocks Study in Amazonas State, Brazil

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

The impacts of historical barriers on floristic patterns of plant groups with different dispersal abilities in the Ryukyu Archipelago, Japan

. 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.

The architectural stratification and woody species diversity in subtropical evergreen broadleaf forests along a latitudinal thermal gradient of the Ryukyu Archipelago, Japan

We examined variations in stand structure and tree growth of a mangrove forest along two gradients: from the river mouth to upper stream and from the riverside to inland, along the Nakara River, Iriomote Island, Japan. Bruguiera gymnorrhiza (L.) Lamk. occurred throughout the intertidal area, though Rhizophora stylosa Griff. and Kandelia candel (L) Druce did not occur upstream. Basal area and maximum tree height of B. gymnorrhiza decreased downstream. The growth rate in stem diameter of B. gymnorrhiza decreased downstream in relation with the soil salinity. The basal area and the maximum tree height of B. gymnorrhiza increased with the distance from the riverside. R. stylosa increased in stem diameter and growth rate toward the riverside.

Carbon and nitrogen pools in a mangrove stand of Kandelia obovata (S., L.) Yong: vertical distribution in the soil–vegetation system

The light-penetration pattern for a mangrove Kandelia obovata canopy was analyzed considering the vertical changes in the light-extinction coefficients for leaves and woody organs. Furthermore, canopy photosynthesis and foliage respiration were estimated on the basis of the constructed light-penetration models. The canopy structure and light-penetration pattern were investigated by use of a destructive method. Seasonal changes in photosynthetic light-response curves and dark respiration of leaves were measured at different canopy depths. The main findings of this study were: (1) the ratio of the cumulative woody silhouette area density C to the cumulative leaf area density F increased downward within the canopy; (2) the light-extinction coefficient for leaves increased from 0.30 to 0.72 downward and the light-extinction coefficient for woody organs was almost constant at 0.77; and (3) ignoring the woody organs and the vertical change in the C/F ratio and light-extinction coefficients for leaves caused ca. ±10 and ±20% errors in annual canopy gross photosynthesis and surplus production, respectively.