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. 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.allometry | metabolic scaling | mixed-power function | whole-plant respiration | simple-power function F rom the smallest seedlings to giant trees, the masses of vascular plants span 12 orders of magnitude in mass (1). The growth rates of most plants, which are generally presented in terms of net assimilation rates of CO 2 , are believed to be controlled by respiration (2, 3). Furthermore, many of the CO 2 -budget models of plant growth and carbon dynamics in terrestrial ecosystems are based on whole-plant respiration rates in relation to plant size (2, 4-7). Thus far, however, there have been few studies of wholeplant respiration over the entire range of plant size from tiny seedlings to large trees. The purpose of the present study was to quantify the allometric scaling of metabolism by directly measuring whole-plant respiration over a representative range of sizes.For the past century, the scaling of metabolic rate with body size has usually been described using an allometric equation, or simple power function, for the form (8-17)where Y is the respiratory metabolic rate (μmol s −1 ), F is a constant (μmol s −1 kg -f ), M is the body mass (kg), and f is the scaling exponent. The exponent f has been controversial, and various values have been reported based on studies of both animals and plants (15). Recently, it was suggested that f = 1 for relatively small plants, based on data for a 10 6 -fold range of body mass (16), including measurements using a whole-plant chamber (18,19). If f = 1, this means that whole-plant respiration scales isometrically with body mass, which may be reasonable in the case of herbaceous plants and small trees because nearly all of their cells, even those in the stems, should be active in respiration. However, it was suggested that f = 3/4 based originally on empirical studies of animal metabolism (8). This idea is consistent with the mechanistic models of resource distribution in vascular systems (10, 11), including the pipe model (20, 21) and models based on space-filling, hierarchical, fractal-like networks of br...

CABI:20153174020Understanding how plants are constructed - i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals - is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259634 measurements collected in 176 different studies, from 21084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01-100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub-sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross-section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the world's vegetation

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 D 0.1 2 H (D 0.1 stem diameter at a height of H/10, H tree height) showed better accuracy of estimation than D 2 (D, DBH) or D 2 H. A moderate relationship was found when the branch weight, leaf weight and leaf area were plotted against D B 2 (D B stem diameter at a height of clear bole length). A strong linear relationship was found between leaf area and leaf weight (R 2 =0.979). The aboveground weight (w T ) showed a strong relationship when plotted against D 0.1 2 H (R 2 =0.958), but very weak relationships were obtained against D 2 (R 2 =0.300) and D 2 H (R 2 =0.316). The w T also showed a proportional relationship (R 2 =0.978) to D 0.1 2 H with a proportional constant of 0.04117 kg cm −2 m −1 (R 2 =0.978). Taking into account the allometric relationships of the weight of aboveground organs or leaf area per tree to different dimensions, such as D 2 , D 2 H, D B 2 and D 0.1 2 H, a standard procedure for estimating the biomass and leaf area index in the K. candel stand, including the shorter trees, is proposed.

Attempts were made to quantify the carbon and nitrogen pools in a monospecific and pioneer mangrove stand of Kandelia obovata Sheue, Liu & Yong, Okinawa Island, Japan. The leaf C and N concentrations on a leaf area basis decreased with increasing PPFD (Photosysthetic Photon Flux Density). The total C and N stocks in foliage were estimated as 3.55 Mg ha -1 and 0.105 Mg ha -1 , respectively. The bark (45.6-48.6% for C and 0.564-0.842% for N) contained significantly higher amount of C (P < 0.05) and N (P < 0.01) than wood (46.2-47.8% for C and 0.347-0.914% N). The total C stock of stem was 23.2 Mg ha -1 in wood and 8.33 Mg ha -1 in bark, and the total N stock was 0.222 Mg ha -1 in wood and 0.116 Mg ha -1 in bark. The root wood (37.1-45.0%) contained significantly higher amount of C than root bark (35.4-40.7%) (P < 0.01). The total C stock of root was 14.2 Mg ha -1 in wood and 12.6 Mg ha -1 in bark, and the total N stock of root was 0.157 Mg ha -1 in wood and 0.155 Mg ha -1 in bark. The soil organic C and total N stocks within 1 m soil depth were estimated as 57.3 Mg ha -1 and 2.73 Mg ha -1 , respectively. The C pool in aboveground biomass (35.1 Mg ha -1 ) was 1.3 times as large as that in belowground biomass (26.9 Mg ha -1 ). However, the soil organic C pool (57.3 Mg ha -1 ) was similar to the total C pool (62.0 Mg ha -1 ) of vegetation, indicating that the mangrove stored a large part of production in the soil. About 50% of the C was in the soil. The N pool in aboveground biomass (0.442 Mg ha -1 ) was 1.4 times as large as that in belowground biomass (0.312 Mg ha -1 ). The soil N stock was 3.3 times as large as the biomass N stock (0.754 Mg ha -1 ).

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