These authors contributed equally to the study.The WBE theory proposed by West, Brown and Enquist predicts that larger plant respiration rate, R, scales to the three-quarters power of body size, M. However, studies on the R versus M relationship for larger plants (i.e. trees larger than saplings) have not been reported. Published respiration rates of field-grown trees (saplings and larger trees) were examined to test this relationship. Our results showed that for larger trees, aboveground respiration rates R A scaled as the 0.82-power of aboveground biomass M A , and that total respiration rates R T scaled as the 0.85-power of total biomass M T , both of which significantly deviated from the three-quarters scaling law predicted by the WBE theory, and which agreed with 0.81-0.84-power scaling of biomass to respiration across the full range of measured tree sizes for an independent dataset reported by Reich et al. (Reich et al. 2006 Nature 439, 457-461). By contrast, R scaled nearly isometrically with M in saplings. We contend that the scaling exponent of plant metabolism is close to unity for saplings and decreases (but is significantly larger than three-quarters) as trees grow, implying that there is no universal metabolic scaling in plants.

The data collected for all five bamboo species are consistent with the "diminishing returns" hypothesis, i.e., the scaling exponents governing the leaf area vs. dry mass scaling relationship are less than one within and across species and are insensitive to light conditions or elevation.

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1. The whole-plant economics spectrum (PES) refers to the trade-offs among the many plant functional traits that are commonly used as indicators of major adaptive strategies, thereby providing insights into plant distributions, ecosystem processes and evolution. However, there are few studies of what may be called the whole-PES that integrates bark, wood and leaf functional traits for different leaf types and growth habits (evergreen vs. deciduous species).2. To address this gap in our knowledge, 6 bark traits, 7 wood traits (including mechanical support and nutrient transport characteristics) and 12 leaf traits (including chemical, structural and physiological characteristics) of 59 representative subtropical woody species were examined using principal component analysis (PCA) to determine PES strategies.3. The economics spectra of bark (BES), wood (WES) and leaves (LES), and the entire PES indicated that major traits represent resource acquisition strategies and conservation strategies clustering on the opposite ends of the PCA axis. A significant correlation was observed among the 25 functional traits. The data indicated that N and P nutrient levels were at the hub of BES, WES, LES and PES interrelationships. Evergreen and deciduous species had different WES and LES, and thus PES resource acquisition strategies. With the exception of the BES, evergreen species clustered on the conservative side, whereas deciduous species clustered on the acquisitive side. Synthesis.The PES presented here informs our understanding of whole-plant responses to environmental differences, particularly regarding the role of N and P traits at the whole-plant level. It also reveals and further supports the notion that evergreen and deciduous species, respectively, manifest conservative and acquisitive strategies, further informing our understanding of species biodiversity maintenance.

The leaf economics spectrum (LES) characterizes multivariate correlations that confine the global diversity of leaf functional traits onto a single axis of variation. Although LES is well established for traits of sun leaves, it is unclear how well LES characterizes the diversity of traits for shade leaves. Here, we evaluate LES using the sun and shade leaves of 75 woody species sampled at the extremes of a within-canopy light gradient in a subtropical forest. Shading significantly decreased the mean values of LMA and the rates of photosynthesis and dark respiration, but had no discernable effect on nitrogen and phosphorus content. Sun and shade leaves manifested the same relationships among N mass , P mass , A mass , and R mass (i.e., the slopes of log-log scaling relations of LES traits did not differ between sun and shade leaves). However, the difference between the normalization constants of shade and sun leaves was correlated with functional trait plasticity. Although the generality of this finding should be evaluated further using larger datasets comprising more phylogenetically diverse taxa and biomes, these findings support a unified LES across shade as well as sun leaves.