A species‐level model for metabolic scaling in trees I. Exploring boundaries to scaling space within and across species

摘要: Summary 1. Metabolic scaling theory predicts how tree water flow rate (Q) scales with mass (M) and assumes identical for biomass growth (G )w ithM. Analytic models have derived general expectations from proposed optima in the of axial xylem conduit taper (taper function) allocation wood space to conduction (packing function). Recent predictions suggest G andQ scale M � 0·7 power 0·75 as an upper bound. 2. We complement this a priori optimization approach numerical model that incorporates species-specific packing functions, plus additional empirical inputs essential predicting Q (effects gravity, size, heartwood, bark, hydraulic resistance leaf, root interconduit pits). Traits are analysed individually, ensemble across types, define 2D ‘scaling space’ absolute vs. its exponent size. 3. All traits influenced many affected M. Constraints driving or any other trait, can be relaxed via compensatory changes traits. 4. The temperate trees overlapped despite diverse anatomy winter-adaptive strategies. More conducting conifer compensated narrow tracheids; extensive sapwood diffuse-porous vessels; limited ring-porous negated effect large vessels. Tropical trees, however, achieved greatest steepest size-scaling by pairing vessels sapwood, combination compatible minimal stress no freezing-stress. 5. Intraspecific all types averaged / 0·63 (maximum = 0·71 ) size-invariant root–shoot ratio. Scaling reached only if conductance increased faster roots than shoots Interspecific could reach , but may require evolution size-biased allometries rather arising directly biophysical constraints. 6. Our species-level is more realistic analytical predecessors provides tool interpreting adaptive significance functional trait diversification relation wholetree use consequent metabolic scaling.