Data from: Shoot growth of woody trees and shrubs is predicted by maximum plant height and associated traits

1. The rate of elongation and thickening of individual branches (shoots) varies across plant species. This variation is important for the outcome of competition and other plant-plant interactions. Here we compared rates of shoot growth across 44 species from tropical, warm temperate, and cool temperate forests of eastern Australia. 2. Shoot growth rate was found to correlate with a suite of traits including the potential height of the species, xylem-specific conductivity, leaf size, leaf area per xylem cross-section, twig diameter (at 40 cm length), wood density and modulus of elasticity. 3. Within this suite of traits, maximum plant height was the clearest correlate of growth rates, explaining 50 to 67% of the variation in growth overall (p < 0.0001), and 23 to 32% of the variation (p < 0.05) in growth when holding the influence of the other traits constant. Structural equation models suggest that traits associated with ‘hydraulics’, ‘biomechanics’, and the ‘leaf economics spectrum’ represent three clearly separated axes of variation, with the hydraulic axis exhibiting the strongest alignment with height and largest independent contribution to growth (in the case of branch thickening). However most of the capacity of these axes to predict growth was also associated with maximum height, presumably reflecting coordinated selection on multiple traits that together influence life histories. 4. Growth rates were not strongly correlated with leaf nitrogen or leaf mass per unit leaf area. 5. Correlations between growth and maximum height arose both across latitude (47%, p < 0.0001) and from within-site differences between species (30%, p < 0.0001). Covariation between growth and maximum height was driven in part by variation in irradiance across sites as well as among canopy positions within sites (23%, p < 0.0001). A significant fraction of this shared variation was independent of irradiance (45%, p < 0.0001), reflecting intrinsic differences across species and sites.

1. 不同植物物种的单个嫩枝（shoot）伸长与增粗速率存在显著差异。这类变异对于植物竞争及其他种间互作的结局具有重要影响。本研究针对澳大利亚东部热带、暖温带与寒温带森林中的44个植物物种，比较了其嫩枝生长速率。
2. 研究发现，嫩枝生长速率与一系列性状相关，包括物种潜在株高、木质部比导率（xylem-specific conductivity）、叶面积、单位木质部横截面积的叶面积、40cm长度处的细枝直径、木材密度及弹性模量（modulus of elasticity）。
3. 在上述性状组合中，植物最大株高是与生长速率相关性最显著的因子，整体上可解释50%~67%的生长变异（p < 0.0001）；在控制其他性状影响的前提下，仍可解释23%~32%的生长变异（p < 0.05）。结构方程模型（structural equation models）结果显示，与水力性状、生物力学性状及叶经济谱（leaf economics spectrum）相关的性状分别构成三个清晰分离的变异轴，其中水力性状轴与株高的关联度最强，且对嫩枝增粗生长的独立贡献最大。然而，这些性状轴对生长的预测能力大多也与最大株高相关，这可能反映了对共同影响植物生活史的多性状的协同选择。
4. 嫩枝生长速率与叶片氮含量（leaf nitrogen）及单位叶面积叶干重（leaf mass per unit leaf area）均无显著相关性。
5. 生长速率与最大株高的相关性既存在于纬度梯度间（解释变异量47%，p < 0.0001），也存在于样地内不同物种间（解释变异量30%，p < 0.0001）。生长速率与最大株高的共变部分由样地间及样地内冠层位置间的光照辐射（irradiance）变异驱动（解释变异量23%，p < 0.0001）。其中有显著比例的共变变异与光照辐射无关（45%，p < 0.0001），这反映了不同物种及样地间的固有差异。