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枝条（shoot）的伸长与增粗速率存在显著种间差异。该变异对于植物竞争及其他种间互作的最终结果具有关键影响。本研究针对澳大利亚东部热带、暖温带与冷温带森林中的44个植物物种，对比分析了其枝条生长速率。 2. 研究结果显示，枝条生长速率与一系列功能性状显著相关，包括物种潜在株高、木质部比导率（xylem-specific conductivity）、单叶面积、单位木质部横截面积的叶面积、40 cm长度处的小枝直径、木材密度（wood density）与弹性模量（modulus of elasticity）。 3. 在上述功能性状组合中，最大株高是与生长速率相关性最显著的预测因子，整体可解释50%~67%的生长速率变异（p < 0.0001）；在控制其他性状的影响后，仍可解释23%~32%的生长速率变异（p < 0.05）。结构方程模型（structural equation models）分析表明，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相互分离的变异轴，其中水力性状轴与株高的关联强度最高，且对枝条增粗生长的独立贡献最大。不过，这些性状轴对生长速率的预测能力大多也与最大株高相关，推测这反映了对协同影响植物生活史的多性状的定向选择。 4. 枝条生长速率与叶片氮含量及单位叶面积叶干重并未呈现显著相关性。 5. 生长速率与最大株高的相关性既存在于纬度梯度之间（解释47%的变异，p < 0.0001），也存在于样地内的物种间（解释30%的变异，p < 0.0001）。二者的协变部分由样地间及样地内冠层位置的光照强度（irradiance）差异驱动（解释23%的变异，p < 0.0001）。该共变变异中有显著比例与光照强度无关（占45%，p < 0.0001），反映了不同物种及样地间的固有差异。