Data from: Environmental drivers and phylogenetic constraints of growth phenologies across a large set of herbaceous species

1. Because perennial herbs of temperate climates develop their aboveground parts every year anew, their success critically depends on the timing and speed of this growth (growth phenology). These parameters can play a role in species coexistence and may differ along environmental gradients. Still, we know little about them, as most phenological data come from observations of flowering and to a lesser degree leafing onset.
2. We collected data on growth phenology of about 400 perennial herbs in a botanical garden to make the results independent of local differences in climatic drivers as much as possible. Using these data, we determined species-specific parameters of Day of peak growth, Day of maturity, and two types of growth rates associated with the change in plant size. Environmental conditions in which these species occur in the field were assessed using Ellenberg indicator values, which express species' optima along gradients of moisture, nutrients and temperature.
3. Both timing and speed of growth estimated in the common garden were affected by light and moisture conditions of the habitats where the species typically occur. All parameters showed phylogenetic conservatism.
4. We identified two relationships among these parameters of growth phenology: (i) species with early peak growth had high relative growth rates in contrast to late species; (ii) tall species showed later peak growth than short species which more often grew early. The first relationship is associated with survival under forest canopy, where species are selected to grow early and fast before trees leaf out, which restricts their size. The latter is associated with (asymmetric) competition for light in open habitats, where the main selection factor is for tall stature, which cannot be attained early in the season.
5. Synthesis: We show that large differences in size growth dynamics among herbaceous species are constrained by a few key tradeoffs involving height at maturity, rate of growth, and time when maximum height is attained. These tradeoffs correspond to major selective forces acting on herbaceous plants in temperate climates.

1. 由于温带气候下的多年生草本植物每年都会重新萌发地上部分，其种群存续成败关键取决于此类生长的时机与速率（生长物候学（growth phenology））。这类参数可对物种共存产生影响，且会随环境梯度呈现差异。但目前学界对其认知仍较为有限：绝大多数物候观测数据仅聚焦于开花期，针对展叶始期的观测占比相对较低。
2. 为尽可能使研究结果不受气候驱动因子的区域差异影响，我们在植物园中收集了约400种多年生草本植物的生长物候学数据。依托这批数据，我们确定了各物种特有的参数：生长峰值日（Day of peak growth）、成熟日（Day of maturity），以及与植株体型变化相关的两类生长速率。我们通过埃伦伯格指示值（Ellenberg indicator values）评估了这些物种在野外的原生境环境条件，该指标可表征物种沿水分、养分与温度梯度的生存最适值。
3. 在同质园实验中估算得到的生长时机与速率，均受到物种原生境光照与水分条件的调控。所有参数均表现出系统发育保守性（phylogenetic conservatism）。
4. 我们在这些生长物候学参数中发现了两类关联：（i）生长峰值较早的物种，其相对生长速率（relative growth rates）显著高于生长峰值较晚的物种；（ii）高大物种的生长峰值晚于矮小物种，而矮小物种往往更早达到生长峰值。第一类关联与林冠下的生存策略相关：在此类生境中，自然选择倾向于让物种在树木展叶前尽早且快速生长，但该策略会限制植株最终体型。第二类关联则与开放生境中的非对称光竞争相关：此类生境的主要选择压力为高大株型，而该性状无法在生长季早期达成。
5. 综合分析：我们的研究表明，温带草本植物间体型生长动态的显著差异，受到若干关键权衡关系的约束，这些权衡涉及成熟株高、生长速率以及达到最大株高的时间。这类权衡对应着温带气候下作用于草本植物的主要选择压力。