Data from: Sampling intraspecific variability in leaf functional traits: practical suggestions to maximize collected information

1. The choice of the best sampling strategy to capture mean values of functional traits for a species/population, while maintaining information about traits’ variability and minimizing the sampling size and effort, is an open issue in functional trait ecology. 2. Intraspecific variability (ITV) of functional traits strongly influences sampling size and effort. However, while adequate information is available about intraspecific variability between individuals (ITVBI) and among populations (ITVPOP), relatively few studies have analyzed intraspecific variability within individuals (ITVWI). 3. Here, we provide an analysis of ITVWI of two foliar traits, namely specific leaf area (SLA) and osmotic potential (or π), in a population of Quercus ilex L. We assessed the baseline ITVWI level of variation between the two traits and provided the minimum and optimal sampling size in order to take into account ITVWI, comparing sampling optimization outputs with those previously proposed in the literature. 4. Different factors accounted for different amount of variance of the two traits. SLA variance was mostly spread within individuals (43.4% of the total variance), while π variance was mainly spread between individuals (43.2%). 5. Strategies that did not account for all the canopy strata produced mean values not representative of the sampled population. The minimum size to adequately capture the studied functional traits corresponded to 5 leaves taken randomly from 5 individuals, while the most accurate and feasible sampling size was 4 leaves taken randomly from 10 individuals. 6. We demonstrate that the spatial structure of the canopy could significantly affect traits variability. Moreover, different strategies for different traits could be implemented during sampling surveys. 7. We partially confirm sampling sizes previously proposed in the recent literature, and encourage future analysis involving different traits.

1. 在维持功能性状（functional traits）变异信息、最小化采样规模与工作量的前提下，筛选可获取物种/种群功能性状均值的最优采样策略，是功能性状生态学领域尚未解决的开放性问题。
2. 功能性状的种内变异（intraspecific variability, ITV）会显著影响采样规模与工作量。尽管目前已有关于个体间种内变异（intraspecific variability between individuals, ITVBI）和种群间种内变异（intraspecific variability among populations, ITVPOP）的充足研究，但针对个体内种内变异（intraspecific variability within individuals, ITVWI）的分析仍相对匮乏。
3. 本研究针对冬青栎（Quercus ilex L.）种群的两种叶部性状——比叶面积（specific leaf area, SLA）与渗透势（osmotic potential，或记为π）开展个体内种内变异分析。我们评估了这两种性状的个体内种内变异基线水平，并结合个体内种内变异的考量需求，给出了最小与最优采样规模，同时将采样优化结果与此前文献中提出的方案进行了对比。
4. 不同因素对两种性状的方差贡献存在差异。比叶面积的变异主要分布于个体内部（占总变异的43.4%），而渗透势的变异则主要分布于个体之间（占总变异的43.2%）。
5. 未覆盖所有冠层层次的采样策略，所得到的均值无法代表被采样种群的真实特征。可充分获取目标功能性状的最小采样规模为：从5个个体中随机采集5片叶片；而兼具准确性与可操作性的最优采样规模则为：从10个个体中随机采集4片叶片。
6. 本研究证实，冠层的空间结构会对性状变异产生显著影响。此外，在采样调查中可针对不同性状采用差异化的采样策略。
7. 本研究部分验证了近期文献中提出的采样规模方案，并呼吁未来开展涵盖更多性状的相关分析。