Abstract Leaf optical properties (reflectance and transmittance spectra of a single leaf) are the key to interpreting remote sensing data regarding the structure and functions of vegetation canopies. These properties are determined by leaf biochemical and anatomical traits, which change seasonally in deciduous species. To reveal the species-specific seasonal patterns in leaf optical properties and their relationship to chlorophyll content and/or mesophyll structure in deciduous trees, we examined these mechanistic relationships in a pioneer species, Betula ermanii, and in sunlit and shade leaves of a late-successional species, Quercus crispula, during their seasonal development. Leaf optical properties were measured from leaf emergence to leaf fall in four years. After leaf unfolding, reflectance in the photosynthetically active radiation (PAR) region decreased gradually, while transmittance dropped rapidly. Both reflectance and transmittance increased before leaf fall. In the near-infrared (NIR) region, reflectance increased and transmittance decreased during the development period. Values of parameter N (the number of compact layers within a leaf in PROSPECT-5 model) in young leaves was very low (1.1 for B. ermanii and 1.0 for sunlit and shade leaves of Q. crispula) but increased rapidly by 30% for B. ermanii and sunlit leaves of Q. crispula and by 20% for shade leaves. N was higher in the order of B. ermanii > Q. crispula sun leaves > shade leaves. The PROSPECT-5 simulation with our measured data showed that the development of mesophyll tissue increases reflectance and decreases transmittance in both NIR and PAR regions, and an increase in chlorophyll decreases both reflectance and transmittance in PAR region. Our results indicate that structural and biochemical development of leaf mesophyll and its interspecific variations are essential biological characteristics for understanding seasonal changes in canopy reflectance. The results of this study will help us to better analyze remotely sensed data.

中文翻译：

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冷温带落叶阔叶树叶片光学特性的物候学及其与叶肉发育的关系。

摘要 叶片光学特性（单片叶片的反射和透射光谱）是解释植被冠层结构和功能遥感数据的关键。这些特性是由叶子生化和解剖特征决定的，这些特征在落叶物种中随季节变化。为了揭示叶片光学特性的物种特定季节性模式及其与落叶树中叶绿素含量和/或叶肉结构的关系，我们研究了先锋物种 Betula ermanii 以及晚在其季节性发展过程中的演替物种 Quercus curlsula。在四年内从叶子出现到叶子落下测量叶子光学特性。叶子展开后，光合有效辐射（PAR）区域的反射率逐渐下降，而透射率迅速下降。在落叶前反射率和透射率均增加。在近红外 (NIR) 区域，开发期间反射率增加，透射率下降。幼叶中参数 N（PROSPECT-5 模型中叶片内的紧密层数）的值非常低（B. ermanii 为 1.1，Q.crispula 的阳光和遮荫叶为 1.0），但快速增加了 30% B. ermanii 和 Q.crispula 的阳光照射叶子和 20% 的遮荫叶子。N 较高的顺序是 B. ermanii > Q.crispula 太阳叶 > 遮荫叶。PROSPECT-5 模拟与我们的测量数据表明，叶肉组织的发育增加了 NIR 和 PAR 区域的反射率并降低了透射率，并且叶绿素的增加降低了 PAR 区域的反射率和透射率。我们的结果表明，叶肉的结构和生化发育及其种间变异是了解冠层反射率季节性变化的重要生物学特征。这项研究的结果将帮助我们更好地分析遥感数据。我们的结果表明，叶肉的结构和生化发育及其种间变异是了解冠层反射率季节性变化的重要生物学特征。这项研究的结果将帮助我们更好地分析遥感数据。我们的结果表明，叶肉的结构和生化发育及其种间变异是了解冠层反射率季节性变化的重要生物学特征。这项研究的结果将帮助我们更好地分析遥感数据。