Vertical integration of leaf area index in a Japanese deciduous broad-leaved forest
Vertical integration of leaf area index in a Japanese deciduous broad-leaved forest
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DOI：
10.1016/j.agrformet.2008.02.011
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发表时间：
2008-06
影响因子：
6.2
通讯作者：
K. Nasahara;H. Muraoka;S. Nagai;Hiroaki Mikami
中科院分区：
文献类型：
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作者：
K. Nasahara;H. Muraoka;S. Nagai;Hiroaki Mikami
叶面积指数（LAI）是森林生态系统研究中的重要物理量，但由于森林冠层的垂直复杂性，LAI的现场测量常常存在误差。在本研究中，我们通过考虑落叶阔叶林冠层垂直复杂性，建立了一种实用的 LAI 现场测量方法。首先，我们建立了一个半经验模型，用于单位叶面积的叶片干质量的垂直积分。我们还量化了每种树种的凋落物。这些数据使我们能够估计每个物种秋季的 LAI。通过在整个生长季节定期对一些固定样本芽进行原位监测，我们能够估计每个物种叶面积的季节性（作为每个时间点的年度最大值的比例）。通过利用这种季节性来推断 LAI 值占落叶季节 LAI 数据的比例，我们能够估计全年的 LAI。 2006 年，我们在日本中部（高山）的冷温带落叶林中应用了这种方法，并验证了 LAI 测量的传统方法：植物冠层分析仪 (LAI-2000) 和冠层追踪辐射和结构 (TRAC) 方法。 TRAC 估计的 LAI 与我们的结果非常一致，但使用 LAI-2000 估计的 LAI 只是使用我们的方法估计值的一半。使用断面积数据作为物种特定叶面积的代理可以节省劳动力和时间。我们的方法对于研究多个物种的动态和相互作用非常有用，因为它可以估计每个物种的 LAI 及其季节变化。
Leaf area index (LAI) is an important quantity in the study of forest ecosystems, but field measurements of LAI often contain errors because of the vertical complexity of the forest canopy. In this study, we established a practical method for field measurement of LAI in the canopy of a deciduous broadleaved forest by accounting for its vertical complexity. First, we produced a semi-empirical model for the vertical integration of leaf dry mass per unit leaf area. We also quantified the litterfall for each tree species. These data enabled us to estimate the LAI of each species in autumn. By periodic in situ monitoring of some fixed sample shoots throughout the growing season, we were able to estimate the seasonality of leaf area (as a proportion of the annual maximum value at each point in time) of each species. By using this seasonality to extrapolate LAI values as a proportion of the LAI data in the leaf-fall season, we were able to estimate LAI throughout the year. We applied this method in a cool-temperate deciduous forest in central Japan (Takayama) in 2006 and validated conventional methods of LAI measurement: the plant canopy analyzer (LAI-2000) and the Tracing Radiation and Architecture of Canopies (TRAC) approach. LAI estimated by TRAC was in good agreement with our results, but LAI estimated using the LAI-2000 was only half the value estimated using our method. The use of basal area data as a proxy for species-specific leaf areas may save labor and time. Our method will be useful for studying the dynamics and interactions of multiple species because it can estimate LAI and its seasonal changes for each species.