Key message

We assessed even-aged stand vertical distributions of LiDAR returns and found that tree species, age, and crown cover each have a distinct pattern that together explains up to 47% of the variation.

Abstract

Light detection and ranging (LiDAR) provides information on the vertical structure of forest stands enabling detailed and extensive ecosystem study. The vertical structure is often summarized by scalar features and data-reduction techniques that limit the interpretation of results. Instead, we quantified the influence of three variables, species, crown cover, and age, on the vertical distribution of airborne LiDAR returns from forest stands. We studied 5428 regular, even-aged stands in Quebec (Canada) with five dominant species: balsam fir [Abies balsamea (L.) Mill.], paper birch (Betula papyrifera Marsh), black spruce [Picea mariana (Mill.) BSP], white spruce (Picea glauca Moench) and aspen (Populus tremuloides Michx.). We modeled the vertical distribution against the three variables using a functional general linear model and a novel nonparametric graphical test of significance. Results indicate that LiDAR returns from aspen stands had the most uniform vertical distribution. Balsam fir and white birch distributions were similar and centered at around 50% of the stand height, and black spruce and white spruce distributions were skewed to below 30% of stand height (\(p\)<0.001). Increased crown cover concentrated the distributions around 50% of stand height. Increasing age gradually shifted the distributions higher in the stand for stands younger than 70-years, before plateauing and slowly declining at 90–120 years. Results suggest that the vertical distributions of LiDAR returns depend on the three variables studied.

中文翻译：

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树种、树冠覆盖和年龄作为机载 LiDAR 返回垂直分布的决定因素

关键信息

我们评估了 LiDAR 返回的等龄林分垂直分布，发现树种、年龄和树冠覆盖率各有不同，共同解释了高达 47% 的变化。

抽象的

光探测和测距 (LiDAR) 提供有关林分垂直结构的信息，从而能够进行详细而广泛的生态系统研究。垂直结构通常由限制结果解释的标量特征和数据缩减技术来概括。相反，我们量化了物种、树冠覆盖和年龄这三个变量对林分机载 LiDAR 回波垂直分布的影响。我们研究了魁北克（加拿大）的 5428 个普通、等龄林分，其中有五种优势树种：香脂冷杉 [ Abies balsamea (L.) Mill.]、纸桦 ( Betula papyrifera Marsh)、黑云杉 [ Picea mariana (Mill.) BSP ]、白云杉（Picea glauca Moench）和白杨（Populus tremuloides米克斯。）。我们使用功能通用线性模型和新的非参数显着性图形检验对三个变量的垂直分布进行建模。结果表明，来自白杨林的 LiDAR 返回具有最均匀的垂直分布。香脂冷杉和白桦分布相似，集中在林分高度的 50% 左右，黑云杉和白云杉分布偏向于林分高度的 30% 以下 ( \(p\)<0.001)。增加的树冠覆盖集中了大约 50% 的展位高度的分布。随着年龄的增长，年龄小于 70 岁的林分的分布逐渐升高，然后在 90-120 岁时趋于稳定并缓慢下降。结果表明，LiDAR 回报的垂直分布取决于所研究的三个变量。