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首页> 外文学位 >Large tree crowns in closed forest canopies: Measuring structure and estimating light.
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Large tree crowns in closed forest canopies: Measuring structure and estimating light.

机译：封闭的林冠中的大树冠：测量结构并估算光线。

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Trees compete for light. Crown traits are the result of an evolutionary history dominated by this fact, and species exhibit a range of strategies including characteristic shapes and light-foraging abilities in response to this competition. Shape plasticity and crown asymmetry result from the growth and death of branches over long time scales. It is impossible to track every branch in stand-scale forest models, and there are no good approaches that accurately capture the emergent tree-level properties of this branch-scale process. Most forest models therefore ignore tree shape and asymmetry.;Models of tree size and shape are important in both scientific research and in evaluating policy questions. Light absorption in large canopy trees determines their own demographic rates and sets the template of light levels that drives understory growth and mortality, driving both community and ecosystem processes. Models that ignore crown shape and asymmetry could lead to faulty inferences and predictions.;Our work attempts to overcome some of the difficulties in both measuring and modeling large crown shape and light availability. We develop a new approach to extracting three-dimensional crown structural information from high resolution digital stereo imagery to accurately measure crown structure of over nine hundred well-studied large canopy trees. We also present a statistical model that integrates multiple data sources into estimates of the "true" but unmeasurable light available to individual trees. Third, we develop two crown models for forest simulations that capture their space-filling nature with minimum detail, and we parameterize these models from data; one models crown shape, the other crown location. Fourth, we investigate the relationship between light availability and growth.;We extract extensive fine-scale structural detail from the imagery, and generate detailed crown envelopes. We find that light availability predicts the growth rates of large trees primarily for shade intolerant species, while shade tolerant species show little correlation between light and growth. We dramatically improve the ability of forest models to predict exposed canopy area and canopy status from a small number of commonly available inputs. Finally, we successfully model the direction of crown movement and the population-level distribution of crown asymmetry.
机译：树木争光。冠状特征是这一事实主导的进化史的结果，物种表现出一系列应对这一竞争的策略，包括特征形状和光觅食能力。形状的可塑性和冠的不对称性是由于分支在较长时间内的生长和死亡所致。不可能在标准规模的森林模型中跟踪每个分支，并且没有好的方法可以准确地捕获此分支规模过程中新兴的树级属性。因此，大多数森林模型会忽略树木的形状和不对称性。树木的大小和形状的模型在科学研究和评估政策问题中都非常重要。大冠层树的光吸收决定了他们自己的人口统计比率，并确定了驱动林下生长和死亡率，驱动社区和生态系统进程的光水平模板。忽略冠状形状和不对称性的模型可能导致错误的推论和预测。;我们的工作试图克服在测量和建模大型冠状形状和光可用性方面的一些困难。我们开发了一种新方法，可从高分辨率数字立体图像中提取三维冠状结构信息，以准确测量经过研究的九百多棵大树冠的冠状结构。我们还提供了一个统计模型，该模型将多个数据源集成到单个树木可用的“真实”但无法测量的光的估计中。第三，我们为森林模拟开发了两个树冠模型，这些模型以最小的细节捕获了它们的空间填充特性，并从数据中参数化了这些模型。一个模型冠的形状，另一个模型冠的位置。第四，我们研究了光的可用性与生长之间的关系。；我们从图像中提取了广泛的精细结构细节，并生成了详细的冠状包络。我们发现光的可用性主要预测大树的生长速度，主要用于不耐荫的物种，而耐荫的物种显示光与生长之间的相关性很小。我们大大提高了森林模型从少量常用输入中预测裸露的冠层面积和冠层状态的能力。最后，我们成功地建模了冠的运动方向和冠不对称的总体水平分布。

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