Quantifying tree biomass is an important research and management goal across many disciplines. For species that exhibit predictable relationships between structural metrics (e.g. diameter, height, crown breadth) and total weight, allometric calculations produce accurate estimates of above-ground biomass. However, such methods may be insufficient where inter-individual variation is large relative to individual biomass and is itself of interest (for example, variation due to herbivory). In an East African savanna bushland, we analysed photographs of small (<5 m) trees from perpendicular angles and fixed distances to estimate above-ground biomass. Pixel area of trees in photos and diameter were more strongly related to measured, above-ground biomass of destructively sampled trees than biomass estimated using a published allometric relation based on diameter alone (R2 = 0.86 versus R2 = 0.68). When tested on trees in herbivore-exclusion plots versus unfenced (open) plots, our predictive equation based on photos confirmed higher above-ground biomass in the exclusion plots than in unfenced (open) plots (P < 0.001), in contrast to no significant difference based on the allometric equation (P = 0.43). As such, our new technique based on photographs offers an accurate and cost-effective complement to existing methods for tree biomass estimation at small scales with potential application across a wide variety of settings.

中文翻译：

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使用摄影估计小树的地上生物量

量化树木生物量是许多学科的重要研究和管理目标。对于在结构指标（例如直径、高度、冠幅）和总重量之间表现出可预测关系的物种，异速生长计算可以准确估计地上生物量。然而，如果个体间的变异相对于个体生物量很大并且本身是令人感兴趣的（例如，由于食草动物的变异），这种方法可能是不够的。在东非热带稀树草原丛林中，我们从垂直角度和固定距离分析了小 (<5 m) 树木的照片，以估计地上生物量。照片中树木的像素面积和直径与实测值的相关性更强，2= 0.86 与 R2= 0.68）。当在草食动物排除地块与无围栏（开放）地块中的树木上进行测试时，我们基于照片的预测方程证实，排除地块中的地上生物量高于无围栏（开放）地块（P < 0.001），相比之下没有显着基于异速生长方程的差异（P = 0.43）。因此，我们基于照片的新技术为现有的小规模树木生物量估计方法提供了准确且具有成本效益的补充，并具有在各种环境中的潜在应用。