1. Large-scale data compilation is increasing steadily in tropical forest research, but the lack of standardized methods for data collection limits drawing inference from large datasets and cross-biome analyses. Different inclusion methods and minimum tree diameter threshold are among these varying factors. To tackle this issue, we evaluated how different approaches for tree sampling affects our understanding of diversity and functioning in different tropical vegetation types.
2. We used a unique dataset of 44 inventory plots (43.54 ha) encompassing an aridity gradient: evergreen moist forests, semideciduous and deciduous tropical forests. Data were collected using the by-tree inclusion method, in which, all stems are measured if the equivalent diameter of the tree reaches the minimum threshold. We simulated the impact of adopting different inclusion methods (by-stem and by-tree) and different minimum diameter thresholds on the estimation of number of trees and stems, biomass and species richness. We used linear and nonlinear mixed models to investigate the effect of minimum diameter threshold and inclusion method on our different response variables. We also evaluated species chance to be sampled under different minimum inclusion criteria.
3. Inclusion method and minimum diameter threshold mainly affect the estimation of number of trees and stems and species richness, especially in deciduous and semideciduous forests, where resprouting is a prevalent strategy. In these forests, many trees that have several stems do not reach the minimum size individually when adopting the by-stem method, yet they do reach the minimum size threshold when all stems are considered together. For these environments under water stress, our analysis showed that using large minimum sizes, such as the 10 cm typically used in rainforests, implies large sampling losses, especially when used jointly with the by-stem inclusion method.
4. The by-tree inclusion method represents an alternative approach that offers a more reliable sampling in different vegetation types, particularly in those habitats where resprouting is a widely encountered strategy along all age classes. We demonstrate the infeasibility of adopting broad and standard minimum thresholds for different tropical vegetation types, particularly considering their widely different ecological strategies.

中文翻译：

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热带森林结构和多样性：方法选择的比较

1. 热带森林研究中的大规模数据汇编正在稳步增加，但缺乏标准化的数据收集方法限制了从大型数据集和跨生物群落分析中进行推断。这些不同的因素包括不同的包含方法和最小树径阈值。为了解决这个问题，我们评估了不同的树木采样方法如何影响我们对不同热带植被类型的多样性和功能的理解。
2. 我们使用了包含干旱梯度的 44 个清单地块（43.54 公顷）的独特数据集：常绿潮湿森林、半落叶和落叶热带森林。使用逐树包含方法收集数据，其中，如果树木的等效直径达到最小阈值，则测量所有茎。我们模拟了采用不同的包含方法（按茎和按树）和不同的最小直径阈值对估计树木和茎的数量、生物量和物种丰富度的影响。我们使用线性和非线性混合模型来研究最小直径阈值和包含方法对不同响应变量的影响。我们还评估了在不同的最低纳入标准下采样的物种机会。
3. 包含方法和最小直径阈值主要影响对树木和茎的数量和物种丰富度的估计，特别是在落叶和半落叶林中，重发是一种普遍的策略。在这些森林中，许多具有多个茎的树木在采用逐茎法时并没有单独达到最小尺寸，但是当所有茎一起考虑时，它们确实达到了最小尺寸阈值。对于这些受水胁迫的环境，我们的分析表明，使用较大的最小尺寸，例如热带雨林中通常使用的 10 厘米，意味着大量的采样损失，尤其是与分茎包含方法结合使用时。
4. 按树包含的方法代表了一种替代方法，它可以在不同的植被类型中提供更可靠的采样，特别是在那些重新发芽是所有年龄段广泛使用的策略的栖息地中。我们证明了对不同热带植被类型采用广泛和标准的最低阈值是不可行的，特别是考虑到它们广泛不同的生态策略。