Abstract Aims To determine whether species that contribute most to a plot’s biomass are the most abundant (high local abundance at plot scale) or the most frequent (occur the most across plots at landscape scale), or both. In the tropical Andes, these patterns may change with elevation. This study assesses the contribution to plot’s above-ground biomass (AGB) of the plant community abundance pattern –the prevalence of within-plot dominant species– and the over-occurrence of regionally frequent species, in an elevation gradient. Methods We considered all trees ≥2.5 cm DBH from 446 0.1 ha plots in an Amazonia-Andes 260–4350 m elevation cline in N Bolivia. Plot AGB was calculated as the sum of AGBs for all stems contained. We grouped plots into four bins segregated by elevation and ran a bootstrap analysis over subsets of 58 random plots per bin with 100 iterations. Simpson evenness index (ED) for all species in each plot was used as a measure for its species abundance. Values for each plot’s species frequency was calculated as the mean of all species’ in the plot mean frequencies across the bin (i.e. the fraction of plots where each species occurs). We used linear models to correlate plot AGB with (1) elevation and mean annual precipitation (MAP), and (2) ED, plot species frequency and elevation. We performed all analyses at the species, genus and family levels. Results Plot AGB was related negatively with elevation, and thus positively with MAP, and also negatively with plot ED and plot species frequency, all significant. Plot species abundance therefore contributes positively to explain the relationship with AGB along elevational gradients, while plot species frequency does so negatively (i.e. less frequent species contribute more to a plot’s AGB across elevation). AGB, for both generic and familial levels was also significantly and negatively correlated with ED, but not related with plot species frequency biomass at these taxonomic levels. Conclusions Plot AGB was mainly associated with elevation and floristic composition where species, genera and families tended to be abundant at the local (plot) scale. Species that were less frequent at the regional scale contributed with more AGB regionally, while frequency at generic and familial scales did little to explain AGB patterns. This association seems stronger at lower elevations for all taxonomic levels while decreases toward higher elevation. Our study reveals a relationship between plot structural features like C stocks –influenced by species local abundances– and the distribution of taxa across the landscape.

中文翻译：

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沿安第斯海拔梯度的物种丰度和频率对地上森林生物量的贡献

摘要目的 确定对地块生物量贡献最大的物种是最丰富的（在地块尺度上局部丰度高）还是最频繁（在景观尺度上跨地块出现最多），或两者兼而有之。在热带安第斯山脉，这些模式可能会随着海拔的升高而变化。本研究评估了植物群落丰度模式对地块地上生物量 (AGB) 的贡献——地块内优势物种的普遍性——以及在海拔梯度中区域频繁物种的过度出现。方法 我们考虑了玻利维亚北部亚马逊-安第斯山脉 260-4350 米海拔的 446 个 0.1 公顷地块中所有 ≥2.5 厘米 DBH 的树木。绘图 AGB 计算为包含的所有茎的 AGB 总和。我们将图分成四个按高程分隔的箱，并对每个箱的 58 个随机图的子集进行了 100 次迭代的引导分析。每个地块中所有物种的辛普森均匀度指数 (ED) 用作其物种丰度的度量。每个地块的物种频率的值计算为地块中所有物种的平均值，在跨箱的平均频率中（即每个物种出现的地块的比例）。我们使用线性模型将地块 AGB 与 (1) 海拔和年平均降水量 (MAP) 以及 (2) ED、地块物种频率和海拔相关联。我们在物种、属和科水平上进行了所有分析。结果地块AGB与海拔呈负相关，因此与MAP呈正相关，与地块ED和地块物种频率呈负相关，均显着。因此，地块物种丰度对解释与沿海拔梯度的 AGB 的关系有积极的贡献，而地块物种频率则是负面的（即，频率较低的物种对地块跨海拔的 AGB 贡献更大）。AGB，对于一般和家族水平，也与 ED 显着负相关，但与这些分类水平的地块物种频率生物量无关。结论 小区 AGB 主要与海拔和植物区系组成有关，其中种、属和科在当地（小区）尺度上趋于丰富。在区域尺度上频率较低的物种在区域上贡献了更多的 AGB，而在一般和家族尺度上的频率几乎不能解释 AGB 模式。对于所有分类学水平，这种关联在较低海拔处似乎更强，而随着海拔升高而降低。我们的研究揭示了地块结构特征（如受物种当地丰度影响的 C 库）与整个景观中的分类群分布之间的关系。