Biotic homogenization (BH), the process by which β-diversity erodes, is suspected to be severe among plant communities due to widespread anthropogenic disturbances. However, few studies have directly linked anthropogenic disturbance with patterns of BH. The US National Wetlands Condition Assessment (NWCA) provides an opportunity to investigate patterns of β-diversity related to anthropogenic disturbances. Our objectives were to compare β-diversity between highly, intermediately and less-disturbed herbaceous emergent wetlands across the temperate region of the conterminous US, and to identify species with greatest influence on β-diversity patterns within disturbance categories. Using species occurrence and abundance data, average distances to group centroids in ordination space were used to assess wetland β-diversity across a disturbance gradient. Species contributions to β-diversity were calculated per disturbance category. Compared to the least and intermediately disturbed wetlands, highly disturbed wetlands had significantly lower β-diversity based on species abundances across the study area. When using only species occurrences, highly disturbed wetlands had significantly lower β-diversity than intermediately disturbed wetlands. No significant differences were found amongst disturbance categories at the within-site scale. The invasive grass Phalaris arundinacea had the greatest influence on β-diversity, especially in the most disturbed wetlands. Our results demonstrate that anthropogenic disturbances have homogenized regional botanical diversity. This homogenization is a function of disturbance intensity, which, after a threshold is crossed creates environmental conditions that lead to the local dominance of a single, widespread invader. This process is repeated across the region, scaling up to homogenize the flora of the entire region.

中文翻译：

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美国本土湿地植被的生物同质化由 Phalaris arundinacea 和人为干扰驱动

由于广泛的人为干扰，生物同质化 (BH) 是 β 多样性侵蚀的过程，被怀疑在植物群落中很严重。然而，很少有研究将人为干扰与 BH 模式直接联系起来。美国国家湿地状况评估 (NWCA) 为研究与人为干扰相关的 β 多样性模式提供了机会。我们的目标是比较美国本土温带地区高度、中度和较少干扰的草本新兴湿地之间的 β 多样性，并确定干扰类别中对 β 多样性模式影响最大的物种。使用物种出现和丰度数据，到排序空间中组质心的平均距离用于评估扰动梯度上的湿地 β 多样性。每个干扰类别计算物种对β多样性的贡献。与干扰最少和中度干扰的湿地相比，基于整个研究区域的物种丰度，高度干扰的湿地具有显着较低的 β 多样性。当仅使用物种出现时，高度干扰的湿地的β多样性显着低于中度干扰的湿地。在现场范围内的干扰类别之间没有发现显着差异。入侵草 Phalaris arundinacea 对 β 多样性的影响最大，尤其是在最受干扰的湿地中。我们的结果表明，人为干扰使区域植物多样性同质化。这种同质化是扰动强度的函数，其中，越过门槛后，环境条件会导致单一的、广泛的入侵者在当地占据主导地位。这个过程在整个地区重复进行，按比例扩大以统一整个地区的植物群。