Long-term data sets documenting temporal changes in vegetation communities are uncommon, yet imperative for understanding trends and triggering potential conservation management interventions. For example, decreasing species diversity and increasing non-native species abundance may be indicative of decreasing community stability. We explored long-term plant community change over a 40-year period through the contribution of data collected in 2019 to two historical datasets collected in 1979 and 1999 to evaluate decadal changes in plant community biodiversity in a tidal freshwater marsh in the Fraser River Estuary in British Columbia, Canada. We found that plant assemblages were characterized by similar indicator species, but most other indicator species changed, and that overall α-diversity decreased while β-diversity increased. Further, we found evidence for plant assemblage homogenization through the increased abundance of invasive species such as yellow flag iris (Iris pseudacorus), and reed canary grass (Phalaris arundinacea). These observations may inform concepts of habitat stability in the absence of direct anthropogenic disturbance, and corroborate globally observed trends of native species loss and non-native species encroachment. Our results indicate that within the Fraser River Estuary, active threat management may be necessary in areas of conservation concern in order to prevent further native species biodiversity loss.

记录植被群落时间变化的长期数据集并不常见，但对于了解趋势和触发潜在的保护管理干预措施至关重要。例如，物种多样性的减少和非本地物种丰度的增加可能表明群落稳定性下降。我们通过将 2019 年收集的数据与 1979 年和 1999 年收集的两个历史数据集相结合，探索了 40 年来的长期植物群落变化，以评估弗雷泽河口潮汐淡水沼泽植物群落生物多样性的十年变化。加拿大不列颠哥伦比亚省。我们发现植物组合具有相似的指示物种特征，但大多数其他指示物种发生了变化，总体α多样性下降，而β多样性增加。此外，我们通过黄旗鸢尾（ Iris pseudacorus）和芦苇金丝雀草（Phalaris arundinacea ）等入侵物种丰度的增加发现了植物群落同质化的证据。这些观察结果可以为在没有直接人为干扰的情况下栖息地稳定性的概念提供信息，并证实全球观察到的本地物种丧失和非本地物种入侵的趋势。我们的结果表明，在弗雷泽河口内，在保护关注的地区可能需要积极的威胁管理，以防止本地物种生物多样性进一步丧失。