Institut de recherche en biologie végétale, Université de Montréal and Jardin botanique de Montréal, Montréal, Québec, Canada.
Québec Centre for Biodiversity Science, McGill University, Montréal, Québec, Canada.
PLoS One. 2020 Feb 13;15(2):e0229146. doi: 10.1371/journal.pone.0229146. eCollection 2020.
Global changes in climate and land use are occurring at an unprecedented rate, often triggering drastic shifts in plant communities. This study aims to reconstruct the changes that occurred over 35 years in the plant communities of temperate bogs subjected to indirect human-induced disturbances. In 2015-17, we resurveyed the vascular flora of 76 plots located in 16 bogs of southern Québec (Canada) first sampled in 1982. We evaluated changes in species richness, frequency of occurrence and abundance, while considering species shade-tolerance and preferential habitat. We calculated beta diversity as between-site similarities in composition, and evaluated differences between the two surveys using tests for homogeneity in multivariate dispersion. We found a significant increase in species richness and beta diversity over the last 35 years associated with major species turnovers, indicating a biotic differentiation of the Sphagnum-bog plant communities. These changes were mostly associated with an increase in the abundance and frequency of shade-tolerant and facultative species, suggesting a global phenomenon of woody encroachment. Because the observed changes occurred in a few decades on sites free of in situ human disturbances, we suggest that they were likely induced by the synergic effect of the agricultural drainage occurring in the surrounding mineral soils, climate warming, and nitrogen atmospheric depositions. We also believe that further changes are to be expected, as the triggering factors persist. Finally, our results highlight the need for increased bog conservation or restauration efforts. Indeed, a rise in beta diversity due to the introduction of nearby terrestrial species could induce biotic homogenization of the bog flora with that of surrounding habitats and ultimately impoverish the regional species pool.
全球气候和土地利用的变化正以前所未有的速度发生，这往往导致植物群落发生剧烈变化。本研究旨在重建 35 年来受到间接人为干扰的温带泥沼植物群落所发生的变化。2015-17 年，我们重新调查了位于加拿大魁北克南部 16 个泥沼中的 76 个样地的维管植物区系，这些样地在 1982 年首次采样。我们评估了物种丰富度、出现频率和丰度的变化，同时考虑了物种的耐荫性和偏好栖息地。我们将 beta 多样性计算为不同样地之间组成的相似性，并使用多元离散的同质性检验来评估两次调查之间的差异。我们发现，在过去的 35 年中，物种丰富度和 beta 多样性显著增加，与主要物种更替有关，这表明 Sphagnum 沼泽植物群落的生物分化。这些变化主要与耐荫和兼性物种的丰度和频率增加有关，这表明全球范围内出现了木质植物侵入的现象。由于观察到的变化是在没有现场人为干扰的地点在几十年内发生的，我们认为这些变化可能是周围矿质土壤中农业排水、气候变暖以及氮大气沉降的协同作用引起的。我们还认为，由于触发因素持续存在，预计还会出现进一步的变化。最后，我们的结果强调了增加泥沼保护或恢复工作的必要性。事实上，由于引入了附近的陆生物种，beta 多样性的增加可能会导致沼泽植物区系与周围栖息地的生物同质化，并最终使该地区的物种库变得更加贫瘠。
