State Key Laboratory of Plant Diversity and Specialty Crops, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China; Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China; University of Chinese Academy of Sciences, Beijing, China.
TUD Dresden University of Technology, Forest Zoology, Tharandt, Germany.
Sci Total Environ. 2024 Jul 20;935:173343. doi: 10.1016/j.scitotenv.2024.173343. Epub 2024 May 21.
Niche convergence or conservatism have been proposed as essential mechanisms underlying elevational plant community assembly in tropical mountain ecosystems. Subtropical mountains, compared to tropical mountains, are likely to be shaped by a mixing of different geographic affinities of species and remain somehow unclear. Here, we used 31 0.1-ha permanent plots distributed in subtropical forests on the eastern and western aspects of the Gaoligong Mountains, southwest China between 1498 m and 3204 m a.sl. to evaluate how niche-based and biogeographic processes shape tree community assembly along elevational gradients. We analyzed the elevational patterns of taxonomic, phylogenetic and functional diversity, as well as of individual traits, and assessed the relative importance of environmental effects on these diversity measures. We then classified tree species as being either tropical affiliated or temperate affiliated and estimated their contribution to the composition of biogeographic affinities. Species richness decreased with elevation, and species composition showed apparent turnover across the aspects and elevations. Most traits exhibited convergent patterns across the entire elevational gradient. Phylogenetic and functional diversity showed opposing patterns, with phylogenetic diversity increasing and functional diversity decreasing with elevation. Soil nutrients, especially phosphorus and nitrogen, appeared to be the main abiotic variables driving the elevational diversity patterns. Communities at lower elevations were occupied by tropical genera, while highlands contained species of tropical and temperate biogeographic affinities. Moreover, the high phylogenetic diversity at high elevations were likely due to differences in evolutionary history between temperate and tropical species. Our results highlight the importance of niche convergence of tropical species and the legacy of biogeographic history on the composition and structure of subtropical mountain forests. Furthermore, limited soil phosphorus caused traits divergence and the partitioning for different forms of phosphorus may explain the high biodiversity found in phosphorus-limited subtropical forests.
生境趋同或保守被认为是热带山地生态系统中植物群落沿海拔梯度组装的重要机制。与热带山脉相比，亚热带山脉可能受到不同物种地理亲缘关系的混合影响，其机制仍不清楚。在这里，我们使用了 31 个 0.1 公顷的永久性样地，这些样地分布在中国西南部高黎贡山东、西两侧的亚热带森林中，海拔范围为 1498-3204 米，以评估基于生境和生物地理过程如何沿海拔梯度塑造树木群落组装。我们分析了分类学、系统发育和功能多样性以及个体特征的海拔模式，并评估了环境效应对这些多样性测度的相对重要性。然后，我们将树种分为热带附属种和温带附属种，并估计它们对生物地理亲缘关系组成的贡献。物种丰富度随海拔升高而降低，物种组成在东西两面和海拔高度上都有明显的变化。大多数特征在整个海拔梯度上表现出趋同模式。系统发育和功能多样性表现出相反的模式，系统发育多样性随海拔升高而增加，而功能多样性则随海拔升高而降低。土壤养分，特别是磷和氮，似乎是驱动海拔多样性模式的主要非生物变量。较低海拔的群落由热带属占据，而高海拔则包含热带和温带生物地理亲缘关系的物种。此外，高海拔处高的系统发育多样性可能是由于温带和热带物种的进化历史差异所致。我们的研究结果强调了热带物种生境趋同的重要性以及生物地理历史对亚热带山地森林组成和结构的影响。此外，有限的土壤磷导致了特征的分化，而不同磷形式的分配可能解释了在磷限制的亚热带森林中发现的高生物多样性。
