Departamento de Biología, Escuela Politécnica Nacional del Ecuador, Quito, Ecuador.
School of Geography, University of Leeds, Leeds, United Kingdom.
PLoS One. 2022 Apr 20;17(4):e0263508. doi: 10.1371/journal.pone.0263508. eCollection 2022.
Understanding variation in tree functional traits along topographic gradients and through time provides insights into the processes that will shape community composition and determine ecosystem functioning. In montane environments, complex topography is known to affect forest structure and composition, yet its role in determining trait composition, indices on community climatic tolerances, and responses to changing environmental conditions has not been fully explored. This study investigates how functional trait composition (characterized as community-weighted moments) and community climatic indices vary for the tree community as a whole and for its separate demographic components (i.e., dying, surviving, recruiting trees) over eight years in a topographically complex tropical Andean forest in southern Ecuador. We identified a strong influence of topography on functional composition and on species' climatic optima, such that communities at lower topographic positions were dominated by acquisitive species adapted to both warmer and wetter conditions compared to communities at upper topographic positions which were dominated by conservative cold adapted species, possibly due to differences in soil conditions and hydrology. Forest functional and climatic composition remained stable through time; and we found limited evidence for trait-based responses to environmental change among demographic groups. Our findings confirm that fine-scale environmental conditions are a critical factor structuring plant communities in tropical forests, and suggest that slow environmental warming and community-based processes may promote short-term community functional stability. This study highlights the need to explore how diverse aspects of community trait composition vary in tropical montane forests, and to further investigate thresholds of forest response to environmental change.
了解树木功能性状沿地形梯度和随时间的变化，有助于深入了解塑造群落组成和决定生态系统功能的过程。在高山环境中，复杂的地形已知会影响森林结构和组成，但它在决定性状组成、群落气候耐受性指数以及对环境变化的响应方面的作用尚未得到充分探索。本研究调查了在厄瓜多尔南部地形复杂的热带安第斯森林中，树木群落作为一个整体以及其单独的生命史成分（即死亡、存活、繁殖树木）在八年时间内，功能性状组成（表现为群落加权矩）和群落气候指数如何随地形变化而变化。我们发现地形对功能组成和物种气候最适值有很强的影响，因此与地形较高位置的群落相比，位于较低地形位置的群落由适应温暖和湿润条件的获取性物种主导，而地形较高位置的群落则由适应寒冷的保守性物种主导，这可能是由于土壤条件和水文条件的差异。森林功能和气候组成随时间保持稳定；我们发现，在生命史群体中，对环境变化的基于性状的响应证据有限。我们的研究结果证实，在热带森林中，细微的环境条件是构成植物群落的关键因素，并表明环境缓慢变暖以及基于群落的过程可能会促进短期的群落功能稳定性。本研究强调了需要探索热带山地森林中群落性状组成的不同方面如何变化，并进一步调查森林对环境变化的响应阈值。
