Changes in tree functional composition across topographic gradients and through time in a tropical montane forest

Abstract

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.

The effect of climate change on Arcto‐Tertiary Mexican beech forests: Exploring their past, present, and future distribution

“…Patterns of species distribution reflect the interaction between many factors, such as microenvironmental, elevation, anthropic activities, intra‐ and interspecific relations, topography, and physiological features of the tropical species (Báez et al, 2022 ; Rahbek et al, 2019 ). In this comprehensive study, we considered specific environmental variables (Fang & Lechowicz, 2006 ; Rodríguez‐Ramírez, Sánchez‐González, & Ángeles‐Pérez, 2018 ) to simulate the potential distribution for Mexican beech ( Fagus mexicana ).…”

Tree species composition along environmental and disturbance gradients in tropical sub-montane forests, Tanzania

“…The most dominant families with a high number of species were: Leguminosae (28), Rubiaceae (19), Moraceaea (13), Malvaceae (11) and Sapotaceae (10). The most common genera with the highest number of trees were Albizia (5), Ficus (5) and Celtis (5). Also, the most dominant species, in terms of IVI were Leptonychia usambarensis K. Schum(151.8), Cephalosphaera usambarensis (Warb.)…”

“…Tropical montane forests are characterized by complex ecological systems resulting from dramatic changes of physical and geographic properties [1] such as topography [2][3][4][5], including; slope [6], aspect [1,5], climate [7,8], soil [9] and their interactions [10][11][12] from the base to the summit of mountains [13] creating a multitude of microhabitats [3]. Tropical montane forests are the most unique, with high diversity of vegetation [14,15], but they are also among the most threatened ecosystems by anthropogenic activities [5,16,17]. Forest disturbances, particularly selective removal of trees [18], have impact on the species composition and dominance on mountainous landscape [11,19], particularly on the lower elevations [20].…”

Temporal shifts in the functional composition of Andean forests at different elevations are driven by climate change

“…Many studies assessing the effects of climate change on tree communities focused mostly on temperature changes, and VPD tended to be neglected (Báez et al, 2022;Feeley et al, 2011).…”