Abstract
Screening species-rich communities for the variation in functional traits along environmental gradients may help understanding the abiotic drivers of plant performance in a mechanistic way. We investigated tree leaf trait variation along an elevation gradient (1000–3000 m) in highly diverse neotropical montane forests to test the hypothesis that elevational trait change reflects a trend toward more conservative resource use strategies at higher elevations, with interspecific trait variation decreasing and trait integration increasing due to environmental filtering. Analysis of trait variance partitioning across the 52 tree species revealed for most traits a dominant influence of phylogeny, except for SLA, leaf thickness and foliar Ca, where elevation was most influential. The community-level means of SLA, foliar N and Ca, and foliar N/P ratio decreased with elevation, while leaf thickness and toughness increased. The contribution of intraspecific variation was substantial at the community level in most traits, yet smaller than the interspecific component. Both within-species and between-species trait variation did not change systematically with elevation. High phylogenetic diversity, together with small-scale edaphic heterogeneity, cause large interspecific leaf trait variation in these hyper-diverse Andean forests. Trait network analysis revealed increasing leaf trait integration with elevation, suggesting stronger environmental filtering at colder and nutrient-poorer sites.
Highlights
Screening species-rich communities for the variation in functional traits along environmental gradients may help understanding the abiotic drivers of plant performance in a mechanistic way
The elevation-level means of specific leaf area (SLA), foliar N and Ca, and foliar N/P ratio of the studied species decreased from 1000 to 3000 m, while dry matter content and leaf thickness and toughness increased
The analysis of trait variance partitioning with Bayesian mixed models revealed for most traits a dominant influence of phylogeny, except for SLA, leaf thickness and foliar Ca, where elevation had the largest influence
Summary
Screening species-rich communities for the variation in functional traits along environmental gradients may help understanding the abiotic drivers of plant performance in a mechanistic way. We investigated tree leaf trait variation along an elevation gradient (1000–3000 m) in highly diverse neotropical montane forests to test the hypothesis that elevational trait change reflects a trend toward more conservative resource use strategies at higher elevations, with interspecific trait variation decreasing and trait integration increasing due to environmental filtering. Elevated temperatures and a higher evaporative demand expose many mountain forest plants with adaptation to cool-humid climates to stress, which may result in reduced vitality and productivity[5], and often upward movement of biota and the thermophilisation of TMF communities[6,7] The consequences of these changes for ecosystem integrity and functioning are difficult to predict due to the high abiotic and biotic complexity of TMF landscapes, which change with topography and elevation over short spatial distances[3,8,9]. Empirical evidence supporting this assumption in tropical forests is scarce
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