Globally, functional traits are weak predictors of juvenile tree growth, and we do not know why

Abstract

Summary1. Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates. 3. We tested these alternative hypotheses using data on 27 352 juvenile trees, representing 278 species from 27 sites on all forested continents, and extensive functional trait data, 38% of which were obtained at the same sites at which growth was assessed. Data on potential evapotranspiration (PET), which summarizes the joint ecological effects of temperature and precipitation, were obtained from a global data base. 4. We estimated size-standardized relative height growth rates (SGR) for all species, then related them to functional traits and PET using mixed-effect models for the fastest growing species and for all species together. 5. Both the mean and 95th percentile SGR were more strongly associated with functional traits than with PET. PET was unrelated to SGR at the global scale. SGR increased with increasing SLA and decreased with increasing wood density and seed mass, but these traits explained only 3.1% of the variation in SGR. SGR-trait relationships were consistently weak across families and biogeographic zones, and over a range of tree statures. Thus, the most widely studied functional traits in plant ecology were poor predictors of tree growth over large scales. 6. Synthesis. We conclude that these functional traits alone may be unsuitable for predicting growth of trees over broad scales. Determining the functional traits that predict vital rates under specific environmental conditions may generate more insight than a monolithic global relationship can offer.

The value of biodiversity for the functioning of tropical forests: insurance effects during the first decade of the Sabah biodiversity experiment

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Disentangling the effects of environment and ontogeny on tree functional dimensions for congeneric species in tropical forests

“…In particular, although there is some degree of plasticity during leaf expansion, leaf morphology and chemistry are mostly fixed once the leaf is fully expanded. Therefore, morphological and chemical traits are often too integrative to be tightly linked to physiological variations that occur at daily or seasonal scales (Paine et al , ; Yang et al , ).…”

Functional traits explain the Hutchinsonian niches of plant species

“…The surface depicts the response of intrinsic population growth rate (r 0 ) to two environmental variables [minimum winter temperature (T min ) and maximum summer temperature (T max )]. However, recent studies show that functional traits have rather weak relationships to demography (Paine et al, 2015;Yang et al, 2018) and vital rate elasticities (Adler et al, 2014). The orange point on the vertical axis is the global maximum population growth rate (r max ).…”