Climatic and soil factors explain the two-dimensional spectrum of global plant trait variation

Abstract

Plant functional traits can predict community assembly and ecosystem functioning and are thus widely used in global models of vegetation dynamics and land–climate feedbacks. Still, we lack a global understanding of how land and climate affect plant traits. A previous global analysis of six traits observed two main axes of variation: (1) size variation at the organ and plant level and (2) leaf economics balancing leaf persistence against plant growth potential. The orthogonality of these two axes suggests they are differently influenced by environmental drivers. We find that these axes persist in a global dataset of 17 traits across more than 20,000 species. We find a dominant joint effect of climate and soil on trait variation. Additional independent climate effects are also observed across most traits, whereas independent soil effects are almost exclusively observed for economics traits. Variation in size traits correlates well with a latitudinal gradient related to water or energy limitation. In contrast, variation in economics traits is better explained by interactions of climate with soil fertility. These findings have the potential to improve our understanding of biodiversity patterns and our predictions of climate change impacts on biogeochemical cycles.

Global relationships in tree functional traits

“…Prior research has identified a key set of functional traits that summarize the spectrum of form and function across the plant kingdom, with leaf economics and plant size being the dominant trait axes underpinning life-history strategies 5 , 14 – 16 . Yet, because such studies have traditionally focused only on a small handful of traits estimated at the species level—often heavily biased towards leaf traits 17 —the full dimensionality of trait space remains unknown. This is particularly problematic for trees, which, due to their size, longevity, ontogeny, and unique structural properties, have distinct characteristics and face novel abiotic stressors relative to herbaceous plants 6 , 13 , 18 – 21 .…”

“…A key limitation when exploring functional trait relationships is the sparsity inherent in most plant trait databases 5 , 17 , 29 , 30 . Such restrictions limit traditional analyses to a small subset of traits and species where there is complete coverage, often capturing only a tiny fraction of known species (e.g.…”

“…<1% of all plants 5 ). To overcome this limitation, studies increasingly use imputation approaches to estimate species-level trait averages using phylogenetic and taxonomic information 17 , 30 , 31 . Yet, because these approaches focus solely on species-level averages (i.e.…”

Projecting the futures of plant traits across habitats in Central Europe

“…In our case, the latter was difficult to implement because the same categorical variables (i.e., woodiness and biogeographical status) would be included in many interaction terms with intercorrelated environmental predictors (Figure S19), which might have led to spurious results (Duncan & Kefford, 2021). Finally, the obtained projections of future trait change were highly uncertain (Figures S8-13), which indicates that other important predictors of trait composition need to be identified and incorporated into further analyses (e.g., soil variables, Joswig et al, 2022). (projected per-cell posterior standard deviations).…”

Mycorrhizas shape the evolution of plant adaptation to drought

“…The adaptation of plants to contrasting gradients of water availability has facilitated major ecological transitions on Earth, such as the migration from exclusively aquatic environments to terrestrial habitats (Rubinstein et al ., 2010; Oliver et al ., 2020), and the subsequent expansions across nearly all land surfaces (Joswig et al ., 2021), of which about half are currently susceptible to droughts (Mishra & Singh, 2010). These worldwide evolutionary adaptations in plants have coexisted for millions of years with strategic associations between plant roots and mycorrhizal fungi (Redecker et al ., 2000; Brundrett & Tedersoo, 2018a; Oliver et al ., 2020), which influence the drought tolerance and survival of extant plant species (Augé, 2001; Lehto & Zwiazek, 2011).…”