Decomposing leaf mass into metabolic and structural components explains divergent patterns of trait variation within and among plant species

Abstract

Across the global flora, photosynthetic and metabolic rates depend more strongly on leaf area than leaf mass. In contrast, intraspecific variation in these rates is strongly mass-dependent. These contrasting patterns suggest that the causes of variation in leaf mass per area (LMA) may be fundamentally different within vs. among species.We used statistical methods to decompose LMA into two conceptual components – ‘photosynthetic’ LMAp (which determines photosynthetic capacity and metabolic rates, and also affects optimal leaf lifespan) and ‘structural’ LMAs (which determines leaf toughness and potential leaf lifespan) using leaf trait data from tropical forest sites in Panama and a global leaf-trait database.Statistically decomposing LMA into LMAp and LMAs provides improved predictions of trait variation (photosynthesis, respiration, and lifespan) across the global flora, and within and among tropical plant species in Panama. Our analysis shows that most interspecific LMA variation is due to LMAs (which explains why photosynthetic and metabolic traits are area-dependent across species) and that intraspecific LMA variation is due to changes in both LMAp and LMAs (which explains why photosynthetic and metabolic traits are mass-dependent within species).Our results suggest that leaf trait variation is multi-dimensional and is not well-represented by the one-dimensional leaf economics spectrum.

Functional composition of epiphyte communities in the Colombian Andes

“…The leaf areaphotosynthetic spectrum was associated with variation from high to low stomatal density and conductance. A large leaf area in epiphytes must be developed by an increase in photosynthetic components at the expense of mass (Katabuchi et al 2017). A large leaf area in epiphytes must be developed by an increase in photosynthetic components at the expense of mass (Katabuchi et al 2017).…”

Functional ecology of congeneric variation in the leaf economics spectrum

“…Within growth regimes and discounting the marginal HPLL response in mass‐based expression, foliar N can also be considered to be mass proportional, which would be consistent with expectations from N : P stoichiometry (Elser et al ., ). But contrary to expectations under the proportionality hypothesis (Osnas et al ., , ; Katabuchi et al ., ), photosynthetic capacity and dark respiration did not show pure mass proportionality in these Carex species. Instead their mixed‐proportional responses were part of a web of scaling relationships mediated by plasticity in LMA (cf.…”

“…Recent papers on modes of trait expression (Osnas et al, 2013(Osnas et al, , 2018Katabuchi et al, 2017) offer novel insights into the traditional view that species with a greater LMA tend to have longerlived leaves in compensation for their lower photosynthetic capacity (Wright et al, 2004). Osnas et al (2013) shifted the focus from variation in LMA per se to the degree to which individual gas exchange and foliar nutrient traits are proportional to leaf area vs leaf mass.…”

“…Analyzing the nature of the scaling relationships within the suite of LES traits, we also can test the hypothesis that variation in leaf gas exchange rates and nutrient concentrations will be mass-proportional in congeneric herbaceous species with similar, relatively short leaf life spans (Osnas et al, 2018). More generally, we consider the expectation that, among congeners, plasticity should be organized around changes in LMA that influence photosynthetic capacity and metabolic rates affecting optimal leaf life span (Katabuchi et al, 2017).…”

“…The relationships change across ecological scales (Messier et al, 2010(Messier et al, , 2016 and among particular taxonomic groups. Support for the LES erodes when the range of comparison is narrowed to congeners (Mason & Donovan, 2015;Muir et al, 2017;Bahar et al, 2018), species (Niinemets, 2015;Anderegg et al, 2018), species within a functional group (Li et al, 2015(Li et al, , 2017, or co-occurring species in a single locality (Messier et al, 2016(Messier et al, , 2018aKatabuchi et al, 2017). Countergradient responses are also well documented, that is, situations where relationships between LES traits are strong but contrary to global trends (Lusk et al, 2008;Russo & Kitajima, 2016;Anderegg et al, 2018).…”