Global leaf sulphur stoichiometry and the relationships with nitrogen and phosphorus: phylogeny, growth form and environmental controls

Sulphur (S) is an essential bioelement with vital roles in serving
regulatory and catalytic functions, and tightly coupled with N and P in
plants. However, globally stoichiometric patterns of leaf S and its
relationships to leaf N and P are less well studied. We compiled 31,939
records of leaf-based data for 2,600 plant species across 6,652 sites
worldwide. All plant species were divided into different phylogenetic taxa
and growth forms. Standard major axis analysis was employed to fit the
bivariate element relationships. A phylogenetic linear mixed effect model
and a multiple regression model were used to partition the variations of
bioelements into phylogeny and environments, and then to estimate the
importance of environmental variables. Global geometric mean leaf S, N and
P concentrations were 1.44, 15.70 and 1.27 mg g-1, with significant
differences among plant groups. Leaf S-N-P positively correlated to each
other, ignoring plant groups. The scaling exponents of LN-LS, LP-LS and
LN-LP were 0.64, 0.76 and 0.79 for all species, but differed among plant
groups. Both phylogeny and environments regulated the bioelements. The
variability, rather than mean temperature controlled the bioelements.
Phylogeny explained more for the concentrations of all the three
bioelements than environments, of which S was the one most affected by
phylogenetic taxa.