allowed us to quantify the relationships of leaf economics to climate
at a scale not previously possible. Here we report some global
outcomes from our analyses.
We focus on six key features of leaves that together capture many
essentials of leaf economics. (1) Leaf mass per area (LMA) measures
the leaf dry-mass investment per unit of light-intercepting leaf area
deployed. Species with high LMA have a thicker leaf blade or denser
tissue, or both. (2) Photosynthetic assimilation rates measured
under high light, ample soil moisture and ambient CO2 are here
called photosynthetic capacity (Amass) for brevity. Photosynthetic
capacity is influenced both by stomatal conductance and by the
drawdown of CO2 concentration inside the leaf (carboxylation
capacity). (3) Leaf nitrogen (N) is integral to the proteins of
photosynthetic machinery, especially Rubisco8,13. The photosynthetic
machinery is responsible for drawdown of CO2 inside the leaf,
a process also affected by leaf structure14,15. (4) Leaf phosphorus (P)
is found in nucleic acids, lipid membranes and bioenergetic molecules
such as ATP. Phosphorus derives from weathering of soil
minerals at a site, in contrast to nitrogen, much of which may be
fixed from the atmosphere by plants. (5) Dark respiration rate
(Rmass) reflects metabolic expenditure of photosynthate in the leaf,
especially protein turnover and phloem-loading of photosynthates16.
(6) Leaf lifespan (LL) describes the average duration
of the revenue stream from each leaf constructed. Long LL requires