At breakfast this morning, had a conversation with Colin Prentice about what the patterns of foliar N concentrations were along climatic gradients. He thought they should go up as temperatures and precipitation dropped.
I thought they wouldn't change much. I remember that I had analyzed the data on the side when we did the global foliar 15N data, but couldn't remember for certain.
Here's the relationship for 12,600 leaves after taking into account whether plants were N2 fixers or not.
Not much pattern. Across the global temperature gradient leaves might be 3 mg g-1 higher in cooler places. Similar shift along the global precipitation gradient.
Why this might be interesting is a longer question...