Global biogeography of autotroph chemistry: is insolation a driving force?

• Published in: Oikos 2013-08, Vol.122 (8), p.1121-1130
• Main Authors: Borer, Elizabeth T., Bracken, Matthew E. S., Seabloom, Eric W., Smith, Jennifer E., Cebrian, Just, Cleland, Elsa E., Elser, James J., Fagan, William F., Gruner, Daniel S., Harpole, W. Stanley, Hillebrand, Helmut, Kerkhoff, Andrew J., Ngai, Jacqueline T.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biochemistry; Biogeography; Biological and medical sciences; Editor's choice and Forum; Fundamental and applied biological sciences. Psychology; General aspects; Marine; Plant biology; Terrestrial ecosystems; Tissues
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1111/j.1600-0706.2013.00465.x

Photoautotroph nitrogen (N) and phosphorus (P) tissue concentrations can influence ecosystem function via processes including growth, decomposition, and consumption, and may reflect traits maintaining coexistence. Studies in terrestrial systems have led to hypotheses that latitudinal trends in the N and P content of leaves may be driven by soil substrate age, environmental temperature, or season lenght; however, terrestrial patterns alone cannot differentiate these mechanisms. Here, we demonstrate that broad geographical patterns of N and P in freshwater and marine multicellular photoautotrophs are concordant with those in terrestrial ecosystems. Our > 6800 record database reveals that mean tissue N and P increase with latitude in all ecosystems, but P increases more rapidly, causing N:P to decline; mean N:P scaling within individuals also is identical among systems, despite very different evolutionary environments. A partitioning of the variance in these data suggests that species composition and local environmental context likely lead to the variation observed within a latitudinal band. However, the consistency of trends in photosynthetic tissue chemistry across Earth's ecosystems suggests that biogeographical gradients in insolation and growing season length may constrain tissue N and P, whereas global trends in temperature, nutrient supply, and soil substrate age are unlikely to generate the consistent latitudinal trends among ecosystems. Thus, this cross-ecosystem comparison suggests a new hypothesis, global patterns of insolation, while also providing a new perspective on other mechanisms that have been hypothesized to underlie latitudinal trends in photosynthetic tissue chemistry.