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Open Access Publications from the University of California

Potassium, phosphorus, or nitrogen limit root allocation, tree growth, or litter production in a lowland tropical forest.

  • Author(s): Wright, S Joseph
  • Yavitt, Joseph B
  • Wurzburger, Nina
  • Turner, Benjamin L
  • Tanner, Edmund VJ
  • Sayer, Emma J
  • Santiago, Louis S
  • Kaspari, Michael
  • Hedin, Lars O
  • Harms, Kyle E
  • Garcia, Milton N
  • Corre, Marife D
  • et al.

Published Web Location

We maintained a factorial nitrogen (N), phosphorus (P), and potassium (K) addition experiment for 11 years in a humid lowland forest growing on a relatively fertile soil in Panama to evaluate potential nutrient limitation of tree growth rates, fine-litter production, and fine-root biomass. We replicated the eight factorial treatments four times using 32 plots of 40 x 40 m each. The addition of K was associated with significant decreases in stand-level fine-root biomass and, in a companion study of seedlings, decreases in allocation to roots and increases in height growth rates. The addition of K and N together was associated with significant increases in growth rates of saplings and poles (1-10 cm in diameter at breast height) and a further marginally significant decrease in stand-level fine-root biomass. The addition of P was associated with a marginally significant (P = 0.058) increase in fine-litter production that was consistent across all litter fractions. Our experiment provides evidence that N, P, and K all limit forest plants growing on a relatively fertile soil in the lowland tropics, with the strongest evidence for limitation by K among seedlings, saplings, and poles.

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