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

Wright, S. Joseph; Yavitt, Joseph B.; Wurzburger, Nina; Turner, Benjamin L.; Tanner, Edmund V. J.; Sayer, Emma J; Santiago, Louis S.; Kaspari, Michael; Hedin, Lars O.; Harms, Kyle E.; Garcia, Milton N. and Corre, Marife D. (2011). Potassium, phosphorus or nitrogen limit root allocation, tree growth, or litter production in a lowland tropical forest. Ecology, 92(8) pp. 1616–1625.

DOI: https://doi.org/10.1890/10-1558.1

Abstract

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 40x40 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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