POLYPHENOL CONTROL OF NITROGEN RELEASE FROM PINE LITTER

THE importance of dissolved organic nitrogen in ecosystem nutrient fluxes and plant nutrition is only beginning to be appreciated(1,2). Here we report that the polyphenol concentration of decomposing Pinus muricata litter controls the proportion of nitrogen released in dissolved organic forms relative to mineral forms (NH4+ + NO3-). We have previously shown that concentrations of polyphenols in P. muricata foliage vary along an extreme soil acidity/fertility gradient(3). Apparently this feedback to soil conditions controls the dominant form in which litter nitrogen is mobilized, facilitating nitrogen recovery through pine-mycorrhizal associations, minimizing nitrogen availability to competing organisms, and attenuating nitrogen losses from leaching and denitrification. Polyphenol control of nitrogen dynamics helps explain the convergent evolution of tannin-rich plant communities on highly leached soils.