Nitrogen form and concentration interact to affect the performance of two ecologically distinct Mediterranean forest trees |
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Authors: | Mercedes Uscola Juan A Oliet Pedro Villar-Salvador Eugenio Díaz-Pinés Douglass F Jacobs |
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Institution: | 1. Forest Ecology and Restoration Group, Departamento de Ciencias de la Vida, Universidad de Alcalá, Campus Universitario A.P. 20, 28805, Alcalá de Henares, Madrid, Spain 2. Departamento de Silvopascicultura, Escuela de Ingeniería Forestal y del Medio Natural, Universidad Politécnica de Madrid, 28040, Madrid, Spain 3. Division of Bio-Geo-Chemical Processes, Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, 82467, Garmisch-Partenkirchen, Germany 4. Department of Forestry and Natural Resources, Hardwood Tree Improvement and Regeneration Center, Purdue University, West Lafayette, IN, 47907-2061, USA
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Abstract: | Most studies examining inorganic N form effects on growth and nutrition of forest trees have been conducted on single species from boreal or temperate environments, while comparative studies with species from other biomes are scarce. We evaluated the response of two Mediterranean trees of contrasting ecology, Quercus ilex L. and Pinus halepensis Mill., to cultivation with distinct inorganic N forms. Seedlings were fertilized with different NH4 +/NO3 ? proportion at either 1 or 10 mM N. In both species, N forms had small effects at low N concentration, but at high N concentration they markedly affected the plant performance. A greater proportion of NH4 + in the fertilizer at high N caused toxicity as it reduced growth and caused seedling death, with the effect being greater in Q. ilex than in P. halepensis. An increase in the proportion of NO3 ? at high N strongly enhanced growth relative to low N plants in P. halepensis but had minor effects in Q. ilex. Relatively more NH4 + in the fertilizer enhanced plant P concentration but reduced K concentration in both species, while the opposite effect occurred with NO3 ?, and these effects were enhanced under high N concentration. We conclude that species responses to inorganic N forms were related to their ecology. P. halepensis, a pioneer tree, had improved performance with NO3 ? at high N concentration and showed strong plasticity to changes in N supply. Q. ilex, a late successional tree, had low responsiveness to N form or concentration. |
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