Seedling response of Nothofagus species to N and P: linking plant architecture to N/P ratio and resorption proficiency

AGÜERO, MARIANA; PUNTIERI, JAVIER; MAZZARINO, MARÍA JULIA; GROSFELD, JAVIER; BARROETAVEÑA, CAROLINA

TREES-STRUCTURE AND FUNCTION

SPRINGER

Lugar: Berlin; Año: 2014 vol. 28 p. 1185 - 1195

0931-1890

Previous studies on mature forests of NW Argentinean Patagonia indicated that N is the main growthlimiting nutrient in most dominant tree species, while P limitation is uncommon, despite the soils? volcanic origin. This pattern was inferred from leaf N/P ratios and resorption proficiencies, but has not been experimentally tested. We conducted a greenhouse trial with seedlings of two deciduous species of high timber quality, Nothofagus nervosa and N. obliqua, and soils characteristic of each species. Seedlings were fertilized with three levels of N (100, 200 and 400 mg kg-1 soil) with or without the concurrent application of a single P dose (60 mg kg-1 soil) during their second growing season. Response variables were morphological descriptors of shoot and root growth, N and P concentrations in green and senescent leaves and ectomycorrhizal infection. Both species were primarily limited by N: the addition of N resulted in higher shoot and root masses, an increased number of nodes, taller stems and greater basal and root diameters, while no effect of P was found. N/P ratios in green leaves and N and P resorption proficiencies indicate that with increased N availability P can become a secondary-limiting nutrient for N. nervosa. This was accompanied by the maintenance of ectomycorrhizal infection and mass allocation to roots in this species. The steep growth response of N. obliqua to N addition may signal a strong competitive capacity of this species when growing in soils of high N availability.