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

AGÜERO, M.; PUNTIERI, J.; MAZZARINO, M.J.; GROSSFELD, J.; BARROETAVEÑA, C.

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 isthe main growth-limiting nutrient in most dominant tree species, while P limitation isuncommon, despite the soils´ volcanic origin. This pattern was inferred from leaf N/Pratios and resorption proficiencies, but has not been experimentally tested. Weconducted a greenhouse trial with seedlings of two deciduous species of high timberquality, 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 orwithout the concurrent application of a single P dose (60 mg kg-1 soil) during theirsecond growing season. Response variables were morphological descriptors of shootand root growth, N and P concentrations in green and senescent leaves, andectomycorrhizal infection. Both species were primarily limited by N: the addition of Nresulted 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 ingreen leaves and N and P resorption proficiencies indicate that with increased Navailability P can become a secondary limiting nutrient for N. nervosa. This wasaccompanied by the maintenance of ectomycorrhizal infection and mass allocation toroots in this species. The steep growth response of N. obliqua to N addition may signala strong competitive capacity of this species when growing in soils of high Navailability.