INVESTIGADORES
BERTILLER monica Beatriz
artículos
Título:
Patterns of nitrogen conservation in shrubs and grasses in the Patagonian Monte, Argentina
Autor/es:
CARRERA, A.L.; SAIN, C.L; BERTILLER, M.B
Revista:
PLANT AND SOIL
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2000 vol. 224 p. 185 - 193
ISSN:
0032-079X
Resumen:
We analysed the main plant strategies to conserve nitrogen in the Patagonian Monte. We hypothesized that thetwo main plant functional groups (xerophytic evergreen shrubs and mesophytic perennial grasses) display differentmechanisms of nitrogen conservation related to their structural and functional characteristics. Evergreen shrubsare deep-rooted species, which develop vegetative and reproductive growth from spring to late summer coupledwith high temperatures, independently from water inputs. In contrast, perennial grasses are shallow-rooted species with high leaf turnover, which display vegetative growth from autumn to spring and reproductive activityfrom mid-spring to early-summer, coupled with precipitation inputs. We selected three evergreen shrubs (Larreadivaricata Cav., Atriplex lampa Gill. ex Moq. and Junellia seriphioides (Gilles and Hook.) Moldenke) and threeperennial grasses (Stipa tenuis Phil., S. speciosa Trin. and Rupr. and Poa ligularis Nees ex Steud.), characteristicof undisturbed and disturbed areas of the Patagonian Monte. N concentration in expanded green and senescedleaves was estimated in December 1997 (late spring) and June 1998 (late autumn). Deep-rooted evergreen shrubsdisplayed small differences in N concentration between green and senesced leaves (low N-resorption efficiency),having high N concentration in senesced leaves (low N-resorption proficiency). Shallow-rooted perennial grasses,conversely, showed high N-resorption efficiency and high N-resorption proficiency (large differences in N concentration between green and senesced leaves and very low N concentration in senesced leaves, respectively). Thelack of a strong mechanism of N resorption in evergreen shrubs apparently does not agree with their ability tocolonize N-poor soils. These results, however, may be explained by lower N requirements in evergreen shrubsresulting from lower growth rates, lower N concentrations in green leaves, and lower leaf turnover as comparedwith perennial grasses. Long-lasting N-poor green tissues may, therefore, be considered an efficient mechanismto conserve N in evergreen shrubs in contrast with the mechanism of strong N resorption from transient N-richtissues displayed by perennial grasses. Evergreen shrubs with low N-resorption efficiency provide a more N-richsubstrate, with probably higher capability of N mineralization than that of perennial grasses, which may eventuallyenhance N fertility and N availability in N-poor soils.