INVESTIGADORES
GOLLUSCIO Rodolfo Angel
artículos
Título:
Minimal plant responsiveness to summer water pulses: ecophysiological constraints of three species of semiarid Patagonia
Autor/es:
GOLLUSCIO RA; V SIGAL ESCALADA; J PÉREZ
Revista:
Rangeland Ecology and Management (ex JRM)
Editorial:
SOC RANGE MANAGEMENT
Referencias:
Lugar: Boulder, Colorado; Año: 2009 vol. 62 p. 171 - 178
ISSN:
1550-7424
Resumen:
In arid ecosystems, a
few large summer rains frequently differentiate wet years from dry ones.
However, use of this additional < water by plants has limited experimental
evidence. We applied a 16-mm summer water pulse (12% of mean anual
precipitation) to two plant communities of the Patagonian steppe, and compared
responses of three dominant species, which can be ordered by decreasing
xerophytism and increasing rooting depth and summer activity: 1) colapiche,
evergreen dwarf shrub (Nassauvia glomerulosa [Lag.] Don); 2) coiro´n amargo,
evergreen grass (Stipa speciosa Trin. et Rupr.); and 3) neneo, drought
deciduous shrub (Mulinum spinosum [Cav.] Pers.). Shallow-rooted species (S.
speciosa and N. glomerulosa), which use wáter from dry soil layers, showed a greater
leaf water potential response to watering than deep-rooted species (M.
spinosum). Leaf water potential response was greater and quicker in xerophytic
species than in mesophytic ones (N. glomerulosa.S. speciosa.M. spinosum).
However, this response only translated into leaf conductance and transpiration
responses for coiro´n amargo, probably because the species with winter
phenological cycle (N. glomerulosa) is less able to utilize summer water inputs
than species with a summer phenological cycle (S. speciosa). The lack of
response of deep-rooted M. spinosum in leaf conductance, transpiration, and
photosynthesis may have been due to the high leaf water potential of control
plants. Instead, in S. speciosa and N. glomerulosa net photosynthesis decreased
below zero following watering, suggesting the start of growth pulses. The
complex chain of plant processes triggered by rainfall, and the constraints
imposed to different species by rooting depth, phenology, and xerophytism,
could explain the frequent low response to both large rainfall events and
above-average rainfall years in this arid community. Our results suggest that,
paradoxically, water may be suboptimally used at local scales in arid rangeland
ecosystems.