IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
artículos
Título:
Crab herbivory regulation of plant facilitative and competitive processes in argentinean marshes
Autor/es:
JUAN ALBERTI; MAURICIO ESCAPA; OSCAR IRIBARNE; BRIAN SILLIMAN; MARK BERTNESS
Revista:
ECOLOGY
Editorial:
Ecological Society of America
Referencias:
Año: 2007
ISSN:
0012-9658
Resumen:
Interactions among plants have been hypothesized to be context dependent,
shifting between facilitative and competitive in response to variation in physical and biological
stresses. This hypothesis has been supported by studies of the importance of positive and
negative interactions along abiotic stress gradients (e.g., salinity, desiccation), but few studies
have tested how variation in biotic stresses can mediate the nature and strength of plant
interactions. We examined the hypothesis that herbivory regulates the strength of competitive
and facilitative interactions during succession in Argentinean marshes dominated by Spartina
densiflora and Sarcocornia perennis. Spartina densiflora is preferred by the dominant herbivore
in the system, the crab Chasmagnathus granulatus. We experimentally manipulated crab
herbivory, plant structure, and shade, and we found that when herbivory was low in the spring
and summer, competitive interactions between plants were dominant, but in the fall, when
herbivory was highest, facilitative interactions dominated and Spartina densiflora survival was
completely dependent upon association with Sarcocornia perennis. Moreover, experimental
removal of Sarcocornia perennis across recently disturbed tidal flats revealed that while
Sarcocornia perennis positively affected small Spartina densiflora patches by decreasing
herbivory, as patch size increases and they can withstand the impact of herbivory, competitive
interactions predominated and Spartina densiflora ultimately outcompeted Sarcocornia
perennis. These results show that herbivory can mediate the balance between facilitative and
competitive processes in vascular plant communities and that the strength of consumer
regulation of interactions can vary seasonally and with patch size.