INVESTIGADORES
DALEO Pedro
artículos
Título:
Beyond competition: the stress-gradient hypothesis tested in plant-herbivore interactions
Autor/es:
DALEO, P.; IRIBARNE, O.
Revista:
ECOLOGY
Referencias:
Año: 2009 vol. 90 p. 2368 - 2374
ISSN:
0012-9658
Resumen:
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The stress-gradient
hypothesis predicts that interactions among plants are context dependent,
shifting from facilitation to competition as environmental stress decreases. Although
restricted to facilitation/competition, the mechanistic model behind the hypothesis
is easily modified to include other negative interactions that are as important
as competition in structuring natural communities, e.g., herbivory. To evaluate
this hypothesis we experimentally tested if the balance between the
facilitative and trophic effect of an intertidal, burrowing, herbivorous crab
in marsh plants is context dependent and shifts from positive to negative as
stress decreases. By sampling salt marshes differing in sediment size
characteristics, we show that sites with larger sediment particle size had less
stressful oxygen levels than sites with fine sediment particles, and that the
level of stress was reduced by the presence of crab burrows. We then conducted
a factorial experiment manipulating sediment size and crab presence. Results
show that, by decreasing soil anoxic stress, crabs increase plant growth in
stressful zones, but their ecological importance as herbivores increases in
more benign zones. Our findings suggest that the balance between positive and
negative interactions along stress gradients is more important than previously
perceived and also applies to facilitation and herbivory between animals and pl