||Differences between symmetric and asymmetric facilitation matter: exploring the interplay between modes of positive and negative plant interactions
||Lin, Y.; Berger, U.; Grimm, V.; Ji, Q.-R.
||Journal of Ecology
||asymmetry; competition; metabolic scaling theory; plant population and community dynamics; plant–plant interaction; self-thinning; spatial pattern; stress-gradient hypothesis; symmetry
(positive interaction) has received increasing attention in plant
ecology over the last decade. Just as for competition, distinguishing
different modes of facilitation (mutualistic, commensal or even
antagonistic) may be crucial.
- We therefore introduce the new
concept of symmetric versus asymmetric facilitation and present a
generic individual-based zone-of-influence model. The model
simultaneously implements different modes of both facilitation and
competition among individual plants via their overlapping zone of
influence. Because we consider facilitation modes as a continuum related
to environmental context, we integrated this concept with the
stress-gradient hypothesis (SGH) by exploring differences in spatial
pattern formation in self-thinning plants along a stress gradient in our
- The interplay among modes of interaction creates
distinctly varied spatial patterns along stress gradients. When
competition was symmetric, symmetric facilitation (mutualism)
consistently led to plant aggregation along stress gradients. However,
asymmetric facilitation (commensalism) produces plant aggregation only
under more benign conditions but tends to intensify local competition
and spatial segregation when conditions are harsh. When competition was
completely asymmetric, different modes of facilitation contributed
little to spatial aggregation.
- Symmetric facilitation
significantly increased survival at the severe end of the stress
gradient, which supports the claim of the SGH that facilitation should
have generally positive net effects on plants under high stress levels.
Asymmetric facilitation, however, was found to increase survival only
under intermediate stress conditions, which contradicts the current
predictions of the SGH.
- Synthesis. Our modelling study
demonstrates that the interplay between modes of facilitation and
competition affects different aspects of plant populations and
communities, implying context-dependent outcomes and consequences. The
explicit consideration of the modes and mechanisms of interactions (both
facilitation and competition) and the nature of stress factors will
help to extend the framework of the SGH and foster research on
facilitation in plant ecology.
|Persistent UFZ Identifier
|Lin, Y., Berger, U., Grimm, V., Ji, Q.-R. (2012):
Differences between symmetric and asymmetric facilitation matter: exploring the interplay between modes of positive and negative plant interactions
J. Ecol. 100 (6), 1482 - 1491