INVESTIGADORES
BERTILLER monica Beatriz
artículos
Título:
Seed dispersal by wind: towards a conceptual framework of seed abscission and its contribution to long-distance dispersal. Journal of Ecology.
Autor/es:
PAZOS, G. O.; GREENE, D.F; KATUL, G; BERTILLER, M.B.; SOONS, M
Revista:
JOURNAL OF ECOLOGY (PRINT)
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2013 vol. 101 p. 889 - 904
ISSN:
0022-0477
Resumen:
1. Diaspore abscission determines many aspects of seed dispersal by wind. While there is yet no
complete mechanistic framework for understanding abscission by wind, empirical studies to date
have suggested that abscission generally (i) occurs above some threshold wind speed and (ii)
depends on the drag force generated by the wind.
2. We revisit these findings and formulate two alternative hypotheses for abscission mechanisms
based on a simple model of a forced harmonic oscillator: large diaspore displacement [through a
maximum deflection threshold, (MDT)] and material fatigue [through a maximum cumulative stress
threshold (MCST)]. We use simulations of abscission events based on these hypotheses and experiments
on diaspore abscission of three Patagonian grasses and a cosmopolitan herb to test the performance
of two abscission functions differing in whether they have a threshold wind speed for
abscission. We also quantify the effects of non-random diaspore abscission on dispersal distances
using a well-tested model for seed dispersal by wind.
3. Both the MDT and MCST hypotheses appear realistic and indicate that while the instantaneous
wind speed determines abscission, the history of wind speeds experienced prior to the detachment
from the plant also plays a role.
4. An evaluation of abscission functions against simulated and experimental abscission data shows
that while the presence of a threshold wind speed in theory appears unrealistic, in practice a threshold
may appear to exist in high-wind-speed environments where all diaspores are blown off the
plant before the abscission layer can develop sufficiently to break during lower wind speeds.
5. Under non-random diaspore abscission, high-wind-speed events during otherwise calm periods
increase long-distance dispersal (LDD), thereby decreasing differences in dispersal distances between
low- and high-wind-speed environments.
6. Synthesis. We formulated two realistic mechanisms of diaspore abscission by applying concepts
from materials science: large diaspore displacement and material fatigue. These reveal that the ambient
wind speed ?history? experienced by a diaspore plays an important role in the timing of abscission
and in the distance travelled, without any thresholds, and that the effect of the diaspore?wind
interaction on LDD varies between environments with different wind speed regimes