Timing of propagule release significantly alters the deposition area of resulting aerial dispersal

Savage, David G.; Barbetti, Martin J.; MacLeod, William J.; Salam, Moin U.; Renton, Michael

doi:10.1111/j.1472-4642.2009.00634.x

Cited by 37 publications

(39 citation statements)

References 44 publications

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“…For plant seeds, models have shown that the probability distribution of dispersal distances (dispersal kernel) is the result of a complex interplay between species traits, most importantly propagule settling velocity and release conditions, and external factors such as atmospheric conditions, topography and vegetation (Soons et al 2004, Schippers and Jongejans 2005, Savage et al 2010, Nathan et al 2011. All else being equal, small seeds disperse further than large seeds due to their lower settling velocity and thus longer expected airborne time.…”

Section: Introductionmentioning

confidence: 99%

Do small spores disperse further than large spores?

Norros

Rannik

Hussein

et al. 2014

Ecology

104

103

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In species that disperse by airborne propagules an inverse relationship is often assumed between propagule size and dispersal distance. However, for microscopic spores the evidence for the relationship remains ambiguous. Lagrangian stochastic dispersion models that have been successful in predicting seed dispersal appear to predict similar dispersal for all spore sizes up to -40 microm diameter. However, these models have assumed that spore size affects only the downwards drift of particles due to gravitation and have largely omitted the highly size-sensitive deposition process to surfaces such as forest canopy. On the other hand, they have assumed that spores are certain to deposit when the air parcel carrying them touches the ground. Here, we supplement a Lagrangian stochastic dispersion model with a mechanistic deposition model parameterized by empirical deposition data for 1-10 microm spores. The inclusion of realistic deposition improved the ability of the model to predict empirical data on the dispersal of a wood-decay fungus (aerodynamic spore size 3.8 microm). Our model predicts that the dispersal of 1-10 microm spores is in fact highly sensitive to spore size, with 97-98% of 1 microm spores but only 12-58% of 10-microm spores dispersing beyond 2 km in the simulated range of wind and canopy conditions. Further, excluding the assumption of certain deposition at the ground greatly increased the expected dispersal distances throughout the studied spore size range. Our results suggest that by evolutionary adjustment of spore size, release height and timing of release, fungi and other organisms with microscopic spores can change the expected distribution of dispersal locations markedly. The complex interplay of wind and canopy conditions in determining deposition resulted in some counterintuitive predictions, such as that spores disperse furthest under intermediate wind, providing intriguing hypotheses to be tested empirically in future studies.

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Section: Introductionmentioning

confidence: 99%

Do small spores disperse further than large spores?

Norros

Rannik

Hussein

et al. 2014

Ecology

104

103

View full text Add to dashboard Cite

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“…; Savage et al . ) and the probability of reaching favourable site conditions for germination (Nathan et al . ; Cousens, Dytham & Law ).…”

Section: Introductionmentioning

confidence: 99%

Seed dispersal by wind: towards a conceptual framework of seed abscission and its contribution to long‐distance dispersal

et al. 2013

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Summary1. 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.

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“…Different organisms develop and reproduce at differing speeds, and dispersal may be active rather passive, and thus directed towards a suitable host. The timing, distance and direction of dispersal events will depend on the dispersal mechanism and the environment and also on the timing of propagule release in relation to environmental conditions . Also, the probability of landing on a particular paddock usage or verge area outside the mapped area could be made a proportion of that inside the mapped area.…”

Section: Discussionmentioning

confidence: 99%