Wind Dispersal of Artifical Fruits Varying in Mass, Area, and Morphology

Abstract

We used a field experiment to quantify the independent effects of variation in several fruit characteristics and in wind speed on dispersal of the windblown samaras of the tropical tree, Tachigalia versicolor. On Barro Colorado Island, Panama, we simultaneously released 15 different types of artificial models of these fruits, varying in seed mass, fruit area, and basic morphology, from the top of a 40—m tower, dropping them under five different wind conditions. In general, the horizontal distance a model fruit moves from the base of the tower is proportional to the average wind speed to which it was subject during the whole of its descent, divided by the square root of its wing—loading (wing—loading is the force of gravity on the fruit divided by its projected surface area). This relation was observed for fruits with masses from 1.0 to 1.9 g, with areas from 9 to 76 cm2, and with (wing—loading)1/2 from 15.3 to 30.6 mPa. Two separate changes in the design of the fruit, but with no change in the wing—loading value from that of T. versicolor, caused the models to have either a more rapid rate of descent despite the appropriate aerodynamic motion, or an improper aerodynamic motion resulting in a pronounced increase in rate of descent. Model fruits that had the lowest wing—loading (achieved by decreasing seed mass or increasing fruit area) or that were blown by the strongest mean winds were dispersed the greatest mean distances and were scattered most evenly and over the widest area. A change in wing—loading or wind speed changed dispersal distance the least and the evenness of the distribution the most. Variation in wind speed has the potential to override the effect of variation in mass or area on dispersal, unless the differences in mass or area among models are quite large.

Is the Seed Dispersal Related to Spatial Pattern of Individuals in Populations? The Case of Dalbergia cearensis

“…The absence of seeds at distances greater than 13 m in both areas suggests that the species has low-dispersal ability over long distances. Seed dispersal at small distances the mother plant may be reducing the likelihood of D. cearensis reach new safe places for the establishment of the species [29]. The pattern of seeds abundance-distribution due to an around adults, conclude that the seed dispersion for D. cearensis fits in the Gaussian plume models, or because the number of seeds is lower near adults, or gets higher in intermediate distances and then decreases in farthest distances [29].…”

“…Seed dispersal at small distances the mother plant may be reducing the likelihood of D. cearensis reach new safe places for the establishment of the species [29]. The pattern of seeds abundance-distribution due to an around adults, conclude that the seed dispersion for D. cearensis fits in the Gaussian plume models, or because the number of seeds is lower near adults, or gets higher in intermediate distances and then decreases in farthest distances [29]. For many species, flowering is spatially aggregated and then, seed dispersal and germination are often aggregated [4].…”

“…That is what gave Rusch [10] by identifying an aggregated pattern in the seed bank similar to seedling recruitment. Moreover, part of the fruits of D. cearensis is dispersed together with their compact axillary panicles this fact entails an increase in weight and decreases the efficiency of wind dispersal [29]. This feature for short dispersion may be responsible, at least in part, by a group of plants which are formed in the vicinity of the parent plants.…”

Supplying Biomass for Small Scale Energy Production

“…alder); a combination of methods may be used. Studies of wind-mediated seed dispersal for different species indicate the following order of decreasing dispersal: birch>elm=maple>alder>hornbeam>beech>oak (Augspurger and Franson, 1987;Okubo and Levin, 1989;Willson, 1990;Karlsson, 2001 Both downy (Betula pubescens Ehrh.) and silver (Betula pendula Roth) birch produce many seeds.…”

Dispersal potential of Scaevola crassifolia (Goodeniaceae) is influenced by intraspecific variation in fruit morphology along a latitudinal environmental gradient

“…Manipulation of seeds or fruits, or the construction of mimics (artificial seeds or fruits), is one method of investigating relationships between dispersal and intraspecific variation in seed or fruit traits such as mass, area and the presence of appendages (Augspurger and Franson 1987;Hughes and Westoby 1992;Yang et al 2012). Although many seed and fruit traits are frequently proposed to be associated with particular dispersal vectors, the traits associated with hydrochorous dispersal have rarely been demonstrated experimentally.…”