Relationship between seed morphological traits and wind dispersal trajectory

Abstract

The structure and dynamics of plant populations and communities are largely influenced by seed dispersal. How the wind dispersal trajectory of seeds shifts with differences in seed morphology remains unknown. We used a wind tunnel and video camera to track the dispersal trajectory of seven species of Calligonum whose seeds have different kinds of appendages and other morphological traits, using variable wind speeds and release heights to determine the relationship between seed morphological traits and wind dispersal trajectory. Concave-, straight-line-, horizontal-projectile- and projectile-shaped trajectories were found. Dispersal trajectories such as the horizontal projectile (HP) and projectile (P) tended to have a long dispersal distance. Straight line (SL) and concave curve (CC) trajectories tended to have a short dispersal distance. Seeds with bristles and large mass tended to have SL and CC trajectories, those with wings or balloon and small mass tended to have HP and P trajectories. Wind speed tended to have a stronger influence on the dispersal trajectory of light and low-wing-loading seeds, and release height tended to have a stronger influence on the dispersal trajectory of heavy and high-wing-loading seeds. Thus, seed wind dispersal trajectory is not only determined by seed morphological characteristics but also by environmental factors such as wind speed and release height.

Plant canopy may promote seed dispersal by wind

“…Increased dispersal distance may due to induction of an updraft by wind hitting the plant canopy or by change in direction of diaspores that collide with a plant part can change the original dispersal trajectory and increase dispersal distance. Wind conditions can be altered when wind passes through a plant canopy, such as by the generation of an updraft, increasing of vertical wind speed, and reducing of horizontal speed 39 , 45 , 46 . Low horizontal wind speed will decrease diaspore dispersal distance, but an updraft or vertical wind speed can increase dispersal time, thereby increasing diaspore dispersal distance.…”

“…The projected area of diaspore was scanned with a digital scanner, and measured with analysis software (Motic Image Plus 2.0, Motic China Group Co., Xiamen, China), and project area range of 29 diaspores were 5–604 mm 2 . The wing loading was calculated as seed mass divided by projected area 38 , 39 , and wing loading range of 29 diaspores were 0.04–2.1 mg mm −2 . Terminal velocity was measured with a camera described by Zhou et al (2020), and terminal velocity range of 29 diaspores were 0.7–40 m s −1 (Table 2 ).…”

OUP accepted manuscript

“…However, the ITVsm of anemochorous species was not different from that of autochorous species, implying no obvious structural limitation on intraspecific anemochorous seed size variation. Moreover, relative to zoochorous seeds, the dispersal distance of anemochorous seeds was generally short, and determined mainly by wind speed, the shape and type of dispersal appendages and seed mass ( Greene and Johnson 1993 ; Savage et al 2014 ; Zhou et al 2019 ). Therefore, a strong seed mass variation helps maternal plants of anemochorous species spread seeds to different locations to avoid sibling competition ( Savage et al 2014 ; Traveset et al 2014 ; Zhang et al 2020 ).…”

Responses of secondary wind dispersal to environmental characteristics and diaspore morphology of seven Calligonum species

“…All diaspores were air dried and preserved in a laboratory for experiments. Diaspores of the genus Calligonum are achenes with four types of appendages (wings, bristles, balloon, and wings + thorns; Abdurahman et al, ; Zhou et al, ). Pictures of diaspores, methods for measuring morphological and aerodynamic traits of the tested diaspores and their characteristics are showed in Zhou et al, .…”