Photos from the Field: Predicting the Terminal Velocity of Dipterocarp Fruit

James R. Smith, Robert Bagchi, Chris J. Kettle, Colin Maycock, Eyen Khoo and Jaboury Ghazoul, (2016). Predicting the terminal velocity of dipterocarp fruit. Biotropica, 48: 154–158. doi: 10.1111/btp.12316

We measured the terminal velocity of helicopter-like fruit from the Dipterocarpaceae family and present a model predicting the terminal velocities for all dipterocarp species in the Malesiana region. A ballistic model of seed dispersal using the observed terminal velocities predicted dispersal distances of 17–77 m under normal atmospheric conditions. These data are of applied use in parametizing models of species coexistence, forest regeneration and habitat connectivity in Southeast Asian tropical forests.

The fruit of the Dipterocarpaceae have elongated sepals which form wings causing the fruit to gyrate when abscised by the mother tree. The Dipterocarpaceae flower and fruit synchronously during mast-fruiting events, which occur roughly every two to seven years. During these mast-fruiting events the crowns of fruiting trees are clearly visible due to the brown coloration of the large fruit crops. (Photo: James Smith).

The fruit of the Dipterocarpaceae have elongated sepals which form wings causing the fruit to gyrate when abscised by the mother tree. The Dipterocarpaceae flower and fruit synchronously during mast-fruiting events, which occur roughly every two to seven years. During these mast-fruiting events the crowns of fruiting trees are clearly visible due to the brown coloration of the large fruit crops. (Photo: James Smith).

Immature Dryobalanops lanceolata fruit. Dipterocarp fruit wings desiccate as they ripen, turning from yellow/red/green to brown before they are abscised by the mother tree. (Photo: James Smith).

Immature Dryobalanops lanceolata fruit. Dipterocarp fruit wings desiccate as they ripen, turning from yellow/red/green to brown before they are abscised by the mother tree. (Photo: James Smith).

Mature fruit from 16 species of Dipterocarpaceae, including Shorea parvifolia shown here, were collected from the ground during the 2014 mast-fruiting event. (Photo: James Smith).

Mature fruit from 16 species of Dipterocarpaceae, including Shorea parvifolia shown here, were collected from the ground during the 2014 mast-fruiting event. (Photo: James Smith).

 

 

All fruits were given a unique identification number and the wing lengths, widths and fresh fruit mass were measured. (Photo: James Smith).

All fruits were given a unique identification number and the wing lengths, widths and fresh fruit mass were measured. (Photo: James Smith).

The first author, James Smith, prepares to release a dipterocarp fruit from a tree tower in Danum Valley, Malaysian Borneo. Dipterocarp fruit were experimentally released to measure their terminal velocities (rate at which the fruit descends through the air column). We regressed species terminal velocity against fruit wing-loading (fruit mass divided by wing area), generating a model from which terminal velocities of dipterocarp fruit can be predicted from their morphological dimensions.

The first author, James Smith, prepares to release a dipterocarp fruit from a tree tower in Danum Valley, Malaysian Borneo. Dipterocarp fruit were experimentally released to measure their terminal velocities (rate at which the fruit descends through the air column). We regressed species terminal velocity against fruit wing-loading (fruit mass divided by wing area), generating a model from which terminal velocities of dipterocarp fruit can be predicted from their morphological dimensions.

A Parashorea tomentella fruit gyrating after experimental release from the tree tower. (Photo: James Smith).

A Parashorea tomentella fruit gyrating after experimental release from the tree tower. (Photo: James Smith).