Tag Archives: wind

dubius research that blows you away

Image: Cpl. James L. Yarboro, US Marine Corps/US Department of Defense.

Image: Cpl. James L. Yarboro, US Marine Corps/US Department of Defense.

Elegant research should always be applauded (or publicised, which is what I’m doing here!). And they don’t come more elegant than David Greene and Mauricio Quesada’s seminal study entitled ‘The differential effect of updrafts, downdrafts and horizontal winds on the seed abscission of Tragopogon dubius’ (Functional Ecology 25: 468–472, 2010). Acknowledging that many plant species enhance wind-dispersal of their seeds (anemochory) by such features as lift-promoting wings and drag-producing fibres, the pair hypothesised that evolution would also increase dispersal capacity through the development of mechanisms that promote abscission by updrafts rather than downdrafts. Using this cosmopolitan weed, they show precisely that: a combination of morphological traits and achene orientation make updrafts much more likely than downdrafts to abscise a seed. That, and the even-more-elegant hairy pappus of the fruits, help the propagules to float away from their parent to start a new life (germination-enabling and seedling-establishment-sufficient conditions permitting!). The duo speculate – sensibly (and as all good papers should!) – that such mechanisms are common and will eventually be seen as a crucial component of long-distance seed movement for almost all wind-dispersed species. Nice work! Other species, however, use more opportunistic agents so sow their seed. For example, Kimberley Taylor and colleagues in a Montana State University Extension publication describe field studies that show the extent to which vehicles collect and disperse seeds, particularly ‘noxious weeds’. Amongst their findings were that more seeds are picked up when vehicles were driven ‘off-trail’ than on-trail, up to 5500 seeds per mile compared to approx. 400, respectively. The study at military sites showed many times more seeds were collected by vehicles driven under wet conditions than under dry conditions, but up to 99 % of seeds stayed attached to a truck after travelling 160 miles under dry conditions. Furthermore, tracked vehicles picked up more seeds than wheeled vehicles. Somewhat predictably (but disappointingly for us autohydrophobes), to help curtail spread of weeds into non-infested areas, they recommend… washing vehicles… frequently(!). Let us hope military vehicles returning from their various, far-flung war zones don’t bring back unwelcome hitch-hikers (of the botanical – or any other – kind!)