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Modelling seed retention curves for eight weed species on clothing

Ansong, Michael, Pickering, Catherine, Arthur, James Michael
Austral ecology 2015 v.40 no.7 pp. 765-774
Bidens pilosa, Chloris gayana, Conyza canadensis, Cynodon dactylon, Drymaria, Paspalum urvillei, Poa annua, Sporobolus, clothing, ecological invasion, hiking, humans, models, risk, seed dispersal, seeds, walking, weeds
Humans can unintentionally disperse plant propagules (herein referred to as seeds) including weed seeds from clothing when hiking. There is limited experimental or observational information, however, about unintended human‐mediated seed dispersal, particularly from different types of clothing. We experimentally assessed the probability of seed detaching from socks and trousers along a 5 km standardized route for eight common environmental weeds: Bidens pilosa L., Chloris gayana Kunth., Conyza canadensis L., Cynodon dactylon L., Drymaria cordata (L.) Willd. ex Schult., Poa annua L., Paspalum urvillei Steud. and Sporobolus elongatus R.Br. Seed detachment varied among species on both types of clothing, but seeds more easily detached from trousers than socks. When different models were fitted to the data, a three‐parameter generalized exponential model with curves provided the best fit. The curves were leptokurtic, with peak close to the seed source and a long flat tail, which indicates that most seeds dispersed from clothing fall close (within 5 m) to the point of attachment with only a small proportion of seeds dispersed over long distances. Combining attachment and detachment data for the same species, we estimated the actual numbers of seeds potentially dispersed over a hike of 5 km. The study indicates that most seeds are likely to be dispersed at the start of walks, although the actual number of seeds will vary depending on several factors such as the behaviour of the hiker and the amount of weed seeds present at the start of the walk. Those few seeds dispersed much further may, however, be more important in terms of plant invasions. Covering socks with gaiters and avoiding walking through weedy areas such as road edges and car parks before starting walks could minimize the risk of seeds attaching to clothing and hence being dispersed.