Do Horses Spread Non-Native Plants on Trails?

by: Stith T. Gower, PhD
February 11 2007 Article # 8846
[From THE HORSE http://www.thehorse.com/viewarticle.aspx?ID=8846 ]

Can plant and weed seeds contained in horse manure, hooves, and hay cause nonnative plant species (plants that were introduced to that ecosystem but do not grow there naturally) to spread along trails and into parks and forests? This is an ecological question that often arises. Stith T. Gower, PhD, of the Department of Forest Ecology and Management at the University of Wisconsin-Madison, has determined that while there are seeds from weed and non-native plant species in horse manure and hay, the plants that result don't survive or spread on trails. Therefore, horses do not appear to be a major source for the introduction of nonnative species.

"Nonnative plant species pose a serious ecological and economic threat to managed and natural ecosystems," said Gower. "Therefore, there is a great need to identify major sources for the introduction of non-native species and implement management plans to reduce or eliminate their introduction. Horses have been suggested to be an important source for the introduction of nonnative plant species along trails, but the data are largely anecdotal."

The objectives of two studies were to determine if horse hay, manure, and hoof debris samples contained seeds from nonnative species, and if so, whether their seeds would germinate and establish on the trails.