Poster: Environmental physiology

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Abs # P01001: Role of Horses in Spreading Non-Native Invasive Plants into Natural Areas of San Francisco Bay

Presenter:	Ghosh, Sibdas       Contact Presenter
Authors	Ghosh, Sibdas  (A)   Quinn, Lauren  (A)   Williams, Desaree  (A)   Alas, Monika  (A)   Davis, Bonnie  (A)   Kolipinski, Mietek  (B) (A)
Affiliations:	(A): Dominican University of California (B): National Park Service

There have long been comments, assumptions, hypotheses and anecdotal information that some seeds viably pass through the horse gut. Once in horse manure, they ultimately sprout, grow and germinate. Supposedly, some of which could be noxious or invasive weeds. We did not find any conclusive literature references to any scientific programs that validate the long held hypothesis about noxious or invasive weeds that may come from horse manure. Thus, we have investigated the role horse manure on environmental spread of noxious/invasive weeds in natural areas of California. Forty five samples were collected from selected locations throughout the San Francisco Bay Area. Each sample was divided into halves: one of which was allowed to air dry while the other was refrigerated. After one week, both dry and wet samples were weighed and planted individually in sterile 4 inch pots containing weed free soil. A random number selection process for pot locations in trays was computer generated along with 10 control samples which contained no horse manure. Of ninety pots, 34 plants germinated in 21 pots of which 12 represent dry and 9 represents wet samples respectively. These germinated plants were identified as toad rush (Juncus bufonius), Italian ryegrass (Lolium multiflorum), bur-clover (Medicago polymorpha), summer mustard (Hirschfeldia incana), cudweed (Gnaphalium luteoalbum), purslane (Portulaca oleracea), dooryard knotweed (Polygonum aviculare), and cheeseweed (Malva niceaeensis). Except for the toad rush, all plants are non-native to the USA. However, none of these plants are found to be listed as CDFA (California Department of Food and Agriculture) noxious weeds.