61 



i Idaho. The Heirvard population currently appeeurs secure, although 



it is very sanall. 



WASHDKTTON : Timber hcurvest activities are not ejqaected to have 

 any direct iitpacts on the kncwn sites. Associated activities, 

 such as road construction, yeunding, decking, etc. , could have 

 localized inpacts. 



Grazing does occur at a majority of the sites in Washingtcxi. In 

 general, it does not appeeu: to pose an intnediate threat, 

 althou^ it may eventually, through changes in nutrient levels 

 and successioncil cilteration towaixis more weedy ^secies (J. Gamon, 

 pers. oomn. ) . 



3. Potential threats: As discussed, timber harvesting in the 

 Swan Valley in Montana is likely to continue in the 

 foreseeable future. Further ijppacts to areas oontainirig 

 ponds inhabited by H. aquatilis may occur as a result. In 

 Idaho, the single known population is located on private 

 land; 2dthouc^ the site is willed to the National Audubon 

 Society, the habitat is adjacent to a paved highway, eind may 

 be subject to inpacts from road itainteranoe. Other 

 potential threats to this population eure not foreseen. 

 However, disturbances in bottanland habitats are expected to 

 continue throughout northern Idciho, reducing the li3celihood 

 that additional populations of Howell ia aouatilis will be 

 ' found. 



A potentled ecological threat observed in Montana involves 

 the encroachment of Fhalauris arundinacea (Reed Caneury Grass) 

 into wetlands inhabited by H. aouatilis . Because of the 

 tenacity and rapid growth of the former, it poses a major 

 threat to many wetland eoosystans; it is capable of forming 

 dense monocultures which result in declines in other wetland 

 ^secies (Apfelbaum and Sams 1987) . Several stands have 

 becone established at the recently preserved Swan River 

 Qxbcv (005) site in Montana, and iirpacts on H. aquatilis 

 are being monitored closely. Fhalaris arundinacea also 

 appeeurs to increase in wetland areas in Oregon, especially 

 where some siltation has occurred (J. Kagan, pers. ocnn.). 

 In Washingtc*!, however, H. aouatilis is persisting in some 

 ponds where p. arundinacea has apparently been doninant for 

 many years (J. Gamon, pers. oonm.). 



B. Overutilizaticn for cmnercial, sporting, scientific, or 

 educational purposes: No significant existing or potential 

 threats known. 



C. Disease or predation: HcMellia aquatilis may be susceptible to 

 sane inpacts from grazing by native animals which use the pothole 

 pond habitats. Also, as discussed above, two ponds in Montana 



^ have been impacted in the past by livestock grazing, aind the 



f historical California population may have been extirpated by 



livestock use. In Idaho, edthouc^ livestock do not feed 



