disturbance. Tracts of older forest are uncommon, and hence they are considered of considerable importance for conservation. The Ottawa River has large areas of wetlands. Some of the more biologically important wetland areas include (going downstream from Pembroke), the Westmeath sand dune/wetland complex, Mississippi Snye, Breckenridge Nature Reserve, Shirleys Bay, Ottawa Beach/Andrew Haydon Park, Petrie Island, the Duck Islands and Greens Creek. The Westmeath sand dune/wetland complex is significant for its relatively pristine sand dunes, few of which remain along the Ottawa River, and the many associated rare plants. Shirleys Bay has a biologically diverse shoreline alvar, as well as one of the largest silver maple swamps along the river. Like all wetlands, these depend upon the seasonal fluctuations in the water level. High water levels help create and maintain silver maple swamps, while low water periods allow many rare wetland plants to grow on the emerged sand and clay flats. There are five principal wetland vegetation types. One is swamp, mostly silver maple. There are four herbaceous vegetation types, named for the dominant plant species in them: Scirpus, Eleocharis, Sparganium and Typha. Which type occurs in a particular location depends upon factors such as substrate type, water depth, ice-scour and fertility. Inland, and mostly south of the river, older river channels, which date back to the end of the ice age, and no longer have flowing water, have sometimes filled with a different wetland type, peat bog. Examples include Mer Bleue and Alfred Bog. Major tributaries include: Bonnechere River Coulonge River Dumoine River Gatineau River Kipawa River du Lièvre River Madawaska River Mattawa River Mississippi River Montreal River Rivière du Nord Noire River Petawawa River Rideau River Rouge River South Nation River Communities along the Ottawa River include (in down-stream order): Kitcisakik Anicinape Community Long Point First Nation Moffet, Quebec Angliers, Quebec Notre-Dame-du-Nord, Quebec Temiskaming Shores, Ontario Ville-Marie, Quebec Témiscaming, Quebec Thorne, Ontario Mattawa, Ontario Deux Rivières, Ontario Rapides-des-Joachims, Quebec Laurentian Hills, Ontario Deep River, Ontario Sheenboro, Quebec Petawawa, Ontario Pembroke, Ontario Westmeath, Ontario Waltham, Quebec Fort-Coulonge, Quebec La Passe, Ontario Campbell's Bay, Quebec Portage-du-Fort, Quebec Bristol, Quebec McNab/Braeside, Ontario Arnprior, Ontario Quyon, Quebec Ottawa, Ontario Gatineau, Quebec Masson-Angers, Quebec Clarence-Rockland, Ontario Thurso, Quebec Plaisance, Quebec Papineauville, Quebec Montebello, Quebec Fassett, Quebec L'Orignal, Ontario Grenville, Quebec Hawkesbury, Ontario Carillon, Quebec Saint-André-Est, Quebec Rigaud, Quebec Saint-Placide, Quebec Kanesatake Hudson, Quebec Oka, Quebec Vaudreuil-sur-le-Lac, Quebec Vaudreuil-Dorion, Quebec Pincourt, Quebec Norway Bay,