Upper Tanana , Tanacross ). Other fish species are pike (Upper Tanana , Tanacross ), grayling (Lower Tanana , Upper Tanana , Tanacross ), lingcod (Upper Tanana and Tanacross ) and sucker (Upper Tanana , Tanacross ). Fishing at Mansfield Lake and Fish Creek for whitefish, pike, and grayling began in the late spring and continued until mid-July and was a major harvest activity; whitefish was an especially important and perennially reliable food source. All band members except the very young children assisted in harvesting and processing the catch. The spring fish harvest provided a welcome dietary change after a long winter of eating mostly dried fish and meat. Fish not eaten fresh were processed and dried on drying racks for later consumption. Both fresh and dried fish were cooked in boiling water, produced by placing heated stones into a birch bark basket. The white spruce (Picea glauca) and black spruce (Picea mariana) are the dominant tree, with its maximum tree line being held at around 4,000 feet. Above this limit only stunted willows and alders are found. In the lowlands, several ferns such as the ostrich, wood, beech and oak fern are found. Beginning in late spring and continuing throughout the summer and early fall months, both adults and children gathered a variety of plants and vegetative materials. Fruit and berries (Lower Tanana , Tanacross , Upper Tanana ), edible roots (esp. Indian potato or wild carrot Hedysarum alpinum Lower Tanana ), and assorted plants (esp. wild rhubarb Polygonum alaskanum) were eaten fresh, preserved for later consumption, or used for medicinal purposes. Birch bark of paper birch (Lower Tanana , Tanacross and Upper Tanana ) and spruce roots (Tanacross ) were needed to make baskets, cooking vessels, tools, cradleboards, and canoes. The Upper Tanana use lingonberries (Vaccinium vitis-idaea) as a food source. They boil the berries with sugar and flour to thicken, eat the raw berries, either plain or mixing them with sugar, grease or the combination of the two, fry them in grease with sugar or dried fish eggs, and make them into pies, jam, and jelly. They also preserve the berries alone or in grease and store them in a birchbark basket in an underground cache, or freeze them. They also use them in their traditional medicine, eating the berries or using the juice of the berries for colds, coughs, and sore throats. Kinship The Tanana kinship