Wildlands

Wetlands
Refuge wetlands include upland basins, ice-formed lakes on the flats, river flooded lowlands, oxbows, and bog lakes. Spring runoff, rain, and river flooding recharge Koyukuk's lakes, but water depths and shorelines can vary from year to year. Lake depths seldom exceed 15 feet and usually are much shallower. Water temperatures in these shallow lakes can reach 70°F or more in mid-summer, creating ideal conditions for growth of aquatic plants and invertebrates. Among the aquatic plants, duckweed (Lemna sp.), horsetail (Equisetum spp.), water milfoil (Myriophyllum sp.), mare's tail (Hippuris vulgaris), and smartweed (Polygonum sp.) are abundant. One or more of 12 species of pondweed (Potamogeton spp.) occur in almost all lakes. Indicators of bog lakes include water lily (Nuphar polysepalum), pygmy water lily (Nymphaea tetragona), water hemlock (Cicuta douglasii, C. mackenziana), water parsnip (Sium suave), and bladderwort (Urtricularia macrorhiza). Several species of graminoids including sedge (Carex), bluejoint grass (Calamagrostis canadensis), and foxtail (Hordeum) provide cover on exposed shorelines. A variety of forbs grow on recently exposed soils along shorelines.

Shallow seasonally-flooded basins (locally called “grass lakes”) are also common along the Koyukuk River. Grass lakes are usually winter-filled during spring breakup and flooding, but otherwise are dry meadows with many showing the beginnings of shrub and forest succession. The drier portions of grass lakes are vegetated primarily by bluejoint grass and occasionally arctic-bentgrass (Arctagrostis latifolia), an important food for geese. Carex aquatilis, C. rostrata, C. capitata and other sedges dominate in the wetter areas. Other species that occur in grass lake habitat include bog rosemary (Andromeda polifolia), bog cranberry (Oxycoccus microcarpus), sundew (Drosera anglica, D. rotundifolia), and the marsh cinquefoil (Potentilla palustris). During flooding, sedges, and occasionally bluejoint grass will survive as emergent vegetation in water depths exceeding four feet. Shorelines of bog lakes vary in character, but nearly always contain buckbean (Menyanthes trifoliata), wild calla (Calla palustris), various sedge species, and burr-reed (Sparganium hyperboreum); cattails (Typha latifolia) are less common on the refuge.

Last updated: July 22, 2008