Wildlife & Habitats
Stone Lakes NWR Habitats
Resource Management
Bird & Other Species List

Stone Lakes NWR is composed of a rich mosaic of habitats across several properties that are managed by the Service. Below are some of the many habitat types as outlined in the Final Environmental Impact Statement:

Wetlands

The two main types of wetlands found on the refuge are perennial wetlands and seasonal wetlands.

Perennial wetlands support perennial, herbaceous plant species on sites with high perennial soil moisture and seasonal to permanent soil saturation or inundation. Permanently saturated and semipermanently inundated sites support the herbaceous, emergent vegetation of freshwater marshes. Permanently inundated sites with water to 6 feet deep support tule marsh, dominated by common tule. Semipermanently flooded sites with shallow water (less than 4 feet deep) support cattail marsh. Seasonally flooded, saturated sites upland from tule and cattail marshes support smartweed marsh.

Seasonal wetland communities occur on sites that are ephemerally or seasonally inundated or saturated. Seasonal wetland plants are annuals or perennials adapted to survival under both waterlogged and dry conditions. Seasonal marshes occur in low-lying areas that collect rain and runoff, at the upland ends of blind sloughs, and in river overbank floodlands. These marshes are inundated though long periods in winter and spring and dry completely in summer. Seasonal marsh vegetation is transitional between that of perennial freshwater marsh and vernal pools. Seasonal marshes retain water for longer periods than vernal pools and support a variety of wetland species, including spike-rushes, rushes, sedges, cockle bur, and smartweed.

Artifical seasonal wetlands managed for waterfowl typically support mostly annual vegetation types, including low-growing swamp timothy or picklegrass and taller stands of watergrass, smartweed, dock, and alkali bulrush. These habitats generally consist of mudflats that are exposed in early spring following dewatering and before the germination of annual vegetation begins.

Vernal pools are a unique type of seasonal wetland that form on soils with a shallow hardpan or claypan layer, which prevents percolation and allows water to pond on the surface. Many plant species are completely or predominantly restricted to vernal pool habitats. During winter, vernal pools plants germinate underwater. As the water evaporates in spring, concentric rings of wildflowers bloom in the pools bottoms. By early summer, most vernal pool plants have produced seed and died. Common vernal pool species include Pacific foxtail, Fremont's goldfield, downingia, flowering quillwort, meadowfoam, tricolored monkeyflower, whitehead navarretia, and field owl's clover.

Grasslands

Grasslands are open habitats supporting grasses and forbs with little or no woody vegetation. Most plant species germinate in late fall or early spring, grow and flower in spring, reproduce in late spring and early summer, and spend the dry season in dormant stages (seed or rootstock).

As a result of cultivation, livestock grazing, changes in fire regimes, and other disturbances, most of the grasslands in California are dominated by annual, non-native grasses and forbs. These communities usually occur on clay-rich soils that are moist or waterlogged in winter and very dry in summer. Characteristic species are wild oats, bromes, and filarees. Before Euroamerican settlement, most of Central Valley grassland was dominated by native purple needlegrass. Open areas between the tussocks of this perennial bunchgrass supported many wildflowers, including owl's clover, lupine, farewell-to-spring, and brodiaeas. This native grassland community, known as valley needlegrass grassland, has been almost completely replaced by annual grassland.

Another native perennial grassland, valley wildrye grassland, was once common on seasonally flooded or saturated, low-elevation sites, often adjacent to riparian habitats and freshwater marshes. Valley wildrye grassland is dominated by creeping wildrye, with California mugwort and stinging nettle as common associates.

Woodlands & Savannas

Woodland communities support trees at densities intermediate between forests and savannas, usually between 30% and 50% canopy cover. Savannas support scattered trees over a grassland understory.

Valley Oak Woodland is found on the refuge, defined by scattered valley oaks on deep, well-drained alluvial soils. The understory is usually annual grassland, but more moist sites support shrubs such as poison oak. Valley oak woodland is often transitional between valley oak riparian forest and valley oak savanna.

Riparian

Three Great Valley riparian forest types occur within the refuge: cottonwood, mixed, and valley oak. Mature riparian forests are diverse, multilayered communities associated with occasional to frequent flooding of perennial subsurface water.

Cottonwood riparian forest occurs along perennial streams where inundation occurs every spring. The forest canopy is dominated by Fremont cottonwood and Goodding's willow typically draped with California grape vine. The understory often supports California box elder, California blackberry, buttonbush, and elderberry.

Sites with inundation frequency and duration intermediate between cottonwood and valley oak riparian forest sites support mixed riparian forest. This highly diverse and structurally complex community is transitional between cottonwood riparian and valley oak riparian forest communities. Canopy dominates include Fremont cottonwood, valley oak, Goodding's willow, red willow, yellow willow, California black walnut, and California sycamore. Common understory dominates include California box elder, Oregon ash, poison oak, and buttonbush. The California grape vine often envelopes trees and shrubs, giving the forest a jungle-like appearance.

The highest floodplain terraces, subject to the least frequent inundation, support valley oak riparian forest. The dense forest canopy is dominated by valley oak with associated tree species of Oregon ash, California sycamore, and California black walnut. The understory shrubs and vines include California blackberry, poison oak, and wild rose.