This small, but important, property was donated by Helen and Ruth Dahl in 1988. It is located along the Saco River of the Mt. Washington Valley and protects one of the finest, accessible examples of Silver Maple/Sugar Maple/White Ash floodplain forest in the state. Used as farmland throughout the 1800s and early 1900s, much of the property has matured into forestland, but NH Audubon maintains some open areas for less-common wildlife species, especially early successional or shrubland birds. A major restoration of the sanctuary including invasive species control, hydrological improvements to the wetlands, improved visitor services, and trail restoration was completed in 2011. The trail system provides access to all of the sanctuary’s varied habitats, including upland pine forest, early successional forest, field, floodplain forest, wetlands, riverine, and even a cobble barren plant community. Several rare plants are protected and actively managed on this sanctuary. Nest boxes are provided for several species of birds. The NRCS’s Wetland Reserve Program (WRP) holds a conservation easement on the sanctuary.
Visitors may notice shredded stumps and vegetation that remains from field management work in 2020, in which several acres of young forest were cut back to promote early successional (shrubland) habitat. As the area regrows, these spots will again be full of breeding warblers, buntings, and other birds that depend on this limited habitat feature. The Saco River in spring may flood into the lower portions of the sanctuary, boosting regeneration thanks to its deposits of nutrients. The Dahl Sanctuary is an excellent place to observe wildlife like birds, amphibians, and mammals, and it is open for public exploration on a year round basis.
Parking is limited to a small lot adjacent to the LL Bean from Route 16 South.
Floodplain forests are increasingly difficult to come by in NH. They contain some of the highest-quality agricultural soil, and as a result many have been ditched or drained for farming. Further, development and dams have altered hydrology of these wetlands, resulting in poor regeneration of the floodplain plant species. Human disturbance can jeopardize these natural communities through the spread of invasive species and inappropriate recreation.
Floodplain forests are unique because of their periodic flooding. These regular disturbances, which deposit silt and sand along the banks of waterways, help create and maintain unique communities of plants that tolerate flooding and require nutrient-rich soils. Floodplain forests contribute many free ecological services to our society: they help filter pollutants to prevent them from entering streams, improve water quality, are critical in controlling erosion, and help buffer rivers against catastrophic flooding.
These increasingly rare plant communities support wildlife species that includes many species of mammals, blue-gray gnatcatcher, and red-shouldered hawk. At the Dahl Wildlife Sanctuary, we are taking steps to restore hydrology, remove invasive plant species, and limit recreation within sensitive areas.
MAIN TRAILHEAD is located next to the LL Bean parking lot at the junction of Rts. 16 & 302.
Another access point is from the privately-owned Saco River Campground.
PINE TRAIL – Red Markers
1/2 mile, one-way; about 25 minutes round-trip
An easy walk that features three pine species and sits atop an esker (glacial feature)
SILVER MAPLE/FIELD TRAIL LOOP – Yellow Markers
1 Mile loop, about 1 hour round-trip
A level loop hike that winds through restored and historic floodplain forests and a variety of field habitats. Begins from the main trailhead.
BEACH TRAIL – Yellow Markers
1/2 mile, one-way; about 25 minutes round-trip
Runs from the campground to a riverine cobble barren with rare plant populations. Please stay on the trail!
From the trailhead, follow the woods roads downhill through the woods to a trail junction. A segment of the trail ends at an open cobble barren along the river with beautiful views of the region. Waterbird species such as spotted sandpiper, belted kingfisher, and common merganser can be found here during the breeding season. Only the upstream portion of the barren is owned by NH Audubon; the rest is owned by the Town of North Conway.
An example of the globally-rare hudsonia – silverling river channel community occurs along the upper portion of the cobble barren at the edge of the forest, where it forms a narrow strip of vegetation on the channel shelf above the river. Grasses, forbs, mosses, and lichens are the dominant life forms, although vegetation is sparse overall. Widely scattered shrubs and saplings are also present. The substrate on the surface ranges from a thin layer of nearly pure sand to a mixture of sand, gravel, and small cobbles that have been deposited by the Saco River.
Two state-threatened plants occur in this community, hairy hudsonia (Hudsonia tomentosa) and silverling (Paronychia argyrocoma). There are over three hundred patches of silverling on the Audubon portion of the cobble barren. These patches range in size from a single stem to 3 square feet. The hairy hudsonia is less common here, occurring in scattered clumps that total only about 4 square feet of cover. Hairy hudsonia is most frequently associated with the sandier zones found near the highest areas of the channel, which are often farthest from the river itself. The distribution of silverling is similar, but it extends further out onto the cobble.
Besides the hudsonia and silverling, other characteristic plant species here include little bluestem, early goldemod, Rand’s goldenrod, biennial evening primrose, jointweed, panic grass, and intermediate pinweed. Sand sometimes forms low, tear-shaped mounds behind vegetation clumps. These mounds are aligned with stream flow direction, and are the result of deposition in lower velocity eddies behind the plants.
This natural community is currently known only from river channel barrens along the Saco River in New Hampshire and Maine. Its restricted distribution likely corresponds to a combination of flood-related disturbance and soil conditions along the river profile. Above open cobble shores, river channel barren zones are scoured enough to prevent most woody plant growth, but stable enough for perennial species such as hairy hudsonia and silverling to survive and sometimes thrive. Still higher is a sandy environment that is heavily vegetated by shrubs, saplings, and a variety of grasses and forbs. At this height in the channel, floodwater velocities slow to the point where depositional processes outpace erosion. The forested floodplain occurs above this zone.
Backtracking to the trail junction across the stream bed, a loop trail leads to the right around a field edge that is being managed for early successional habitat. Nest boxes here are used by Eastern bluebirds, tree swallows, house wrens, and black-capped chickadees, and many species of wildlife depend upon the young forest habitat for food and cover. Continuing around the field, you will reach a silver maple – false nettle – sensitive fern floodplain forest, a dynamic natural community that in New Hampshire is primarily associated with large and medium-sized rivers affected by periodic and temporary flooding. At the Dahl Sanctuary, the canopy is dominated by silver maple, which forms a tall, arching, cathedral-like ceiling above the level floodplain adjacent to the river channel. Other trees such as American elm, sugar maple, white ash, and basswood also occur as associates. Barred owl and red-shouldered hawk both make their nests in this canopy, and floodplain specialist songbird species can be found here during the breeding season.
The understory is distinguished by a diverse and variable suite of herbaceous plants including an abundance of sensitive fem and false nettle. Other species present in the herb layer include drooping woodreed, drooping sedge, wild sarsaparilla, wood nettle, Canada mayflower, northern short husk grass, sessile-leaved bellwort, hairy Solomon’s seal, inflated sedge, ostrich fem, white baneberry, red baneberry, large enchanter’s nightshade, wakerobin, tall meadow-rue, and northern lady fem. Shrubs and understory trees are more common at the edges and in canopy gaps and include ironwood, choke cherry, mountain holly, red elderberry, meadowsweet, dwarf raspberry, Virginia creeper, maple- leaved viburnum, poison ivy, and partridgeberry.
There is a high degree of microtopographic variation on the ground within the floodplain forest community, with sand deposits, riparian vernal pools, old oxbows, and flood channels occurring throughout, allowing for a high diversity of plant life and wildlife. Evidence of denning mammals, nesting birds, and breeding amphibians can often be found throughout the floodplain forest understory. Return to the parking area by way of the loop trail, which c01mects back with the old woods road. From here, you can explore some of the other side trails within the sanctuary. Of particular interest is corridor extending to the Pine Trail (which permits snowmobile access in winter), a short spur trail dominated by a second- growth upland forest bordering Route 16.
Photos, from the top: Dahl Wildlife Sanctuary, by Phil Brown; view of the floodplain at Dahl, by Phil Brown.