Montane sandy basin marsh  (S1)

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Montane sandy basin marsh is a rare community type found only in the White Mountains and North Country regions. The nearly-closed basins occur in flats at the base of steep slopes and are only breached at very high water levels, and at other times they act as vernal pools. They lack the suite of coastal plain species found in more southerly basin marshes, but contain royal fern (Osmunda regalis), Canada rush (Juncus canadensis), mannagrass (Glyceria borealis), water bulrush (Scirpus subterminalis), meadowsweet (Spiraea alba), and northern blue flag (Iris versicolor), among others. There is considerable variation in species composition from basin to basin. 

Distinguishing characteristics of these basin marshes are the topographic association with nearly-closed basins, broadly fluctuating water levels, and the absence of coastal plain species found in other basin marsh communities further south. They are primarily found at the interface of mountain slopes and mixed outwash deposits, such as those of the Saco River valley. They tend to have larger watersheds than their more southern counterparts and have very broad fluctuations in water levels (of up to two meters or more) between spring and late summer. They have outlets that are breached only during high water periods, after which the basins are effectively closed (vertical fluctuations only). This is a broadly defined community, and variation from one basin to another is substantial in the five documented examples. Two have steep side-slopes with unusual mixtures of upland and wetland species.

Characteristic vegetation: A variety of common, broadly-distributed marsh plants are characteristic. Some of these include royal fern (Osmunda regalis), Canada rush (Juncus canadensis), northern floating mannagrass (Glyceria borealis), water bulrush (Scirpus subterminalis), meadowsweet (Spiraea alba), speckled alder Alnus incana), northern blue flag (Iris versicolor), pale mannagrass (Puccinellia pallida), mud rush (Juncus pelocarpus), and common beggarticks (Bidens frondosa). Coastal plain species are notably absent.

Two of the known sites are distinct from other basin marshes in the state: they have steep side-slopes several meters in width that support a mixture of wetland basin vegetation and upland forest species, apparently indicative of widely fluctuating water levels. These slopes have a sparse cover of shrubs and herbs including highbush blueberry (Vaccinium corymbosum), winterberry (Ilex verticillata), Canada mayflower (Maianthemum canadense), bracken (Pteridium aquilinum), poverty oat-grass (Danthonia spicata), royal fern (Osmunda regalis), dwarf raspberry (Rubus pubescens), and mosses. No mature trees grow in this zone. These two basins receive considerable upland runoff inputs, but only maintain surface drainage at very high water events. Water fluctuations during the remainder of the year appeared to be entirely due to the balance of groundwater inputs and evapotranspiration losses. Soil at one site consists of a thin (2 cm) fibric organic layer over a black, very sandy A horizon grading to very mucky coarse sand (to 50 cm). The B horizon consists of coarse, very stony sandy gravel.

There is considerable variation in plant species composition and cover in the wetter basin zones both within and between montane sandy basin marsh examples. Some observed vegetation patterns include royal fern - blue flag marsh; marsh fern (Thelypteris palustris) - sallow sedge (Carex lurida) marsh; sensitive fern (Onoclea sensibilis) - mannagrass (Glyceria striata) - moss marsh; and diverse-leaved water starwort (Callitriche heterophylla) - moss mudflat.


Good examples of this community occur below Bragdon Ledge (Albany) and Sugarloaf Mountain (Albany).

Montane sandy basin marshes usually occur within upland forest surroundings, in isolation from other wetland communities, but groups of these basins can be considered sand plain basin marsh systems.