Natural Communities of NH -- Photo Guide

Atlantic white cedar - giant rhododendron swamp  (S1)



The globally rare Atlantic white cedar - giant rhododendron swamp occurs at fewer than ten locations in New England, and the only one north of Massachusetts is in Manchester. In this community, giant rhododendron (Rhododendron maximum) shrubs form a strikingly dense understory beneath a canopy composed primarily of Atlantic white cedar (Chamaecyparis thyoides) trees.

This community type is similar to Atlantic white cedar - yellow birch - pepperbush swamp, and scattered plants characteristic of that type are also found in this type, but it differs for at least two reasons. First, giant rhododendron constitutes a majority of the understory cover and is a substantial contributor to total site biomass. Therefore it probably has a substantial influence on litter and soil quality. Second, the dense shading by giant rhododendron appears to exert a significant influence on other vegetation. This community is relatively species-poor compared to other types. Tall shrubs other than giant rhododendron are generally sparse. The herbaceous layer is also sparse.
 

Characteristic vegetation: Giant rhododendron shrubs form a dense understory beneath a canopy composed primarily of Atlantic white cedar. Red maple (Acer rubrum) is present and sometimes codominant, yellow birch (Betula alleghaniensis) is present in low abundance, and black gum (Nyssa sylvatica) is occasional. Sphagnum moss is abundant. Other species that may be present include hemlock (Tsuga canadensis), highbush blueberry (Vaccinium corymbosum), male berry (Lyonia ligustrina), mountain holly (Nemopanthus mucronatus), cinnamon fern (Osmunda cinnamomea), and three-seeded sedge (Carex trisperma). Besides giant rhododendron, no plant species are restricted to this type.


A good example of this community (and the only one in NH) occurs at the Manchester Cedar Swamp Preserve (Manchester).

Atlantic white cedar - giant rhododendron swamp occurs as part of a coastal conifer peat swamp system.


Atlantic white cedar - giant rhododendron swamp at Manchester Cedar Swamp Preserve (photo by Ben Kimball for the NH Natural Heritage Bureau)
Atlantic white cedar - giant rhododendron swamp at Manchester Cedar Swamp Preserve
(photo by Ben Kimball)

Atlantic white cedar - giant rhododendron swamp at Manchester Cedar Swamp Preserve (photo by Ben Kimball for the NH Natural Heritage Bureau) Giant rhododendron at Manchester Cedar Swamp Preserve (photo by Ben Kimball for the NH Natural Heritage Bureau)

Atlantic white cedar - giant rhododendron swamp at Manchester Cedar Swamp Preserve (photo by Ben Kimball for the NH Natural Heritage Bureau)
Atlantic white cedar - giant rhododendron swamp at The Nature Conservancy's
Manchester Cedar Swamp Preserve in Manchester, NH (photo by Ben Kimball)

Sphagnum moss pool in an Atlantic white cedar - giant rhododendron swamp in Manchester (photo by Ben Kimball)
Sphagnum moss pool in an Atlantic white cedar - giant rhododendron swamp 
in Manchester (photo by Ben Kimball) 


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