SUMMARY OF FINDINGS

NATURAL COMMUNITY MAPPING OF THE BERLIN POND WATERSHED

Brett Engstrom and Marc Lapin

3 May 2005

A natural community map has been recently completed for the entire 6661-acre watershed of Berlin Pond.  As defined in Wetlands, Woodlands, and Wildlands by Elizabeth Thompson and Eric Sorenson, a natural community is “an interacting assemblage of organisms, their physical environment, and the natural processes that affect them”.  Natural communities range in size from a vernal pool, which may be less than one-quarter acre, to a northern hardwood forest, which may be thousands of acres. The mapping process included information from many sources, including aerial photographs, soil maps, geology maps, National Wetlands Inventory maps, plus field surveys.  It is important to realize that this natural community map is not a land cover map.  So areas that are currently hayfields are not mapped as grasslands, but are mapped as the forested community types that would naturally occur if the areas had not been cleared for agriculture.  Even the interstate highway does not appear on the map.  The final map product is a set of polygons created digitally using ArcGIS.  Each polygon is attributed with natural community type, size, plus other information specific to that particular area.

Summary findings from this natural community mapping project are listed below.

• Extensive rich northern hardwood forest occurs on the slopes of Irish Hill and Paine Mountain.  This uncommon natural community type is found where there a great diversity of wildflowers and ferns resulting from naturally high soil fertility.
• Five rich fens were discovered in the watershed.  This rare natural community is an open wetland often found on gentle slopes of land underlain by limestone.  Occurring where there is mineral rich groundwater discharge, rich fens are characterized by a unique assemblage of mosses, sedges, and herbs.  Some species of birds, small mammals, and dragonflies are often associated with rich fens.
• Many seepage forests occur along the lower stretches of the extensive slope to the east of the pond and wetlands south of the pond.  This new natural community type (i.e. not found in Wetlands, Woodlands, and Wildlands) is under review for addition to the Vermont natural community classification.  Found where there is gradual groundwater discharge, seepage forests are characterized by soils with a mix of seasonally high water table and shallow peat layers.  In the Berlin Pond watershed, the canopies of these forests vary in composition.  They can be dominated by conifers (hemlock or northern white cedar), hardwoods (black and white ash, sugar maple, and yellow birch), or a mix of conifers and hardwoods.  Because they are not capable of being mapped directly from aerial photographs, these wetland forest communities are not found on National Wetland Inventory maps. 
• The watershed contains many small wetlands, especially vernal pools and seeps, not previously mapped.  These are often critical habitat for amphibians.
• The extensive shallow emergent marsh  and associated swamps at the south end of the pond is a important wetland complex in the Central Vermont region.  These marshes are vital habitat for a large suite of mammals, birds, and invertebrates, as well a wide diversity of plants.
• The watershed supports several northern white cedar swamps.  There are several examples of this uncommon community in the vicinity of the pond, only one of which was previously documented.
• A very large population of male fern (Dryopteris filix-mas) and its associated hybrids occurs in the watershed.  While previously known from the watershed, the population of this state-threatened plant was found to be much more extensive. 
• Several other rare to uncommon plants were documented in the watershed, including summer sedge (Carex aestivalis), Minnesota sedge (Carex albursina), hoary willow (Salix candida), and millet-grass (Milium effusum). 

Produced by

The Berlin Conservation Commission

 Thanks  to the Vermont Land Trust and the Vermont River Conservancy for their assistance in this land conservation effort.