NATURAL COMMUNITIES OF YELLOW BOGS IN . LEWIS, BLOOMFIELD AND BRUNSWICK, VERMONT E. Thompson Nongame & Natural Heritage Program ABSTRACT Yellow Bogs in Essex County, Vermont is a unique ecological area characterized by boreal, lowland forests and extensive bog systems. Within the area, black spruce swamps, lowland bogs and other wetlands were delineated into natural area sites and were mapped and described. Endemic plant and animal species were also identified and described for each site; many of these species are restricted to the Nulhegan Basin, of which Yellow Bogs is a part. Recommendations are provided for the management of the rare plants and natural communities of the area Technical Report 14 1989 Nongame & Natural Heritage Program Vermont Fish & Wiidiife Department Waterbury, VT 05676 (802)244-7331 INTRODUCTION The Nulhegan Basin, the lowland area east of Island Pond and mostly north of Vermont Route 10~, exemplifies the boreal lowland character of the Northeast Kingdom. Here are found the state's most extensive bogs and softwood swamps, the only breeding populations of certain boreal b i rds, rare boreal plants, and abundant moose and other northern species. The Nulhegan Basin (not specifically the Nulhegan River watershed but the lowland area that is within that watershed) is an area roughly circular in outline, about 10 miles in diameter, of relatively flat topography. The Basin is sharply demarcated on all sides by prominent hills and mountains. The flatness of this circle in comparison w.lth the surrounding hills is striking when viewed from a plane or on a topographic map (see Figure 1) . Although the area has relat.ively little topography within itself, it is nevertheless relativel y high; the- basin sits at approximately 1100 to 1400 feet elevation. Geologically, the basin is a "soft pluton". The bedrock in the basin itself is granitic rock, while the surrounding hills are generally schists or other similar metamorphic rock. The pluton was formed when molten magma underneath the crust of the earth was pushed upward by volcanic force. The magma did not erupt as a volcano but remained just below the surface, which was composed of metamorphic sedimentary rocks. The heat of the magma further metamorphosed the rock at the surface, making it very hard and resista~t to weathering. Over time, however, weatheri ng did occur, finally revealing the igneous rock below the surface rock. With more time, this igneous rock (a relatively soft granitic rock known as quartz monzonite) weathered more quickly than the surrounding,. hardened rock. Hence, a ring of resistant rock now surrounds the basin, where softer rock has gradually eroded away. During more recent geological time, the basin has become an area of glacial outwash. Following the last glaciation, the basin was likely full of flowing water while surrounding highlands were dry. Hence the basin is full of sand and grav el deposits overlying the granite bedrock. Yellow Bogs is an area that has no formal boundary demarcation, but is generally considered .to encompass the northeastern quarter or so of the Nulhegan Basin. The area considered in this study is shown in Figure 2. It is mostly within the town of Lewis, although small portions of Brunswick and Bloomfield are included as well. It is mostly east of the • Yellow Branch of the Nulhegan and north of Vermont Route 105. All waters in the study area flow southeast into the Nulhegan River and thence east into the Connecticut at Bloomfield. l OBJECTIVES The purposes of this study, as presented in the proposal, were: l. To map and describe the rare and exemplary natural communities of the Yellow Bogs area. 2. To locate and document any rare plants in the Yellow Bogs area. 3. To provide management suggestions for the natural communities and rare plants that can be integrated with management requirements for the rare animals present in the area. METHODS To meet these objectives, the following methods were used: l. Color infrared aerial photos at 1:20,000 scale were examined to determine areas of potentially significant natural communities. 2. The area was surveyed by small plane in April and October, prior to and following field work. 3. Se~eral areas identified from air photos and the flight were visited on foot during June, July and August. Species lists and community descriptions were made. 4. Areas of significant natural communities were mapped. RESULTS Map of Significant Natural Communities The results of the work are summarized on the attached map. This map should be used as the basis of information for planning and conservation work. Eight sites (some composed of several smaller sites) are identified as locations for significant natural communities and/ or rare plant habitat. These eight areas were assigned site names by the author. It should be noted that the natural area boundaries shown on the map are approximate only. In some cases the natural area boundary includes some non­ significant habitat that is regarded as important buffer area for the significant sites. The boundaries between natural communities are also only approximate; these communities (especially black spruce swamp and lowland bog) grade into one another and cannot be cleanly demarcated on a map . 2 significant Natural Communities - Description Three types of significant areas are identified: black spruce swamp, lowland bog, and other wetlands. Generalized description of these three types follow. Specific site descriptions for some of the areas can be found in Appendix I, and a list of plants found during the inventry is found in Appendix II. Black Spruce swamps - Black spruce stands are scattered throughout the Yellow Bogs area, but only the most extensive and/or least disturbed are identified here. These are wetlands, generally with shallow accumulations of peat, in which black spruce is the dominant tree. The trees are small, with diameters of 4 to 8 inches on the average. Although black spruce (Picea mariana) dominates in the canopy, balsam fir (Abies balsamea) and tamarack (Larix laricina) are present as well. The shrub layer is sparse, with scattered individuals of mountain holly (Nemopanthus mucronata), withe-rod (Viburnum cassinoides), red maple (Acer rubrum) and balsam fir. Where black spruce swamps intergrade with lowland bog areas, the spruce is more stunted and is present in the shrub layer as well as in the canopy. Other species are present in these transition areas as well. The ground layer in black spruce swamps is dominated by mosses such as Thuidium delicatulum, Pleuroziwn schreberi, Ptilium crista­ castrensis, and Sphagnum species. Scattered herbaceous plants are pink lady's slipper (Cypripedium acaule), snowberry (Gaultheria hispidula) and goldthread (Coptis qroenlandica) • The rare mountain cranberry (Vaccinium vitis-idaea) is found in these areas as well as upland forests in Yellow Bogs. Lowland bogs - Several small areas of lowland bog are present within the Yellow Bogs area. They are usually associated with black spruce stands, probably occupying the .sites where the peat is deepest. They are mostly small areas, with low species diversity. Black spruce is the dominant tree in these bogs, but the individuals are never as large as in the adjacent black spruce swamps. Stunted tamarack are present as well. There is a well-developed shrub layer, with such characteristic species as labrador tea (Ledum groenlandicum), bog laurel (Kalmia polifolia), rhodora (Rhododendron canadense), and black chokeberry (Aronia melanocarpa) . Characteristic herbs are carex disperma, small cranberry (Vaccinium oxycoccos), three-leaved false-solomon's seal (Smilacina trifolia), sundew (Drosera rotundifolia), and pitcher plant (Sarracenia purpurea). Sphagnum fuscum and other species of Sphagnum form a nearly continuous carpet under the herbaceous and woody vegetation. The largest of the lowland bogs is the westernmost one in the study area ("Western Bog"). In this bog there occurs a large population of the rare bog sedge, carex exilis. 3 Other wetlands - These are either open sedge meadows or shrub {alder) thickets. These are not uncommon communities in Vermont, so only the most extensive or otherwise unusual examples .are identified here. One of the wetland areas identified is actually an old blowdown, but is of ecological interest because of the successional processes that are taking place here. Succession has not been studied at the site, but it appears that paludification, or "swamping" is taking place here as in other areas of Yellow Bogs. Paludification is a process in which a landscape becomes wetter when a peatland raises its own water table and expands into adjacent upland areas. This process is probably active throughout much of the Yellow Bogs area, but is perhaps most dramatic in areas that have been cleared either naturally or by humans. Paludification is enhanced in cleared areas because evapotranspiration is significantly reduced with the loss of the canopy. Paludification, either natural or disturbance-induced, is a common phenomenon in northern climates but is fairly unusual in mostly temperate Vermont. Therefore paludif ied areas of both types in Yellow Bogs could serve as important research sites. DISCUSSION The results of this and other studies that have been done in Yellow Bogs are clear evidence that this is an important and highly unusual area in Vermont. The following can be said about the ecological significance of Yellow Bogs: Nowhere in Vermont is there such a high concentration of boreal bog systems. Nowhere in Vermont are there such extensive black spruce swamps. At least two rare boreal plant species occur in Yellow Bogs. The bryophyte {moss and lichen) flora, whicp has not been studied, may very well be unusual in Vermont. Paludification, an ecological process which appears to be rare in Vermont, occurs here and has likely contributed to the present-day character of Yellow Bogs. The area provides a significant amount of habitat for several boreal bird species; it is one of only a few significant areas of boreal bird habitat in Vermont.