A Natural History of Millbrook Marsh,
A Wetland In An Urbanizing Setting
Species of Special Concern
The earlier studies of Millbrook Marsh included the 1954 thesis, A Flora of Centre County, Pennsylvania, by R. A. Pursell. Of the calcareous fen located on private property, he wrote: "An interesting point about these species is that most of them are either quite rare for the County or for the State." (Pursell 1954, p. 21.) At this time also there are 7 known species of Pennsylvania Endangered, Threatened, or Rare status in Millbrook Marsh, with a possibility of others not yet identified. Under the Pennsylvania Wild Plant Conservation Act, the classification of "Endangered" includes species in imminent danger of extinction or extirpation throughout their range in Pennsylvania. The "Threatened" classification includes species that may become endangered within the foreseeable future throughout their range in Pennsylvania. Rare species are those that are at risk of becoming endangered or threatened due to low numbers. The Pennsylvania Flora database lists 177 wetland obligate or facultative wetland species whose classification under the Pennsylvania Wild Plant Conservation Act is Endangered, Threatened or Rare (Rhoads 1998).
The calcareous fen at the south edge of the marsh supports a variety of emergent wetland plants. Most importantly, it is habitat for many of the species of special concern that are or could be found at Millbrook. Fens such as this one are some of the most unique communities, dominated by sedges, grasses and forbes or shrubs and herbaceous plants. In Pennsylvania, they are found mostly in two physiographic regions, the Ridge and Valley Province and the Appalachian Plateaus (see Chapter 4, Geology). They are typically very small, as is the fen of Millbrook Marsh, although at 1 ha it is one of the largest in Pennsylvania (Stack et al. 1991). Among other things, their size results in serious vulnerability to changes in land use in the vicinity and overpumping of wells (Davis 1993). This is part of the reason for so many calcareous fen species to warrant special concern status. The WPC study of fens (1995) resulted in the finding of endangered, threatened and rare species, including a pondweed (Zannichellia sp.), sedges (Carex spp.) and spike rushes (Eleocharis spp.) many of which are endemic to calcareous wetlands (Westerfield 1959, PennDOT 1981, Western Pennsylvania Conservancy 1995).
Carex schweinitzii, Pennsylvania Threatened, was seen at Millbrook in the past (Westerfield 1959), though has not been identified there recently. Various spike rushes, Eleocharis spp. were encountered (PennDOT 1981), but not identified to species. There are 9 other Pennsylvania Endangered spike rushes, 5 of them, E. compressa, E. elliptica, E. quadrangulata, E. tenuis, and E. caribaea, could possibly be found at Millbrook, and 2, E. pauciflora and E. rostellata, would most likely be found in the calcareous fen. E. intermedia and E. robbinsii, both Pennsylvania Threatened species and E. olivacea, a Pennsylvania Rare species are others that might also possibly be found in Millbrook Marsh in subsequent studies. Species Galium was found (Brooks et al. 1996) though the species of bedstraw was not identified. Galium labradoricum is a Pennsylvania endangered bedstraw, most often found in sphagnum bogs and moist banks. Ranunculus species also occurs in Millbrook Marsh. Ranunculus fascicularis is Pennsylvania endangered, and though it is a facultative upland species, it is often found on calcareous soils. The wetland obligate, Ranunculus longirostris, is PA threatened, and found in calcareous water (Rhoads 1998). This could well be found in the Millbrook Marsh fen. Other rare plants found in calcareous fens, but not recently identified at Millbrook, are Jacob’s ladder (Polemonium vanbruntiae), Spreading globeflower (Trollius laxus var. laxus), and Showy lady’s slipper (Cypripedium reginae). Jacob’s ladder, a facultative wetland species and Spreading globeflower, a wetland obligate species, are both on the Pennsylvania endangered list. Spreading globeflower was found in the past in "Thompson’s Meadow" (PennDOT 1981), which probably included all of the marsh area along Thompson Run up to Thompson Spring and including the present extent of Millbrook Marsh. A colony of Trollius laxus Salisb. existed at Centre Furnace, which was presumably part of Thompson’s Meadow at one time. It was apparently extirpated by the time of the writing of "A Flora of Centre County, PA" in 1954 (Pursell 1954). The rare calciphile, Showy lady’s slipper, has declined not only due to habitat destruction, but also because of over collection (Davis, 1993).
A special protection evaluation report was prepared for the Spring Creek Basin in July 1990 (Quality Assessment Unit, Department of Environmental Resources 1990) which listed about a dozen species of special concern. Though some of the plants mentioned in the preceding paragraphs have not yet been identified in Millbrook Marsh, the habitat here is one in which they might be found in later vegetation surveys.
Map 9 shows the major distinctions in vegetation types at Millbrook. The hydric associations include Cattail/Rush/Sedge, Black Willow/Silver Maple/Elm and others, and Emergent Calcareous Fen vegetation. The mesic associations consist of woody communities including Elm/Walnut and others, and herbaceous communities including Goldenrod/Aster/Broomsedge and others. There are 6 major types of non-native vegetation: Mown Turfgrass, Crown Vetch/Turfgrass and Others, Tartarian Honeysuckle/Rose and Others, Plantation, Pasture, and High Density Urban. These are found mostly at the outskirts of the marsh, but the Honeysuckle and Rose have spread throughout the site, varying in density. They are the most invasive of the non-natives at this time, and have caused portions of the marsh to become almost impassable. Several of these problematic species existent in Millbrook Marsh warrant remedial measures so as not to cause irreversible damage to the native plant communities.
On to Non-Natives and Invasives