Mt. Bethel Fen Complex,, Northampton County, PA
Lower New England/Northern Piedmont Ecoregion

Site Description:

The Mt. Bethel Fen Complex lies in the lower reaches of the Jacoby Creek Valley, a small, third order tributary to the Delaware River, just below the Delaware Water Gap. An unconsolidated aquifer system, composed mainly of lime-rich sands and gravels, feeds this fen complex from a series of high-volume springs and seeps. Ground Penetrating Radar studies suggest that the local basins supporting these fens are generally clay-lined. The aquifer system is a series of kame and kame terrace deposits enclosed by a basin defined by the valley wall Martinsburg Shales, which are overlain by ground moraine of variable thickness. Piezometric and chemical signature studies suggest that the origin of the discharge water is primarily the lime-rich kame and kame terrace deposits, with lesser contributions from the hillslope ground morainal material. The series of limestone formations underlying the valley may also contribute to the discharge systems to a lesser extent.

The fen complex and its associated primary aquifer cover approximately 2,000 acres and the entire watershed potentially tributary to the fens covers approximately 4,000 acres. Our primary target for conservation at this site, the fen community, occurs as a series of small patch communities imbedded within the lower reaches of the aquifer recharge area. The area encompassing the targets constitutes a Functional Site. Evidence for site function includes good water quality and the persistence of spring flow even during severe drought.

 

 

Recognized by botanists since the turn of the century as a botanical wonder, the Mt. Bethel Fens contains an unusual plant community found only in eastern Pennsylvania and New Jersey. Mt. Bethel's state rare calcareous fen communities are some of the best examples in their range. Their unique vegetation derives from their extremely alkaline water chemistry (a pH greater than seven) and the cool conditions of the water-soaked soils.
 

Beaver dominated area in fen complex

 

Conservation Highlights 
  • Community-based staff person has achieved leadership role within the township, as co-chair of the Township’s Environmental Advisory Council on environmental matters and will help guide Comprehensive Planning process and subsequent zoning regulations.
  • Engaged in a very successful partnership with an academic institution, Lehigh University. Partnership has resulted in quarterly hydrologic monitoring of the site, GPS surveys, the creation and maintenance of a GIS database, and a seismic investigation.
  • Environmental Planner hired to balance projected growth with natural resource protection. Planner provided a natural resource protection plan, water resource protection ordinances, and tailored the stormwater ordinance to provide for enhancing/maintaining recharge while prohibiting dimunition of surface water quality.

 

LEO- Lehigh Earth Observatory students performing field work

 

 

Conservation Targets

 

Open Sedge (Carex stricta, prairea, lacustris) fen: Carex stricta,-Carex prairia Herbaceous Alliance: Hillside Graminoid-forb fen-(G2G3) Savadge Fen Imbedded within the Shrub Association is a seep community, which shows some floristic differences from the shrub community.

 

The primary targets for the Mt. Bethel Fens Complex are:

The Mt. Bethel Fen Complex supports an impressive variety of state imperiled conservation targets, both at the community level as well as individual species. The complex is listed as a Basin Graminoid-forb fen natural community and is state imperiled as reported by the Pennsylvania Natural Heritage Data Center. The Mt. Bethel Fen community is one of the best examples of this community type across its limited range and is the best example in Pennsylvania. At present the community remains in excellent condition.

 

Major Threats

 

There are a variety of threats to the fens and its species. Of most immediate concern is the abundance of two very aggressive weeds-phragmites (Phragmites australis) and purple loosestrife (Lythrum salicaria L.). These two plants are capable of displacing the native fen plants. Of equal concern is maintaining the hydrologic system upon which the fens depend. An abundance of uncontaminated, high pH water feeding the fens is critical to maintaining its species. Without the quantity of water, the fens will quickly change into shrub wetlands and eventually into forested wetlands. If water quality is degraded, the weedy species will be favored to the exclusion of the native flora.

Succession constitutes a third threat to the fen complex. Our paleoecological studies suggest that these fen communities did not appear in their current form until after European contact. We believe that the current communities were formed by clearing and then light grazing of these wetland areas.

 

Spring flow in Savadge Fen. Flow is perennial. Maintenance of the quality and quantity of the these flows is crucial for the continued existence of the fen ecosystem.

 

 

Major Science and Stewardship Activities 

 

LEO - Lehigh Earth Observatory  student monitoring well 

  • An aggressive program of WEED MANAGEMENT.
  • A Hydrogeologic study assessed fen water quality, quantity, and the potential recharge sources to the fens.
  • A Seismic investigation provided information regarding the subsurface stratigraphy as well as recharge sources to the fens.
  • A Paleoecological Analysis of the fens provided a long-term vegetational and successional context for future management strategies.
  • An integrated Management and Monitoring Plan has been developed to determine the health of the complex while also assessing the success of our management efforts.

 


More Information

For more information, please contact Su Fanok at sfanok@tnc.org