Background and Basic Ecology of JHNWR
The 1200-acre John Heinz National Wildlife Refuge at Tinicum is the most urban refuge managed by the USFWS. This unique refuge protects approximately 200 acres of the remaining freshwater tidal marsh within Pennsylvania and represents an important migratory stopover along the Atlantic Flyway.
The refuge contains a variety of ecosystems unique to Pennsylvania and the Philadelphia metropolitan area including tidal and non-tidal fresh water marsh, freshwater tidal creek, open impoundment waters, coastal plain and riparian forests, and early successional grasslands.
Many of the ecosystems within the refuge have been degraded, damaged, or even destroyed as a result of numerous historic impacts. One of our goals here at the Refuge is preserving and restoring these vitally important ecosystems.
Non-Tidal and Tidal Freshwater Marshes
What is a marsh?
A marsh is a wetland frequently or continually inundated with water. Marshes usually have soft-stemmed plants that are adapted to wet soil conditions. There are many types of marshes, at JHNWR we have two types of freshwater marshes: tidal and non-tidal.
Non-tidal freshwater marsh:
Non-tidal marshes are the most common wetlands in North America. They occur along streams or in shallow water around lakes, ponds and rivers. These marshes can have water from a few inches to a few feet deep; some dry out completely at times.
Tidal freshwater marsh:
Tidal freshwater marshes are upstream from tidal salt marshes and downstream from non-tidal freshwater marshes. One of the most significant influences on a tidal freshwater marsh is the daily, lunar tidal fluctuations in water level.
Function and value of freshwater marshes:
Freshwater marshes are one of the most productive ecosystems on earth. They can sustain a vast array of plant and wildlife communities. Like all marshes, they recharge groundwater supplies and reduce damage caused by storms.
Coastal plain and riparian forests:
The sandy soils of the Mid-Atlantic Coastal plain and warm coastal air moving up from the Delaware Bay allows coastal plain forests normally found farther south. This forest type is dominated by sweet-gum and oaks.
Floodplain forests are found along river systems and develop in areas that flood on an annual basis. Areas that flood frequently might include Sycamore, Silver maple, Elm, and Cottonwood. Permanently wet areas would have species such as White Oak or Red Maple.
Grasslands and native meadows:
In this area, grasslands and native meadows are an early successional stage for forested lands that occur due to disturbance (fire, flood, or human disturbance).