National Park Service

Eastern Rivers and Mountains Network (ERMN)

Rare Riparian Plant Community Monitoring

Monitoring site at the Delaware Water Gap NRA
Monitoring site at the Delaware Water Gap NRA

Protocol Documents

Summary Reports

Resource Briefs

Vital Signs

Rare, Riparian Plant Communities including “Riverscour” plant communities


The ERMN, with more than 211 miles of river, contains diverse, unique, and globally significant plant communities associated with the floodplains and other geomorphic and hydrologic features of large rivers. The riparian zones of the Delaware, New, Gauley, and Bluestone Rivers are very diverse, both floristically and in terms of number of vegetation associations (plant communities). Eighteen different riparian vegetation associations were described on the Delaware River in UPDE and/or DEWA. Twenty-three riparian vegetation associations were described among NERI, GARI, and BLUE. Some of these associations are very common, found in numerous river systems in the eastern United States. However, 14 of these associations are globally rare; they occur in very few places in the world and are at least moderate risk of extinction or elimination due to extreme rarity, very steep declines, or other factors. These rare vegetation associations also provide unique habitats on which numerous rare plant species depend. Nearly 50 state-rare plant species occur in the riparian zones of the Delaware, New, Gauley, and Bluestone Rivers. The Eastern Red-cedar - Virginia Pine Flatrock Woodland in NERI hosts 8 rare species, while the Calcareous Riverside Outcrop / Calcareous Riverside Seep in DEWA supports over 20 rare plant species.

The network has developed conceptual ecological models for riparian plant communities in the Delaware, New, Gauley, and Bluestone River systems. The conceptual ecological models for these riparian plant communities indicate that the plant communities are shaped by two critical factors:

  • Geomorphology — the underlying bedrock, sedimentary geology, and landforms in and around the river channel. These factors control what types of substrates or sediments are available for the plants to grow in.
  • Flow regime — the timing and volume of water that flows through the river. Fluctuations in the flow regime are influenced by rain, storm events, and melting snow; however the flow regime can be highly altered by dams that influence not only the flow regime, but also the water temperature and the transport of sediment. Scour by ice and water during high flows is an important disturbance that strongly influences the composition and structure of riparian plant communities. Plants that thrive in riparian habitats have reproductive strategies and morphological adaptations that allow them to flourish in the dynamic riparian environment.

Monitoring Effort


Monitoring Objective

The objective of this monitoring protocol is to detect trends in the following variables:

  • Species composition, as measured by:
    1. Dominance (i.e. relative importance values)
    2. Proportion of species richness and cover held by native and non-native species.
  • Community structure (e.g. shift from herbaceous-dominated to shrub-dominated).
  • Presence and abundance of invasive plant species.
  • Litter and soil depth to bedrock.

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Last Updated: December 30, 2016 Contact Webmaster