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CEGL006475 Platanus occidentalis - Fraxinus pennsylvanica - Acer negundo / Sanicula odorata - Elymus virginicus Floodplain Forest
Type Concept Sentence: No Data Available
Common (Translated Scientific) Name: American Sycamore - Green Ash - Box-elder / Clustered Black-snakeroot - Virginia Wildrye Floodplain Forest
Colloquial Name: Potomac Gorge Ice-Scour Floodplain Forest
Hierarchy Level: Association
Type Concept: This association is restricted to a 50-hectare, high-gradient floodplain in the lower portion of the Potomac Gorge in Maryland and the District of Columbia. It is likely strongly influenced by infrequent, but catastrophic, ice jams which occur in this narrow section. It differs from other floodplain forests of the gorge in that many of the canopy trees exhibit obvious evidence of past mechanical damage by ice or flood. In addition, soils are shallower and there are scattered bedrock exposures. The vegetation is a somewhat open, even-aged forest codominated by Platanus occidentalis and Fraxinus pennsylvanica. Acer saccharinum, Juglans nigra, and Populus deltoides are usually present but not dominant. The subcanopy is composed of Acer negundo, with Ulmus americana at lower cover. The shrub layer cover ranges from 5-40% and is composed primarily of Lindera benzoin and small Acer negundo. Vine cover is generally greater than 8%. The most constant native herbs in 10 plot samples are Elymus virginicus, Sanicula odorata, Viola sororia, Verbesina alternifolia, Hydrophyllum canadense, Carex blanda, Arisaema triphyllum, Poa pratensis, Geum canadense, Amphicarpaea bracteata, Festuca subverticillata, Carex jamesii, and Polygonum virginianum. However, the exotics Ranunculus ficaria and Microstegium vimineum are rampant, each averaging 25-50% cover in these plots, and many additional exotics are present at lower constancy and mean cover.
Diagnostic Characteristics: No Data Available
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This vegetation type is supported by analysis of regional data for the NCR parks vegetation mapping project and is represented by 10 plots. However, it separates only weakly from the more widespread ~Acer saccharinum - Acer negundo / Ageratina altissima - Laportea canadensis - (Elymus virginicus) Floodplain Forest (CEGL006217)$$ in analysis and is known from only one 50-hectare site globally.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available
Floristics: This is a somewhat open forest that appears relatively even-aged, with few large trees, most likely because of regeneration of a large proportion of trees following the catastrophic ice jam flood of 1948. Platanus occidentalis and Fraxinus pennsylvanica together comprise 40-60% of the tree canopy layer. Acer saccharinum, Juglans nigra, and Populus deltoides are usually present but not dominant. The subcanopy is composed of Acer negundo, with Ulmus americana at lower cover. The shrub layer cover ranges from 5-40% and is composed primarily of Lindera benzoin and small Acer negundo. Vine cover is generally greater than 8%. Amphicarpaea bracteata and Lonicera japonica are frequent on shrubs and herbaceous vegetation, and Parthenocissus quinquefolia, Toxicodendron radicans, and several species of Vitis are the most frequent tree climbers. The most constant native herbs in 10 plot samples are Elymus virginicus, Sanicula odorata, Viola sororia, Verbesina alternifolia, Hydrophyllum canadense, Carex blanda, Arisaema triphyllum, Poa pratensis, Geum canadense, Amphicarpaea bracteata, Festuca subverticillata, Carex jamesii, and Polygonum virginianum. However, the exotics Ranunculus ficaria and Microstegium vimineum are rampant, each averaging 25-50% cover in these plots, and many additional exotics are present at lower constancy and mean cover. Small-scale (1-3 m wide), linear swales (flow channels) within this type support hydric vegetation, including a number of Carex spp., Cardamine bulbosa (= Cardamine rhomboidea), Eleocharis acicularis, Lysimachia nummularia, and others.
Dynamics: The catastrophic elimination of much woody biomass may give fast-growing, intolerant species and species better able to sprout and grow rapidly from adventitious buds a competitive advantage and may explain the relative infrequency of Acer saccharinum compared to more protected forests on floodplains along the Potomac. Slightly coarser textured, more shallow soils (bedrock is evidently nearer the soil surface), and patterns of seedling establishment following major disturbances are alternative explanations. In the absence of further catastrophic and widespread ice damage, this forest may, over a long period, succeed to ~Acer saccharinum - Acer negundo / Ageratina altissima - Laportea canadensis - (Elymus virginicus) Floodplain Forest (CEGL006217)$$, which occupies lower gradient floodplains at the same relative elevation upstream on the Potomac.
Environmental Description: This association is restricted to a 50-hectare, high-gradient floodplain in the lower portion of the Potomac Gorge in Maryland and the District of Columbia. It is likely strongly influenced by infrequent, but catastrophic, ice jams which occur in this narrow section. Many trees in this floodplain forest in this section have resprouted from stumps of those felled or broken off by ice jams and other flood damage. The mean flooding-recurrence interval for this type is 2.2 to 4.1 years (from Log Pearson III approximation) (1.4 to 3.9 years from 68 year record). Percent inundation (from 68 year record) is 0.10-0.25%, and annual probability of flooding (Log Pearson III approximation) is 25-45% (Lea 2000). Soils of this association (CEGL006475) coarse-textured (sandy loams; mean particle size (phi): 3.1 to 2.0), and some bedrock (generally less than 0.5% cover) is exposed. Soil depth is predominantly more than 30 cm, and soils would likely be classified as Entisols or Inceptisols. Occasional narrow linear swales (high water channels), which apparently follow joints in the underlying bedrock, are small-scale features within this type; soils in these are finer textured, more poorly drained, and are evidently wetland soils.
Geographic Range: The type is known only from a 50-hectare area of the Potomac River gorge in Maryland and the District of Columbia.
Nations: US
States/Provinces: DC
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.802106
Confidence Level: Low - Poorly Documented
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 1 Forest & Woodland Class | C01 | 1 |
| Subclass | 1.B Temperate & Boreal Forest & Woodland Subclass | S15 | 1.B |
| Formation | 1.B.3 Temperate Flooded & Swamp Forest Formation | F026 | 1.B.3 |
| Division | 1.B.3.Na Eastern North American-Great Plains Flooded & Swamp Forest Division | D011 | 1.B.3.Na |
| Macrogroup | 1.B.3.Na.1 Silver Maple - American Sycamore - Hackberry species Floodplain Forest Macrogroup | M029 | 1.B.3.Na.1 |
| Group | 1.B.3.Na.1.b <i>Acer saccharinum - Platanus occidentalis - Liquidambar styraciflua</i> Floodplain Forest Group | G673 | 1.B.3.Na.1.b |
| Alliance | A3701 American Sycamore - Green Ash - Tuliptree Central Appalachian-Piedmont Floodplain Forest Alliance | A3701 | 1.B.3.Na.1.b |
| Association | CEGL006475 American Sycamore - Green Ash - Box-elder / Clustered Black-snakeroot - Virginia Wildrye Floodplain Forest | CEGL006475 | 1.B.3.Na.1.b |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Platanus occidentalis - Fraxinus pennsylvanica - Acer negundo / Elymus (riparius, virginicus) Forest (Lea 2000)
- Eastern Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boston, MA.
- Lea, C. 2000. Plant communities of the Potomac Gorge and their relationship to fluvial factors. M.S. thesis, George Mason University. Fairfax, VA. 219 pp.