One of the biggest challenges to new delineators, and even some experienced wetland delineators, is getting the plant community mapping done right. This is a very important task as it serves as the basis for where and why the wetland sampling points are located where they are. As you may recall, the US Army Corps of Engineers Wetland Manuals require that each plant community should be represented by a sampling point.
The Regional Supplements are not much help on this. They describe in very generic terms what some of the common plant communities in the region and even sub-region are. For example, this is an excerpt from the Eastern Mountains and Piedmont Regional Supplement.
Northern Mountains and Piedmont (MLRAs 147 and 148 of LRR S):
This sub region includes the northern Appalachian ridges and valleys (MLRA 147) and the northern Piedmont (MLRA 148). The ridge-and-valley portion is underlain by Paleozoic sandstones, conglomerates, limestones, and shales, whereas the Piedmont portion is underlain by generally older metamorphic and igneous rocks. The central portion of the Piedmont also contains sandstones, conglomerates, and shales that were laid down in the ancestral Atlantic Ocean during the Triassic period. Average annual rainfall over most of the sub region ranges from 31 to 52 in. (785 to
1,320 mm), and average annual temperature ranges from 44 to 57 °F (7 to 14 °C) (USDA Natural Resources Conservation Service 2006).
Only about 55 percent of the ridge-and-valley portion of the sub region and 25 percent of the Piedmont portion are forested today. Agricultural and urban development makes up the remainder of the sub region. Common tree species in forested areas include white oak, black oak, northern red oak, bear oak (Q. ilicifolia), chestnut oak, American elm, hickories, tulip tree, Virginia pine, pitch pine (P. rigida), eastern redcedar, and other species (Society of American Foresters 1980; USDA Natural Resources Conservation Service 2006).
As you can see, there is a general description of the trees found in the region. However, there is not much else. In this example understory species are not mentioned and there is no discussion of the other plant communities in this area. The Corps goes on to later extol the need to identify the plant communities.
“The manual uses a plant-community approach to evaluate vegetation. Hydrophytic vegetation decisions are based on the assemblage of plant species growing on a site, rather than the presence or absence of particular indicator species. Hydrophytic vegetation is present when the plant community is dominated by species that require or can tolerate prolonged inundation or soil saturation during the growing season.”
So, getting this right is particularly important. To help you with this, I have a few tips and tricks to get you started.
First, you need to identify a plant community text for your region. For example in North Carolina, the Classification Of The Natural Communities Of North Carolina Third Approximation by Michael P. Schafale and Alan S. Weakley (1990) is a great reference document for understanding how these plant communities are distinguished.
This is an excerpt of the vegetation description for a specific plant community. Location, geology, soils and other features are described relative to this community type.
Carolina Hemlock Bluff
Vegetation: The canopy is well developed, though not always closed, owing to extreme rockiness and steepness. Tsuga caroliniana is the dominant trees; species such as Quercus montana (prinus), Pinus rigida, Pinus pungens, Quercus rubra, or Tsuga canadensis often occur. Undergrowth is generally a dense layer of heaths, especially Kalmia latifolia, Rhododendron catawbiense, Gaylussacia spp., and Vaccinium spp. The herb layer is very sparse below the dense shrub growth. Species may include Gaultheria procumbens, Mitchella repens, Chimaphila maculata, Galax urceolata (aphylla), Xerophyllumasphodeloides, and Trilliumundulatum. Bryophytes (Dicranumspp., Leucobryumalbidum, and L. glaucum) and lichens (Cladonia spp. and Cladina spp.) are sometimes prominent.
From this description alone you would be able to develop a plant list and assign wetland indicators.
In just about every state there exists a plant inventory and classification text. Most of these are published by a state land grant university. These are usually the major agricultural institutions. However, in the North Carolina example one professor is from NC State and the other is from the University of NC. NC State has a major agricultural program. UNC is more of a research institution. This collaboration has produced a terrific document and a great example of universities working together. Just don’t bring up basketball.