Southern Blue Ridge Mafic Woodland Seep, USNVC CEGL004994, Acer rubrum – Pinus strobus / Alnus serrulata – Physocarpus opulifolius / Solidago patula – Parnassia grandifolia Woodland (G1/S1), a type of Mafic Fens and Seeps. Photo by Gary P. Fleming, DCR.
Rare and Protected
The Southern Blue Ridge Mafic Woodland Seep is a critically imperiled type of small-patch wooded wetland found in Floyd County, VA. It is described and classified in Virginia Department of Conservation and Recreation’s system of Ecological Groups and Community Types as a type of Mafic Fens and Seeps.
If you’re unfamiliar with both Virginia’s system and the concept of community types in general, scroll down.
This rare ecosystem is found in only a few places in the world, including at Buffalo Mountain in Floyd County and The Glades in Grayson County, VA both in the Southern Blue Ridge. It is also found at Big Meadows, Madison County, VA in the Northern Blue Ridge. Pinus strobus Eastern White Pine co-dominates the canopy with Acer rubrum Red Maple “in seepage areas on mineral soil weathered from amphibolite and ultramafic rocks of the Southern Blue Ridge. Occurrences are generally linear, following braided, rocky drainages with internal hummocks of organic-rich soil.” (NatureServe)
To see the more than 60 other species associated with Southern Blue Ridge Mafic Woodland Seeps, visit Mafic Fens and Seeps at Virginia DCR, download the spreadsheet of survey data, and go to the CEGL004994 tab. The balance of species have a 20% constancy value, meaning they were found at one out of five locations surveyed.
A community type is like a giant group of companion plants that grow together in particular climates, soils, moisture levels, and so on. Plants that grow together in the absence of human disturbance tend to be described as “intact ecosystems” or, in Virginia, as “Natural Heritage Communities.” Unlike plants which grow together after or during human disturbance (such as around farming or in suburban back lots), these intact ecosystems are understood to comprise groups of native plants that have co-evolved together over millions of years, and to have worked out competition and mutualism so as to have arrived at a highly productive and stable ecosystem that supports many forms of life, as well as performing many other functions such as sequestering carbon, filtering and storing water, and holding soil against erosion in a multi-layered, redundant, and organic efficiency.
The felt sense when visiting these intact ecosystems is often described as harmony or beauty by unscientific nature lover types.
Virginia DCR Definition
“Community Types are plant assemblages that exhibit similar total species composition and vegetation structure and that occur under similar habitat conditions, and, for the most part, repeat across the landscape. The Community Type level is equivalent to the Association level of the United States National Vegetation Classification System (USNVC).” (Fleming and Patterson 2021, p. iii) Read DCR’s full Introduction to the Third Approximation of the Natural Communities of Virginia which discusses the overall hierarchy of the system, their survey methods, and more.
The United States National Vegetation Classification System (USNVC) Natural Vegetation Classification system defines natural vegetation as “‘vegetation where ecological processes primarily determine species and site characteristics’. Human activities may influence vegetation interaction, but do not dominate or remove ecological processes.” The Association level is the finest most specific description in the overall classification system. (USNVC, n.p.). Visit Natural Vegetation Classification at usnvc.org to see more.
The Southern Blue Ridge Mafic Woodland Seep described on this page is a Virginia Natural Heritage Community type as well as a USNVC Association.
A plant community of this kind will tend to endure in a kind of dynamic equilibrium until a disturbance such as a wildfire or a landslide triggers a second type of cycle: succession. In the opening created by this disturbance, fast growing “pioneer” type plants will colonize the area almost immediately. These plants may not be present at all in the mature natural community that was there before flood, fire, or landslide. Alongside the pioneer plants, seedlings of the mature parent plants may shoot up as well, making their bid for the sun at last. Pioneer plants tend to be short lived and sun-loving, and as the longer-lived plants mature, these pioneers will begin to die and get shaded out. The disturbed area will then move through a relatively stable subclimax phase as more plants colonize the area from the surrounding native seedbank, before eventually reaching climax or old growth phase. This old growth or climax phase is typically what is being described in the Virginia Natural Heritage Communities.
The key phrase to understanding both old growth plant communities and Virginia’s Natural Heritage Communities is “in the absence of human disturbance.” Unfortunately, this doesn’t really exist on planet Earth anymore, especially not in North America. Between invasive species proliferation through accidental introduction and the ornamental nursery trades, decimation of virgin landscapes through resource extraction, and the loss of native peoples with their ancient land management practices, the North America that existed prior to European contact has utterly vanished and been largely forgotten. And perhaps the absence of human disturbance hasn’t existed for thousands of years anywhere humans have lived, and human disturbance has only entered a new modern phase.
Nonetheless, federal and state governments have identified special natural areas which merit protection and study. In Virginia, these “Natural Heritage Resources are defined in the Virginia Natural Area Preserves Act of 1989 (Section 10.1-209 through 217, Code of Virginia), as the habitats of rare, threatened, and endangered plant and animal species; exemplary natural communities, habitats, and ecosystems; and other natural features of the Commonwealth.” (Fleming and Patterson 2021, p. i)
The Natural Communities of Virginia Classification of Ecological Groups and Community Types described at www.dcr.virginia.gov/natural-heritage/natural-communities/ are this state’s most intact ecosystems, and/or its exemplary or rare natural areas. These will be referred to repeatedly throughout the Floyd Native Plants website and are held as a kind of reference standard or living model for healthy native plant communities under specific regional conditions (such as elevation, soil, slope exposure and so on). Studying them can provide another way to understand the plants themselves, their preferences, their capabilities, their ecological niches.
Virginia’s Community Nomenclature
“As a rule, species are listed in descending order of importance and structural position (i.e., overstory species are listed first, followed by understory species, then herbs and low shrubs). Species used as nominals have high constancy (generally > 60%, but occasionally > 50% if especially diagnostic). Nominal species in the same stratum are separated by a dash (-) while different strata are separated by a slash (/). Species listed in parentheses are less constant, but locally important, in a type. When two species are listed within parentheses, it means that either one or both may be important in a given stand. The typical physiognomy (i.e., forest, woodland, shrubland, etc.) and, for tidal wetland communities, hydrologic regime are included at the end of the formal community type name.” Virginia DCR, Summary of Procedures for Collection and Analysis of Vegetation Data, retrieved December 28, 2023.
Fleming, Gary P. and Karen D. Patterson 2021. Natural Communities of Virginia: Ecological Groups and Community Types: a listing with conservation status ranks. Natural Heritage Technical Report 21-15. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, Virginia. 31 pages.
Fleming, G.P., K.D. Patterson, and K. Taverna. 2021. The Natural Communities of Virginia: a Classification of Ecological Community Groups and Community Types. Third approximation. Version 3.3. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. www.dcr.virginia.gov/natural-heritage/natural-communities/ [Accessed: 26-12-2023]
NatureServe. 2023. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. [Accessed: December 26, 2023].