|Photo by the Atlas of Florida Plants Database|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Liliopsida - Moncots|
| Andropogon virginicus|
|Natural range of Andropogon virginicus from USDA NRCS Plants Database.|
Andropogon virginicus is a monoecious perennial graminoid. It reaches 3-6 ft (0.91-1.83 m) in height and bunches together producing clumps (i.e. bunchgrass). The fruits of A. virginicus are classified as an achene and caryopsis.
Its primary distribution ranges from eastern Texas, Oklahoma, and Kansas eastward to the coast of the Atlantic Ocean and as far north as Illinois, Michigan, New York, Massachusetts. It is also found in Puerto Rico, Ontario Canada, California, and was introduced in Hawaii.
Andropogon virginicus is commonly found in longleaf pine savannas, savannas, flatwoods, maritime wet grasslands, disturbed pinelands, other wetlands, old fields, roadbanks, and disturbed sites with sandy low fertility soils. With such a wide range of habitats, A. virginicus has been shown to adapt to ecotones of varying water availability; in granite outcrops A. virginicus is more resistant to water loss than in old field habitat. In Illinois old field succession, A. virginicus becomes dominant in the 4th year of succession and remains present in later stages. Similar results in Mississippi show A. virginicus establishing in the 5th year of succession and remaining through the 15th year of the 16 year study.
A. virginicus is also known for its allelopathic effects on surrounding organisms. In Oklahoma, studies have shown inhibition of seedling growth in species in the pioneering (e.g. Amaranthus palmeri, Bromus japonicus), primary (e.g. Amaranthus retroflexus), and secondary (e.g. Aristida oligantha, Andropogon scoparius) stages of old field succession. It also inhibits growth and nodulation legumes, including Lespedeza stipulacea and Trifolium repens. Inhibition has also been documented in free living and symbiotic nitrogen fixing bacteria (i.e. Azotobacter and Rhizobium). Such inhibitions may work to keep nitrogen availability low, thereby engineering its environment to keep its competative advantage over other species.
Flowers bloom between September and November, producing a yellow flower. Flowering usually occurs at, or shortly after, dawn as it is triggered by light. Seeds develop fine hairs along the racemes giving raceme clusters a broom-like appearance.
Seed bank and germination
In Hawaii where A. virginicus is exotic, the abundance of seeds in the seed rain and the seed bank vary between seasons. Persistent seeds were found ranging from around 90-130 seeds m-2 which allows for this species to wait for disturbances and then quickly colonize the area. Seed banks in a New Jersey old field succession site showed seed to primarily occurr in the top 3 cm of soil and to reach densities around 350 seeds m-2. It is also worth noting seedlings from A. virginicus seeds did germinate from the seed bank until the 5th year of succession. This appearance in the seed bank coincides with the establishment of A. virginicus on the 4th and 5th years of other successional studies in Illinois and Mississippi. Although seeds enter the seed bank during October and November, germination does not begin until mid January and may require a cold period prior to germination.
A review of early studies suggests A. virginicus can be nearly eliminated by fires. However, more recent studies suggest A. virginicus is a pyrophyte that helps create a fire driven system by adding fuel to the fire and thereby promoting increases in fire frequency and size. It maintains extremely high dead:live biomass ratios during most of the year at 80-90%. Additionally, it can burn at high relative humidity (85-90%) and fuel moisture (20-25%). When burned, it recovers quickly and with increased vigor. Following a November 28, 2015 burn, resprouts were noted 38 days after the fire. Densities peak in the second or third growing season following burns and then decline, being replaced by pines.
Use by animals
A. virginicus can encompass 2-5% of the diet for large mammals and terrestrial birds as well as occasionally being used as cover for terrestrial birds.
Conservation and Management
A. virginicus is considered a noxious weed in Hawaii submontane zones where it was introduced and spread in the 1960's and 1970's. Part of its successful invasion could be due to its ability to quickly invade disturbed lands, including those recently burned.
Cultivation and restoration
References and notes
- Weakley A. S.(2015). Flora of the Southern and Mid-Atlantic States. Chapel Hill, NC: University of North Carolina Herbarium.
- USDA, NRCS. (2016). The PLANTS Database (http://plants.usda.gov, 30 November 2017). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- Plant database: Andropogon virginicus. (13 December 2017).Lady Bird Johnson Wildflower Center. URL: https://www.wildflower.org/plants/result.php?id_plant=ANVI2
- Catling P. M., Reznicek A. A., Riley J. L. (1977). Some new and interesting grass records from southern Ontario. Canadian Field-Naturalist 91(4):350-359.
- "Smith C. W. and Tunison J. T. (1992). Fire and alien plants in Hawai'i: Research and management implications for native ecosystems. Alien plant invasions in native ecosystems of Hawaii: management and research. Cooperative National Park Resources Studies Unit, Honolulu 394-408.
- Rice E. L. (1972). Allelopathic effects of Andropogon virginicus and its persistence in old fields. American Journal of Botany 59(7):752-755.
- Chapman R. H. and Jones, Jr. S. B. (1975). Ecotypic differentiation in Andropogon virginicus (Gramineae). Bulletin of the Torrey Botanical Club 102(4):166-171.
- Bazzaz F. A. (1975). Plant species diversity in old-field successional ecosystems in southern Illinois. Ecology 56:485-488.
- Battaglia L. L., Minchin P. R., and Pritchett D. W. (2002). Sixteen years of old-field succession and reestablishment of a bottomland hardwood forest in the lower Mississippi alluvial valley. Wetlands 22(1):1-17.
- Campbell C. S. (1982). Cleistogamy in Andropogon L. (Gramineae). American Journal of Botany 69(10):1625-1635.
- Campbell C. S. (1983). Wind dispersal of some North American species of Andropogon (Gramineae). Rhodora 85(841):65-72.
- Kirkman, L. Katherine. Unpublished database of seed dispersal mode of plants found in Coastal Plain longleaf pine-grasslands of the Jones Ecological Research Center, Georgia.
- Drake D. R. (1998). Relationships among the seed rain, seed bank, and vegetation of a Hawaiian forest. Journal of Vegetation Science. 9(1):103-112.
- Leck M. A. and Leck C. F. (1998). A ten-year seed bank study of old field succession in central New Jersey. The Journal of the Torrey Botanical Society 125(1):11-32.
- Keever C. (1950). Causes of succession on old fields of the Piedmont, North Carolina. Ecological Monographs 20(3):229-250.
- Garren K. H. (1943). Effects of fire on vegetation of the southeastern United States. Botanical Review 9(9):617-654.
- Hodgkins E. J. (1958). Effects of fire on undergrowth vegetation in upland southern pine forests. Ecology 39(1):36-46.
- Hughes F., Vitousek P. M., and Tunison T. (1991). Alien grass invasion and fire in the seasonal submontane zone of Hawai'i. Ecology 72(2):743-747.
- Observation by Edwin Bridges in northern Highlands County, FL, January 5, 2016, posted to Florida Flora and Ecosystematics Facebook Group January 6, 2016.
- Lemon P. C. (1949). Successional responses of herbs in the longleaf-slash pine forest after fire. Ecology 30(2):135-145.