PIEDMONT/MOUNTAIN CANEBRAKE Concept
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PIEDMONT/MOUNTAIN CANEBRAKE Concept: Piedmont/Mountain Canebrakes are communities dominated by dense thickets of Arundinaria gigantea, treeless or with an open canopy. No well-developed examples are known to remain in North Carolina. Distinguishing Features: Piedmont/Mountain Canebrakes are distinguished by having a dense shrub layer of Arundinaria gigantea, occurring with limited tree cover. Areas of cane that appear to be naturally developed, or are restored in plausible natural settings, should be regarded as this type. Areas where Arundinaria occurs at low to moderate density under a typical forest canopy are not included, nor are stands of Arundinaria appalachiana in uplands. Abundance of Arundinaria gigantea in a forest may suggest past occurrence of a canebrake but should not be taken as proof of a former canebrake without additional evidence. Methods of finding sites of past canebrakes, other than definitive site-species historical descriptions, are not known. Piedmont/Mountain Canebrakes are distinguished from Peatland Canebrakes by occurring different regions, different environments, and in being dominated by Arundinaria gigantea rather than Arundinaria tecta. Synonyms: Arundinaria gigantea ssp. gigantea Shrubland (CEGL003836). Ecological Systems: South-Central Interior Small Stream and Riparian (CES202.706); South- Central Interior Large Floodplain (CES202.705). Sites: Piedmont/Mountain Canebrakes may potentially occur in either small or large floodplains. They are believed to be primarily in the Mountain Region but could occur in the upper Piedmont. Soils: Piedmont/Mountain Canebrakes could potentially occur on any floodplain soil. If particular soil conditions are necessary, they are not known. Hydrology: Canebrakes occurred on drier floodplain sites; they presumably were flooded intermittently for brief periods. Vegetation: The vegetation is characterized by a dense stand of Arundinaria gigantea, which may be 10 to 20 feet tall or more. Trees may be absent, but an open or sparse canopy of any of the trees of any of the Montane Alluvial Forest subtypes may be present. Other shrubs may occur at low density beneath the cane or may be more abundant in open spots. Range and Abundance: Ranked G2? This community has largely disappeared from North Carolina. Only a couple of small, poorly developed examples of questionable origin are known. The former abundance, acreage, and distribution in North Carolina is unclear. It is generally believed to have been more prominent in the Mountains. Though Native Americans in the Piedmont were reported to use cane, and large cane stalks were reported to have been seen, it is less clear if there were well-developed canebrakes. The rough range map in Triplett, et al. (2010) show Arundinaria gigantea occurring only in the Blue Ridge and possibly western Piedmont in North Carolina, though it extends into the Coastal Plain in Georgia and southern South Carolina. The NVC association is attributed to a very wide range, extending from Virginia to Florida and westward to Texas and Missouri, and the NVC description cites several places where remnants occur. The nearest substantial remnant appears to be near the Ocmulgee River in the Georgia Piedmont or upper Coastal Plain. Associations and Patterns: Piedmont/Mountain Canebrakes are generally described as large patch communities, though it is unclear how extensive examples in North Carolina were. They presumably were smaller than those on the much larger floodplains farther west. They presumably occurred with various floodplain forests and likely bordered uplands at the edge of floodplains. Variation: Nothing is known of the variation in this community. It is unlikely that the NVC association was uniform over the large range of climate and physiography to which it is attributed. Dynamics: Most of what is believed about canebrake dynamics is interpreted from historical sources. The widespread belief that they were maintained by fire is almost certainly true; the climate and sites where they occurred are capable of supporting forests. However, it is likely that a dense stand of cane is competitive enough to inhibit tree establishment even without fire. This likely was a situation of alternative stable states, where the flammability of dense cane promoted intense fires that would kill trees and sustain canebrakes, while the limited flammability in floodplain forests dampened fires. Because Arundinaria can spread by rhizomes, established canebrakes might be able to expand into adjacent forests as long as fire was sufficiently frequent, but might shrink in periods when fire became infrequent. If canebrakes with open tree canopies exist, may be a nonequilibrium situation, where previously established trees persist but cannot reproduce. It is assumed by many that fire intervals were very frequent and were largely human caused. As with the fire regime in other communities, most fires may have been ignited by humans near their settlements, but it is less clear that fires would not have occurred without them. The existence of numerous species adapted to fire required a period of evolution much longer than human presence in the hemisphere. It is also likely that fire frequencies as high as often believed to have occurred around human settlements would not have been good for Arundinaria, which replenishes its biomass more quickly than trees but likely still requires several years free of fire to retain vigor. It is widely believed, as stated in the NVC description, that canebrakes are early successional communities and may have all gotten their start in abandoned aboriginal fields. However, it is a misleading characterization to group them with typical ruderal-dominated early-successional vegetation. Arundinaria gigantea is like most bamboos in fruiting only extremely rarely. Unlike the wind-dispersed herbs and trees that we presently see capturing abandoned clearings, it could invade only from well-established stands on the edge. Canebrakes are unlikely to have been a frequently shifting community. While trees are likely to replace them if there is no fire, it is probably better to view them like prairies and barrens, as a stable community that is maintained by burning at an appropriate frequency and does not readily recover from disturbances that kill the dominant plants. Before native human populations were decimated by disease, they practiced shifting agriculture in sites similar to where canebrakes are believed to have occurred. Thus, it is possible that canebrakes were created by abandoned fields. However, Arundinaria could capture old fields before trees did only if there were frequent fire. It thus seems unlikely that widespread invasion coincided with the decline in human population if it depended solely on a human-caused fire regime. Canebrakes probably were not attractive places for aboriginal shifting agriculture. Without plows, the Arundinaria rhizomes could not be eliminated as trees could by girdling, and cane would have quickly regrown as it did from fires. Given the usefulness of cane, it seems more likely that people would have maintained them as a source of material. But the vast size of canebrakes reported in other states seems far beyond what people could have used or chosen to maintain. Comments: The most definitive historical references to extensive canebrakes are from states farther west, primarily those around the Mississippi River. Smaller canebrakes are reported in the Cumberland Plateau, Rare species: No rare species are known to be associated with this community. References: Platt, S.C., and C.G. Brantley. 1997. Canebrakes: An ecological and historical perspective. Castanea 62:8-21. Triplett, J.K., K.A. Oltrogge, and L.G. Clark. 2010. Phylogenetic relationships and natural hybridization among the North American woody bamboos (Poaceae: Bambusoideae: Arundinaria). American Journal of Botany 97:471-492. .