VEGETATION, HYDROLOGY AND HUMAN DISTURBANCE 



The area remains a high-quality wetland, despite the history 

 of vegetation change in the Dismal. The present forest canopy 

 ranges from about 50 to 75 yrs in age, with scattered remnant 

 individuals and clusters of much older cypress and black gum. This 

 vegetation has been mapped using color infrared aerial photography 

 by Gammon and Carter (1979). The canopy is composed almost 

 entirely of Nyssa sylvatlca bif lora and red maple in most areas, 

 with either species being locally dominant. Cypress or loblolly 

 pine are important in a few small areas. Sweet gum can be found 

 occasionally in the canopy, but is not abundant. 



Locally, red maple, sweet bay ( Magnolia virginiana )or holly 

 ( Ilex opaca ) form a thin subcanopy. Clethra alnifolia and Smilax 

 are the most common species in the shrub stratum, occasionally 

 forming a nearly closed layer. Because of deep shade and low 

 nutrient availability, the herb flora is depauperate, comprising 

 only a handful of species, and these very thinly distributed in 

 most areas. 



As discussed in the introduction to this report, the Dismal 

 has undergone nearly two centuries of human disturbance, 

 beginning with construction of the Dismal Swamp Canal. Under- 

 standing present vegetation will require a variety of scientific 

 studies, investigation of vegetation along moisture, edaphic 

 and topographic gradients in the region, as well as recorded 

 historical events and descriptions of early travelers. 



Examination of color infrared aerial photography (NASA 

 UAg 1045 153.22, 2 December 1972) shows little observable change 

 from vegetation along ditches to that of areas remote from 

 drainage. The absence of a visible gradient from mesic species 

 near ditches to more hydric species farther from drainage is 

 remarkable in view of the fact that these ditches are cut to a 

 depth of several feet below the land surface. During wet periods 

 they can be seen carrying away surplus water at a rate which 

 must be several times faster than that which occurred in the 

 original situation. The lack of a vegetation gradient suggests 

 that the peat is relatively impermeable to lateral movement of • 

 water and that water visible in ditches and canals in wet 

 seasons is primarily due to shallow surface runoff. 



This function of ditches was partially simulated in nature 

 by a dendritic drainage pattern, remnants of which can be seen 

 in the headwaters of the major streams draining the Dismal. 

 That the streams sometimes carried a flow surprisingly rapid 

 for a swampy area is documented by Kearney (1901) and Ruff in 

 (1861). 



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