of this trampled area may be covered by fill as construction proceeds. A 

 more significant vegetation loss occurs during excavation of a 5-m (15-ft) 

 wide borrow ditch and burial of some bordering marsh by fill. The width 

 of the latter zone is 10 to 13 m (30 to 40 ft). This direct loss results 

 in an immediate decrease in food and cover for the consumers in the area. 

 In cases where the existing vegetation is a pest species, flora destruc- 

 tion may be considered beneficial for several reasons: (1) it reduces 

 the reproductive potential of the pest species, (2) it opens dense stands 

 of vegetation and increases the "edge effect," and (3) it might allow the 

 zone to be invaded by more desirable species. The total area affected is 

 usually small in comparison to the remaining area of undisturbed marsh, 

 and the effects on transpiration, evaporation, sediment trapping, fire, 

 available nutrients, and peat accumulation are insignificant. However, as 

 each new ditch and wellsite is excavated, the carrying capacity of the 

 intact marsh is decreased. Cumulative effects are unknown, and the thresh- 

 old point (where one additional road will significantly affect the marsh) 

 is obscure. 



The depth and number of ruts by marsh vehicles are dependent upon the 

 total number of trips and the degree to which vehicles retrace existing 

 tracks. In areas that are submerged continuously (or nearly so), the 

 depressions are less likely to significantly alter water movement pat- 

 terns. In such regions, confinement of marsh vehicle traffic to a narrow 

 corridor may be wise. However, in areas of higher elevation, deep ruts 

 resulting from retraced trails will form depressions for the movement of 

 water and, if deep enough, may result in standing bodies of water during 

 wet seasons. The orientation and depth of the depressions determine 

 whether they (1) remain for long periods of time and (2) alter the water 

 regime of given area of land by increasing or decreasing the frequency of 

 submergence/ emergence, average depth, and duration of submergency. Areas 

 dominated by maiden cane may be replaced by stands of rushes, sedges, 

 canes, or other emergent species when the frequency and/or duration of 

 submergence increases. The converse may occur when frequency and/or dura- 

 tion of submergence decreases. Although the total area affected is site 

 specific, it is usually small when compared to the total area of undis- 

 turbed marsh. Because both of these vegetation types support the same 

 consumers, no significant changes in fauna would be expected. 



The depressions allow a faster runoff of surface and standing water in 

 localized areas, but this drying effect on adjacent regions is usually 

 small. The long-term effects on suspended sediments and nutrients are 

 slight. 



If vehicle tracks occur in areas of the marsh where isolated ponds exist, 

 intramarsh circulation could be affected. Depressions could connect 

 individual water bodies and increase the intermixing of their contents. 

 Waterfowl and wading bird use would be expected to increase in these new 

 depressions retaining standing water. At the ecosystem level, however, 

 this increase is insignificant. 



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