2. Primary ecological alterations 



2.1 Possible creation of ruts or depressions in the land surface 



2.2 Trampling and crushing of vegetation at the station locations 



2.3 Possible creation of pathway for increased saltwater inundation 



2.4 Possible creation of pathway for increased rate of flow of 

 runoff 



3. Attribute alterations 



The movement of vehicles and workers over the marsh surface crushes 

 vegetation. The vegetation may be completely uprooted and destroyed 

 in some areas depending upon the soil moisture conditions and the 

 type of transportation that is utilized. The vegetation loss 

 results in an immediate decrease in food and cover for the consumers 

 in the area. The total area affected is usually ^ery small in 

 comparison to the remaining area of productive vegetation because 

 (1) the gravity meter is quite portable, (2) data stations are not 

 located along predetermined straight lines, and (3) the stations are 

 not regularly spaced. Stations may frequently be accessed by boat 

 or by foot; a maximum of one lightweight surface vehicle is neces- 

 sary for the entire operation. Furthermore, this vehicle need not 

 travel straight-line paths across the marsh surface; it can make 

 maximum use of existing roads or canals. Therefore, the effects on 

 consumers, nitrogen fixation, and detritus export are negligible. 



The above discussion indicates total vehicular traffic associated 

 with gravity surveys is less than that associated with seismic 

 surveys. Nevertheless, any marsh-surface vehicle may potentially 

 alter local land elevations. The depth and number of ruts created 

 by marsh buggies is dependent upon the number of vehicles and the 

 degree to which they retrace existing tracks. In areas that are 

 submerged daily, the depressions are less likely to significantly 

 liter water-movement patterns. Hence, in areas near the estuary, 

 ;onfinement of marsh buggy traffic to a narrow corridor may be wise. 

 However, in areas further removed from the estuary, deep ruts result- 

 ing from retraced trails would form a depression for the movement of 

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

 after the tide has receded. The orientation and depth of the depres- 

 sions determine whether they (1) remain for long periods of time and 

 (2) increase or decrease the frequency of inundation of a given area 

 of land. Areas dominated by saltgrass or shore grass may be replaced 

 by stands of smooth cordgrass when the frequency and/or duration of 

 inundation increases. The converse may occur when frequency and/or 



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