4. Key attribute alterations 



The alteration which leads to the most significant impacts on the 

 ecosystem is the creation of depressions in the land surface. 

 Effects which are large in areal extent and long term may result 

 from induced changes in waterflow regimes. As discussed earlier, 

 the total area affected (and thus, the kinds and numbers of con- 

 sumers) is site specific. 



Gravity preexploration. 



1. Activity sequence 



Gravity surveys may involve the placement of a relatively small 

 piece of equipment on the marsh surface. This unit (the gravity 

 meter) may be carried to stations by truck, marsh buggy, boat, or 

 foot. Survey crews are not required since data need not come from 

 predetermined locations. It is necessary only to plot the locations 

 of the data-collection stations on a map. A small amount of vegeta- 

 tion is trampled during the placement of the gravity meter. Several 

 minutes are required for data collection; the unit is then packed 

 and carried to the next station. The number of stations required 

 for a gravity-meter survey is less than the number of shot holes 

 necessary for a seismic survey. Two men with adequate transporta- 

 tion can efficiently conduct a gravity-meter survey. 



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 localized change in direction of water flow 



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 



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