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• VEGETATION <br />Open: The open riparian forest appears to potentially be the result of a dense, mature riparian <br />forest that is beyond prime stage and is in rapid decline. These forests often contain large amounts of or <br />evidence of the presence of large trees that have died. As a result of the death of many of the trees that <br />formed the mature forest unit described above, the surviving individuals are presented with prodigious <br />amounts of growth resources that were previously shared between many trees. This can result in the <br />development of large to very large individual cottonwoods separated by rather large distances. Canopy <br />cover can still be high, but much below 100%, and tree density is usually low. These open forests <br />composed of large, widely separated trees are less common than other forms because usually floods remove <br />the forest before it can develop to this point. However, just because these forests are uncommon does not <br />mean they are not very valuable as habitat. They have much lower habitat value than peak maturity <br />forests, but greater value than the young, dense forest that is composed almost totally of trees and little <br />else. The old forests often exhibit a short life span and are replaced by grassland or shrub and grass. <br />One significant factor in the development and life span of these forests involves hydrology and the <br />changes in hydrology as the river channel deepens and the water table declines. Because riparian vegetation <br />is known to be quite sensitive to the depth of the water table, even small changes in the water cable can <br />have significant effects on the vegetation character. Over the course of 100 years the river channel may <br />deepen several inches or even as much as a foot, depending on normal stream gradients, channel changes <br />elsewhere, flood events, etc. Furthermore, over time, the sandy and gravelly soils that helped establish a <br />cottonwood dominated forest in the first place tends to become somewhat more clayey, especially if soils <br />on nearby hills contain significant amounts of clay. The increasing soil density reduces the hydrologic <br />flowthrough resulting in less water resources and selecting for those trees with the deepest and strongest <br />root sys[ems. <br />Both of these units (Dense and Open Riparian Forests) occur on and adjacent to this site. But no <br />mining will occur in either of these units. There may be some disturbance, but the original soils will be <br />maintained and therefore the original forest should be replaced to some extent where it is removed. <br />Sedge wetland; Sparse: This unit occurs in only one location -along the outlet edge of the irrigated <br />pastures on the western phase and at the outer edge depression of a very old river meander. This unit <br />occurs underneath a dense, but mature cottonwood forest. It is also found in a nearly closed, narrow basin <br />that extends along the outside edge of a river meander that was probably abandoned by the river 70 or 80 <br />years ago. <br />The vegetation in this area is very sparse due to the frequent inundation by irrigation tailwater. <br />Only scattered sedges and grasses are present. This area is occupied primarily by hydrophytes, but it is not <br />known whether the soils or hydrology are appropriate to make it a jurisdictional wetland. By some <br />wetland definitions, it is clearly wetland, but because it is disconnected from other units and is maintained <br />by irrigation tailwater it might not be jurisdictional and might actually die if that water is removed. Based <br />on the elevations between the river and the ground, it is probable that the water table is too deep to <br />support a jurisdictional wetland without irrigation. <br />In the event it is decided that this area will need to be affected, a full wetland delineation will be <br />needed to determine if it is jurisdictional and provide the information needed for proper permitting. <br />Sandbar WillOw~TamariX: This unit occurs on low elevation areas just above the level of the river. <br />Groundwater support is nearly continuous and flooding is not out of the question. The growth is dense, <br />Grisenti Farms Gravel Pit Original Application Exhibit J Page J-3 <br />