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<br />Much of this surface is composed ofloamy soils. In certain locations, the low terrace surface <br />supports mature cottonwood and box elder stands that were established when this was the active <br />floodplain. The tap roots of these mature stands are connected to the underlying water table, but <br />the understories are usually composed of upland species due to the lack of near-surface <br />groundwater. The high terrace-alluvial fan surface is situated more than 6-feet above the <br />floodplain level. It is relatively unaffected by the present-day river process and hydrology. <br />Wetland/riparians found on the high terrace are associated with tributary drainages and seeps that <br />collect irrigation return flows from adjacent tablelands. <br /> <br />2.3 WetlandlRiparian Plant Communities <br /> <br />Based on the 2001 inventory studies completed by Frontier, a total of approximately 234 acres of <br />wetland/riparian habitats occur within the ranch parcels (Table 2), with nearly all of this acreage <br />occurring within the river's zone-of-influence. As stated in Chapter I, this acreage tally is <br />updated from the 171 acres estimated in Volume II of the FSEIS in the Wetlands Mitigation <br />Opportunities Report. These 234 riparian acres will be the base to mitigate for the loss of 134 <br />acres of wetlands within Ridges Basin and along Basin Creek in excess of the 1.5 to 1 ratio <br />committed to in the FSEIS and the ROD. <br /> <br />Four broad types of wetland/riparian habitats were identified: 1) Riparian Forest/Scrub-Shrub, 2) <br />Riparian Meadow, 3) Riverine and 4) Emergent Wetlands. Nearly all of the wetland/riparian <br />habitats occur within the river's zone-of-influence. Emergent wetlands comprise a very small <br />amount of habitat acreage (14.7 acres) and are only found in Tract II (North) and Tract III of the <br />Huntington Ranch (Table 2). These wetlands are dominated by bulrush, cattail, and sedges and <br />are generally found in areas that are perennially wet, such as old meander scars that collect <br />irrigation return flows or seeps along the valley wall on the high terrace. <br /> <br />Riparian forest/scrub-shrub is the most abundant habitat type (142.5 acres total) and is commonly <br />found on both channel bar and floodplain terraces. In its native condition, it is dominated by <br />cottonwood trees and willows and has a herbaceous understory of riparian grasses. The <br />functional condition of this habitat is dependent on the presence of a multilayered canopy with <br />structural components in the tree, shrub and herbaceous stratum, and the absence of non-native <br />plants such as tamarisk and Russian olive. Riparian meadow (76.8 acres total) occurs mostly on <br />the floodplain terrace. In its native condition, riparian meadow is dominated by riparian grasses, <br />sedges, rushes, and wildflowers. The functional condition of this habitat is affected greatly by <br />the removal of vegetation by livestock grazing, and the presence of non-native plants such as <br />thistle, chicory, leafy spurge, cheatgrass and knapweed. <br /> <br />The riparian forest/scrub-shrub and riparian meadow habitats were subclassified into Type I, <br />Type 2 or Type 3 habitats, with Type I having the best habitat values. The subclassification is <br />based on the presence/absence of undesirable weed species, vegetative cover, and habitat <br />structure. Reference standards were developed separately for each of the habitat subclasses. A <br />report describing the methodology and criteria that were used for developing the reference <br /> <br />-13- <br />