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<br />oaJol1 <br /> <br />intensity; WI refers to wetland vegetation with high <br />biomass intensity.) [See Table 1 and Box 3.] <br /> <br />Generally, the team found three types of wetland <br />ecosystem in the study area: <br /> <br />1) riparian deciduous forest and woodland in areas <br />subject to periodic river flooding (Zones 1-5) <br />dominated by the mesophytic cottonwood and <br />willow trees in the north (Zones 1-3), and by the <br />phreatophyte tamarisk and other salt-tolerant shrubs <br />as the river approached the tidal zone to the south <br />(Zones 4 & 5). <br /> <br />Photo 6. Dry mudflats In the Colorado River delta. <br /> <br />E \J'F ;::>\; \}1,:_\!-;-;: '-':: :c.\i:5.: F;":;\~=: <br /> <br /> <br />2) maritime, submergent mud flats dominated by the <br />endemic Palmer's salt grass in the tidal portion of <br />the river (Zone 6). <br /> <br />3) brackish marshlands dominated by cattails and other <br />emergent hydrophytes in areas flooded with agricul- <br />tural drainage water in the eastern side of the delta <br />(Zone 7). <br /> <br />Dense gallery forests of cottonwood and willow in the <br />northeastern delta (Zones 1-3) are considered among <br />the most valuable habitat types in the lower Colorado <br />River region (Ohmart et aI., 1988). These trees have <br />prevailed through droughts and intense floods.33 Above <br /> <br /> <br />33 Zone 1 is notable for its dense willow stands, which are now so rare they are no longer listed as a habhat class along the river above Morelos Dam. <br />Zones 2 and 3 contain approximately 3700 acres (1500 ha) of cottonwood and willow gallery forest, while only 250 acres (100 ha) of gallery forest remain on <br />the Unhed States' stretch of river. <br /> <br />23 <br />