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<br />002721 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />flood irrigating. Approximately 1,380 cottonwoods, 370 willows, 3,560 honey <br />mesquites, 45 palo verdes, 80 California fan palms, and 100 quailbush were planted. <br />Trees and shrubs were in cardboard tubes ten centimeters in diameter and 40 em long. <br />Nitrogen fertilizer was applied using a liquid injector system. Undesirable vegetation <br />was controlled by applying "Arsenal," and a systemic insecticide "Orthene" was applied <br />to control physllids. Three-foot tall-chicken wire baskets were installed around all <br />plants, which were irrigated with a drip system (12 gallons each day for the first 30 <br />days; reduced to 3 days a week through September 1987) (Pinkney 1992). Cottonwoods <br />and willows were also planted in an erosional depression located immediately adjacent <br />to the agricultural fields. The depression is roughly 1.5 ha in area and lies <br />approximately two meters below the elevation of surrounding lands. <br />Results: As of 1990, approximately 53 percent of the total numbers of individuals <br />originally planted had survived (Pinkney 1992). Of this amount, more than 90 percent <br />was honey mesquite and palo verde. The only other plant species with more than 50 <br />percent survival was quailbush. All of these plants occur outside the erosional <br />depression. Of all the cottonwoods and willows that were planted, only those planted <br />in the erosional depression survived. This relatively low elevational area receives <br />periodic runoff from an adjacent agricultural field. Cottonwood and willow in this <br />depression are over 18 m (60 feet) high and appear healthy. As long as the adjacent <br />field is irrigated, this area will have sufficient moisture to support the existing <br />cottonwood and willow. As of 1997, honey mesquite, palo verde, and quailbush have <br />established in scattered locations throughout the south end of the site. <br />Lessons Learned: The relatively mesic environment of the erosional depression appears <br />to have been crucial to the survival of native, obligate riparian plants. This underscores <br />the importance of both understanding the depth to the saturated zone when <br />revegetating with obligate riparian plants and taking advantage of landscape features <br />that may be characterized by higher water availability. <br /> <br />Site #3 <br />Cibola National Wildlife Refuge Saline Site <br />Location and Size: The Cibola National Wildlife Refuge is located in La Paz County, <br />Arizona, due west of Cibola, Arizona. The Cibola NWR is located approximately at <br />River Mile 99 on the lower Colorado River in La Paz County, Arizona. The <br />revegetation site is located in the northeast corner of the refuge and consists of eight-6 <br />m * 9 m (20 ft * 30 ft) plots. <br />Objective: To better understand the feasibility of establishing native plants in highly <br />saline soils. <br />Completion Date: September 1986 <br />Pre-Project Site Conditions: The site was essentially void of woody plants at the time of <br />planting and soils were classified as dense clays. Depth to saturated soils was <br />estimated at about 1.5 m (roughly four ft) and soil salinity ranged from 6,000 ppm to <br />60,000 ppm (Pinkney 1992). <br />Project Strategy: Prior to seeding, all plots were flooded in an attempt to leach out the <br />salts in the soil profile. The plots were seeded and raked in September 1986. Four of <br /> <br />Page 9 <br />