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<br />002723 <br /> <br />Opportunities for Ecological Improvement Along the Lower Colorado River <br />Mark Briggs and Steve Cornelius <br />7/24/97 <br /> <br />Results: Dredge Spoil plantings were counted in June 1990. At that time, an additional <br />150 more cottonwoods had established naturally. Natural recruitment of honey <br />mesquite and palo verde is also occurring (Pinkney 1992). Willow numbers continued <br />to decline since the first inventory was completed. In 1997, there appears to be <br />significant differences in survival rates and overall plant health between plantings on <br />the west side of the levee and those on the east side, with establishment rates and plant <br />vigor on the west side of the levee (adjacent to the agricultural fields) appearing much <br />greater. This was also reported by Pinkney (1992). <br />Lessons Learned: Particularly in arid climates, providing sufficient water to revegetated <br />plant materials is critical for success. At the Dredge Spoil site, plants adjacent to the <br />agricultural fields have established in greater numbers and appear less stressed than <br />those on the opposite side of the levee. Along the lower Colorado River, planting in <br />areas that are likely to receive agricultural runoff may improve the effectiveness of the <br />revegetation effort Establishing riparian habitat for avian insectivores adjacent to <br />agricultural land can provide benefits for both wildlife and farmers (Anderson 1984). <br /> <br />Site #S <br />Farmer's Market Bridge <br />Location and Size: This project consists of two sites located roughly 200 meters from the <br />Colorado River along a levee that runs parallel to the river due west of Cibola, Arizona. <br />The levee can be accessed via Farmer's Market Bridge road. The southern site is <br />roughly.4 hectares (one acre) and the northern site is roughly .8 hectares (two acres). <br />Objective: To re-establish native riparian trees. <br />Completion Date: 1986 <br />Pre-Project Site Conditions: Both sites were void of woody plants prior to project <br />initiation. Soils were generally sandy and depth to saturated soils was estimated to <br />vary between 10 and 20 feet (3 m to 6 m) [beneath the surface of the soil] (John Sweat, <br />pers. comm., 1997). <br />Project Strategy: A total of 65 willow (Salix gooddingil), cottonwood (Populus fremontil), <br />and screwbean mesquite (Prosopis pubescens) were planted at the two locations. Poles <br />and seedlings were used in the revegetation effort Plantings were irrigated with a drip <br />system for the first two summers. <br />Results: Survival of planted species was higher in the north site than in the south site, <br />possibly due to higher water availability. Twenty trees survive on the southern site. Of <br />these, only one willow and six cottonwoods were found and all show obvious signs of <br />water stress (stunted growth, canopy die-back, thick and yellow leaves). In <br />comparison, mesquite appeared much healthier, averaging roughly 5 m in height with <br />spreading, relatively full canopies. <br />Lessons Learned: Using plant materials that are adapted to current hydrologic conditions <br />is a key ingredient to success. In particular, evaluating depth to saturated zone prior to <br />planting can provide planners with critical information for selecting appropriate plant <br />materials. <br /> <br />Page 11 <br />