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• Water was delivered during the 2005 growing season by drip irrigation to the <br />transplanted aspen saplings via acomputer-controlled system that timed the daily <br />application of water through calibrated emitters. The four water treatments (high, <br />medium, low, non-irrigated control) were randomly assigned to one of the four blocks <br />in each of the two soil types, with all 50 trees in each block receiving the same <br />amount of water (Figure 1). <br />Water was delivered to the irrigated trees using a gravity fed drip system, supplied <br />by a 2000 gallon tank located 207 vertical feet upslope from the test site that <br />provided an adequate head to maintain water pressure greater than 60 lbs. The tank <br />was filled by Seneca Coal Company workers as needed, generally once or twice a <br />week. Drippers delivered water at 1 gallon/minute, and were programmed to deliver <br />water daily at 1.3, 0.6, and 0.3 gaUday/tree for the high, medium, and low irrigation <br />levels; equivalent to 14.4, 7.2, and 3.6 inches of precipitation per month. The non- <br />• irrigated control received no supplemental water. Irrigation treatments were applied <br />daily during the eady morning. Drippers required 4 Ibs pressure for activation; the <br />valve box and distribution lines were configured so that head pressure down stream <br />of the valves did not exceed this value to avoid leakage between irrigation <br />treatments (Figure 1). Soil moisture and temperature sensors were located in each <br />plot and data were recorded hourly. Standard meteorological conditions were <br />monitored at an automated weather station located at the center of the plot, and data <br />recorded hourly inGuded wind speed, wind direction, relative humidity, and <br />precipitation. Hourly soil temperature, moisture content, and matrix potential were <br />also monitored at one tree in each watering treatment. All data were recorded on a <br />Campbell 23x data logger, which also was programmed to activate the irrigation <br />solenoids. Power was supplied by 12 V batteries charged by a solar panel. <br />In addition to the watering study, we also obtained growth and survival data from <br />three other types of young aspen trees: 1) Natural sprouts that had grown from roots <br />buried in un-irrigated areas of the fresh and stored soil adjacent to the irrigated <br />