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(cm), basal caliper (mm), number of basal sprouts (count), length of the terminal leader (cm), <br />and length of each of the next three sprouts on upper portion of tree (cm). Disease and insect <br />infestation were recorded again at the end of the growing season. <br />Water status, or leaf water potential, of the plants was measured on June 22, July 21, and <br />September 20 as near to dawn as possible (%s hr predawn to %2 hr after sunup) to capture the <br />minimum stress before rapid morning transpiration has depleted leaf moisture. One afternoon <br />measurement was also conducted on August 18 to indicate maximum stress under high radiation <br />loading when transpiration would be highest. Treatment, ambient temperature, time of sampling <br />and exuding pressure level was recorded. Leaves were collected from the different treatments at <br />random to minimize time of sampling biases. <br />Leaf water potential will increases as water is withheld from the plant and plant water stress <br />increases. Water status measurements required removing one fully matured leaf randomly <br />selected from trees in each treatment and measured for water holding capacity using a Plant <br />Water Status Console. The leaf was removed from the plant and immediately placed in a sealed <br />chamber with the petiole extending through a sealing hole in the chamber. A fresh slightly <br />angled cut was made and nitrogen gas was delivered to the leaf under slowly increasing pressure <br />until water exudes from the petiole surface. The pressure necessary for this to occur is an <br />indication of the leaf water potential or water holding capacity of the leaf, an indication of the <br />water stress and thus physiological stress of the plant. Different plants from each treatment were <br />selected at each testing to minimize leaf loss from sampling. From 2-3 total measurements were <br />made from each treatment each day of measurement. Number of measurements depended on the <br />. time necessary for each measurement, so that all measurements fall within the dawn-time <br />window. Each day of measurements included leaves from all irrigation treatments. Size of <br />sampled leaf was recorded as length from tip to petiole (mm), and maximum width (mm). An <br />empirical equation was developed to relate width and length to actual leaf area. <br />Results (2005-2006) -The first two years of the study have provided significant results worth <br />reporting here. Supporting data have been presented in earlier reports. The study was initially <br />conducted to demonstrate the effectiveness of supplemental irrigation on growth and survival of <br />transplanted cuttings; but additional experimental conditions allowed examination of additional <br />factors. Factors examined in the experiment were: irrigation (four levels of watering), soil type <br />(roto-cleared/fresh, dozer-cleared/stored, or undisturbed), plant type (transplanted rooted sprouts, <br />natural sprouts, potted plants) and fencing (fenced or not fenced). Since not all treatment <br />combinations existed and none of the treatments were replicated, statistical analyses and <br />inferences are limited. For example, differences in growth or survival between Yoast, II-W roto- <br />cleared soil sprouts, and I1-W irrigated treatments may be due to differences in soil disturbance, <br />genetic stock of aspen, transplant type, fencing, or microclimatic differences between sites, <br />treatments not independently replicated for this study. <br />This study was considered a case study relevant only for this one location. Nevertheless, several <br />observations were evident from the study that might be helpful for future aspen management and <br />to identify areas for additional research.