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2) commercially -grown potted aspen seedlings that were planted in an non - irrigated <br />fenced area approx 1 km from the irrigation study site, and; <br />3) Natural aspen sprouts growing in an un -mined area of the Yoast mine that had been <br />cleared of mature aspen. None of these study sites were replicated, so the survival, <br />growth, and water status findings are applicable only for that site; and comparability of <br />different un- replicated treatments within the same site must be made with caution. <br />Although the commercially -grown potted aspen trees were planted on dozer - cleared soil, <br />it was not determined if the roots grew out of the potting mix into the dozer - cleared soil <br />during this first year of study. <br />Natural sprouts were growing at random spacing, about 1 ft to 8 ft apart. Natural sprouts <br />selected for measurement were thinned to no closer than 5 ft spacing. The potted and <br />natural trees in all locations were from unknown genotypes, likely different from the <br />irrigated study transplants. The natural sprouts on the roto - tilled soil were all likely from <br />the same genotype since the soil came from the same area; but they were likely different <br />from those on the dozer - tilled soil. Similarly, the natural sprouts on the dozer - cleared soil <br />were possibly from the same genotype. <br />Data Collected <br />Prior to bud break, height of each tree, number of branches, disease and insect infestation, <br />and length of terminal leader dieback was recorded for each tree. Water status and tree <br />growth were measured periodically throughout the experiment. Physical measures of <br />growth were height (cm), basal caliper (mm), number of basal sprouts (count), length of <br />the terminal leader (cm), and length of each of the next three sprouts on upper portion of <br />tree (cm). Disease and insect infestation were recorded again at the end of the growing <br />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 ('/2 hr predawn to '/2 hr after sunup) to capture <br />the minimum stress before rapid morning transpiration has depleted leaf moisture. One <br />afternoon measurement was also conducted on August 18 to indicate maximum stress <br />under high radiation loading when transpiration would be highest. Treatment, ambient <br />temperature, time of sampling and exuding pressure level was recorded. Leaves were <br />collected from the different treatments at random to minimize time of sampling biases. <br />Leaf water potential will increases as water is withheld from the plant and plant water <br />stress increases. Water status measurements required removing one fully matured leaf <br />randomly selected from trees in each treatment and measured for water holding capacity <br />using a Plant Water Status Console. The leaf was removed from the plant and <br />immediately placed in a sealed chamber with the petiole extending through a sealing hole <br />in the chamber. A fresh slightly angled cut was made and nitrogen gas was delivered to <br />the leaf under slowly increasing pressure until water exudes from the petiole surface. The <br />pressure necessary for this to occur is an indication of the leaf water potential or water <br />holding capacity of the leaf, an indication of the water stress and thus physiological stress <br />