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water could recover. Root zone soil samples were also submitted to the soils testing <br />laboratory for determination of saturated paste extract conductivity. <br />Root growth: <br />Aspen is a relatively short-lived disease and injury susceptible tree that relies on periodic <br />re- sprouting from lateral roots to maintain its presence on a site (Shepperd 2005). <br />Therefore, the development and lateral extension of new roots is critical for the ultimate <br />survival and re- establishment of any aspen planted on mined lands. We quantified new <br />root development since planting by excavating randomly selected surviving plants during <br />2007, washing soil from the roots to quantify total root biomass and new root growth. <br />Trees were chosen from each of the different irrigation, soil, and transplant treatments <br />studied. Soil was carefully loosened and roots exposed by washing soil away with a high <br />pressure water jet. Once roots were exposed, the spread of any lateral roots away from <br />the planting site was measured as distance from the tree base and as total length of each <br />root. Root masses were separated by size class and total below - ground biomass dry <br />weight was measured. It is particularly crucial to see if roots have extended beyond the <br />planting hole for transplants or beyond the potting mix for potted aspen. This root <br />extension is necessary for survival of the trees and the ultimate re- establishment of <br />natural aspen clones. Roots must also reach a large enough size, and be close enough to <br />the surface, for suckering. <br />Physiological status: <br />• Monitoring of leaf water potential during 2005, a wet growing season, indicated that <br />varying irrigation treatment did not affect leaf water stress condition of the plants. <br />However, additional physiological conditions of the plant that affect growth and survival <br />were unknown. Other physiological conditions, such as stomatal conductance, <br />photosynthesis, and respiration, may show response to drought prior to indication by <br />plant water status; or at the least indicate which trees are stressed and not likely to <br />survive. Therefore, we collected limited additional physiological measurements of the <br />transplants under each irrigation treatment, including photosynthesis, respiration, and <br />transpiration. This would allow a better evaluation of the physiological stress conditions <br />occurring under specific irrigation treatments; and the physiological conditions favorable <br />for survival. <br />Competing vegetation: <br />Invasive annual weeds including tumbleweeds and thistles were common in the <br />plantations in 2005 and 2006, as well as numerous native herbaceous species. We <br />controlled competing vegetation in the irrigation and root - sprout treatments by repeatedly <br />hoeing and cutting all weeds growing around study trees. Landscape fabric placed around <br />potted trees when they were planted prevented weeds from growing next to those trees. <br />The aggressive nature of weeds suggests that vegetative competition may be important in <br />survival and growth of aspen trees. The inability of easily controlling competing <br />• <br />