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diameter growth, and survival were considerably less with these plants than with natural <br />• sprouts or potted plants during the first year <br />of the study, but the transplanted trees grew well the second and third year of the study <br />(depending on treatment). Potted plants survival was 100% and growth on these trees <br />appeared better than transplanted cuttings the first year. Growth of the transplants was <br />better than potted plants in subsequent years. <br />III. Soil type —Roto- cleared soil provided sufficient natural sprouting to provide an <br />adequate stand of aspen trees, and these trees appeared to grow better and survival <br />appeared higher than adjacent transplanted trees growing in the same soil in the first two <br />years of the study. Dozer - cleared soil which had been temporarily stored, had <br />considerably lower numbers of natural sprouts than roto - cleared soil, and stocking was <br />sparse (data not shown). Natural sprouts appeared to have greater total leaf area and <br />greater stem diameter growth on roto - cleared soil than dozer - cleared soil, but terminal <br />leader growth appeared similar on both soil types (data presented in earlier reports). <br />Natural root sprouts had no lateral branches. Leaves also appeared to be larger on these <br />trees (data not shown). Nevertheless, these trees apparently experienced somewhat <br />greater pre -dawn water stress in July and September than trees in the irrigated treatments, <br />including the irrigated controls with no water added. The data suggest that pre -dawn <br />water stress levels as high as 14 bars, and afternoon water stress levels as high as 20 -25 <br />bars, were not of sufficiently high levels to cause enough stress to reduce survival or <br />growth of these trees. Soil moisture stress appeared to be less with transplanted sprouts in <br />the irrigation experiment, including the un- irrigated controls, than with natural root <br />sprouts or potted plants. It is interesting to note that leaves appeared smaller and terminal <br />growth appeared less on these apparent less - stressed transplanted trees, suggesting that <br />growth of root sprouts, potted plants, and natural sprouts was not limited by the apparent <br />higher moisture stress levels they experienced. Maximum leaf water potentials at mid- <br />afternoon found stress levels of about 25 bars or less, levels that appeared unrelated to <br />treatment, or to growth and survival. <br />The growth data suggest that roto - cleared soil could have provided additional nutrients or <br />other benefits, perhaps mycorhizae, for tree growth. Weed growth appeared greater on <br />roto - cleared soil than dozer - cleared soil (data not shown). <br />IV. Fencing - Fencing is necessary to obtain an adequate stand of aspen, regardless of the <br />sources of the trees. The unfenced Yoast site had severe damage from ungulates, <br />including breakage of stems, browsing, and rubbing damage. Most trees at this site had <br />some form of injury. Yet, growth and survival of these trees was good, suggesting that <br />the undisturbed soil presence of an extensive parent root system is ideal for growth of <br />aspen. Nevertheless, fencing of these trees is recommended to produce an adequate stand <br />of mature aspen. <br />CONCLUSIONS (2005- 2006): <br />I. Growth and survival did not appear to be related to irrigation treatment, likely a <br />consequence of the high rainfall during the 2005 and 2006 growing seasons. <br />