2009-11-19_PERMIT FILE - C1982057

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of the 10 non - weeded trees survived after 3 years. Most of the vegetative competition consisted of annual herbs, perennial grasses, and weed species. Weed present were primarily various thistle species. Shading was not a factor, since the trees were larger and growing above the competing vegetation canopy. The soil moisture data suggest competition between surface vegetation and trees for a limited amount of available water. CONCLUSIONS Irrigation: Best growth and survival was with low or no irrigation, but salinity of irrigation water in the first two years of the experiment reduced growth of trees receiving high and medium amounts of irrigation. Reclaimed soils were not saline, but salinity levels were high enough in irrigation water from local ponds to reduce growth of aspen. Care must be taken to provide low saline water when irrigating planted aspen trees on reclaimed lands. Low level irrigation and no irrigation growth and survival were similar, suggesting that enough rainfall and soil moisture occurred for the years this experiment so that irrigation was not necessary. It is expected but not tested in this experiment, that supplemental irrigation with clean water may have increased growth and survival above non - irrigated trees. It is expected that all surviving trees now have developed enough root system after three years that further irrigation is not needed. Plant source: Transplanted trees from local sources grew best once established. Most natural suckers did not survive without weeding. Potted plant had a high rate of survival, but growth was lower then for transplants and natural sprouts. Roots of potted aspen general stayed in the augured potting hole. This also occurred for a few of the transplanted trees in the more compact stored dozer cleared soil on the irrigation treatment plots, the same soil type where this occurred for the potted plants. Soil type: Best growth and survival occurred on roto - cleared (fresh) soil compared to dozer cleared (stored) soil. More natural sprouts from residual root segments were evident in roto- cleared soil. It is expected that higher number of natural sprouts was due to the shorter length of soil storage and the soil characteristics rather than the clearing method. The dozer cleared soil appeared to be more compacted and was less well drained than the roto - cleared soil, and it is expected that these physical characteristics were more important to tree growth than the method of clearing. Also, storage effects on the soil were likely more important than method of clearing. Weed control: r� U