Laserfiche WebLink
weeded plots on roto - cleared soils, suggesting that these conditions are best for aspen <br />. growth and survival. Plant top and root growth on these plants would seem to verify that <br />finding. Plant water status measurements indicated that when these tests were conducted <br />during the 2007 growing season (June 28 and August 1) the plants were not water <br />stressed, with pre -dawn leaf water potential pressures not exceeding 10 bars and most <br />often less than 5 bars (Figures 10 -11). <br />Root growth: <br />Root growth of transplants was best in weeded plots on roto - cleared soil and lateral roots <br />extended far from the base of the original tree (Figures 12). They were of sufficient size <br />(4 mm or more) where suckering could begin, but many were too deep (15 cm or deeper), <br />a result of the deep planting of the transplanted trees. Trees in other treatments are <br />surviving and roots are extending out, but it will take additional years for most to obtain <br />sufficient size at depths necessary for suckering. In any case, suckers are more likely to <br />appear after injury or death of parent trees when apical dominance is inhibited. Roots <br />growing from the potted trees were mostly confined to the potting hole. This was also <br />true for some of the transplants on dozer - cleared soil, perhaps a result of the high density <br />and compaction of this dozer cleared and stored soil. <br />Depth of the roots systems for the transplanted aspen ranged from about 15 to 40 cm, <br />with transplants in the roto - cleared soil planted somewhat deeper than those on the dozer <br />cleared soil. These depths are too deep to allow effective suckering. Even though roto- <br />• cleared trees were planted somewhat deeper than dozer - cleared trees, growth was better <br />on the roto - cleared trees. It is expected that trees planted deep will take longer to produce <br />roots at a depth conducive to suckering, but those deep planted trees that survived are <br />now producing shallower roots. Lateral root systems were already developing on most of <br />the transplanted trees, and roots were observed near the surface several meters from the <br />base of some trees suggesting that these trees were becoming well established. Apical <br />dominance of the rapidly growing transplanted trees likely prevented suckering of these <br />lateral roots. It is expected that enough root system has developed that further irrigation <br />of these trees is not necessary. <br />Competing vegetation: <br />Weeds were an important competitor for soil moisture in the planted aspen plots. Soil <br />moisture was higher in the weeded plots, suggesting more soil moisture available for tree <br />growth in these plots (Figure 4). Weeding was particularly important for survival of <br />natural sprouts occurring from residual aspen roots in the replaced topsoil. Trees growing <br />on weeded plots grew considerably better and had higher rates of survival. Of 34 natural <br />sprouted trees initially marked for study on the roto - tilled fresh soil in year 1, half were <br />weeded and half un- weeded in years 2 and 3. All of the weeded trees survived into year 3 <br />while only 4 of the un- weeded trees survived the first three years of the experiment. Of <br />0 the 21 natural sprouts on the dozer - cleared stored soil, 8 of the 11 weeded trees but only 2 <br />