Laserfiche WebLink
Results of Sampling: Table 3 shows the results of the sampling for 2008 with a comparison <br />with the results in 2006 and 2007. Sampling in 2008 utilized the same method as in previous years. <br />It is evident from the photographs as well as the table that the vegetation did not change <br />much in 2008 other than to become yet fuller and taller. On the average the cottonwoods gained <br />about another foot in height and the willows showed comparable gains relative to their ultimate <br />dimensions. As noted above, much of the gain was due to repair of damages incurred during the long <br />period of browsing impact from cattle. These gains were much less dramatic than in 2007 and that <br />may indicate the trees are reaching a point where competition for light and space is becoming <br />limiting. If that is the case, then the next step in the development will probably involve some natural <br />thinning as the strongest plants begin to crowd out the weaker plants. <br />Density remains very high, but density here is not actually the density of the plants, other than <br />for willows, but is shoot density. Most of the "trees" here are probably shoots from a rather few <br />individual trees. It is clear that for trees of this size to have a density of around 3,000 individuals per <br />acre is absurd. That said, it is also clear from the data that the small, new trees that developed <br />primarily in the understory in 2007, did not make it into 2008. In 2008 the smallest tree sampled was <br />still about 3.5 feet tall. Competition or shade effects are likely the cause of the demise of the new <br />arrivals. <br />Between 2007 and 2008, the population numbers stabilized in both cottonwood and willow. <br />This would indicate the population has probably reach a maximum capability for the site. As size <br />continues to increase it is likely the tree numbers will decline, but the willows should remain fairly <br />stable as they are not actually associated with the tree growth. The willows, in fact, live in a slightly <br />different local habitat than the trees. <br />Cover: Cover values for this stand of trees has now reached about 72% over the entire <br />exclosure, not counting the slope on the east side. This cover value is probably near the maximum <br />and is not likely to change much as the number of plants decline. The survivors will quickly take up <br />the space formerly occupied by the dearly departed. <br />Change in Height: The rapid gains in height between 2006 and 2007 did not continue in <br />2008. There were still significant gains, but the growth curve seems to have reached a temporary <br />plateau. Competition for space here is very intense and shade effects from adjacent trees has <br />probably had a negative effect on the growth rate of all the trees. Until some natural thinning occurs, <br />growth increases may remain on a steady but slow curve. Although thinning could be done to force a <br />selection for the tallest trees, that would be unwise. There is no way to know which plants to remove <br />and with the possibility that many of these plants may actually be parts of a few separate plants, <br />thinning could weaken an entire group of cloned stems derived from suckers. The result would be a <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 12