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Results of sampling: Table 1 presents the results from Exclosure 1 in the format described <br />above in the Methods section, that is, a three year summary. Some interesting patterns come from a <br />review of the three years of data. Overall, it is evident that willow is increasing rapidly and <br />cottonwood, although fairly stable, seems to be losing some ground. The cottonwoods have generally <br />declined in density since 2007, but the density is much higher than they were in 2006. However, the <br />willows have increased in density about five times. This is not unexpected as the habitat here is <br />generally on the wet side. What is unexpected is that mean plant height has not changed very much <br />for cottonwood or willow. Maximum height has generally increased, but on the whole, minimum <br />height has changed little. <br />What this means is that although the taller plants are a little taller, they are also more <br />abundant. But new plants and young plants are still a significant part of the population and that <br />results in little change in the mean height even though density is increasing rapidly. At this point, <br />there seems to be a hint that cottonwood, except perhaps in the localized dry areas, is being crowded <br />out by willows or at least is being negatively affected by the abundant willows. It is still likely that <br />some cottonwoods will eventually dominate the site physically, but it is also likely that they will not <br />become the huge trees cottonwoods can sometimes become. There will continue to be intense <br />competition from willows far into the future. <br />Although not included in the data, but evident in the photographs, the cottonwoods that are <br />higher on the slope where the habitat is a bit drier and there are fewer willows to contend with, are <br />doing far better than the cottonwoods down in the low elevation areas of the exclosure. Some of <br />these are suckers from nearby mature trees that had their roots cut when the sand was extracted. They <br />have the support of a larger, more competitive root system from the parent plants. It now appears that <br />it may be these fringe cottonwoods that are likely to be the most successful, with smaller <br />cottonwoods down in the more moist land. <br />Cover: Cover values are based on the total transect area rather than that area which was <br />occupied by the total of the projected area of the woody plants as was done last year. This was <br />changed to reflect the real cover value over the entire exclosure. In the future cover will have to be <br />measured by a line intercept method as overlap of plants has now become significant and calculation <br />based on vertical projection of each plant's dimensions is creating cover values that are somewhat <br />excessive. Nevertheless, for 2008, the total cover in the exclosure was calculated at 15.8% with 2% <br />in cottonwood and 13.8% in willow. <br />Change in height: Now that there are three years of data available, examining the change <br />in height over that time period can be examined to look for trends. As described above, mean height <br />seems to be fairly stable with both cottonwood and willow. Maximum height has increased some and <br />minimum height is stable. These seems to indicate that the vegetation is becoming more uniform in <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 6