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Results of Exclosure Studies <br />hi the previous two reports, the emphasis was on the results of the current year. Now that <br />there is three years of data, it is possible to do some meaningful comparisons to see what kind of <br />trends are developing. Thus, the emphasis this year is in comparing the data from 2006, 2007, and <br />2008, rather than reporting highly detailed results from the 2008 sampling. <br />METHODS- The same transects were used this year as were used in previous years. All of the <br />same data were collected in 2008 as in previous years, but in this report only the key points relevant <br />to a comparison of the three years is reported. <br />The tables compare the data for each transect in each exclosure as well as the combined <br />transect data. The latter provides a view of what is happening in each exclosure and provides a <br />means to see differences and trends. Throughout this study, the emphasis has been on cottonwood <br />recovery with willow growth being a distant second in importance. This is because willow, although <br />important in the overall riparian vegetation, is not what is important in the recovery of the riparian <br />forest. It is already known that willow is a major element in the recovery of the vegetation in the <br />stream corridor and clearly provides the major biomass in the woody plants there. But the ultimate <br />goal of the recovery effort rests with the cottonwood trees and the development of new riparian <br />forest. It is also already known that in the existing riparian forest, finding a willow in the mature <br />forest is a rare event indeed. Therefore, concentrating on cottonwood growth and recovery should be <br />the main thrust of the monitoring effort. Where willow and cottonwood coexist to a large degree, <br />such as in Exclosure 1, following both species is important because the patterns of change seen in <br />one species may well influence the patterns of change in the other species. In the other exclosures, <br />with the exception of the northern end of Exclosure 2, willow is either a minor component or <br />completely absent as is the case in Exclosure 5. Thus, with some exclosures, in some years willows <br />were measured and in other years they were ignored because it was apparent that cottonwood was <br />clearly dominating the willows in every way. In most of the exclosures, except in quite wet areas, <br />willow will essentially be eliminated over time. The two extremes are Exclosure 1 where a willow- <br />cottonwood association will continue for years to come and Exclosure 5 where willows have already <br />been eliminated by a blend of cottonwood dominance and the lack of sufficient moisture to support <br />willow except on the streamside boundary of the exclosure. <br />In the mature vegetation being sought, it is known that there is not a strong overlap between <br />willow and cottonwood. As the species sort themselves out and establish themselves in different <br />portions of the environmental gradients, cottonwood dominance and willow dominance tend to <br />diverge over time with the willow more restricted to the wetter stream corridor and the cottonwood <br />dominating the slightly more elevated streamside environments. It is well known that cottonwood <br />does not have a great deal of tolerance for flooded soils while willows often prefer those soils. This <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 <br />Page 4