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EXCLOSURE3- <br />General Description for 2008: This is the smallest of the five exclosures, but the one that <br />is most distinctive ecologically. Some of the trees here have already achieved the height requirement. <br />Density in the tree dominated portions of the exclosure is high. <br />What was most distinctive about this exclosure was the extreme amount of browsing impact. <br />Although one could use this site as an example that large trees can develop in spite of intense <br />browsing, that argument is not actually valid. This site is in an unusual habitat in that it is out of the <br />main channel, although connected to it, and located in what is effectively a basin between an <br />elevated island to the north and the more elevated bank to the south and east. Thus, unlike most other <br />locations of strong invasion of cottonwood, this site is protected from the larger, scouring floods that <br />effectively reset the successional clock in more exposed locations. So, in a sense, this exclosure <br />represents a habitat were browsing impact has been intense but the trees, although still young, were <br />initially of a larger size because of a highly favorable habitat that is rarely found on this as well as <br />most streams. <br />On the other hand, at least some of the high density and cover is an artifact of the browsing <br />impact. Some of the larger trees had been so severely impacted by browsing that the main shoot was <br />killed by girdling. To survive these trees have produced abundant adventitious shoots ("suckers"). <br />Therefore, although the stem density is very high, it is likely that there are actually only a few <br />individual trees in this small area. Many of the smaller "trees" are more likely "suckers." From <br />certain positions some of the small stems appeared to form lines of fairly evenly spaced shoots back <br />in 2006, but now that pattern is no longer evident. This growth pattern is indicative of root sprouting, <br />although without excavation or the introduction of radioactive tracers it cannot be confirmed. In <br />combination with the evidence of extreme amounts of browsing, it is very likely that many of what <br />are considered individual plants in the sampling are actually part of a single plant. This is not <br />actually a problem as this kind of growth pattern is common naturally in cottonwood that are <br />subjected to frequent intense floods. Along major rivers and streams, trees that have multiple stems <br />originating at the base are produced by damage to the main shoot and loss of apical dominance. As a <br />result several stems become dominant and the trees grow into what amounts to a very large shrub- <br />like growth form. <br />As the photographs show, growth in this exclosure was dense in 2008. Not only are <br />maximum heights obviously greater than 2006, but the leaf density is now so high one cannot even <br />see through the grove of trees anymore. In 2006 the pattern of trimmed lower branches that results <br />from browsing was still very evident even in October. But in 2007 that pattern vanished and became <br />essentially a wall of cottonwood leaves. With increased food producing resources that pattern <br />intensified in 2008. <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 11