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EXCLOSURE4- <br />General Description for 2008: Exclosure 4 is a short distance downstream from Exclosure <br />3 and occupies a broad moist to wet habitat between two islands. It is not nearly as protected from <br />heavy flows as Exclosure 3 and appears to have a history of far more severe and consistent browsing <br />impact in the past. At the initial stages of the study, many of the cottonwoods had rather thick trunks, <br />but the height is not proportionate to the trunk diameter and numerous branches on the trees had <br />been "pruned" by browsing impact. The primary stand of cottonwood trees here follows a weaving <br />line along a more or less south to north direction roughly paralleling the stream corridor which is <br />about 100 or so feet to the west of the exclosure. Examination of the topography where the <br />cottonwood trees are most abundant shows it is a former stream bank with a relief of a few inches. <br />On aerial imagery it is even more apparent that the zone where the trees are abundant is a former <br />stream bank. Most of the cottonwood trees are growing on the more elevated portion of the old <br />stream bank and a habitat favorability pattern similar to Exclosure 3 is evident, although not quite as <br />apparent. Cottonwoods on the stream side of the old stream bank are less abundant than on the <br />slightly more upland portion of old stream bank. An additional complication in the habitat <br />characteristics is a very wet zone between the outer (more inland) portion of the old stream bank and <br />the steeper bank and slope that rises to the level of the current mature cottonwood forest that is <br />located about 50 to 100 feet east of the steep slope. Similar lines of trees are evident in the mature <br />forest so it appears that historically this pattern of cottonwood trees establishing more or less linear <br />groves is not new to this portion of the stream corridor. <br />The photographs show there was considerable additional growth here in 2008, although the <br />trees are still much smaller than those in Exclosure 3. It is likely the trees in Exclosure 3 developed <br />from branches of cottonwood trees buried in the ground while the trees in Exclosure 4 and in all the <br />other exclosures developed from seedlings. In effect, the trees in Exclosure 3 had a head start on all <br />the others because they developed from wood that already contained considerable food resources <br />rather than having to start from a tiny seed. The banded pattern along the former streambank remains <br />prominent, but trees in wetter areas or areas not associated with the former streambank also made <br />considerable gains, as shown in the photographs. <br />Results of Sampling: The sampling results for this exclosure are shown in Table 4. As <br />done elsewhere the table focuses on a three year comparison. <br />The cottonwood population seems to have stabilized and very few new plants were found. <br />The dense grass-rush undergrowth probably limits invasion of new plants. <br />No willows were found in 2007, but this year several new, rapidly growing ones appeared. <br />This is probably a reflection of the wetness of the 2007 season and good local water supply in 2008. <br />The willows probably were there in the 2007 sampling but just could not be seen in the thick <br />herbaceous growth. The ones that were sampled in 2006 died. <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 14