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EXCLOSURE4- <br />General Description for 2007: 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 neazly as protected from <br />heavy flows as Exclosure 3 and appears to have a history of far more severe and consistent grazing <br />impact in the past. Many of the cottonwoods have rather thick trunks, but the height is not <br />proportionate to the trunk diameter and numerous branches on the trees have been "pruned" by <br />grazing impact. The primary stand of cottonwood trees here follows a weaving line along a more or <br />less south to north direction more or less paralleling the stream corridor which is about 100 or so feet <br />to the west of the exclosure. Examination of the topography where the cottonwood trees are most <br />abundant shows it is a former stream bank with a relief of a few inches. On aerial imagery it is even <br />more apparent that the zone where the trees aze abundant is a former stream bank. Most of the <br />cottonwood trees are growing on the more elevated portion of the old stream bank and a habitat <br />favorability pattern similar to Exclosure 3 is evident, although not quite as appazent. Cottonwoods on <br />the stream side of the old stream bank are less abundant than on the slightly more upland portion of <br />old stream bank. An additional complication in the habitat characteristics is avery wet zone between <br />the outer (more inland) portion of the old stream bank and the steeper bank and slope that rises to the <br />level of the current mature cottonwood forest that is located about 50 to 100 feet east of the steep <br />slope. Similar lines of trees are evident in the mature forest so it appeazs that historically this pattern <br />of cottonwood trees establishing more or less lineaz groves is not new to this portion of the stream <br />corridor. <br />The photographs show there was considerable growth here in 2007, although the trees aze <br />still much smaller than those in Exclosure 3. It is likely the trees in Exclosure 3 developed from <br />branches of cottonwood trees buried in the ground while the trees in Exclosure 4 and in all the other <br />exclosures developed from seedlings. In effect, the trees in Exclosure 3 had a head start on all the <br />others because they developed from wood that already contained considerable food resources rather <br />than having to start from a tiny seed. The banded pattern along the former streambank remains <br />prominent, but trees in wetter areas or aeeas not associated with the former streambank also made <br />considerable gains, as shown in the photographs. <br />Results: The sampling results for this exclosure are shown in Table 4. Because the <br />sampling in 2006 utilized alternating quadrats, adjustments had to be made to the 2006 results to <br />account for the change in methodology so the results could be compazed. <br />Tree dimensions here are rather variable with cottonwood heights ranging from about 14 to <br />18 inches up to about 8 feet. But the height SSD does not show high variability. This is verified in <br />the photographs in that most of the cottonwoods are of more or less the same height. The trees that <br />are small aze ones that have recently appeazed or aze in marginal habitats, generally excessively wet. <br />Density is still high as expected with trees that average 4 to 5 feet tall. <br />2007 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 18 <br />