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EXCLOSURE5- <br />Description: Of the five new exclosures, this one contains the oldest growth. The <br />exclosure is on the north side of an island inhabited by several large and very healthy cottonwood <br />trees. The site is reasonably protected by the island from heavy flows. Topographically, the exclosure <br />is somewhat different from the other four exclosures. Much of this site is moderately elevated above <br />the stream channel to the west. This slight bench is more elevated than was the case in the <br />cottonwood zone in Exclosure 4. Visually, as seen in the photographs, this exclosure has a much <br />broader distribution of cottonwoods than any exclosure other than Exclosure 1. Furthermore, the <br />cottonwoods appear to have extremely consistent heights with few plants projected above the general <br />blanket of cottonwoods. Willow is rare in this exclosure, although willow growth a short distance <br />toward the stream from the western fence line is robust and very dense. <br />About 50 to 100 feet north west of this exclosure is the old South Exclosure established in <br />1996 when Schmidt Construction assumed the permit. Exclosure 5 shows some characteristics <br />similar to the southern end of that exclosure. However, the southern end of that exclosure is very <br />near the stream channel and directly receives heavy flows. Exclosure 5, on the other hand, is <br />protected and more elevated. Topographically, it is similar to the habitat where the rows of larger <br />trees were planted in the South Exclosure. But it is quite evident that tree density here far exceeds the <br />density present in the planted area in the South Exclosure. <br />Results: In this exclosure no willows were encountered in any of the sampling in 2006, <br />2007, or 2008. Therefore, all the data pertains only to cottonwood. There have been a few losses over <br />the three years, but for the most part the population of cottonwood is very stable with an even <br />distribution that limits competition effects to some extent. The density seems to have stabilized at <br />somewhere around 1,000 trees per acre. That is still very high for a cottonwood forest, but not at all <br />unusual for a developing cottonwood forest at this stage. In some habitats, that density can be <br />maintained until the trees are as much as six to ten inches in diameter and 20 to 30 feet tall. Once <br />that size is achieved, natural thinning will eliminate the smaller and the weaker trees. The losses that <br />have occurred may be due to a small amount of this type of thinning as an examination of the trees <br />themselves shows a fairly large range in the condition of the trees. That is, not all the trees are <br />equally healthy and it appears that some of the weaker trees are showing signs of reduced leaf area <br />and increases in dead twigs. Other trees though have dense leaf growth and very little dieback of <br />twigs and branches. That usually is a sign of competitive selection. <br />Cover: Cover is about 30% to 50% over a large area in this exclosure. In fact, in <br />proportion to the exclosure dimensions, this exclosure has the highest cover over the largest area, <br />even though the cover percentage is moderate. These trees have a very uniform distribution and that <br />pattern often produces a network of blank areas between the individual trees when of this size. This <br />2008 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 17