2010-12-29_REPORT - M1988044 - Laserfiche WebLink

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gaining height rather than width. That said, the larger cottonwoods are clearly beginning to produce more spread in their branches rather than just tall, narrow spires that contribute little to the cover values. Still, though, willow constitutes nearly all the cover in the woody component at this exclosure. Overall Conclusions: It appears at this point the recovery of this vegetation is like a double- layered cake. The bottom or foundation layer is the removal of browsing impact from the area. That alone accounts for a major amount of the gain during the study. This is evident in that even though browsing continued outside the exclosure for part of the first year, giving the protected vegetation a head start on recovery, by the end of the first season the unprotected vegetation was gaining rapidly. By the end of the second season, differences between protected and unprotected vegetation became subtle and during the third, very favorable growth year equalization was essentially achieved to a point where the only function of the fences anymore is to show where the exclosure ends the rest of the world begins. But there is an important, although subtle, second layer here and that has to do with the pattern and amount of precipitation. There have been four full years of influence from precipitation. The first year had a somewhat dry summer preceded by a very wet winter; the second year had an adequate winter followed by a intensely dry summer until August, the third year had a somewhat dry winter and quite wet summer, while 2010 had a wet winter, moist spring, and dry summer until late in the season. The gains in the first year are probably attributed mostly to the removal of browsing impact with the addition of improved groundwater from the previous wet winter. But the summer was not particularly wet that year. The second year saw terrible dryness and, once again, a plummeting water table. Yet gains were still made, although as the percent change graph shows, not much was gained. If there were still improvements being made as a result of browsing removal they were pretty much overwhelmed by the dryness. The third year saw an entire season of not only good moisture but reliable moisture. This resulted in a major gain in height and a large jump in the percent change from the previous year. Although there may still have been some influences from grazing removal such as little topgrowth and large root system under the influence of browsing to a large root system producing explosive topgrowth without a browsing influence, those effects were probably minimal by 2009. The fourth year, 2010, is interesting though in that gains in height was considerable in spite of the fairly dry and hot summer. This is indicative of a woody vegetation that has achieved full establishment and is only minimally affected by variations in precipitation. Root systems have expanded enough that there is some "insurance" against dry conditions so the plants can still put on excellent growth even when moisture is limited. That is usually an indicator that the vegetation has 2010 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 10