2010-12-29_REPORT - M1988044 - Laserfiche WebLink

Home Browse Search

ultimately being very successful. In between are the three older exclosures which have their own range of variations as discussed elsewhere. Comparing the exclosures to the recovery of the entire stream corridor after removal of grazing shows very similar patterns of development. In very wet areas the vegetation is strictly wetland with rushes and bull rushes dominating and producing a dense carpet of growth. Going from there to slightly drier areas produces a blend of the wetland herbaceous species and willow with cottonwood absent. Moving further toward the dry end cottonwood appears among the willows (Exclosures I and 4) but the willows maintain a strong dominance. Dry the site more and a very dense and rapid growth cottonwood vegetation appears with sparse willow growth (Exclosure 3). The next step results in a thick stand of cottonwood with essentially no willow such as that found in Exclosure 5. Exclosure 2 diverges somewhat from this more or less linear continuum and shows what happens when there is a very wide range of micro-environmental conditions that range from wet to dry. Here the wet is like the herbaceous wetland while the small, very sandy dry spots have essentially no woody vegetation. The diverse mosaic in Exclosure 2 produces widely spaced cottonwoods and scattered willows with an understory that looks to be fairly upland. If pressed to make a prediction as to which condition will ultimately produce the largest cottonwood trees I would have to say that Exclosure 2 is the most likely because of the low competition and a resource utilization in the herbaceous growth that is probably fairly independent of the resources accessed by the woody vegetation. In the other exclosures competition factors are operating at intense levels and that often results in the development of multiple developmental plateaus that can exhibit strong shifts in species dominance. That is not to say that large cottonwoods will not develop in the other exclosures. They most certainly will, but it is a more precarious path for each tree as it strives to reach that point of strong physical dominance. One important conclusion can be drawn at this point. It is now clear that nearly all of the Coal Creek corridor is in the process of returning to a well vegetated stream channel. Although mined areas recovered very nicely to herbaceous conditions without protection from grazing, where protected (e.g. the two earlier exclosures) the woody vegetation also recovered. Now that grazing has been terminated both mined and unmined riparian areas are rapidly returning to a pre-grazing condition. Although the future is still subject to change if a major flood were to occur, all of the materials are present to allow for a rapid post-flood recovery and the vegetation that has developed would also limit flood damages allowing for an even more rapid recovery. These exclosures have clearly shown the developmental pathways possible in this recovery and provides a good resource to guide future management. At some point, highly managed grazing might be allowable again. But grazing in the riparian corridor must not occur for many more years and even then only on a strongly limited scale. The damages inflicted by uncontrolled grazing was clearly the greatest impact on the riparian corridor and far greater than the damages incurred by well planned shallow depth sand mining. If the riparian corridor is to be preserved then grazing should be prohibited or managed to a 2010 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 18