2011-07-20_REPORT - M1988044 (2)

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controlled with the final clean up of a few remaining plants in the autumn of 2010. The Tamarix invasion location will be monitored throughout the summer to be sure no more plants appear. Such monitoring will likely need to continue for a few more years so prolonged seed dormancy effects do not bring back the infestation. Canada thistle has shown a significant decline as a result of control efforts. It is still found in several areas and a few new colonies have been found. However, it appears the control efforts are beginning to beat back its explosive growth and expansion in 2009. The native grasslands continue to exhibit rapid expansion and continued recovery from the removal of grazing. Density has continued to increase in the uplands and the numerical prevalence of annual grasses such as cheatgrass (downy brome) continues to decline. The density of spurge also declines as a result of both control efforts and increased competition from natives. Spurge is still common, as it always will be on this site, but its dominance has declined remarkably in response to increased competition by native species. Unfortunately, in some areas where spurge was formerly very abundant and was reduced by chemical and biological controls now seem to have a new problem weed attacking. In these locations musk thistle and close relatives (the ones with the big magenta flowers) appear to have taken over. In previous reports this was stated to be a risk as a result of the reduction of spurge. In some places these thistles have become particularly dense and are affecting the natural vegetation. Fortunately, this problem is not common on mined areas, but there are still a few large patches even there. Most of the invasion of these species is more on the flat bottomlands east of the forest and south of the former ranch headquarters. There the thistles have become as dense as the spurge ever was. If these areas are controlled with herbicide then seeding must occur after treatment to close the habitat holes into which these opportunistic species invade. Until the grass component can be increased in these areas the land will likely enter into a weed dominant cycle where one species is dominant for a few years and that is replaced by another species. Eventually, it will go back to the original weed species and start the cycle all over again. By densely seeding the area with aggressive natives such as western wheatgrass the cycle steps can be disrupted and the resources that encourage weed invasion will be diverted to utilization by more desirable species. Two of the five new riparian exclosures were quantitatively sampled in early fall of 2010. Analysis of the data and comparison to previous data showed continued gains in growth. The protection of the trees has reaped considerable benefit with woody biomass continuing to increase The large gains in 2007 and 2008 were not generally seen as the vegetation has clearly reached a developmental plateau that is density restricted. Until density declines through environmental selection, rapid gains in height will be limited to areas where the density restricted plateau has not been reached. In fact, the density is so great in Exclosure 1 and to some extent in Exclosure 2 the sampling method will need to be changed because the older approach of laying transect lines is physically impossible to do with sufficient accuracy without damaging the vegetation. Overall, the bottomland vegetation at the end of the 2010 growing season was about as it was at the end of 2009. There is a continued slow decline of the oldest cottonwoods, but with a new generation rapidly gaining along the stream those losses are of less significance. It is sad to see the old and often beautiful giant cottonwoods slowly dying off, but that is the natural process in these riparian forests and there is nothing that can be done about it. Exclosures 3, 4, and 5 were not sampled, as approved by the Corps. However, they were photographed again from the same locations as prior years. A comparison of 2010 to 2009 photographs of these exclosures showed continued, but slowing, development of the riparian vegetation. The decline in the rate of development was completely expected as these vegetation units Status report for 2009 due July 15, 2010 Page 2 of 13