2013-07-11_REPORT - M1988044 (2)

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wet April and early May which charged deeper soils with moisture fairly well. That has allowed the spurge to show more vigor, but it does not appear that the amount of spurge has actually increased significantly. In fact, because the grass is also so much stronger this year, spurge may have actually declined slightly. Tamarix control, begun six years ago, appeared to have reached its goal of eradication. However, on a June 25 trip to that area to treat some Canada thistle that was introduced in the 2012 flood, a single three foot tall Tamarix was found and was treated. No others were found on the June 19 or June 25 inspections. The intense stream flows in early June 2012 undoubtedly had an impact on weed intensity and distribution. One of the areas heavily impacted was the location of the Tamarix population. It is beneficial that the population of Tamarix had been reduced prior to this flood event or this species would have likely been spread far down the riparian corridor and therefore even more difficult to control. However, if there were any remaining Tamarix that were uprooted and carried downstream or dormant seed was in the soil, this species may have actually expanded its distribution. This is not likely, but because it is possible, this species should be watched for between the South Lowland and at least the confluence of Coal Creek and the East Valley drainage. The presence of Cheatgrass or Downy Brome (Bromus tectorum) is well known on this site. This year, because of the wet spring, this annual grass is very abundant in all areas of the site. Any conditions, such as a wet spring, that favor the growth of annuals will also favor this tenacious and difficult to control species. That is certainly the case this year. And with such a robust growth the seed bank will be well replenished making up for any declines due to seed mortality in the previous dry years when this species was far less abundant. In the damaged streambed on the south end another weed was found that had never been found in this area before. One small patch of Canada thistle was found during the inspection for Tamarix. This was treated on June 25 and a few other small patches were found nearby. No others were found in the area, but, like Tamarix, now that this species has arrived it will need to be watched for closely and controlled quickly. This species undoubtedly arrived with the flood waters and must have come from a considerable distance upstream. Prior examinations of the stream channel upstream from this area never noted the presence of this species. Thus, this species may have come from Elbert County or even Douglas County and was transported miles downstream into this area. It is important to control this species quickly as it can spread easily and once well established can be difficult to eradicate. B. New weed species: No new species have been noted, other than the Canada thistle arrival noted above. This species is present in small numbers elsewhere, but finding it in the stream channel itself is a first. That said, the thistle was growing in a rather sandy, dry spot that probably provides some access to groundwater without flooding the roots and rhizomes. Bull and musk thistle control, and similar species as well, has been effective in reducing that Status report for 2013 due July 15, 2013 Page 12 of 16