, 2002, Wright et al., 2003, Wright, 2009 and Bartel et al., 2010), nutrient processing Bcl-2 inhibitor and biogeochemical reactions ( Correll et al., 2000 and Rosell et

al., 2005), and carbon storage over time scales of 101–103 years ( Wohl et al., 2012), and (iii) a stable ecosystem state that can persist over periods of 102–103 years ( Kramer et al., 2012 and Polvi and Wohl, 2012). Removal of beaver, either directly as in trapping, or indirectly as in competition with grazing animals such as elk or climate change that causes small perennial streams to become intermittent, drives the beaver meadow across a threshold. Several case studies (e.g., Green and Westbrook, 2009 and Polvi and Wohl, 2012) indicate that within one to two decades the beaver meadow becomes what has been called an elk grassland (Wolf et al., 2007) (Fig. 3). As beaver dams fall into disrepair or are removed, peak flows are more likely to be contained within a mainstem channel. Secondary channels become inactive and the riparian water table declines. Peak flows concentrated in a single channel are more erosive: the mainstem channel through the former beaver meadow incises and/or widens, and sediment yields to downstream KRX-0401 mouse portions of the river increase (Green

and Westbrook, 2009). Nutrient retention and biological processing decline, organic matter is no longer regularly added to floodplain and channel storage, and stored organic matter is more likely to be oxidized and eroded. As floodplain soils dry out, burrowing rodents can introduce through their feces the spores of ectomyccorhizal fungi, and the fungi facilitate encroachment by species of conifer such as Picea (spp.) that require

the fungi to take up soil nutrients ( Terwilliger and Pastor, 1999). Once a Etomidate channel is incised into a dry meadow with limited deciduous riparian vegetation that supplies beaver food, reestablishment of beaver is difficult, and the elk meadow becomes an alternative stable state for that segment of the river. Beaver were largely trapped out of the Colorado Front Range during the first three decades of the 19th century (Fremont, 1845 and Wohl, 2001), but beaver populations began to recover within a half century. Beaver population censuses for selected locales within the region of Rocky Mountain National Park date to 1926, shortly after establishment of the park in 1915. Censuses have continued up to the present, and these records indicate that beaver were moderately abundant in the park until circa 1976. As of 2012, almost no beaver remain in Rocky Mountain National Park. This contrasts strongly with other catchments in the Front Range, where beaver populations have remained stable or increased since 1940.