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Because tamarisk releases seed later in the season and over a longer period of time than <br />cottonwood, delayed peak flows could provide favorable conditions for tamarisk establishment. <br />hi addition to being used to enhance recruitment of desirable species, the recruitment box <br />concept can also be used to inhibit undesirable species from becoming established. <br />Variability in flow from year to year plays an important role in maintenance of species rich plant <br />communities relative to an area with ample moisture but a stabilized hydrograph (Figure 4). On <br />any given year, the flow regime may facilitate recruitment and establislunent of one species, <br />while excluding another. Natural variations in the hydrograph include flood, drought, and <br />variously timed events. Developing an understanding of which events support desirable or <br />targeted species and those that hinder <br />undesirable species helps to inform management decisions to achieve desired goals. <br />Because flow regime is a principle driver of riparian plant community stn~cture, considerations <br />of the magnitude of the peak, the level and duration of low flows, and the tinting and rate of <br />change in flow can assist in understanding the trade offs of various managed flows and help to <br />refine how we use flow to meet specific management objectives. <br />~~~]~} <br />3{~~~] <br />25(]0 <br />~ ~'~ <br />~~~~ <br />~~~~ <br />.~] ~!~ <br />~ecruit~nent suit~bl~ <br />band •,., stage [~~~lin~ <br />~; 2.5 crnld <br />4~~ <br />4' <br />I <br />f I <br />I ~'' I <br />I <br />i ~~ -.~ I <br />I sped dls~~r~a I <br />I I <br />I I <br /> <br />Figure 3. The recrnitment boY model ilh~strates the period of tune over which cottomvood seedlings are <br />most likely- to smti~ive and provides guidelines for the tinting and rate of drawdown (the convention is stage <br />decline, however discharge is show n here) for optimal cottomvood recrnitment. Such bniidelines could be <br />used only when excess water is available. Hydrograph from Dolores River at Dolores April tluoi~gh <br />August 1978 (Modified from Mahoney and Rood 1998). <br />48 <br />