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Peabody Twentymile Coal Company <br />2005 Fish Creek AVF Riparian Vegetation Monitoring <br />3. Diminution or cessation of surface water flows leading to a reduction in hydric <br />vegetation communities. <br />Observations in 2003 of drowned sage communities in swamped depressions and <br />bank-full sections of the creek suggested that hydric vegetation was increasing with <br />increased surface subsidence. Some of the 2004 observations supported the conclusions <br />of the 2003 study; sage brush communities were being drowned and replaced by hydric <br />vegetation in selected areas within the Fish Creek flood plain. Further, 2004 observations <br />suggested that slight changes in the groundwater elevation may have caused a progressive <br />change in vegetation composition. This change in vegetation composition between 2003 <br />and 2004 was most obvious throughout Transect 12, where Silver sagebrush and native <br />mesic graminoids were in the process of colonizing a former mesic improved pasture. <br />Alternatively, this shift in vegetation community composition may have been caused by <br />climate and/or grazing pressure. <br />In summary, two trends were observed at Fish Creek in 2003 and 2004: first, <br />sage communities were being replaced by hydric species in swamped depressions <br />associated with lower elevations, and second, historic improved pastureland communities <br />were being invaded by Silver sagebrush and native mesic graminoids. Additional <br />monitoring efforts were required to substantiate any projection regarding the effects of <br />subsidence on the vegetation community composition and riparian chazacteristics of Fish <br />Creek. <br />2003 Transects <br />In 2005, two trends were observed among the 2003 transects: there was a <br />decrease in the silver sage pastureland community and an increase in the improved <br />pasture mesic community. Several factors are likely influencing these shifts in vegetation <br />cover. First, annual variability in ground cover observations may be due to slight <br />differences in the walked transects thereby generating measurement error. Secondly, <br />heavy grazing pressure and trampling by cattle contributed to silver sage bush mortality <br />on three of the 12 transects. Thirdly, as the ground subsides, the ground water table is <br />lowered. Drought conditions may also contribute to the lowering of the ground water <br />table. Whatever the cause, topographic shifts in the ground water table and variability in <br />Habitat Management, Inc. Page 6 3/14/2006 <br />