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<br />e <br /> <br />e <br /> <br />- <br /> <br />Veaetation <br />The riparian vegetation in the study area is dominated by <br />woody plant species. The most common trees are, crack willow <br />(Salix fraqilis), plains cottonwood (Pooulus deltoides), ash <br />(Fraxinus oensvlvanica var. lanceolata), and chinese elm (Ulmus <br />oumila). Plant species nomenclature follows Weber (1990). Only <br />plains cottonwood is native, the other three tree species were <br />introduced as ornamentals and have escaped cultivation. The <br />understory is populated by russian olive (Eleaqnus anqustifolia), <br />chokecherry (Padus virqiniana ssp. melanocaroa), and wild plum <br />(prunus americana). Russian olive is very common and is native <br />to Asia. The ground is covered by dense lawns of the European <br />smooth brome grass (Bromoosis inermis). This species has been <br />introduced for hay production and has escaped cultivation <br />throughout the Front Range and dominates many riparian zones. <br />While the floristic composition of the vegetation does not <br />indicate a pristine ecosystem, there are abundant ecological <br />functions and values created by the woody vegetation that anchors <br />the streambanks, provides organic matter for the aquatic food <br />chain, and habitat for a variety of wildlife, as well as scenic <br />beauty. No rare native plant species were seen. <br />Cottonwoods are reproducing sexually in the study area and <br />several different ages of trees occur. Cottonwoods disperse <br />their short-lived seeds in the spring. Seeds must contact bare <br />wet mineral soil to germinate. The dense mats of smooth brome <br />grass throughout the study area prohibit seeds from contacting <br />the soil, thus flooding is required to scarify this soil, or <br />deposit fresh sediment to create suitable habitat for seedling <br />establishment. <br />The established vegetation, and more importantly young <br />seedlings and saplings of woody plants require abundant <br />groundwater which is provided to by Little Dry Creek through the <br />alluvium. It is important that high stream flow events recharge <br />the alluvial system. However, the data analyses show that <br />groundwater levels rise and fall rapidly indicating that there is <br /> <br />15 <br />