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Persistent vegetation Wetland vegetatian <br />formed by emergent hydrophytic plants with <br />stems that normally remain standing until <br />the beginning of the following growing <br />season (e.g., cattails and bulrushes}. <br />Phosphorus A nutrient essentia{ to plant <br />growth. Phosphorus is ti�e nutrient most <br />commonly limiting plant growth in lakes. <br />PhospF�orus Export 7he amount of <br />phosphorus carried off of a given area of <br />land by stormwater. <br />Phytoplankton Open water algae; it forms <br />the base of the lake's food chain and <br />produces oxygen. <br />Prairie An upland plant community <br />composed of grasses and forbs. Prairies <br />generaEly lacfc trees; shrubs, if present, are <br />not prominent. <br />Presettlement A term used for convenience <br />to denote the time perioci before Euro- <br />American settlers moved into the Region. <br />The Region was actually settled by <br />Arnerican Indians for thousands o# years <br />before European-Americans arrived. <br />Range (geographic) The lirnits of the <br />geagraphic distribution of a species or <br />graup. <br />Rate Control: A term that refers to <br />controlling the rate at which water is <br />discharged from a watershed. Rate control <br />is oiten accomp�ished by creating ponds- <br />either by excavation or berming- to <br />temporarily store runoff, then discharging <br />the stored water at a slower rate to <br />downstream areas. Further reductions in the <br />rate at which water is released irom a pond <br />can be accomplished by reducing the size of <br />fhe outlet, such as through installation of a <br />wall in the outlet structure with a hole <br />(orifice) through it. <br />Rein#roduced species Species that had <br />been eliminated frorn areas where they <br />occurred historically and were later released <br />back into the area by humans. <br />Remnant A por�ian or fragment of a natural <br />community that has survived while the rest <br />of the community has been destroyed by <br />logging, urba� development, clearing of land <br />for cultivation, and other human activities. <br />Residence Time The amount of time it <br />takes for water flowing i�to a lake #o equal <br />the lake volume. The shorter the residence <br />time, the more incoming water the lake is <br />receiving relative to its volume. <br />Rhizome A horizantal underground plant <br />stem. <br />Savanna An upland pEant community <br />formed of prairie herbs with scatterecf trees <br />or groves of trees. The canopy cover of <br />trees in a savanna is generally between 10 <br />and 70%. <br />Secchi Disc A device measuri�g the depth <br />of lighi penetration in water, typicalEy a 9- <br />inch, white circular plate attached to a rope. <br />Used to measure water transparency. <br />Sedge Any of a number of grasslike plants <br />oi the family Cyperaceae. <br />Sedimentation �he process by which <br />matter (usuaiiy soil particles) settles on a <br />substrate following transport by water, wind, <br />or ice. <br />Seepage The slow, ciif�use oozing of <br />groundwater onto the earth's surface. <br />Shallow Lake Lakes wi#h mean depth of <br />less than 10 feet <br />Shrub layer A vegetation fayer, usually less <br />that 6 ieet high, of shrubs and tree <br />seedlings. <br />Shrub swamp A wetland comrnunity <br />dominated by a nearly continuous to <br />continuous canopy (70 to 140% cover) of <br />shrubs, such as willows and alders. <br />Subcanopy A vegetation layer, composed <br />of patches of individuafs of appraximately <br />equal height, that is lower than the canopy <br />layer; a�ten refers to a layer of saplings, ta[I <br />shrubs, or small trees between 6 and 35 feet <br />high. <br />Submergeni Describes an aquatic plant <br />that grows entirely under water. <br />Substrate The surface layer of organic or <br />mineraf material-such as till, outwash, or <br />bedrock-from whicY� the soil is formed. <br />Succession The change i� vegetation over <br />time. <br />Swale A broad, shallow depression in a till <br />plain or broad river piain. <br />Swamp A wetland community with a fairiy <br />continuaus to continuous canopy of shrubs <br />or trees, such as speckled alder, black ash, <br />or tamarack. 5wamps generally occur in <br />shallow basins or wet depressions. <br />�Talus Rocks and other coarse mineral <br />debris that accumulate at the base of a clif# <br />or steep slope. <br />Terrace A sandy and gravelly alluv9al plain <br />borctering a river. Terraces represent #ormer <br />1 Many of the deiinitians used in this section are <br />borrowed from Minnesota's St. Croix River Valley and <br />Anoka Sand lai�, Worcha et al, Minnesota DNfi, 1995. <br />Glossary 5 <br />