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<br /> RPM,Inc.,25049 E.Alder Dr.,Aurora,CO 80016 Phone:(303)854-7499 Email:h1humphries2@comcast.net
<br /> Climatic Features
<br /> Average annual precipitation across the MLRA extent is 14 to 17 inches,and ranges from 13 inches to over 18 inches,depending on location
<br /> The average is 15 inches.Precipitation increases from north to south.Mean Annual Air Temperature(MAAT)is 50°F in the northern part and
<br /> increases to 52°F in the southern part.Portions of Morgan and Weld counties(in the northern part)are cooler and drier,the MAAT is 48°F,
<br /> and average precipitation is 13 to14 inches per year.Two-thirds of the annual precipitation occurs during the growing season from mid-April to
<br /> late September.Snowfall averages 30 inches per year,area-wide,but vanes by location from 20 to 40 inches per year.Winds are estimated
<br /> to average 9 miles per hour annually.Daytime winds are generally stronger than at night,and occasional strong storms may bring periods of
<br /> Nigh winds with gusts to more than 90 mph High-intensity afternoon thunderstorms may arise The average length of the freeze-free period
<br /> (28°F)is 155 days from April 30th to October to 3rd.The average frost-free period(32'F)is 136 days from May 11th to September 24th.July
<br /> is the hottest month,and December and January are the coldest months.Summer temperatures average 90'F and occasionally exceed
<br /> 100°F.Summer4humidity is low and evaporation is high.Winters are characterized with frequent northerly winds,producing severe cold with
<br /> temperatures occasionally dropping to-30°F or lower.Blizzard conditions may form quickly.For detailed information,visit the Western
<br /> Regional Climate Center websiW Western Regional Climate Center>Histoncal Data>Westem U S.Climate summaries,NOAA Coop
<br /> Stations>Colorado http:lh~.wrcc.dd.edti/summary/Chmsmco.htmi Eastern Colorado was strongly affected by extended drought conditions
<br /> in the"Dust Bowl'period of the 1930's,with recurrent drought cycles in the 1950s and 1970s Extreme to exceptional drought conditions have
<br /> re-visited the area from 2002 to 2012,with beef interludes of near normal to normal precipitation years.Long-term effects of these latest
<br /> drought events have yet to be determined.Growth of native cool-season plants begin about April t and continue to mid-June.Native warm-
<br /> season plants begin growth about May 1 and continue to about August 15.Regrowth of cool-season plants occur in September in most years,
<br /> depending on moisture.Note:The climate described here is based on historic climate station data in the past 30 to 50 years,and is averaged
<br /> to provide an overview of annual precipitation temperatures,and growing season.Future climate is beyond the scope of this document.
<br /> However,research to determine the effects of elevated CO2 and/or healing on mixed-grass prairie ecosystems,and how it may relate to
<br /> future plant communities 0.e,potential shifts in dominant and sub-dominant groups,changes in growing season length responses of cool-
<br /> season and warm-season grasses,etc.)is ongoing
<br /> Averaged
<br /> Frost-free period(days): 129
<br /> Freeze-free period(days). 150
<br /> Mean annual precipitation(inches): 1539
<br /> Plant Communities
<br /> Ecological Dynamics of the Site
<br /> The information in this ESD,including the state-and-transition model diagram(STM),was developed using archeological and historical data.
<br /> professional expenence,and scientific studies.The information is representative of a dynamic set of plant communities that represent the
<br /> complex interaction of several ecological processes.The plant composition has been determined by study of rangeland relic areas,areas
<br /> protected from excessive disturbance,seasonal use pastures,short durationitime controlled grazing strategies,and historical accounts.
<br /> The Sandy Bottomland ecological site is characterized by three states:Reference,Shrub,and Eroded Stale.The Reference State is
<br /> characterized by a dominance of warm-season labgrasses(sand bluestem,prairie sandreed,and swAchgrass).The Shrub State is dominated
<br /> by sand sagebrush and a minor component of understory species(sand dropseed,Friendlier Ihreeawn).The Eroded State is characterized by
<br /> annual(orbs and grasses(sunflower.kochia,Russian thistle,cheatgrass)and early successional plants(sandhill muhty,sand dropseed.
<br /> Fendler threeawn and lemon scurfpea).
<br /> Reference Plant Community
<br /> This is the interpretive plant community.This plant community evolved with grazing by large herbivores,is well suited for grazing by domestic
<br /> livestock and can be found on areas that are property managed with grazing that allows adequate recovery opportunity following each grazing
<br /> occurrence during the growing season.
<br /> The reference plant commundy consists chiefly of warm-season tallgrasses.Principle dominants are sand bluestem,prairie sandreed,and
<br /> sw tchgrass.Subdominant grasses include needle and thread,blue grama,little bluestem,and western wheatgrass.Significant forts and
<br /> shrubs are pacific peavine,evening pnmmse,prairie clovers.leadplant and western sandcherry Cottonwoods may be present.The potential
<br /> vegetation is about 70-85%grasses or grass-like plants,8-15%(orbs and 7-15%shrubs
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