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ESD Printable Report Page 5 of 19
<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 experience,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 duration/time-controlled grazing strategies,and historical accounts.
<br /> The Loamy Plains ecological site is characterized by four states:Reference,Warm-Season Shortgrass,Increased Bare Ground,and Tilled
<br /> States.The Reference State is characterized by co-dominant warm-season shortgrass(blue grama),and cool-season midgrass(western
<br /> wheatgrass,green needlegrass).The Warm-Season Shortgrass State is characterized by a warm-season short bunchgrass(blue grama)and
<br /> stoloniferous grass(buffalograss).The Increased Bare Ground State is characterized by early successional warm-season bunchgrass
<br /> (Fendler threeawn),cool-season short bunchgrass(squirreltail),annual grasses,and annual forbs.The Tilled State has been mechanically
<br /> disturbed by equipment,and includes either a variety of reseeded warm-and cool-season grasses(seeded community)or early successional
<br /> plants as well as annual grasses and forbs(go-back community).
<br /> The degree of grazing has a significant impact on the ecological dynamics of the site.This region was historically occupied by large grazing
<br /> animals such as bison and elk,along with pronghorn and mule deer.Grazing by these large herbivores,along with climatic and seasonal
<br /> weather fluctuations,had a major influence on the ecological dynamics of the site.Deer and pronghorn are widely distributed throughout the
<br /> MLRA.Secondary influences of herbivory by species such as prairie dogs and other small rodents,insects and root-feeding organisms has
<br /> impacted the vegetation and continues today.
<br /> Historically,it is believed,grazing patterns by herds of large ungulates was driven by water distribution,precipitation events,drought events,
<br /> and fire. It is believed that grazing periods would have been shorter,followed by longer recovery periods.These large migrating herds
<br /> impacted the ecological processes of nutrient and hydrologic cycles,by urination,trampling(incorporation of litter into the soil surface),and
<br /> breaking of surface crust,to increase water infiltration.
<br /> This is an important site for livestock grazing,especially beef cattle.Today the management of livestock grazing has been a major influence
<br /> on the ecological dynamics of the site.This management,coupled with the effects of annual climatic variations,largely dictates the plant
<br /> communities for the site.
<br /> Recurrent drought has historically impacted the vegetation of this region.Changes in species composition will vary depending upon the
<br /> duration and severity of the drought cycle,and prior grazing management.Recent drought events(since 2002),have significantly increased
<br /> mortality of blue grama and buffalograss in some locales.
<br /> This site developed with occasional fire as part of the ecological processes. Historic fire frequency(pre-industrial),is estimated at 10-14 years
<br /> (Guyette,2012),randomly distributed,and started by lightning at various times throughout the growing season. It's thought that early human
<br /> inhabitants also were likely to start fires for various reasons(deliberate or accidental). It is believed that fires were set as a management tool
<br /> for attracting herds of large migratory herbivores(Stewart,2002).The impact of fire over the past 100 years has been relatively insignificant
<br /> due to the human control of wildfires and the lack of acceptance of prescribed fire as a management tool.
<br /> Grazing by large herbivores,without adequate recovery periods following each grazing occurrence,will cause blue grama and buffalograss to
<br /> increase. Blue grama and/or buffalograss may eventually form a sod-like appearance.Cool-season grasses such as western wheatgrass and
<br /> green needlegrass will decrease in frequency and production.Eventually green needlegrass will be removed and western wheatgrass may
<br /> persist in depressions. Fourwing saltbush will decrease in frequency and production.American vetch and other highly palatable(orbs also will
<br /> decrease. Fendler threeawn,ring muhly,annuals,and bare ground increases under heavy continuous grazing,excessive defoliation,or long-
<br /> term non-use.Much of this ecological site has been tilled and used for crop production.Other areas of this ecological site have been
<br /> converted to suburban residences and small acreages,especially near the larger communities.
<br /> Mechanical treatment consisting of contour pitting/furrowing,terracing,chiseling,and disking was practiced in the past. It was theorized that
<br /> the use of this high-input technology would improve production and plant composition on rangeland.These high-cost practices have shown to
<br /> have no significant long-term benefits on production or plant composition,and have only resulted in a permanently rough ground surface.
<br /> Prescribed grazing that mimics the historic grazing of herds of migratory herbivores,as described earlier,has been shown to result in desired
<br /> improvements based on management goals for this ecological site.
<br /> The following is a diagram illustrates the common plant communities that can occur on the Sandy Plains site and the community pathways
<br /> (CP)among plant communities. Plant Communities are identified by 1.1, 1.2 etc.and are described in the narrative.Bold lines surrounding
<br /> each state represent ecological thresholds.Transitions(T)indicate the transition across an ecological threshold to another state.Once a
<br /> threshold has been crossed into another state,it may not be feasible to return to the original state,even with significant management inputs
<br /> and practices.The ecological processes plant communities,community pathways,transition and/or restoration pathways will be discussed in
<br /> more detail in the plant community descriptions following the diagram.
<br /> Increased Bare Ground Community
<br /> This plant community develops with heavy continuous grazing and/or occupation by prairie dogs. Red threeawn is the dominant species with
<br /> sand dropseed and ring muhly present in small amounts. Blue grama may persist in localized areas. Pricklypear cactus and fringed sage may
<br /> increase.Introduced annuals such as kochia and Russian thistle are present. Introduced species such as field bindweed can also be present,
<br /> especially on prairie dog towns.
<br /> Litter levels are extremely low.Erosion is evident where flow paths are continuous. Rills may occur on steeper slopes.Wind scoured areas
<br /> may be apparent on knolls or unprotected areas. Plant pedestals caused by wind scouring are common.The nutrient cycle,water cycle and
<br /> overall energy flow are greatly impaired.Organic matter/carbon reserves are greatly reduced.This community is not stable. Desertification is
<br /> https:Hesis.sc.egov.usda.gov/ESDReport/fsReportPrt.aspx?id=R067BY002CO&rptLevel=al... 1/2/2018
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