|
State 1
<br /> Refernce State
<br /> The Reference State is characterized by three distinct plant community phases; Reference,At-Risk, and Low Plant
<br /> Density, Increased Litter Plant Community. The plant communities, and various successional stages between them,
<br /> represent the natural range of variability due to the disturbance regimes applicable to the site.
<br /> Community 1.1
<br /> Reference Plant Community
<br /> This is the interpretive plant community and is considered to be the Reference Plant Community.This plant
<br /> community evolved with grazing by large herbivores, and is well suited for grazing by domestic livestock. It can be
<br /> found on areas that are properly managed with prescribed grazing that allows for adequate recovery periods
<br /> following each grazing event.The potential vegetation is about 70-85%grasses and grass-like plants, 10-15%
<br /> forbs, and 5-15%woody plants. The dominant tall warm season grasses are prairie sandreed, sand bluestem and
<br /> switchgrass. Blue grama dominates the understory. Important cool season grasses and grass-likes are needle and
<br /> thread and sun sedge. Key forbs and shrubs are American vetch, pacific peavine(manystem pea), purple prairie
<br /> clover, and spreading buckwheat.This plant community is diverse, and productive. Litter is properly distributed with
<br /> very little movement off-site, and natural plant mortality is very low. It is well-suited to carbon sequestration,
<br /> effective water cycle, and wildlife use by many species, livestock use, and is aesthetically pleasing. Community
<br /> dynamics, nutrient cycle,water cycle, and energy flow are functioning properly.This community is resistant to
<br /> disturbances except moderate to heavy continuous grazing,tillage, and/or development into urban or other uses.
<br /> Total annual production ranges from 800 to 2,200 pounds of air-dry vegetation per acre and will average 1,650
<br /> pounds during an average year. These production figures are the fluctuations expected during favorable, normal
<br /> and unfavorable years due to the timing and amount of precipitation and temperature. Total annual production
<br /> should not be confused with species productivity,which is annual production and variability by species throughout
<br /> the extent of the community phase.
<br /> Table 5.Annual production by plant type
<br /> Low Representative Value High
<br /> Plant Type (Lb/Acre) (Lb/Acre) (Lb/Acre)
<br /> Grass/Grasslike 600 1300 1690
<br /> ShrubNine 50 150 255
<br /> Forb 150 200 255
<br /> Total 800 j 1650 j 2200
<br /> Figure 7.Plant community growth curve(percent production by month).
<br /> CO6709,Warm-season dominant,cool-season subdominant;MLRA-67B;
<br /> upland coarse textured soils..
<br /> Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
<br /> 0 0 2 7 25 35 15 10 5 1 0 0
<br /> Community 1.2
<br /> At-Risk Plant Community
<br /> This plant community develops with continuous grazing without adequate recovery periods between grazing events,
<br /> and/or extended drought, and/or reduced fire frequency.When compared to the Reference Plant Community sand
<br /> bluestem, prairie sandreed, switchgrass, leadplant and western sandcherry have decreased in frequency and
<br /> production. Blue grama has increased. Sand dropseed, Fendler threeawn, hairy goldaster, croton, slimflower
<br /> scurfpea,western ragweed, stickleaf, heath aster, lupine, loco, milkvetch and plains pricklypear cactus have
<br /> increased. Soils that have a sandy loam or coarser subsoil will show an increase in sand sagebrush. Continuous
<br /> spring grazing with summer deferment will reduce the cool-season component(needle and thread,western
<br /> wheatgrass, sun sedge)of this plant community and increase the warm-season component. Continuous summer
<br /> grazing with spring deferment will reduce the warm-season component(sand bluestem, prairie sandreed, and
<br /> switchgrass)of this plant community and increase the cool-season component.The risk of losing key warm-season
<br />
|