2016-11-04_PERMIT FILE - M2016009 (7)

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condition,whereas the condition of Successional stage and direction ..... ................... those rangelands composed mostly of � Early Middle 0 Late Figure 2.Alien late-successional species have been (Climax) invasive weeds are considered excellent. so aggressive they Rangeland managers have used Climate Climate throw this suc- grazing management as their major cessional system tool.Their objective has been to Plant community into disorder.The balance stocking rates so that graz- Grazing only component g q pp Successional �- y P in is a force equal and opposite to tendency in this model that natural successional tendency when WEEDS can shift the plant the range is in good or excellent community in a condition.Adjustment of stocking Poor Fair Good Excellent desirable direction rates is a continual process based ......................................... is successional on short-term climatic variation and Range condition tendency. compensating for minor vegetation fluctuations.Much of range manage- species,such as the shallow-rooted munity is comprised of fast-growing, ment has focused on techniques to al- Sandberg's bluegrass,which uses short-lived species,typically annual low increased stocking rates without the resources that are available in and biennial plants.As succession causing retrogressive changes in the the upper soil profile early in the progresses,these species alter the site plant community.Many techniques, growing season and during periods enough to allow the establishment such as fencing,salting and watering of light precipitation.As the season and colonization of short-lived pe- systems,are aimed at encouraging progresses, species which initiate rennial plants. Soon these short-lived uniform forage utilization through growth later and continue growth perennial species dominate and alter increased animal distribution.Man- further into the season are needed the site in favor of long-lived pe- aging rangelands using grazing sys- to use available soil resources from rennial plants,eventually producing a tems has worked well in many cases, moderate soil depths.Finally,the di- stable,climax plant community. but only in the absence of invasive verse plant community may include In land once dominated by Idaho alien weeds. a deep taprooted,very late maturing fescue and bluebunch wheatgrass,the species, such as alfalfa or big sage- plant community immediately after a When weeds invade brush. These species are capable of disturbance might be composed pri- When alien or noxious weeds invade extracting resources from deep in the manly of annual and biennial mus- native rangeland,they throw the suc- soil profile and throughout much of tards and a few legume species.As cessional pattern into disorder(Figure the growing season.Although little is succession proceeds,that community 2).Many of these weeds evolved in known about the role of many spe- might become dominated by short- the eastern hemisphere where a long cies within the plant community,it lived perennial species,such as bot- history of intensive disturbance has is generally accepted that maximum tlebrush squirreltail,Thurbers needle- selected for very competitive species. diversity is optimum for energy flow grass or sticky geranium.Eventually, The weeds have usually been intro- through the system as well as nutrient succession may progress to a climax duced without the natural enemies and water cycling. Once a desired community,co-dominated by Idaho that help control their abundance in plant community has been chosen, fescue and bluebunch wheatgrass. their place of origin.These factors an ecologically-based weed manage- Most land managers agree that allow alien weeds to dominate native ment plan can be developed. succession occurs.However,there species.The weeds become climax The succession model is some disagreement as to whether or stable plant communities.How do succession has a fixed end-point for a we manage rangelands dominated by rangeland understand ecologically-based particular site,or whether succession these aggressive weeds? rangeland weed management, varies depending on assorted envi- According to the ecological model must remember the basic ecological principle on which rangelands have ronmental and managerial circum- on which range management has been managed during the past 60p stances.The processes and mecha- been based for the past 60 years,the nisms causing succession are not yet only component shifting plant com- years.This principle states that plant well understood. munities in a desirable direction is communities change over time until managers have con- they reach a final and stable compo- Rangeland g ers the natural successional tendency. dition-classed,monitored and man- Ecological weed management sys- ofchange , called climax.This process aged rangelands based on succession tems must be developed that are of change c called succession. Sec- for decades.Plant communities based on our understanding of the has beary succession occurs after a site dominated by early-successional causes of succession.As mentioned, has been disturbed.Immediately after a disturbance, the plant com- species have been considered in poor we know little about the mechanisms 2