Fire and prairie Oct 12, 2010 From:
Origin of North American Prairies Uplift of Rocky Mountains created a rain shadow Retreat of glaciers Historically shaped by fire, climate, and grazers/browsers /
Uplift and rain shadow
“The Great American Desert”
Three prairies? Western (“shortgrass”) prairie too dry to support much woody vegetation Eastern (“tallgrass”) prairie can support broken to closed canopy forest –this shows the importance of fire to this region – with fire it is a grassland Mixed grass prairie is between these two regions From: Anderson, RC The historic role of fire in the North American Grassland. In: Colins, S, Collins, SL, Wallace, L. eds. Fire in North American Tallgrass Prairies.
Tallgrass Prairie
Mixed Grass Prairie
Shortgrass Prairie
Why grass in grasslands? What adaptations do grasses have to drought? To fire? To grazers? Basal meristems Above ground dormancy C 4 photosynthesis in some grasses
Warm and cold season grasses Warm Season (C 4 ) Cool Season (C 3 ) C 4 have a competitive advantage under drought and high temperatures: C 3 uses 833 molecules of water per CO 2 molecule fixed vs 277 water molecules used by C 4 Water use efficiency! Examples C 4 : big bluestem, indiangrass, bermudagrass, switchgrass, corn, sugar cane Examples C 3 : orchardgrass, fescues, and perennial ryegrass
Time of burning: warm and cold season grasses
Time of burning: perennial and annual forbs
What happens with fire suppression?
What happens with no disturbance?
No Diversity
Other sources of disturbance? Grazing and browsing Bison followed fires Result: patchy Mosaic
Grazing
Browsing
Patch Burn Grazing Cattle focus on grasses instead of forbs Replicates historical patterns esearch/patchburn/index.htm lhttp:// esearch/patchburn/index.htm l
Prairie Fire regime? Frequency? Season? Late spring fire suppresses cool-season grasses Early spring or fall fires favors cool- season grasses over warm-season grasses
TTYGroup: Practical Questions 1.A property has a remnant prairie, but is composed mostly of cool season invasive grasses such as smooth brome and kentucky bluegrass. What fire regime/ management practices would you recommend to manage this property to eventually reduce the invasive species and increase diversity?
TTYGroup: Practical Questions 2. A property has been restored, and is mostly composed of warm season native grasses such as big bluestem and indian grass. What fire regime/management practices would you recommend to maintain these species and increase diversity?
TTYGroup - Outcomes Complete the outcome sheet with your group