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Fire and Savannas

Fire and Savannas. Oct 14, 2010. What is a savanna?. Scattered trees and sometimes shrubs Dense herbaceous understory Often an “ ecotone ”. What is an ecotone?. TTYP – What kinds of environmental factors or disturbances could create an ecotone ?. Savannas throughout the world. Cerrado

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Fire and Savannas

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  1. Fire and Savannas Oct 14, 2010

  2. What is a savanna? • Scattered trees and sometimes shrubs • Dense herbaceous understory • Often an “ecotone”

  3. What is an ecotone? • TTYP – What kinds of environmental factors or disturbances could create an ecotone?

  4. Savannas throughout the world • Cerrado • Serengeti • Madagascar savannas • Australian eucalyptus savannas • Indian savannas

  5. North American Savannas • Prairie/forest transition zone temperate savannas • Oak/mesquite in south • Oak with some hickory in central • Oak to aspen in north • Oak savannas in CA and S.W. • W & S.W. Ponderosa pine • S.E. Pine savannas

  6. Midwestern oak savannas • Ecotonal between prairie and oak/hickory forest • Scattered oak (hickory?) trees • Understory with prairie and forest components • Different terms: • Oak barrens, oak openings, oak grove

  7. Topography • Moisture • Fire • Grazing • Humans • Climate • Soils Shifts in the savanna ecotone • Savanna distribution has changed over time • What factors influenced the distribution of savanna?

  8. TTYP: Shifts in the savanna ecotone • Topography and • Landscape features (e.g. streams) • Moisture • Fire • Grazing • Humans • Climate • Soils How do these factors influence the distribution of prairie, savanna, and woodland? Over what time periods? Are any of these inter-related? How?

  9. Shifts in the savanna ecotone

  10. Shifts in the savanna ecotone • Topography: broken, more ridges, slopes (L) • More soil moisture (M) • Closer to rivers and streams (L/M) • More clayey-loamy soils (L) • Less frequent fires (S) • More humans if suppressing fires (less humans, if no supp.) • Less grazing • Flatter topography (L) • Less soil moisture / drier climate (L/M) • Far from rivers and streams (L/M) • Sandier soils (L) • More frequent fires (S) • More humans if starting fires (less humans if suppressing fires) (S/M/L) • More grazing

  11. Savanna tree species • Bur oak • Thick corky bark, deep roots • Most fire-resistant oak • Adventitious buds along branch resprout • Black oak • Top-killed, but resprouts with vigor • White oak • Moderate fire resistance, good resprouter • Red oak • Not very fire resistant • Low sprouting capacity when top-killed • Mostly on steep north slopes

  12. Savanna shrub species • Gray dogwood, hazelnut, smooth sumac • Clone-formers • Burned to the ground by fire

  13. Savanna ground layer • Herbaceous species • Fuel for fire • Gradient of light environments = high diversity • Species with different light requirements: • Full sun • Full shade • Light shade • Moderate sun • Blend of shade and sun (“true savanna species”): http://oaksavannas.org/savanna-forbs.html#Pruka

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