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Fire and Savannas

Explore the factors that influence the distribution and diversity of savannas, including topography, moisture, fire, grazing, humans, climate, and soils. Learn about shifts in the savanna ecotone and the species that thrive in this unique ecosystem.

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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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