Oak savanna
Encyclopedia
An oak savanna is a type of savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

, or lightly forested grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

, where oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

s (Quercus spp.) are the dominant tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. These savannas were maintained historically through wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

s set by lightning, grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...

, low precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

, poor soil, and/or fires set by Native Americans
Native American use of fire
In addition to simple cooking, Pre-Columbian Native Americans used fire in many and significant ways, ranging from protecting an area from fire to landscape-altering clearing of prairie.-Human-shaped landscape:...

. Although there are pockets of oak savanna almost anywhere in North America where oaks are present, there are three major oak savanna areas: 1) California and Oregon in the west; 2) Southwestern United States and Mexico; and 3) the prairie/forest border of the Midwest.

California oak savannas

The oak savannas of California were dominated by, though not exclusively composed of, Valley oak in the coastal regions' interior valleys and hills of the California chaparral and woodlands
California chaparral and woodlands
The California chaparral and woodlands is a terrestrial ecoregion of lower northern, central, and southern California and northwestern Baja California , located on the west coast of North America...

 ecoregion
Ecoregion
An ecoregion , sometimes called a bioregion, is an ecologically and geographically defined area that is smaller than an ecozone and larger than an ecosystem. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural...

, and in the San Joaquin Valley
San Joaquin Valley
The San Joaquin Valley is the area of the Central Valley of California that lies south of the Sacramento – San Joaquin River Delta in Stockton...

 and Sacramento Valley
Sacramento Valley
The Sacramento Valley is the portion of the California Central Valley that lies to the north of the San Joaquin-Sacramento Delta in the U.S. state of California. It encompasses all or parts of ten counties.-Geography:...

 of the Central Valley ecoregion and terrestrial biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...

.

Oregon oak savanna


Quercus garryana and Quercus kelloggii form oak savanna in the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...

.
  • Oak savanna is found in several areas in the Klamath Mountains ecoregion
    Klamath Mountains (ecoregion)
    The Klamath Mountains ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency in the U.S. states of Oregon and California. It lies inland of the Coast Range ecoregion, extending from the Umpqua Valley in the north to the Sacramento Valley in the south...

    .
  • A small section of Oregon White Oak
    Garry Oak
    Quercus garryana, the Garry Oak, Oregon White Oak or Oregon Oak, has a range from southern California to extreme southwestern British Columbia, particularly southeastern Vancouver Island and the adjacent Gulf Islands. It grows from sea level to 210 m altitude in the northern part of its range, and...

     savanna is preserved at Mount Pisgah Arboretum
    Mount Pisgah Arboretum
    The Mount Pisgah Arboretum is a non-profit arboretum and botanical garden located within the Howard Buford Recreation Area , between the Coast Fork of the Willamette River and the slopes of Mount Pisgah near Eugene-Springfield, Oregon, United States...

     in Eugene, Oregon
    Eugene, Oregon
    Eugene is the second largest city in the U.S. state of Oregon and the seat of Lane County. It is located at the south end of the Willamette Valley, at the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast.As of the 2010 U.S...

    .

Edwards Plateau savanna

The Edwards Plateau
Edwards Plateau
The Edwards Plateau is a region of west-central Texas which is bounded by the Balcones Fault to the south and east, the Llano Uplift and the Llano Estacado to the north, and the Pecos River and Chihuahuan Desert to the west. San Angelo, Austin, San Antonio and Del Rio roughly outline the area...

 of central Texas is distinguished by juniper
Juniper
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the...

-oak savannas, underlain by medium and short grasslands.

Midwestern oak savannas

The oak savannas of the Midwestern United States form a transition zone between the Great Plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

 to the west and the broadleaf and mixed forests
Temperate broadleaf and mixed forests
Mixed forests are a temperate and humid biome. The typical structure of these forests includes four layers. The uppermost layer is the canopy composed of tall mature trees ranging from 33 to 66 m high. Below the canopy is the three-layered, shade-tolerant understory that is roughly 9 to...

 to the east, which were the eastern savannas
Eastern savannas of the United States
The eastern savannas of the United States covered large portions of the east side of the continent until the early 20th century. These were in a fire ecology of open grassland and forests with low ground cover of herbs and grasses....

 prior to European settlement
European colonization of the Americas
The start of the European colonization of the Americas is typically dated to 1492. The first Europeans to reach the Americas were the Vikings during the 11th century, who established several colonies in Greenland and one short-lived settlement in present day Newfoundland...

. Oak savannas are found in a wide belt from northern Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

 and Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

, down through Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

, Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

, northern and central Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

, eastern Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

, and central Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

 to north-central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

, with isolated pockets further east around the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

. The World Wildlife Fund divides the oak savannas into two ecoregions, the Upper Midwest forest-savanna transition
Upper Midwest forest-savanna transition
The Upper Midwest forest-savanna transition is a terrestrial ecoregion that is defined by the World Wildlife Fund. An oak savanna plant community located in the Upper Midwest region of the United States, it is a transitory ecotone between the tallgrass prairies to the west and the temperate...

 and the Central forest-grasslands transition
Central forest-grasslands transition
The Central forest-grasslands transition are a prairie ecoregion of the central United States, part of the North American Great Plains.-Setting:...

, distinguished by the predominant tree species. The bur oak
Bur oak
Quercus macrocarpa, the Bur Oak, sometimes spelled Burr Oak, is a species of oak in the white oak section Quercus sect. Quercus, native to North America in the eastern and midwestern United States and south-central Canada...

 (Quercus macrocarpa) is the dominant species in the north, while the dominant tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 in the south is usually the black oak (Quercus velutina), although the chinquapin oak (Quercus muhlenbergii) is also common. The dominant grass species is typically the little bluestem
Little bluestem
Schizachyrium scoparium, commonly known as little bluestem or beard grass, is a North American prairie grass. Little bluestem is a perennial bunchgrass and is prominent in tallgrass prairie, along with big bluestem , indiangrass and switchgrass...

 (Schizachyrium scoparium). Oak savannas, because of their mixture of grassland and oak forest, typically are inhabited by more species of plant and animal than grasslands, temperate forests, and sometimes understory jungles, combined. The top predator in modern-day Midwest oak savannas is the coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...

. The most prevalent herbivore is typically the gray, brown, or gray-brown squirrel, and/or the white tail deer.

History

Before European settlement, the oak savanna ecosystem was part of a fire ecology
Fire ecology
Fire ecology is concerned with the processes linking the natural incidence of fire in an ecosystem and the ecological effects of this fire. Many ecosystems, such as the North American prairie and chaparral ecosystems, and the South African savanna, have evolved with fire as a natural and necessary...

. Fires, set by lightning or Native Americans, ensured that the savanna areas did not turn into forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

s. Only trees with a high tolerance for fire, principally certain oak species, were able to survive. On sandy soils, black oak (Quercus velutina) predominated. On rich soils bur oak (Quercus macrocarpa) was the major tree in central North America. These savanna areas provided habitat for a many grazing animals, including American bison
American Bison
The American bison , also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds...

, elk
Elk
The Elk is the large deer, also called Cervus canadensis or wapiti, of North America and eastern Asia.Elk may also refer to:Other antlered mammals:...

 and white-tailed deer
White-tailed Deer
The white-tailed deer , also known as the Virginia deer or simply as the whitetail, is a medium-sized deer native to the United States , Canada, Mexico, Central America, and South America as far south as Peru...

.

European settlers cleared much of the savanna for agricultural use. In addition, they suppressed the fire cycle. Thus surviving pockets of savanna typically became less like savannas and more like forests or thickets. Many oak savanna plant and animal species became extinct or rare.

Restoration

In the 1970s, conservation began in the ecological restoration and land-habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

 preservation of the surviving areas and regions of oak savanna. This includes grazing timing, restoration replanting, controlled burns, and basic land acquisitions and conservation easements for nature preserves to protect their space needs.

Current distribution

Surviving pockets of oak savanna can be found throughout the historical range of this ecosystem. Many are protected and maintained by government bodies or non-profit organizations such as The Nature Conservancy
The Nature Conservancy
The Nature Conservancy is a US charitable environmental organization that works to preserve the plants, animals, and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive....

 and the Iowa Natural Heritage Foundation
Iowa Natural Heritage Foundation
The Iowa Natural Heritage Foundation is a statewide non-profit natural conservation organization based in Des Moines, Iowa. The organization has protected more than in 94 of Iowa’s 99 counties and worked on hundreds of different project sites since its inception in 1979. INHF is donor-supported...

. Examples include the Neal Smith Wildlife Refuge
Neal Smith Wildlife Refuge
The Neal Smith National Wildlife Refuge is a federal national wildlife refuge located in Jasper County, Iowa, United States. The refuge, formerly known as Walnut Creek, is named after Congressman Neal Edward Smith, who championed its creation. It seeks to restore the tallgrass prairie and oak...

 in Prairie City, Iowa
Prairie City, Iowa
Prairie City is a city in Jasper County, Iowa, United States. The population was 1,680 at the 2010 census.-History:Prairie City was founded by James Elliot in 1856, for whom it was originally named; it was later changed because there was already another Elliot in the state. The first resident was...

, the Indiana Dunes National Lakeshore
Indiana Dunes National Lakeshore
Indiana Dunes National Lakeshore is a U.S. National Lakeshore located in northwest Indiana and managed by the National Park Service. It was authorized by Congress in 1966. The national lakeshore runs for nearly along the southern shore of Lake Michigan, from Gary, Indiana, on the west to Michigan...

 in Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

, the Oak Openings Preserve Metropark
Oak Openings Preserve Metropark
Oak Openings Preserve Metropark is the largest of the Toledo Area Metroparks. It is a nature preserve located near Swanton, Ohio and is part of the Toledo Metroparks. It is located southwest of the Toledo Express Airport, and contains sand dunes and several rare plant species...

 in Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

, and, in Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

, Pinery Provincial Park
Pinery Provincial Park
The Pinery Provincial Park is a park located on Lake Huron near Grand Bend, Ontario. It occupies an area of 25.32 square kilometres ....

 on Lake Huron
Lake Huron
Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

, and the Chicago Wildlife Fund. An excellent example of a restored oak savanna is Wisconsin's Pleasant Valley Conservancy State Natural Area.

External links

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