Ecoregions denote areas of general similarity

in ecosystems and in the type, quality, and

quantity of environmental resources. Sometimes

called an ecological region or bioregion, it is an

ecosystem (smaller than a biome) with distinct

geography, plants and animals, and receives

uniform solar radiation and moisture.

What is an ecoregion?

Mechanical or physical weathering - is the

process by which rock is broken down into

smaller pieces by physical changes.

Mechanical/Physical Weathering

Temperature Change – a rise in temperature will cause a rock to

expand and a decrease in temperature will cause a rock to contract.

Repeated changes in temperatures will cause the rock to crumble.

Abrasion – rock can be broken down by the action of other rocks; wind,

water, glaciers, and gravity carry different sized pieces of sediment

that can strike a rock causing it to break apart or wear down.

Animal Action – animals digging and burrowing can cause rock to break

apart of become more exposed to other agents of weathering.

Plant Growth – roots of plants break apart rock as they grow and

increase in size.

Mechanical/Physical Weathering

Some ways that rock can be broken down physically include:

The breakdown of rocks by chemical reactions. Occurs more often in locations

with high precipitation rates and high temperatures.

Oxidation – when materials in rock react with the oxygen in air or water

causing a chemical change. (ex. rusting and corrosion).

Acid Rain – Some acids form naturally when chemicals in the atmosphere

combine with water in the air and cause acid precipitation. The acid rain

weathers rock and changes its composition.

Acids from organisms -

Lichen and mosses produce weak acids that break down the rock that they

grow on.

Chemical Weathering

Some ways that rock can be broken down chemically include:

Erosion is the process by which weathered rock pieces are

carried away.

Erosion

• During the process of erosion, sediment is removed from

one area on Earth’s surface and carried to another.

• Erosion is reduced by vegetation (plant life).

• Agents of erosion include the following:

Moving Water – Wind – Glaciers – Gravity

Some formations due to deposition are…

Floodplains – the sediment that is deposited after flood waters recede.

Deltas – when a river flows into an ocean, the river slows down and deposits

the sediment it was carrying.

Alluvial fans – when a stream flows down hill onto a flat land surface, the

sediment forms a fan-shaped deposit.

Beaches – when water moves downhill and meets a non-flowing body of

water, it slows down and deposits the sediment. Waves also help shape the

beach.

Dunes – when wind carrying sand is blocked by an upward slope, it slows

down and deposits the sediment, causing the sand to pile up.

DepositionDeposition - the placement of sediment after being carried from place of

origin.

Alluvial Fan Delta

Texas Ecoregions

Ecoregions in Texas? Why?

Due to its size and geographic location, Texas is unique

among states. Covering 266,807 sq. miles, it is second only to

Alaska in land area. Texas is 860 miles north to south and 773

miles east to west and contains 266,807 square miles with a

624 mile coastline.

As with any large area of land, Texas has a great deal of

variation in climate and landscapes, factors influencing habitat

diversity.

Miles and miles of Texas...

• Its geographic location is a crossroads where eastern habitats meet

western ones and southern subtropical habitats meet northern temperate

ones.

• The annual rainfall can range from eight inches in the deserts of far west

Texas to 56 inches per year in the swamps of east Texas.

• In the Trans-Pecos region, there are almost 100 peaks that are over one

mile high.

Texas has impressive topographic

diversity.

Savanah

Piney Woods

Piney Woods

East Texas Piney Woods is comprised of 27 counties

• Due to abundant precipitation and abundant vegetation

that holds the soil in place, there is very little erosion.

• Thick vegetation near rivers inhibits prevents river

erosion.

• Periodic forest fires allow pine trees to maintain their

status as the dominant ecosystem.

Piney Woods

• Climate: The average annual rainfall is 36 to 50 inches; the

humidity and temperatures are typically high. One of the wettest

regions in Texas.

• Soil: Largely acidic and typically pale to dark gray sands or

sandy loams

• Elevation: Ranges from 200 to 500 feet above sea level

• Geography: Rolling terrain

• Vegetation: Pine and oak; tall hardwood forests; areas of

cropland, planted pastures, native pastures, and rich

bottomlands

Piney Woods

Post Oak Savanah

18 counties fall within the Post Oak Savanah Ecoregion

Post Oak Savanah

• One of the best places to see Texas wildflowers.

• Has gently rolling hills and lightly wooded plains.

• Wildflowers, classified as forbs (fodder), provide

browse or grazing food for deer and other wildlife.

• Moderate rainfall helps shape the land.

• Trees and grasses prevent large amounts of soil

erosion due to water and wind.

Post Oak Savanah

• Climate: Average annual rainfall 28 to 40 inches.

• Soil: Upland soils tend to be light colored, acidic sandy

loam or sands. Bottomland soils tend to be light brown

• to dark gray and acidic ranging from sandy loams to clays.

• Elevation: Ranges from 300 to 800 feet above sea level

• Geography: Gently rolling to hilly terrain

• Vegetation: Oak savannah; patches of oak woodland

alternate with grassland

13 counties make up the Blackland Prairies

Blackland Prairie

• Gets its name from its black, nutrient-rich soils .

• Receive good amounts of rainfall through the year.

• If the land is clear-cut of natural vegetation for

construction, nutrients can easily be eroded.

• If the land is used for farming and it is not

managed well, nutrients will be quickly used up.

Blackland Prairie

• Climate: The average annual rainfall is from 28 to 40 inches.

The northern end of the region has its peak rainfall during

the month of May. Rainfall is fairly uniform over the south-

central region throughout the year.

• Soil: Uniformly dark-colored alkaline clays interspersed

with some gray acidic sandy loams

• Elevation: Ranges from 300 to 800 feet above sea level

• Geography: Gently rolling to nearly level terrain

• Vegetation: Food and forage crops

Cross Timbers and Prairies

43 counties make up the Cross Timbers ecoregion.

Cross Timbers and Prairies• Early travelers through north Texas coined the name "Cross

Timbers" by their repeated crossings of these timbered areas

that proved to be a barrier to their travel on the open prairies

to the east and west.

• The location of the East and West Cross Timbers was well

known by these early travelers who used them as points of

reference for travel.

• As in the rest of the Great Plains, fire, topography, and

drought maintained prairie and established the location of

woodlands.

Cross Timbers and Prairies

• Its rolling hills and dark clay soils that are well-drained.

Well-draining soils allow rainfall to quickly infiltrate the soil

and become groundwater, rather than to become runoff,

which can lead to erosion.

• The limestone in this region is vulnerable to chemical

weathering, so limestone land features are constantly

changing.

• This transitional ecosystem consists of tall and shortgrass

prairies, savannahs, and woodlands.

Cross Timbers and Prairies• Climate: The average annual rainfall is from 26-40 inches.

• Soil: Soils are primarily sandy to loamy.

• Elevation: Ranges from 500 to 1,500 feet above sea level

• Geography: Ranges from savannah and woodland to the east

and south, into shorter mixed-grass prairie to the west.

• Vegetation: Plant communities change dramatically within

short distances resulting in different land use potential for

livestock grazing, farming, wildlife management, or other

uses.

Rolling Plains

The Rolling Plains is comprised of 42 counties

• Soils in this area are most fertile and sought after for crop production

and it is not unusual for natural vegetation of grasses, shrubs, and

some trees to be removed in order to allow farming.

• Periods of drought and then sudden increase in rainfall causes large

amounts of erosion and deplete the soil of nutrients.

• Topographical features are due to the several rivers that flow through

this ecoregion. These rivers weather and erode the land, forming

several canyons in this area. The material eroded by rivers can be

deposited on the outer banks, changing their shape.

• Eroded material may also be deposited at the mouths of the rivers in

the Gulf of Mexico, extending the shoreline.

Rolling Plains

• Climate: Rainfall averages 20 to 28 inches, dry summers with

high temperatures and high evaporation rates.

• Soil: Varies from coarse sands alongside outwash terraces by

streams to clays and shales.

• Elevation: Ranges from 800 to 3,000 feet above sea level

• Geography: Gently rolling hills and broad flats are cut by

several rivers and their tributaries.

• Vegetation: Mesquite and short grass savannah, various

hardwood species along streams, juniper on steep slopes along

rivers.

Rolling Plains

High Plains

• Climate: Multiple extended droughts have occurred several

times over the last 100 years.

• Soil: The texture of surface soils varies from clays in the

North to sands in the South; caliche can be found beneath

surface soils at depths that range from two to five feet.

• Elevation: Ranges from 3,000 to 4,500 feet above sea level

• Geography: Relatively level high plateau.

• Vegetation: Irrigated cropland. Mesquite and juniper are

native vegetation.

High Plains

• Known as the “Texas Panhandle”- is on a high, flat plateau.

• Largest flat area of its size in the world and is mostly flat and

grassy, treeless.

• The region extends to the Palo Duro Canyon-the nation’s 2nd

largest canyon.

• Palo Duro Canyon was formed by water erosion from the Red

River.

• The water deepens the canyon by moving sediment downstream.

• Wind and water erosion gradually widen the canyon over long

periods of time.

High Plains

Trans Pecos Wildlife District and is comprised of 16 counties.

Trans-Pecos

Trans-Pecos• “Desert portion” of Texas.

• Hot dry desert that is cool at night

• Bedrock has a large amount of calcium.

• Home of the tallest mountain in Texas, The Guadalupe

Peak. (8,749 feet).

• Pines and Oaks dominate the tree species.

• Soils are shallow and rocky.

• Soils in the canyon bottoms and valleys are deeper as a

result of deposition.

Trans-Pecos• Climate: 9–15 inches of rain; semi-arid, warm, dry

winters.

• Soil: Generally shallow, saline, and unproductive.

• Elevation: 2,000 feet to mountain ranges. The highest

peak is 8,751 feet above sea level.

• Geography: Salt basins, sand hills, rugged plateaus,

mountain slopes.

• Vegetation: Desert grassland, desert scrub, coniferous

and mixed hardwood forests at mountain peaks.

Trans-Pecos• The majority of plants in this ecoregion are mesquites, cacti,

juniper, and other desert species.

• Deposition after the weathering and erosion of the Guadalupe

and Davis Mountains has formed the soil in this ecoregion.

• In the Chihuahuan Desert, wind acts as the main erosion

agent, creating sand dunes.

• When this ecoregion does receive rain, it can lead to

flashfloods, which can weather and erode the rocks and

sediment.

Comprised of 25 counties

Edwards Plateau and the Llano Uplift

• Commonly referred to as the “Texas Hill Country.”

• Soils and hill slopes are ideal for wineries to grow grapes.

• Plant roots cause mechanical weathering.

• Rainwater runs off into streams or is collected in drainage or

catchment areas that infiltrate into the water table which

“recharges” the Edwards Aquifer located in this ecoregion.

• Flash flooding is common during heavy rainfall.

• The Edwards Aquifer has many underground lakes.

Edwards Plateau and the Llano Uplift

• Erosion has left most of the region with very shallow soils (less than 10

inches) lined with limestone rock layers.

• One prominent feature in the Edwards Plateau is Enchanted Rock

which is a large dome of granite physically weathered through

exfoliation; where sheets of rock peel away from the rock surface.

• Chemical erosion is a common result when rainwater mixes with

carbon dioxide in the atmosphere and soils to form carbonic acid.

The carbonic acid dissolves away limestone and led to the formation

of a large cave system underground.

Edwards Plateau and the Llano Uplift

• Climate: Rainfall averages vary from 25 – 35 inches.

• Soil: The soil allows water to infiltrate very easily

• Elevation: Ranges from 600-3000 ft. in elevation.

• Geography: Springs, stony hills, steep canyons and caves;

many river systems separate the surface, creating a rough

but well-drained landscape.

• Vegetation: Grasslands, juniper/oak woodlands,

shortgrasses, and plateau live oak or mesquite savannah

Edwards Plateau and the Llano Uplift

The South Texas Plains consist of 30 counties

South Texas Plains

• Commonly known as “Brush County.”

• Several major rivers, like the Rio Grande, run through it.

• Overgrazing has allowed nutrient-rich topsoil to erode

away, leaving behind soil more suitable to supporting

shrubs and short trees.

• Extends from the edges of the Hill Country to the Lower

Rio Grande Valley.

• Mostly dry and covered with grasses, thorny brush, and

prickly pear cacti.

South Texas Plains

• Climate: Rainfall averages 24 to 28 inches per year

• Soil: Mostly sands

• Elevation: Elevations are mainly level; less than 150 feet

above sea level

• Geography: Windblown sands and unstable dunes with

grasslands, stands of oak, and salt marshes

• Vegetation: Tallgrass prairie and live oak woodlands,

mesquite savannah, and salt marshes

South Texas Plains

Gulf Coast Prairies and Marshes

The Gulf Coast Prairies and Marshes is comprised of 21 counties

• Wave action, a factor in weathering, erosion, and deposition, is

constant along the Texas Coastline.

• Waves erode beaches in one area, redeposit the sand in different

locations along the shore, form sandbars, and can be carried out

into the ocean to form barrier islands (like Galveston).

• Barrier islands like Galveston, some of the most fragile and

changing landforms on Earth are particularly vulnerable to storms.

• Region vulnerable to extensive flooding from storms and

hurricanes.

• Erosion from storms destroy habitats for animals like: turtles,

seagulls and pelicans.

Gulf Coast Prairies and Marshes

• Climate: Rainfall annually ranges from 30 to 50 inches per year and

has warm temperatures and high humidity.

• Soil: Soils are clay or sand-rich in depending on the location.

• Elevation: Consists primarily of flat plains with low elevations (less

than 150 ft.).

• Geography: Prairies, coastal barrier islands, marshes near the bays,

bayous and estuaries (a partially enclosed area where salty ocean and

the fresh water river form a body of brackish water). Region cut by

streams and rivers flowing into the Gulf of Mexico.

• Vegetation: Includes salt grass, tallgrass prairies, live oak woodlands,

mesquite and acacias, and oaks dispersed along the coast.

Gulf Coast Prairies and Marshes

The key to managing the natural resources of Texas

is to use tools that develop and maintain healthy

ecosystems. Single species must have less attention,

because protecting the system in which they thrive is

most vital. Knowing how each system functions is

imperative for its continued existence.

How can we help protect the ecosystem?

The 5 basic tools that are used to manage ecoregions in

Texas:Axe, Cow, Plow, Fire, Hunting

• The expansion of Ashe juniper has had a tremendous

impact on the ecosystem, causing a decrease in plant

species diversity and an increase in soil erosion. Cedar

breaks loose a significant amount of precipitation

through transpiration and overland flow, leaving

much less water for aquifer recharge.

Axe

• These species of trees must be

selectively cut down to

manage their negative impact.

• Cattle can be used as a tool to manipulate and enhance

wildlife habitat and plant diversity. The main role of grazing

for wildlife management is to reduce the quantity of grass,

allowing sunlight to reach the lower growing forbs, foods

important for wildlife. This creates more structural diversity

and habitats for animals to nest, raise offspring, and hide.

• Allowing the land time to rest is important so cattle owners

rotate cattle grazing using a 3 pasture - 1 herd system, and

the 4 pasture - 3 herd system, allowing the vegetation time to

regrow between feedings.

Cows

• In Many regions across the state, tilling the

soil is an effective approach to setting back

plant succession and promote the growth of

desirable wildlife foods (forbs).

• In a regions like the Edwards Plateau, where

its shallow, rocky soils are highly vulnerable to

erosion, soil disturbance, is not recommended.

Plow

• Controlled burns are an effective tool for ecological

management to remove old growth and stimulate new

growth.

• 20% of upland woodlands should be burned rotational basis,

every 5-6 years

• Increases plant quantity and quality and habitat diversity.

Fire

• Many species are tolerant of

fire, while others require fire

for adequate germination.

• Fire controls cedar growth.

Overpopulation results in:

• lower fawn crops,

• more major die-offs

• smaller body weights

• poorer quality antlers

20 to 40% of the deer population die annually as a

result of malnourishment.

Deer must be harvested and maintained at or

below the carrying capacity of the land.

Hunting

• Endangered species or their habitat must be protected.

• Wildlife cover must be retained.

• Goals must improve food supply and habitats of wildlife.

• Desirable plant species should be protected from removal

• Plant diversity and range health must be the goal.

• Winter turkey roosts should remain totally intact.

• Care must be taken to avoid soil disturbance in highly

erodible areas.

• Ecoregions must be carefully managed.

Protecting the Texas ecoregions means:…