VEGETATIONAL REGIONS OF TEXAS

Vegetational Regions of Texas

1. Pineywoods
2. Gulf Prairies and Marshes
3. Post Oak Savannah
4. Blackland Prairies
5. Cross Timbers and Prairies
6. South Texas Plains
7. Edwards Plateau
8. Rolling Plains
9. High Plains
10. Trans-Pecos, Mountains and Basins

Flora Composition


The makeup of a particular flora (flora = sum of plant species in a particular region or zone) is affected by many factors:

1. CLIMATE
A. Rainfall - total amount & pattern
B. Temperature - Av. temp.'s & rate of change.
C. Latitude and elevation.
2. SOIL TYPES
3. DISTURBANCES, ESPECIALLY HUMAN
4. PLANTS THEMSELVES CAN AFFECT OTHER PLANTS
A. Allelopathy - production of substances toxic to plants
B. New invaders (weeds)
5. FAUNA INTERACTS WITH FLORA

FLORA(S) OF TEXAS


A great variety of rainfalls (8' to 56"), elevations, (sea level to 8751') and soil types have resulted in a very diverse flora (for temperate areas) of about 5500 species.

VEGETATIONAL REGIONS


I. TIMBER BELT - PINEYWOODS AND EAST TEXAS FOREST REGION
A. 200' to 500', rolling hills, large rivers, 35 to 50" rain, acid soils.
B. Composition is pine and pine-hardwood forest with intermittent swamps.
C. Southwestern terminus of forest that extends east to Florida and northeast to Virginia.
D. Flora is very similar to southeastern states.

II. GULF PRAIRIES AND MARSHES
A. Level plain <150', with sluggish rivers, creeks, bayous and sloughs, 30 to 50" rain.
B. Climax vegetation is grassland or post oak savannah but many other plants have invaded.

III. POST OAK SAVANNAH
A. Gently rolling to hilly, 300 to 800', 35 to 45" rain, highly variable soils.
B. May have had more of a prairie composition before settlement, now has a large tree and shrub component.

IV BLACKLAND PRAIRIES
A. Level to gently rolling, 300 to 800', 30 to 40" rain.
B. Dominant plant species are grasses but also much timber present.

V. CROSS TIMERS AND PRAIRIES
A. North central prairies, 25 to 40" rain, diverse soil types.
B. Dominant vegetation type is grassland but dense brush covers some areas and mesquite is well-established.

VI. RIO GRANDE PLAINS
A. Level to rolling, sea level to 1000', 16 to 30" rain with irregular drouths.
B. Open prairies with many small trees and shrubs.

VII. EDWARDS PLATEAU - HILL COUNTRY
A. Hilly, 1000 to 3000', 15 to 33" rain, frequent drouths, soils are shallow and underlain by limestone, caliche, granite, or gneiss.
B. Climax vegetation is grassland or open savannah but many brushy species have invaded.

VIII. ROLLING PLAINS
A. Elevation is 800 to 3000', 22 to 30" rain with summer dry period, many soil types.
B. Prairies with many invaders due to overgrazing.

IX HIGH PLAINS (VIII + IX= PANHANDLE)
A. Level high plateau, 3000 to 4500', 15 to 21" rain with extended drouths.
B. Vegetation is mixed prairies to short-grass prairie.

X TRANS-PECOS, MOUNTAINS, & BASINS
A. Diverse habitats and regions, 2500 to 8500', <12 to 20" rain, variable soils.
B. Many vegetation types from desert to conifer forests.


More information on Texas Vegetational Regions is available from the Tracy Herbarium