Cross Timbers is a geographic and ecological region of the United States that extends in a roughly north‑south band from southeastern Kansas, across central Oklahoma, to central Texas. It is identified by the United States Environmental Protection Agency (EPA) as Level III ecoregion 29, also referred to as the Central Oklahoma/Texas Plains.
Geography
The Cross Timbers occupy a strip of land ranging from 5 to 30 miles (8–48 km) in width. The region lies between the heavily forested eastern United States and the treeless Great Plains, forming a transitional zone that marks the western limit of many eastern deciduous‑forest species and the eastern limit of prairie‑adapted flora and fauna. The ecoregion spans three states—Kansas, Oklahoma, and Texas—and includes parts of the Dallas–Fort Worth metroplex, the western suburbs of the Tulsa and Oklahoma City areas, and portions of north‑central Texas.
Ecology
| Aspect | Description |
|---|---|
| Biome | Central forest‑grasslands transition (WWF) and EPA Level III ecoregion 29. |
| Vegetation | A mosaic of prairie, savanna, and woodland. Woodland areas are dominated by post oak (Quercus stellata) and blackjack oak (Quercus marilandica) on coarse, sandy soils derived from Cretaceous sandstones. In recent decades fire suppression has allowed eastern red‑cedar (Juniperus virginiana) to encroach. Prairie sections consist chiefly of tall‑grass species on finer, drier soils. |
| Fauna | The Cross Timbers constitute a habitat boundary for many mammals and insects, serving as the western range limit for several eastern species and the eastern limit for some Great Plains taxa. |
| Soils | Predominantly sandy, well‑drained soils derived from ancient sandstone and, in the western portion, Pennsylvanian‑age sandstones. |
| Land Use | Historically unsuitable for intensive agriculture due to poor soils and dense oak stands. Present‑day land use is a mix of rangeland, pasture, and limited farmland; portions are also used for oil and gas extraction. Remnant old‑growth oak forests, some over 400 years old, persist in scattered patches. |
History
- Indigenous peoples inhabited the Cross Timbers for millennia, utilizing its oak woodlands for shelter and the prairie for hunting.
- European‑American settlement in the 19th century was limited by the region’s dense oak savannas and lack of arable land. Early explorers described the area as a “crossed timber” belt separating forest and prairie.
- The term “Cross Timbers” entered scientific literature in the early 20th century and was later formalized by the EPA’s ecoregion classification system.
Conservation
Because the Cross Timbers contain some of the least disturbed oak‑savanna ecosystems in the eastern United States, they are a focus of conservation efforts aimed at preserving old‑growth stands, restoring fire regimes, and maintaining habitat connectivity for wildlife. State and federal agencies, as well as non‑profit organizations such as the American Forests and the Cross Timbers Urban Forestry Council, monitor land‑use changes and promote sustainable management practices.
References
- United States Environmental Protection Agency, “Level III Ecoregions of the United States,” ecoregion 29.
- World Wildlife Fund, “Central forest‑grasslands transition” ecoregion profile.
- Texas Parks and Wildlife Department, Cross Timbers ecoregion description.
- “Cross Timbers,” Wikipedia, accessed 2024‑04‑26.