We are fortunate that East Texas has conditions that allow for the growth of many kinds of forests.  Many of these conditions are created by the geology of the area and the diverse array of soils that have been formed by that geology.  Although topography (elevation) in East Texas is not great, like that found in West Texas and in western states, there are very diverse micro-topographies and microclimates that make East Texas Forests diverse.

East Texas Forests mark the end or transition zone (what ecologists call an ecotone) of the great eastern, southern, and northern forests which abut up against other great ecosystems (ecosystems are large areas with all of their habitats) like the coastal prairie ecosystem, the black-land prairie ecosystem, and the oak savannah ecosystem.  An ecotone is a place of diversity, as different ecosystems inter-grade up against and into one another making a more diverse whole system.  Sort of like a “shifting mosaic” (patches of different habitats) on a landscape scale.

Some of the major East Texas Forest Ecosystems (also known as vegetational areas, forest formations, biomes, or life zones) are:

1) Oak – Pine Ecosystem
2) Oak – Hickory Ecosystem
3) Southern Pine – Hardwood Ecosystem
4) Oak – Gum – Cypress Ecosystem

These large ecosystems can be broken down into smaller ecosystems called associations, forest cover types, communities, and vegetation types.  These smaller ecosystems are named by the most prominent dominant tree species that exist in an area and the place this tree exists on the landscape.  For instance, we have American Beech – Southern Magnolia – Loblolly Pine Slope Association, Bald Cypress – Water Tupelo Bottomland Association, and Longleaf Pine – Bluejack Oak Upland Association.

Trees can grow over a wide range of elevations.  However, we can generally classify them by the topographic position where they are usually found.  In East Texas, due to the long growing season, high rainfall, and low elevation, even a few feet or inches height difference can determine what trees are found in a particular forest.  Topographic elevation varies from 0-500 feet (from the coast to the Oklahoma border) in East Texas.  The terms uplands, slopes, and bottomlands are used to denote where plant associations are in terms of topography.

Soil moisture is also a characteristic that determines where trees live.  A hydric soil (like that found in a floodplain) is wet or saturated; a xeric soil is dry (like a deep, sandy bank); and a mesic soil is intermediate between wet and dry (like that found in a terrace or slope just above a river floodplain).

Trees are often classified according to soil moisture differences.  For example, Southern Magnolia is a mesic (intermediate in soil moisture) tree species, a Bald Cypress is a hydric (wet) tree species, and a Shortleaf Pine is a xeric (dry) tree species.

Author: Brandt Mannchen