ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...

RED RIVER AREA
AREA ADJACENT TO THE RED RIVER
RED RIVER AREA/INTRODUCTION 127
There is a narrow band of vegetation, found on the primarily sandy soils adjacent to the
Red River (Fig. 74) in the northernmost portion of East Texas, specifically in the northern
parts of Bowie, Red River, Lamar, Fannin, and Grayson counties, that we are referring to
as the Red River Area. The specialized habitats associated with the Red River have afforded
plants sites where they could survive long-term changes in climate and have also provided
a two-way migration corridor allowing plant species to extend their ranges westward from
the forested areas to the east—and also eastward from the drier habitats to the west (Elisens
et al. 2004). This region is in various ways quite different from the vegetational areas with
which it has sometimes been included (see Fig. 3; Correll & Johnston 1970; Hatch et al.
1990). The westernmost part of this band, in Grayson County, has typically been classified
as part of the Cross Timbers and Prairies (vegetational area 5), and indeed it closely resembles
and grades into the East Cross Timbers. The eastern part of the band has often been
classified as part of vegetational area 3 (Post Oak Savannah) (Correll & Johnston 1970;
Hatch et al. 1990). Such a classification is justified, since portions of the vegetation do
resemble the post oak-dominated savannahs/woodlands typical of vegetational area 3.
However, significant components of the vegetation more typically associated with eastern
or southeastern Texas (vegetational area 1—Pineywoods) extend west along the Red River
in microhabitats with special soil or moisture conditions. In fact, many areas of northern
Lamar, Bowie, and Red River counties are clearly tied vegetationally to the Pineywoods—
a number are even dominated by pines. A specific example is the Pinus echinata-Quercus
alba forest documented for Lamar County by Wilson and Hacker (1986). This forest is
somewhat similar to the Dry-Mesic Mixed Pine-Hardwood Uplands described for the
Pineywoods by Van Kley (page 95). Based on such vegetational patterns, Wilson (1990)
has argued that the generally accepted boundaries of the Pineywoods in northeastern Texas
FIG.74/ PHOTOGRAPH OF THE RED RIVER FROM CARPENTER’S BLUFF BRIDGE IN NORTHEASTERN GRAYSON CO.(PHOTO BY GMD).