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

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

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FIG.7/WIFS (WIDE FIELD SENSOR) SATELLITE IMAGE <strong>OF</strong> <strong>TEXAS</strong>.IMAGERY COURTESY <strong>OF</strong> SPACE IMAGING.<br />

GEOGRAPHIC AREA <strong>OF</strong> <strong>EAST</strong> <strong>TEXAS</strong>/INTRODUCTION 9<br />

Likewise, there are now widespread areas of cedar brakes (Juniperus spp.) and other thickets that<br />

have developed after fire suppression was imposed.The square miles/kilometers considered to be<br />

in each of the three major vegetational areas, the Pineywoods (24,400 square miles/63,200 square<br />

kilometers), the Post Oak Savannah including the Red River Area (20,600 square miles/53,400<br />

square kilometers), and the Blackland Prairie (17,600 square miles/45,600 square kilometers) were<br />

calculated using detailed map data from Glenn Griffith (pers. comm.; see also Fig. 5).<br />

Some correspondence to the vegetational areas outlined here can even be seen in modern<br />

satellite maps (Fig. 7). For example, a band corresponding to the Blackland Prairie can approximately<br />

be recognized.<br />

In virtually any geographic region, the “typical” habitat is modified by microclimates and<br />

migration corridors provided by major rivers (Figs. 8, 9), any unusual levels of precipitation, and<br />

any specialized geologic features. These modifiers allow the occurrence of species not otherwise<br />

typical of that particular region. While these species may be neither abundant nor widespread, they<br />

are important biogeographically, in some cases providing important information about the botanical<br />

history of an area. If the occurrence of such a species is at the margin of its range, it may serve<br />

as an ecological indicator, possibly providing information in the future on important issues such as<br />

climate change or habitat alteration. The East Texas flora has many such examples. Numerous predominantly<br />

eastern species are limited in East Texas to the very eastern portion of the Pineywoods<br />

where precipitation levels average nearly 60 inches (152.4 cm) per year. In some cases plants are<br />

confined to only one or two counties (e.g., Jasper and Newton). An analogous situation occurs

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