ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...
ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...
ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...
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172 INTRODUCTION/SUMMARY DEFINITION <strong>OF</strong> BIG THICKET<br />
The Big Thicket thus represents a biological boundary and is therefore important for a<br />
variety of reasons. For one thing, populations at the extreme margin of a species’ range are<br />
often unique genetically and represent an irreplaceable genetic resource. Second, peripheral<br />
populations are often more sensitive to environmental change and can act as ecological indicators,<br />
serving as an early warning system against changes that may possibly have broader<br />
implications. In the modern world, with humans having the capacity to influence global<br />
climatic processes, such indicators may be vital. From the Texas perspective, the Big Thicket<br />
is important because it represents a unique area within the state—it is only in this relatively<br />
small corner of Texas that numerous plant communities and hundreds of species can be<br />
found. From a slightly broader perspective, the Big Thicket is valuable since it contains one<br />
of the only relatively large protected areas in the entire West Gulf Coastal Plain, an important<br />
regional center of endemism (MacRoberts et al. 2002c). As such, it is critical in protecting<br />
representative samples of numerous unique West Gulf Coastal Plain plant communities and<br />
species. Exemplifying this importance is the fact that two areas within the Big Thicket<br />
(Longleaf Ridge and the Big Thicket-Sandylands Complex) are among the top ten richest conservation<br />
areas in the West Gulf Coastal Plain ecoregion, with Longleaf Ridge considered to<br />
be the richest (Nature Conservancy 2003).<br />
The Big Thicket is also unique within Texas from the standpoint of ecosystem services.<br />
Given its position just north of one of the largest population centers in the state, the role<br />
of the Big Thicket in terms of hydrology (flood control, water purification, etc.) and other<br />
ecosystem services makes it uniquely important to Texas, not only ecologically, but economically<br />
as well.<br />
SUMMARY DEFINITION <strong>OF</strong> THE BIG THICKET<br />
Based on all of the preceding material, how then can one define the Big Thicket? While linked<br />
with the West Gulf Coastal Plain and the rest of the southeastern U.S., we suggest that several<br />
highly interrelated factors when combined can give a reasonable way of defining and delineating<br />
the Big Thicket:<br />
■ Ecological definition of the area as a loblolly pine-white oak-beech-magnolia forest, with a rich<br />
understory of evergreen and deciduous shrubs, numerous climbing vines, and varied herbs, plus<br />
included vegetation types (e.g., xeric sandylands, baygalls, etc.).<br />
■ Biological boundary as the southwestern extreme of the Southeastern Mixed Forest and Outer<br />
Coastal Plain Mixed Forest provinces.<br />
■ Humid subtropical climate—Mild temperatures and high, rather evenly distributed rainfall—<br />
approximately 48 to nearly 60 inches (122 to 152 cm) per year.<br />
■ Geological, hydrological, and edaphic complexity.<br />
■ High levels of habitat diversity and species richness.<br />
In concise terms, the Big Thicket is thus the biological boundary area at the southwestern<br />
extreme of the southeastern U.S., humid subtropical in climate, geologically and hydrologically<br />
complex, rich in species, and characterized by a loblolly pine-white oak-beech-magnolia forest with<br />
many associated and often very distinct vegetation types.<br />
While the Big Thicket is a meaningful and useful concept, its exact boundaries will continue<br />
to be imprecise. Individual species have ranges that can be determined with precision, but<br />
the ranges of different species rarely correspond. As a result, vegetational areas usually cannot<br />
be clearly delimited. Ultimately, it is clear that virtually any vegetational area is a human<br />
concept without precise boundaries. However, an artificial delineation of the Big Thicket,<br />
such as the one presented here (page 167; also see Fig. 94), can provide a practical approximation.<br />
This imprecision does not make the region any less interesting, valuable, or worthy<br />
of conservation. The Big Thicket by any definition is a rich and unique part of Texas and<br />
North America, and one which warrants long-term protection and preservation.