Vegetation of the longleaf pine region of the West Gulf Coastal Plain

Harcombe, Paul; Glitzenstein, J; Knox, R; Orzell, S; Bridges, E

For nearly 20 years we have been studying the Big Thicket of southeast Texas as an example of the vegetation of the western Gulf Coastal Plain. Most of this area is covered by closed forests which vary in structure and species composition along a soil texture gradient. Longleaf pine is a distinctive element, but it is dominant in only a few of the identifiable vegetation types in the region. New ordination analysis confirms western Gulf vegetation patterns and their relationship to soil texture. However, soil phosphorus and nitrogen availability, as well as moisture, may be important in explaining changes in forest composition and structure along the soil texture gradient. The strong relationship between vegetation and soil properties suggests that fire interacts with edaphic factors in influencing the landscape distribution and species composition of plant community types. Longleaf pine in the Big Thicket is dominant on level-to-gently rolling hilltops with sandy surface soils and on some low flat sides. It also occurs in upland stands with other pines, oaks, and hickories characteristic of dry, nutriend-poor sites. Frequently, understory vegetation is dense. It has been suggested that in the past many of these forests were open savannas with a longleaf pine canopy and a grassy groundcover. Stand history data from one oak-hickory-pine stand do indeed suggest that longleaf pine was more important prior to logging early in the century. However, these data also show that several species of oaks also occured frequently in the presettlement forest.

Vegetation of the longleaf pine region of the West Gulf Coastal Plain

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