Composition, Structure, and Developmental Determinants of a Scrub Oak Forest in the West Cross Timbers of North Central Texas

We evaluated composition and community determinative factors of an old-growth, scrub forest on a deep-sand habitat in the West Cross Timbers of north-central Texas. Species composition and vegetation structure were analyzed based on 1) dominance, density, and importance values of woody plants and 2) foliar cover of herbaceous species and woody seedlings or offshoots in the understory. We concluded that this was the potential natural vegetation for this deep-sand site with the sandy soil being the principal determining factor in development and stability of this natural community (i.e., an edaphic climax). We designated this as a sand post oak-saw greenbrier ( Quercus margarettiae - Smilax bona-nox ) community based on the dominant tree and shrub species. The scrub forest consisted of three layers: 1) a closed canopy of sand post oak and blackjack oak ( Q. marilandica ); 2) a shrub layer of six species, including saw greenbrier, a liana that extended into the tree canopy; and 3) an irregular understory of herbaceous plants plus seedlings and clonal shoots of oaks and greenbrier. Herbaceous plants were all native species and included six species of grasses, two of grasslike plants, and five of forbs.