Rarity of oak saplings in savannas and woodlands of the Eastern Edwards Plateau, Texas
Russell, F. Leland
Fowler, Norma L.
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Anecdotal evidence suggests that Quercus fusiformis and Quercus buckleyi, two dominant trees of central Texas savannas and woodlands, are not recruiting to adult size classes on the eastern Edwards Plateau. To evaluate this hypothesis, size distributions of Quercus fusiformis and Quercus buckleyi populations are described. In the majority of savannas and live oak/juniper stands surveyed, Quercus fusiformis saplings and sapling-sized root sprouts (40 cm tall to 5 cm dbh) and small adults (5 to 15 cm dbh) were rarer than mid-sized adults (15 to 25 cm dbh) suggesting that adult recruitment of this species is below replacement rate at most sites. Quercus buckleyi saplings were much rarer than small adults in all mixed woodlands surveyed, suggesting that adult recruitment of this species from seed is not occurring on the eastern Edwards Plateau. Seedlings of Quercus buckleyi and seedlings and seedling-sized root sprouts of Quercus fusiformis (0 to 40 cm tall) frequently were abundant, suggesting that high seedling mortality rates may contribute greatly to poor adult recruitment. Intense browsing pressure by white-tailed deer may be the primary cause of poor adult recruitment of both species. It is unlikely that episodic adult recruitment will maintain populations of either Quercus fusiformis or Quercus buckleyi, as a reduction in seedling mortality rates over many years would be necessary to allow the slow-growing seedlings to escape their vulnerability to browsing herbivores.
- F. Leland Russell