Post Oak decline can be reversed

Tyler—A good portion of Smith County (including the city of Tyler) falls withing the Post Oak Savanna ecoregion. My childhood home in Longview was also surrounded by post oaks as is my farm in rural Shelby County. This ecoregion is in decline, however. The decline of the Post Oak Savanna is one of the greatest yet least recognized conservation stories in Texas. As I prepare for an SFA Gardens lecture on the topic, I've been reflecting on just how much this unique ecosystem has changed during my lifetime.

The Post Oak Savanna once formed a broad transition zone stretching across east-central Texas between the Blackland Prairie to the west and the Pineywoods to the east. It was neither prairie nor forest, but rather a rich mosaic of native grasses, wildflowers, scattered post oaks, blackjack oaks, shrub thickets, wetlands, and small woodlands.

The ecosystem evolved over thousands of years through the combined influences of fire, grazing by large native animals, drought, and climate. Frequent fires, both natural and intentionally set by Native Americans, maintained open grasslands dotted with widely spaced trees. These savannas supported an incredible diversity of plants and wildlife, from little bluestem and Indiangrass to meadowlarks, quail, turkey, pollinators, and countless other species. Today, much of that landscape has vanished.

The decline did not happen overnight. Instead, it resulted from generations of land use changes. Fire suppression allowed woody vegetation to thicken and shade out native grasses and wildflowers. Overgrazing, land clearing, urban expansion, road construction, and the conversion of native habitat to improved pasture further altered the landscape. In many areas, invasive exotics gained a foothold as native plant communities weakened.

Ironically, even the iconic post oak (Quercus stellata) itself has been struggling. Mature post oaks are increasingly affected by soil compaction, root disturbance, climate extremes, construction activities, and old age. Across East Texas, many residents have noticed once-vigorous trees gradually declining or dying. While insects and diseases are often blamed, these are frequently secondary problems that attack trees already stressed by environmental conditions. The lack of seedling tree regeneration is compounding the problem.

What makes this loss particularly troubling is that we are not simply losing trees. We are losing an entire ecosystem and the biological diversity that comes with it. Native grasslands and savannas are among the most endangered habitats in North America. As these systems disappear, so do the wildlife species and native plants that depend on them.

The good news is that restoration is possible. Landowners can protect remaining native habitat, reintroduce prescribed fire where appropriate, manage invasive species, limit disturbance, and plant native grasses and wildflowers. Even homeowners can contribute by preserving mature trees, reducing soil compaction around roots, limiting irrigation, and incorporating native plants into their landscapes.

Conservation begins with appreciation. Many Texans drive through the remnants of the Post Oak Savanna every day without realizing they are seeing one of the state's distinctive ecological regions. Understanding its history helps us recognize what has been lost and what can still be saved.

The Post Oak Savanna may never fully return to its former extent, but with thoughtful stewardship, future generations can still experience fragments of the diverse landscape that once connected the Pineywoods and prairies.

If you’d like to hear more about this subject, attend my free SFA Gardens lecture “Postmortem: The Decline of Post Oaks and an Entire Ecosystem” August 13, 7-8 pm at the Pineywoods Native Plant Center in Nacogdoches. For more information see the SFA Gardens Facebook page, call (936) 468-4129, or email sfagardens@sfasu.edu.

Greg Grant, Ph.D., is the Smith County horticulturist and Master Gardener coordinator for the Texas A&M AgriLife Extension Service in Tyler.