The Future of the Longleaf Pine Savanna

A team of researchers from the Koerner Biodiversity Lab at the University of North Carolina at Greensboro is studying how increasing drought conditions could impact the longleaf pine (LLP) ecosystem. The lab, run by Dr. Sally Koerner, has set up 30 plots to test drought and nutrient enrichment conditions. Their data will help researchers predict how plants and insects in the LLP savanna will react to climate change.

Scorched Earth: Entering the Savanna

If it wasn’t for the humidity, you could have told me this was the road to Lake Tahoe. Young pines spread further than the eye could see, and yet, these woods stood unencumbered by the usual overgrowth that characterizes much of the Old North State.

I was driving down a primitive road in the sandhills of North Carolina with undergraduate field researcher Page Turner. Together, we were trekking into a longleaf pine savanna to rendezvous with her team at their test site.

On my right, a dense cover of wiregrass, pine needles, and flowering vegetation (“forbs,” as the team affectionately referred to them) blanketed the ground.

“You’ll see these shrubby-looking trees called turkey oak,” Turner gestured out the passenger window. “[They’re] not really invasive, but [they’ll] take over the understory and shade-out a lot of the grasses that make the longleaf pine savanna what it is.”

As we neared the site, Page explained how prescribed burns keep these species in check. On our left, a more foreboding stand of pines loomed, their bases blackened by a controlled burn the NC Wildlife Resources Commission had coordinated three days prior. Ironically, this ecosystem was the picture of health; already, wiregrass and longleaf pine sprouts were beginning to repopulate the ashen understory.

The tuft-like sprout of the longleaf pine is reminiscent of a jellyfish’s polyp. Although the shoots appear brown and dried-out, these fledgling trees are well-adapted to periodic burns.

Once at the site, I followed Page through the tree line. Columns of smoke dotted the savanna, scattered throughout like tiny chimneys. The endangered, stern-faced gopher tortoise is native to this ecosystem; it wouldn’t be hard to imagine that these pillars of smoke belonged to a bale of these somber reptiles, all huddled around an underground hearth. Page directed my attention to one such chimney, burning amid the debris of a fallen pine.

The impact from the fall had cleft the tree in two. The split ends burned apart, and the ashy chasm widened as the two pieces grew smaller. As we approached, Page showed me where the fire had incinerated the root system, leaving behind a network of tunnels. The roots of a pine tree can burn for days, and they likely accounted for some of the small fires we saw around us.

Page Turner stands in front of a fallen pine. The flames persisted three days after the prescribed burn that brought it down.

These trees have been marked with parallel white bands to identify them as endangered red-cockaded woodpecker habitats and are consequently protected. These birds play a vital role in their ecosystem, creating cavities used by many other species.

In an unburned section of the savanna, the flower of the prickly pear cactus prepares to bloom.

The Drought and Nutrient Network

Page and I exited the stand of trees and rejoined the team. As we unloaded the shelters’ metal frames, I had a chance to speak with team lead and Ph.D. candidate Alyssa Young and undergraduate researcher William Mann about the project. All members of the team are students at the University of North Carolina at Greensboro, studying ecology.

“It’s a long-term experiment. We’re looking to see how the plant community changes over time,” Young explained. “We also add nutrients, so we’re releasing the plant community from nutrient limitations.”

“The nutrients in the environment limit what is able to grow there,” Mann chimed in. “So, if you allow more nutrients to get into that environment, what else can grow? And would that have a negative effect on the environment?”

This experiment conducted by the Greensboro team is part of a global experiment called NPKDNet, a combination of the Drought-Network and Nutrient-Network. Sites across the world are collaborating to gather data on the effects of drought and nutrient enrichment. These drought shelters were meticulously constructed by Alyssa offsite before being disassembled and transported an hour-and-a-half away to the research site.

A deconstructed drought shelter.

The field team (From left to right: Page Turner, Alyssa Young, and William Terrence Mann Jr.)

“It’s excluding 30 percent of all the rainfall,” Young walked me through the mechanics of the drought shelter. The plastic slats siphon off rainfall before water can touch the plot. Water runs down the slats, into the PVC gutters, and through the drainage pipe, effectively reverse-irrigating the area underneath the shelter.

What does Young and her team hope to learn from studying these plots? I asked Will Mann for an explanation:

“Weather, in general, has been very extreme because of the increased amount of heat and energy in the atmosphere. That also pertains to drought and desertification: Droughts are lasting much longer than they have in previous years because of climate change.

“With more droughts comes a potential for loss of vegetation […] and fauna — especially in environments where droughts aren’t as common but will become more common.”

Studying these plots will allow Alyssa and her team to make predictions about how the LLP savanna, in particular, will react to a warming climate. By analyzing the insect and plant communities and productivity, the Koerner lab can predict how the savanna will respond to global warming and prevent further habitat loss.

“There are about 29 endemic species of animal that would cease to exist without this habitat,” Turned explained. “With less than 3% of the original 92 million acres of longleaf pine savanna remaining, the team serves an important role in conserving the last of this threatened habitat that ‘built the South.’”

The resilient savanna: Just three days after the burn, wiregrass shoots have sprouted from the ashes. Alyssa pointed out that the thin, wiry structure of wiregrass, coupled with its uniform spread across the savanna, helps the fire burn efficiently and evenly across the understory.