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Surface Fire

Longleaf Pine Ecology and Restoration at Riza Nature Preserve, Florida

By Henry Lee Morgenstern

During the 1990s, the State of Florida made a concerted effort to buy up natural areas surrounding and feeding the state’s major lakes and rivers, to help protect groundwater supplies and water quality. One of those areas is now known as the Lake George Wildlife Management Area (LGWMA), covering 60 square miles along the east side of Lake George and the St. John’s River in north-central Florida. On the west side of Lake George is Ocala National Forest, an even larger expanse supporting several threatened ecosystems and one of the few remaining concentrations of black bears in the state. The Lake George area has the second largest population of bald eagles in the lower 48 states. It is part of a major regional wildlife corridor linking the headwaters of the St. Johns River near Melbourne, Florida, with the Okefenokee Swamp in southeast Georgia.

Nestled in the LGWMA is Riza Nature Preserve, a private little forest retreat I purchased in 2005. Although only 30 acres in size, it houses or borders on 5 different ecosystems, with a stream running diagonally into a cypress swamp feeding Lake George. The LGWMA land surrounding Riza is mostly old pine plantations bought by the state, now managed by the county. When this LGWMA land was purchased, it was covered with rows of closely spaced slash pines, which the timber company had planted for wood and pulp. Such thickly planted pine plantations shade out the understory, cover the ground with pine needles that restrict ground cover, and in general offer limited habitat value or wildlife diversity. Over the past 20 years, county land managers have been slowly harvesting and selling off the excess timber in a series of “thinnings,” leaving more widely spaced pines, to promote the re-establishment of historic groundcover, wildlife habitat, and ecosystem values.

Riza was not bought by the state. When I acquired it in 2005, it had been left unmanaged for decades, used, presumably, as a hunting retreat for timber managers. About 50 large remnant Longleaf pines (LLPs), and many large slash pines remained mainly along the perimeter and stream corridor. They were choked by the same mass of oaks, sand pines (a dense, fast-growing, short-lived pine), and impassible understory of native vines, saw palmetto, rotting logs, and woody shrubs that covered the rest of the property. I knew from my studies that Florida had historically been mostly pine forests, kept healthy by regular wildfires. The dense understory was a clear sign that no fires had been through here in a long time. But what was the land historically? And how should I best manage it for healthy ecosystems and wildlife habitat?

To get an answer, I called on the Florida Land Stewardship program. They sent a team of biologists and foresters from the Florida Forest Service and the Florida Fish and Wildlife Conservation Commission to walk the property, take soil and plant samples, and draft a proposed management plan. The fact that there were 100-year-old Longleaf pines on the land, but no younger recruits, told them that this had been historic Longleaf pine habitat.

LLP historic range

LLP historic range

The US Forest Service calls LLP ecosystems “among the most species-rich ecosystems outside the tropics.” When the Europeans came, LLPs were the dominant tree from Texas to Virginia to Florida. They covered wet areas, dry areas, even rocky mountainsides. Today, 97% of those forests have been lost, and of the 3% that remain, most are no longer fully functioning ecosystems. The great biological diversity of plants and animals that depended on them has declined along with the loss of the forest, to the point where pretty much any species that historically depended on the LLP ecosystem is now endangered or threatened.

Healthy LLP Forest

Healthy Ancient LLP Forest

Healthy LLP forests have no mid-story of woody small trees and bushes shading the ground, only large trees and a grassy groundcover. The groundcover is important for several reasons, a primary one being to supply food for the gopher tortoise. Gopher tortoise burrows provide habitat for many other species, like the endangered indigo snake. Other now-endangered species dependent on the LLP ecosystem are the Sherman fox squirrel, Brown-headed nuthatch, Great-crested flycatcher, and Red-cockaded woodpecker.

In 1800, the eastern U.S. was covered with Longleaf pines 3-4 feet in diameter and up to 150 feet tall. So, why are 97% of the LLP forests gone? The easy answer is that, because they were tall and straight and strong and rot resistant with a clear grain, and therefore highly desired for ships and houses, by 1920 most of the eastern U.S. LLPs had been cut down for lumber. But that would not be the best answer to why we only have 3% remaining today. In addition to logging, many of those original forest lands have been converted to farms or cities or highways. But vast areas of former LLPs, way more than 3%, are still woodlands today. Why didn’t the LLP forests just grow back?

Historic logging

Historic logging

The better answer to why only 3% of Longleaf pine ecosystems remain today can be stated in one word: FIRE. During the 20,000 years between the end of the last ice age in North America until Europeans arrived, when LLP ecosystems were taking over the southeast US, the entire area was subject to frequent forest fires, both from lightning, and after Native Americans got here, from natives starting fires to keep the understory open for hunting and travel. Forest fires occurred just about everywhere, about every 1-5 years. The tree that was most successful in using and benefiting from this regular fire was the Longleaf pine.

LLP is so dependent upon fire, that its range was determined by where wildfires could reach. Wetlands, river valleys, rocky mountain streams, anywhere protected from fire, were where the oaks and maples and yellow poplars and hickory and all the other famous hardwoods were. Even the common pines we mostly see today, like slash pine and loblolly pine, historically were only in wetter areas, and are only widespread today because that is what the timber companies replanted after clearcutting the LLPs—because they could be harvested faster than LLPs.

In short, where there was fire, there was Longleaf. And where you stop regular fires, the LLP disappear. To understand the importance of fire to LLP regeneration, we can look at the life cycle of the LLP.

Longleaf pines have male and female pine cones on the same tree. The males spread pollen through the air, which fertilize the seeds which are inside the female cones. The cones you see on the ground have already opened and disbursed their seeds from far up in the canopy to flutter down in the wind. After falling from the tree in the fall, the seeds need exposed soil and sun to germinate.

Longleaf Pine Stages of Growth

The seeds that are lucky enough to find some sunny soil, can then establish themselves into what is called the “grass stage.” They stay in the grass stage for 1 to 7 years, depending on how much rain and sun they get. During this time they are busy putting down an extensive root system, including a central taproot. Once established, the growing bud of the grass stage is below the ground and resistant to ground fires.

LLP Grass stage

LLP Grass Stage

The seedlings stay in the grass stage until they get enough water and sun and time to have good roots and see the sky. This can be one year, or in some cases they can sit around in the grass stage for up to 20 years waiting for enough rain and sun. But usually in about 2-5 years, one spring they start shooting (or “bolting”) into what is called the rocket, or bottle-brush stage, sometimes growing 2-4 feet that summer. At this point the young tree is vulnerable to fire, but once the top growing bud is above fire level—and particularly after the base is over 2″ diameter and bark is established—it becomes increasingly resistant to low ground fires.

At about 6-10 feet tall, side branches start, and the fast-growing “sapling stage” begins. At 30 feet or 10 inches in diameter—perhaps 15 or 20 years—it becomes a mature tree, producing cones. It will increase in height for about 100 years to about 100 feet tall and then grow more slowly for up to 500 years, reaching its maximum size of 3-4 feet across and up to 150 feet tall.

Mature LLP

Mature LLP

The Importance of Fire

In a healthy Longleaf pine forest, regular fires clear out the woody brush between the trees, and only the LLPs and ground cover remain. The fires run through the ground cover, never reaching the branches of the trees. Notice how ingeniously fire fits the LLP life cycle. The fire opens up bare soil and fertilizes it with ashes to allow seeds to germinate; it burns off all the competition while the LLP grass stage survives; the rocket stage quickly leaps above low ground fire level; and after that the bark is fire resistant. So the LLPs thrive while all the competing sprouts of other species are cleared out every few years by fire. That’s why, where there was fire, there was Longleaf pine.

When fire is suppressed—as happened at Riza—the open understory so necessary for LLP regeneration fills with hardwoods and brush. The ground cover is shaded out, no new LLPs sprout, and eventually vegetation grows into the type of dense oak and hardwood forests we now see throughout the Southeast.

Those hardwood forests can look beautiful, and have their place in wetlands and other areas protected from fire. But for the plants and animals of the Longleaf pine ecosystem, they are a disaster. There’s no grassy groundcover for gopher tortoise to eat, no tortoise burrows for indigo snakes to breed in, no open spaces for LLP seedlings to germinate or for deer or fox squirrel to walk and browse through, no 100-year old heartwood for red-cockaded woodpeckers to make their cavity nests in, and no needles or wire grass on the forest floor to carry fires if lightning strikes.

And if you DO get a fire there, instead of a nice, low, cool, safe surface fire, the thick fuel load creates the giant hot forest fires that kill everything in their path, including old, established LLPs. Wetlands that would have stopped a low ground fire are overcome, and even hardwood forests are incinerated.

Forest fire

Forest Fire

The reason that even old, established pines die in fire-suppressed forests is because a “duff layer” has built up. The duff layer is years of unburned pine needles compacted around the base of the tree, which surface feeder roots grow into. When a hot fire burns the duff layer, it burns these surface roots, which kills the tree.

So, now we can answer why there are only 3% of the original LLP forests. Some were converted to farms and towns and roads. But in the majority of the original range, which was still rural forest lands and public forests, two things happened: First, after clearcutting, timber companies replanted slash pine and loblolly and other pines instead of LLP, so there was no LLP re-seeding. Second, fire was suppressed. The oaks and other woody plants invaded and grew so that, even if there were many LLPs left, they couldn’t seed, and built up a duff layer; thus when a fire did eventually come, it killed even the largest of them. That’s what happened out West, and why even the western states are now talking about encouraging more frequent smaller forest fires, so that the fuel load does not build up to where a fire will destroy everything. If there is one thing we should learn from this history, it is that forest fires are our friend, not our enemy, and the more frequent the better. Smoky the Bear, and his message of suppressing forest fires, needs to be retired from the public consciousness.

Restoration

Riza Nature Preserve stands out from the surrounding pine forests in that it has several native ecosystems, and was never cleared or planted, so a native seed bank remained hibernating in the soil. There are no invasive exotic species, only native plants. To the west of the stream are poorly drained (means clay soils where water stands after a rain) pine flatwoods with a Tupelo swamp. To the east of the stream, the land rises to a plateau of sandy (well-drained, dries quickly after a rain) “scrubby flatwoods,” each with its own retinue of plants. And along the stream is a wetter “riverine corridor” with tall healthy hardwoods.

To restore Longleaf pine habitat to any farmed or fire-suppressed area like my flatwoods, three steps are needed: First, eliminate any woody understory (and non-native pasture grasses, if it was used for cattle, which Riza fortunately was not). Second, restore the groundcover. And third, replant the trees. It took 8 years of burning, roller-chopping, and—where thick oaks or sand pines re-sprouted—herbiciding, to knock back the brush enough for LLP to be planted without fear of being shaded out before they could reach their bolting stage. Because the area had never been plowed, native grasses came back naturally once the overstory was gone. Gopher tortoises re-populated, migrating from the surrounding pine forests.

gopher tortoise

Gopher tortoise

In 2013-14, 3,000 LLP seedlings (“plugs”) were planted at Riza, one at a time by hand, using a tool called a “dibble” to make the pilot holes. For the next 3-5 years, shrubs were kept cleared from shading the grass stage seedlings until they could bolt. Now, in 2021, bolting is in full swing. We continue to keep the brush down, so that the LLPs can get tall enough to be above a fire. In a couple of years, we can start a regular rotation of burning every few years, and watch the ecosystem return.

Conclusion

In the 1700s, in the forests of the eastern United States, hundreds of hunters would assemble at dawn in a giant circle, 30 miles across, for what they called a “circle hunt.” As the light rose, they marched toward the center, killing everything that moved.

In one “circle hunt” in Pennsylvania in 1760, the count of dead was 41 cougars, 109 wolves, 112 foxes, 114 bobcats, 18 bears, 2 elk, 98 deer, 111 bison, 1 otter, 12 wolverines, 3 beavers, and 500 smaller animals, not counting birds.

14,000 years ago, the number of mammal species in North America larger than 100 pounds is estimated by the American Museum of Natural History at about 50 species, and there were millions of them. Humans came, and within just a few hundred years, all but a dozen species were hunted to extinction. Some that we lost included the Woolly Mammoth, Giant Ground Sloths, Armadillos, and Beavers as big as Volkswagons, as well as American horses, camels, and lions.

Even our most majestic national forests are bare remnants of the Serengeti that was America before humans entered the picture 13,000 years ago. Restoration of Longleaf pine ecosystems in the Southeast is the least we can do to atone for that somber legacy.

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