Tag Archives: prescribed burn

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The Historical Database Known as Trees (and a new video)

Rob Diaz de Villegas WFSU-TV

IGOR chip- human appreciation 150I like the idea of hiking cross country, unimpeded, for miles at a time.  Trails are great- and usually safer- but the idea that you can have space to literally walk off the beaten path is appealing.  A couple of hundred years ago, you could travel across the entire southeastern coastal plain in this manner.  This was a road paved by fire.  On this blog, we’ve covered how fire creates the pine flatwoods ecosystem with its widely spaced trees, and how and why mankind has had to replicate a process that had happened naturally.  But how do we know how often to burn, and at what time of year?  It would be convenient if we could ask someone who was around before the area was settled.  As it turns out, we can.

Trees have the answers in their rings.  We get a glimpse of this towards the end of the video above, but I wanted to take a closer look at how Dr. Jean Huffman was able to interpret the data locked within trees.

The photo to the right is a detail of a longleaf pine stump cross-section.  In it you can see that the rings alternate in shading between light and dark.  The light wood is early wood.  This is from the beginning of the growing season, typically spring, when a tree usually grows the fastest.  The growth in the summer and fall is darker, and is called late wood.  Winter is the dormant season.  So one light and one dark ring equal one year of growth for the tree.  You may also notice that some rings are wider than others.  Wide rings indicate a higher rainfall, and especially narrow rings indicate drought.  Knowing this, we can start building a master chronology.

A master chronology is made by comparing the relative width of rings in a series of trees. In this way rings in each tree can be dated exactly, even if there are occasional missing rings or false rings in an individual tree. The master chronology can be used to exactly date the rings in individual stumps.  Since longleaf pine is such a long-lived species, there is potentially hundreds of years’ worth of climatological data in its rings.  When you have data for many trees, you can build a reliable chronology that goes back before people started keeping records.  This is a dendrochronology (dendro= tree, chronology= matching events to specific dates based on historical records).

fire scarFinally, you match years in your chronology to fire scars (that’s a scar to the left).  Longleaf pine are a fire resistant species, and it takes a lot to kill the cambium and create a scar.  Because of this, Jean only created fire histories for periods when she had at least three “recorder” trees- enough to establish a pattern.

She determined that there were frequent fires in the area- every one to three years.  That’s enough to keep oak and other woody plants from encroaching on ground cover plants, including the many rare plants of the SJB State Buffer Preserve.  It was strange to just trample over the grass and palmettos in the managed area, and all of the gems potentially hidden underneath them.  It doesn’t exactly adhere to the “Leave no Trace” ethos.  But the reality is that all of it will burn and go away, and then grow back again, and again, and again…

The video features music by Pitx and Airtone.  Thanks to Dr. Jean Huffman for reviewing my text for accuracy.
Next on EcoAdventures North Florida, we’re going to a place where large chunks of land get swallowed up by the earth, and where a river goes underground.  Of course we mean Aucilla Sinks (Wednesday April 11 at 7:30 PM/ ET on WFSU-TV’s dimensions).

Why We Burn- Restoring the Longleaf Pine Ecosystem

Rob Diaz de Villegas WFSU-TV
The longleaf pine/ wiregrass ecosystem was historically common in the coastal plain (low lying flat areas adjacent to the coast) of the Southeast United States.  According to the U.S. Fish & Wildlife Service, this ecosystem has seen a 97% decline.  In our recent excursion along the Apalachicola River, we visited this habitat and learned about efforts to restore it.

IGOR chip- habitat 150

There’s a certain terminology we use when we talk about the wild places of the world. We use words like “pristine,” or “untouched.”  When you hike through a forest along the Florida Trail, there are times where you can imagine that you are the first person ever to walk under the trees that you see.  Of course, much of the time, not only are you not the first person to have seen the trees, the trees look the way they do due to someone’s careful manipulation.  The practice of land management and why it is used can change the way you think about what is “wild.”

Prescribed burn. Courtesy of Florida Fish & Wildlife Conservation Commission.

The video above is about how the Florida Fish and Wildlife Conservation Commission is using prescribed burning in its restoration of longleaf pine habitats.  Longleaf pine had historically thrived because they have the evolutionary advantage of a thick, fireproof bark in what are known as Fire Climax Communities.  This is a habitat in which fire (typically started by lightning strikes) is the primary controlling factor, and so lesser equipped competitors to longleaf pine are eliminated.  This natural process makes for an ecosystem dominated by the thick barked pines.  So why are humans assuming a role usually played by nature?

That goes back to our conception of what is “wild.”  That forest you hike through looks untouched, like I said earlier, but human influence reaches even into its deepest reaches.  For one, we have roads cutting across the forests, and while there are often large expanses of unbroken forest, paved roads keep fire from spreading as far as it once might have.  Another factor is that there is human settlement all around the forest, and uncontrolled fire is a threat to life and property.

Courtesy of the Florida Archive.

Prescribed fire is one tool in the toolset for restoring the longleaf/ wiregrass system.  This was the dominant habitat of the southeast, characterized by a wide spacing of trees (wide enough to ride a wagon through, FWC’s Liz Sparks tells me) that allows for a diversity of ground cover plants.  These cover plants, as Matt points out in the video above, are attractive to the many species that thrive in a longleaf/ wiregrass ecosystem. Ironically, this ecosystem has been drastically reduced as a result of another type of land management- silviculture. As you’ll see in the video above, timber operations replaced longleaf  for slash pine, a faster growing variety of pine with a lesser quality wood but that is far more profitable to grow. The slash pine grew closer together, eliminating the ground cover that is so important to the many birds, reptiles, and amphibians that make the longleaf/ wiregrass system so diverse. That’s why FWC does timber thinning before the burns.

Marsh burn. Courtesy Florida Fish & Wildlife Conservation Commission.

And since this is In the Grass, On the Reef, I did want to mention something I left out of the video, which is marsh burns.  Every 4-6 years, they burn the sawgrass in the freshwater marshes on the Apalachicola River system.  This clears the plants out and allows for new growth; the less dense grass provides nesting cover for many birds.  Wintering waterfowl like canvasback, scaup, and redhead eat submerged vegetation called widgeon grass; periodic burns increase access to this for birds.  As with longleaf ecosystems, fire was a naturally occurring, controlling factor.  The systems evolved with the plants and animals that could best take advantage of these fire events.  Nature may not be able to provide fire to these systems as effectively as it once had; luckily, mankind has flame throwers and ping pong balls full of potassium permanganate.

For more information about these and other Florida Fish and Wildlife land management initiatives, visit their web site.

Watch our latest EcoAdventure, where we visit a lot of this managed land around the Apalachicola River on WFSU’s dimensions- Sunday, February 19 at 10:00 AM/ ET.

Good Fire- watch now!

Watch Good Fire on PBS. See more from WFSU Documentary.

This WFSU documentary, which aired November 30, 2011, takes an in depth look at prescribed burning and its safety and ecological benefits. The video is running off of WFSU-TV’s video on demand site, which features PBS programs like NOVA and Nature as well as local programs, like In the Grass, On the Reef and Florida War Diaries, a look at our local involvement in WWII.