American Holly

American Holly
American Holly

Tuesday, April 1, 2014

Born to Burn

Ecosystems are built around climax species.  In arid lands, these might be grasses, but in wetter areas, the climax vegetation is usually deciduous trees. But there are many ecosystems that exist between grasses and a decisuous forest.  Here at Okefenokee National Wildlife Refuge, one of our ecosystems is a longleaf pine ecosystem  made up of mostly pine trees with a saw palmetto, saw grass,  and shrub understory.  It is called a fire climax community because it has to have frequent fires to maintain itself. 

This system is made up of plants and animals that have developed to live and do well through fires. Some species must have fire to regenerate and the others depend on fire to keep down competing species. The climax species of this ecosystem is the longleaf pine. This a a long-lived pine, living 3-400 years if left to die naturally.

I found this controlled burn with one little hot spot a few days after the main burn a day after I arrived at Okefenokee NWR

The long leaf pine ecosystem once stretched from the coastal plains of Florida to East Texas and comprised some 90 million acres. Today, we have lost 97 percent of that  ecosystem and only have about 2 million acres in scattered blocks.  About half of this is on public lands.

This tree is dear to my heart because, as a young teenager, I moved into an area of Louisiana that had these trees and fell in love with them.  And I have worked to save this ecosystem and it's some 30 plants and animals associated with it that are threatened or endangered, including the star bird, the red-cockaded woodpecker. 

The longleaf pine can't grow in areas that have a lot of dead materials on the ground because the seed can't make good contact with the earth.  Frequent fires keep the undecayed organic material low so seeds can get their start. It also keeps shrubs from overgrowing the young trees and shading them out. 

The seedling comes up as just a bunch of needles.  This stage is called the grass stage and lasts a few years. Nothing much happens above ground, but below the ground, the tree is making an extensive taproot system. If a fire burns across a tree in the grass stage, it may lose its needles but keeps on living and just replaces them. 



Then the tree shoots up 2- 3 or more feet in the next year.  Trees that have only a stem and a top knot of needles are often said to be in the candlestick stage.  They are not resistant to fire in this stage but can usually reach eight or more feet in just three years, after which time, they start to develop a bark thick enough to again make them fire resistant.  They hold their needles, who burn very easily, high above most ground fires. 


A tree that has probably been in the candlestick stage for a year

After eight years, the tree continues to develop thicker and thicker bark which can just flake off if it catches on fire. And even if the outer part of the bark burns, the tree will survive. 


Bark of a tree that has survived a recent fire

These trees are pretty easy to identify.  They have long needles - 8 to 18 inches with (mostly) three needles in a little base called a fascicle. Then grow about  125 feet or more tall and 3-4 feet in diameter. (I did have a friend who told me he has seen pictures of longleaf pine trees so big in diameter,  that only one tree would fit on a flatcar, after it had been sawed to length. (So the entire tree had to be carried by several flatcars. )


The three needles in a fascicle

Longleaf pines have large, beautiful pine cones. These at Okefenokee are smaller than are the ones I'm used to seeing in Louisiana.  They make wonderful frosted Christmas trees,  and great suet feeders. (Once I turned one upside down to prevent house sparrows from landing on it and ended up teaching them to hover while gobbling down the suet I wanted  to only serve to the chickadees, wrens, and woodpeckers.)

Longleaf pinecone on tree

When the pine cones are wet, they are shut.  They dry, open and expose their seeds

Pine cones are monoecious and have male and female cones. The female cones are the big ones we see on the tree.  The male cones are tiny, and fall off the tree as soon as their pollen has blown away to fertilize the female cones. 

Two male cones lying on the ground

Longleaf pines are the favorite nest trees of the red-cockaded woodpecker who also depends on fire to remove the understory and keep the trees thinned out.  This woodpecker is the only one to drill holes in a living tree. It takes it up to two years and is helped if the tree has red-heart disease, which softens and then rots the heart of the tree. 


The white rings mark trees that red -cockaded woodpeckers have drilled holes