Gossamer Tapestry

Reflections on conservation, butterflies, and ecology in the nation's heartland

Sunday, March 16, 2008

Great questions from south of the Mason-Dixon Line

Bluff Spring Fen

My recent post about Gladstone Fen prompted some of great questions from a couple of my good ol' boy readers (though I think Valown is a transplant to the South and may not be eligible for good ol' boy status. But then I'm about as Yankee as you can get, so I know little of these matters).

From North Carolina, Valown asks:
I've read that Fens are usually wet. What normally keeps them clear of shrubs and trees? I would think fire. But you would have to have a cycle that would include a dry period. Is that true, and is fire suppression the culprit there for these areas being overgrown? If you've covered this already in another post point me in that direction.
You're right, it is fire that keeps things open. I did a post on this about 2 months before you started coming by the Tapestry. You can see it here. Fens are not just usually wet, they are by definition wetlands. Because their saturated soils are fed by groundwater, they never really dry out, either. On the other hand, the soil doesn't need to be dry to support a fire- just the vegetation. As you can see in the photo above, the herbaceous layer in the wetland is very dense. The dried sedge stalks support fire very well. Remember my dramatic photos of the cattails burning with 40-foot high flames last spring? They were in standing water. We have previously had fire in still-frozen wetlands burn down to the ice line. It's all quite effective as a management tool.

From Pure Florida, FC wonders:
So, is this fen a natural feature?
It seems to take a lot of management and removal of invasive trees to maintain it.
Are the trees nonnative?
The fen is a natural feature. It's been around since the end of the last ice age. We know that the areas where we are removing trees from were open wetland rather than woodland because the soil in that area is saturated peat rather than loam. You can often tell areas where trees have invatded an open wetland follwoing fire suppression. The soil can't support the weight of many of the trees and they topple over. Sometimes this results in J-shaped trees. The base slowly falls over and the crown growth keeps curving upwards (sorry, no pics of that). So although many of the tree species here are native to this region, they are native invasives that that displace the fen ecosystem as a result of fire suppression.

Regarding your second question, most of us here differentiate between restoration and management. Restoration (in this case tree and brush clearing, as well as any activities needed to coax the native plant community along) is very labor intensive. Management typically involves periodic application of prescribed fire and is much less work. At Bluff Spring Fen, where I do most of my stewardship work, the majority of the fen wetlands are now maintained by fire only. This is typically our goal when we restore a bit of land.

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At 20:15, Blogger valown said...

Thanks for the explanation. I remembered the picture of the cattails on fire, but didn't realize there was water under them. That is pretty wild, a wet area burning. I wish I could get some of the pocosins to burn like that around here. And no, I'm not a good ol' boy yet, but I think the transition might be occurring, albeit slowly.

At 21:44, Blogger Doug Taron said...

valown- Burning in a wetland only works if there is very dense fuel above the waterline/saturated soil. I'm not familiar enough with pocosin to have a feeling for wether this situation exists in them.

Do good ol' boys use vocabulary like 'albeit'?

At 14:32, Blogger Dave Coulter said...

Cool. I gotta get out there this spring!

At 05:28, Blogger valown said...

I reckun there's a chance we use albeit.

At 12:28, Blogger rodger said...

I hadn't realized the fen was a wetland and I've been reading you since you started. I guess I'm not paying enough attention...or I'm just a bad student.

I promise to pay more attention.
I promise to pay more attention.
I promise to pay more attention.

At 16:30, Blogger Kathiesbirds said...

Doug, what an excellent post. I didn't know all of that about Fens being wetlands or any or the rest of it. Fire certainly has its place in the overall health of an ecosystem. By the way, I have a new insect I've posted on my Blog that I'd love for you to identify for me. It just stopped by this morning.

At 08:02, Blogger Ur-spo said...

i have arrived in Michigan and have 4 inches or more of snow to contend with.
I hope there wasn't too much snow for you - I like it but I know you are sick of it by now.

At 14:41, Blogger Doug Taron said...

Dave- When you decide to go, let me know and I'll show you around. I'm there most weekends.

Rodger- Guess I'll have to make you stay after school.

Kathie- Insect ID has been at least attempted.

Spo- Glad you made it to Michigan safely.


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