Credits

Created by Alli Kenlan, Explore Natural Communities Intern Summer 2017; additional voices by Michael Lee. NatureServe.

Sound: Crisp Ocean Waves, recorded by Mike Koenig (soundbible.com). Licensed under Creative Commons: Attribution 3.0.

Music: Montauk Point, by Kevin Macleod (incompitech.com). Licensed under Creative Commons: Attribution 3.0.

Photo: Limestone Oak-Hickory Forest in Antietam National Battlefield Park, by Stephanie Bilodeau, NatureServe. Licensed under Creative Commons: Attribution 4.0.

References:
Soils in Antietam
Geologic Map of Washington County, Maryland
Chinkapin Oak

Transcript

Podcast time: 3:13 minutes

Voice 1: Stop right now, and look at where you are on the Sherrick Farm trail. In this very spot, there were once shallow seas. [sound of ocean waves fades in]

Voice 2: What! No way!

Voice 1: Yup, it's true! You may not see much evidence on the surface of this forest, but if you dig deep enough, there are clues from its past hidden below.

Long ago, when Maryland was under water, it was home to an abundance of marine life. Organisms like corals, oysters, starfish, and algae built shells or exoskeletons out of a chemical compound called calcium carbonate.

Voice 2: Whoa, alliteration alert!

Voice 1: As these critters died, those calcium carbonate shells and exoskeletons began to pile up. Eventually, under lots of pressure and heat, they transformed into limestone. [ocean waves fade out]

Where did that limestone go?

Voice 2: Uh, I dunno

Voice 1: [music starts] Nowhere! It's still under your feet, but much deeper. We call it the bedrock, which is the foundation of the entire forest.

Voice 2: Well, out of sight, out of mind!

Voice 1: Well, not really! The limestone underneath the soil affects the soil characteristics in this part of the forest, which in turn affects what grows here. As limestone is slowly dissolved by the underground movement of water and organisms, it releases chemicals and minerals stored up within the rock, that is, minerals like calcium.

Think about it. When you have an upset stomach, you take an antacid pill.

Voice 2: Like Tums!

Voice 1: Yes! Tums are calcium carbonate! They react with your stomach acid and reduce it. In the same way, the calcium released from the limestone bedrock is dissolved in the groundwater and reduces the acidity of the soil, making it perfect for certain plants to grow here!

So, now let's look at the trees. Scan the canopy for chinquapin oak. You'll recognize it by its scaly-looking bark and teardrop-shaped leaves with saw-toothed edges. You won't see chinquapin oak often, but if you do, you're most likely over limestone bedrock. Bitternut hickory is another tree that loves calcium-rich soil. [Voice 2: Mmm!]

Voice 1: The bark of a mature bitternut hickory looks like fishnet stockings, [Voice 2: Hm!] and its leaves contain seven to eleven smaller leaves called leaflets. Also look for plants in the understory like the heart-shaped leaves of wild ginger and the lemon-scented northern spicebush. All of these are clues that the soil is very rich in nutrients and low in acidity.

Along the open edge of the forest, you'll see a lot of hackberry trees, which are sometimes found growing alongside chinquapin oak. Their lopsided, rough leaves have fine-toothed edges with long pointy tips. Hackberry can grow almost anywhere, but it especially loves, can you guess?

Voice 2: Limestone!

Voice 1: Yes! Hackberry is quick to colonize damaged land where other vegetation has died, so the abundance of hackberry in this particular forest indicates some past disturbance. Eventually, without human interference, the forest will come to be dominated by oaks and hickories through the natural process of succession.

Now that you know what to look for, try to identify the Limestone Oak – Hickory Forest as you hike along!

Voice 2: I'll give it the old college try!

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