The Great BRF Tree Project: Shotgun Sampling

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Dr. Schuster taking aim

Today, I collected leaf samples from six maple trees using a shotgun.

Well, technically, I didn’t use the shotgun.  Dr. William Schuster, the director of Black Rock Forest and an experienced hunter with all of the appropriate certifications, used the shotgun.  But the trees he shot at were trees I had marked a couple of days earlier, and the branches he shot down were branches from which I clipped leaves to test as part of my project.

Let me back up a bit.  In the 1980s and 90s, ecologists started to take an interest in the canopies of tall trees.  They wanted to delve into the canopies of rainforests and examine the complex communities in the tops of redwoods. This interest would develop into the field of canopy research, a collaboration between biologists studying ecosystems and foresters with a deep working understanding of the trees under study.

How does one do research at the top of a tree hundreds of feet tall?  Early methods, which included towers built in the middle of the forest and adapted weather balloons, were expensive at best and hazardous at worst.  Eventually, scientists improved upon these methods; today, tools such as a lift truck more commonly seen at construction sites carry tree ecologists high into the air.  (Black Rock has a lift truck, which I got to ride when a graduate student was using it to track photosynthesis in the canopies of spruce trees last summer.  It was more exciting than most amusement park rides.)

But then, what if you want to study leaves, bark, flowers, fungi, or anything else that might be growing at the top of a tree, but don’t have the time and funds to build a tower or borrow a lift truck?  What if, just to pick a random example, you’re an undergrad student on a limited budget who needs to collect leaf samples from red maple trees in a specific part of Black Rock Forest, but all of the trees in that area are too tall to reach on your own (even with your trusty friend the pole saw)?

In that case, a shotgun – responsibly used – may be a valuable new friend.  One simply aims the gun a high branch and fires a bullet large enough to knock the branch down to the ground.  The technique is much easier explained than performed, though; it’s challenging to aim at thin branches over 30 feet in the air, and often takes several trials to not only hit the desired branch, but also hit it at an angle that will bring it down.  Dr. Schuster explained to me that the best shotguns for this method are those that shoot a case full of large BBs, metal ball projectiles, in a close pattern.  The close proximity of these bullets increases a shooter’s chance of actually knocking down a branch, because one of the BBs will still hit even if the shooter’s aim is slightly off.

Ecologists working at Black Rock Forest have used this method for years, even since before the Consortium was founded.  The forest actually owns its own shotgun and BBs; the gun is kept in a secure location and locked, so that only specific staffers who have received training can use it.  Researchers are also careful to consider their environment when shooting branches, by picking up shot casings rather than leaving them to litter the forest.  I have helped with this part of the process twice now (Dr. Schuster also shot a few branches for me a couple of weeks ago in a different part of the forest), and am becoming adept at spotting the bright red cases amid the forest debris.

Here’s what the process looks like in a short clip; Dr. Schuster demonstrates the trial and error of aiming for high branches (warning for a loud noise):

But sometimes, a researcher can shoot down a branch on their first try, as Dr. Schuster does here (again, warning for a loud noise):

Shotgun sampling is an exciting means of collecting leaf samples – it’s certainly much louder than my usual clippers and pole saw method.  Yet with great branch height comes great responsibility.  As Dr. Schuster and I returned to the Black Rock science center after shooting branches, he realized that his car was low on gas, so he instead drove to the edge of the forest and we waited for another staffer to help us out.  While we waited, he turned on the local radio station – which was playing live coverage of the shooting that occurred this afternoon at the office of a local newspaper in Annapolis, Maryland.  In Dr. Schuster’s hands, a shotgun is a tool for science, but in another person’s hands, this tool quickly becomes a deadly weapon.

We sat in silence for at least half an hour, listening to the broadcast.  I imagined myself in that Annapolis newsroom.  I imagined a shooter invading a Bwog pitch meeting.  I imagined a hundred other scenarios until the shotgun in the back of the car felt less like a fun toy and more like a heavy weight, pulling me down beneath the dirt.

Sometimes, just because something can be a useful tool for science doesn’t mean it should be.  If stricter firearm regulations were imposed, ecologists could always find other ways of collecting branches from tree canopies.  The Annapolis journalists can’t recover so easily.

Photo and videos via Betsy Ladyzhets

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