Acorns Count

The acorn is not only a symbol of fall, but the nuts are a baseline indicator of the current and future health of the forest ecosystem. U.S. Forest Service researchers studying acorns find a bounty of acorns indicates healthy trees and a plentiful food supply for the creatures that form the base of the forest food chain.

BENT CREEK EXPERIMENTAL FOREST — Standing in the woods during the fall sometimes sounds like you are in the middle of a hailstorm. Acorns are falling all around you. Sometimes they fall on you. It sounds silly, but a big acorn hitting on the top of your head can smart a bit. 

“It’s pretty amazing to just stand in the forest and listen when the acorns are falling heavy, but it’s pretty important,” says Jacqui Adams, a Forestry Technician with the United States Forest Service. “A lot of animals use the acorns for food and those acorns are also what is needed to reproduce the oak trees. So really, the future forest is falling all around you.”

The acorn drop is a rite of fall. However most people are so used to seeing it, they simply walk over the seeds of oak trees that cover the ground. But to researchers with the U.S. Forest Service at the Bent Creek Experimental Forest near Asheville, acorns provide a window through which to view the current and future health of the forest. They’ve been studying acorns for years and their research shows just how important a role the lowly acorn plays in the forest ecosystem.

“First of all, acorns are the seeds of oak trees, and people like to have oak trees,” says Cathryn Greenberg, a researcher with the U.S. Forest Service. “Second, acorns are important for wildlife because a lot of game species eat acorns, and if there are a lot of acorns they will get nice and fat and survive the winter and have a lot of babies. On the other hand, if there aren’t enough acorns they won’t have as many babies and their population goes down.”

Greenberg adds that it is not only game species that eat acorns. Mice and other rodents, including squirrels, also find the nuts tasty. And those smaller mammals form the prey base for a variety of raptors, including hawks, as well as foxes and bobcats. The more acorns there are means there will be more food for mice which means there will be more food for carnivores. It’s an intricate food web and it shows that in many ways, the forest is built on a foundation of acorns.

In fact, forest life is so interconnected, the impact of a good or bad year for acorns is reflected in the health of wildlife the following year.

The bottom line: if you know the acorn, you will know the forest.

But to do that, scientists need to know how many acorns the different species of oak trees are producing. That’s the goal of a unique research project that aims to study acorn production and use the information to not only predict the health of the forest but also guide it.

The study begins by researchers grabbing binoculars and scanning the tree canopy.

“It’s impossible to actually count the acorns one by one, but we’re looking to see if the tree has acorns and then if it does, estimating how much of the canopy has acorns,” says Adams, as she scans the treetops.

That estimate of trees and acorn production is then combined with more hands-on research, which requires physically counting acorns. And that’s why dozens of trees in the Bent Creek Experimental Forest have large baskets placed around them. The huge mesh baskets are acorn catchers.

“We place three standard size baskets under the tree and then it becomes a math equation,” says Greenberg, as she shows how the baskets are placed under the crowns of the oak trees. There are five species of oak tree in the Bent Creek Forest.

“If we can measure the number of acorns per unit area, we can then figure out the number of acorns per unit area of crown. And then once we figure out the size of the crown, we know if we are getting this much in this area. We can figure out how much is in the crown.”

Technicians visit the collection baskets about every two weeks. They collect the acorns in the baskets and record the number on charts, which map out the locations of all of the trees with baskets as well as how many acorns have been collected.

The acorns are taken back to the lab to be studied. They are rated by quality, the amount of insect and/or animal damage, and the amount of rot. The acorns are also weighed. All of the information is then combined to calculate the forest’s acorn production, which can then be used to learn the current and future health of the forest.

“This program is benefiting everyone who manages the forest; private land owners, state foresters, natural resource managers in government and the private sector,” says Julia Kirschman, a Technology Transfer Specialist with the U.S. Forest Service. It’s her job to get the information out to the public. “All of those folks use this research because it is all science based. In addition, because these are ongoing studies we have long term data sets so we can follow the trees five, 10 and even 20 years out to see what happens with them.”
And that’s where the science changes from low-tech acorn counting to high tech data crunching. Chad Keyser, a forester with the agency, uses a program called the Forest Vegetation Simulator. The forest service makes it available to foresters in local and state governments as well as private landowners to help manage forests. 

Keyser says the program lays the groundwork for forest management by using acorn production as a guide.

“There are some forests that are managed with the single goal of wildlife production, but we also know of some that are a little more complicated because people want to manage for wildlife but also have some timber production,” explains Keyser as he enters the data of acorn production into the grids. “While you are trying to figure out the optimum management plan, this model will tell you the number of acorns produced. That can help you decide how many oak trees to preserve or harvest or how many more you need to plant.”

And there you have it. Forest management guidance provided by a tiny, but mighty, acorn.

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