The Keystone Species
by Josh Palumbo, Forest Management Coordinator
I welcome you to The Nature Foundation at Wintergreen’s attempt to bring some nature and knowledge into your home. The Nine Minute Naturalist borrows from NPR’s lovely 90-Second Naturalist podcast. Since we all have a bit more time on our hands, the goal is to take something that is happening out in our environment and stimulate your brain for roughly nine minutes. Don’t let something as “minor” as a quarantine to keep you from learning. I hope you enjoy!
No parent makes proclamations of a favorite child nor do employers make it well known who is the most important employee. Our ecosystem is not coy in playing favorites. There is one species that claims the status as “favorite” or “most important”. That species is the oak. This edition of the Nine Minute Naturalist will explain why the oak is the keystone species of the Wintergreen ecosystem.
Those of us that traverse the environment at Wintergreen all have favorites. My favorite species at Wintergreen, for example, are downy serviceberry, Canada lily and chipmunks. While I love them, the health of the ecosystem is not dependent on these three species. They are dependent on oaks. The forest type of Wintergreen is Oak-Hickory. This simply means the two dominant tree species are oaks and hickory. Oaks are the species we pass most often as we hike along our trails and are the key component to ecosystem health.
The obvious source of contribution to ecosystem health is dropping from the heights at this moment, acorns. Over 100 vertebrate species rely on acorns to make it through the fall and winter months. Species such as deer, bear, gray squirrels, chipmunks, wild turkeys, crows, blue jays, raccoons, rabbits and opossum use the autumn acorn crop to prepare for the tough months ahead. Oaks are split into two types: red and white. Like wine, the red and white acorns are different from each other. White oak acorns are the preferred variety for wildlife. White oak acorns have less tannin, an astringent chemical in plants, thus a more palatable taste to wildlife. Red oak acorns tend to be higher in fat, protein and calories. White oaks germinate quickly after reaching the soil, while reds lie dormant for months. Wildlife tends to seek out white oak acorns early in the autumn and turn their focus to red oak acorns in winter and into the spring.
Whole populations ebb and flow with the production of acorns. The correlation between acorn production and fawns is very strong. Deer produce more twin and triplet fawns after bumper acorn crop years. The Nature Foundation studies the yearly acorn production. If you have ever hiked the Fortunes Ridge or Lower Shamokin Falls trails you may have noticed trees painted with white and red stripes. These markings allow us to study the yearly production of acorns for 75 white and 75 red oak trees at Wintergreen.
Oaks provide other valuable landscape benefits. A key contribution is carbon sequestration. Oaks pull carbon out of the atmosphere and lock it in plant tissue. Plants with the biggest root systems have the greatest ability to lock it in the soil and oaks have tremendous root systems. These wonderful root systems hold water in the landscape better than almost any plant. Also, their large canopy softens and slows rain thus creating a slow movement of water through the watershed. The longevity of oaks stabilizes the forest community. This enduring presence tend to make these forest communities more resilient.
Oaks have not always been the primary keystone species at Wintergreen. In the early 1900s, American chestnut shared the role with oaks. Chestnuts comprised approximately 30% of the forest in the Blue Ridge and Appalachian Mountains. Sadly, the chestnut blight arrived and changed the ecosystem in a tremendously swift manner. Currently in the United States, 75% of oak species are listed in the “conservation concern” category. Although nothing like the immediate landscape change from the chestnut blight, oak decline is happening all over our ecosystem.
The longevity of oaks combined with slow reproductive rate make them very susceptible in a rapidly changing environment. Predisposing factors such as poor soils, advanced tree age and prolonged drought make up the first level of stress in the complex known as oak decline. The second level is inciting factors such as frost and defoliating insects which may kill the tree but usually initiate decline by depleting food reserves and causing dieback. The final level is contributing factors such as secondary insects or diseases that lead to the ultimate mortality. These final “nails in the coffin” are things like Armillaria root rot that only attack trees in a state of decline.
Our Wintergreen landscape has seen a ton of factors of various stress levels. Most of our oak population in the open space of Wintergreen is mature to overmature to begin with. The oaks in our development are mature and many have been stressed with human stressors such as driveways and houses built on the root system. Our oaks have been through years of gypsy moth attack, suffering partial defoliation year after year. Our wet weather in 2018 and 2019 is a contributing factor in death of many white oak species such as white and chestnut oaks, according to the Virginia Cooperative Extension. Adding in factors such as root rot and ambrosia beetles and you have a species in decline.
While there is not much that can be done for the oaks in the open space, you can aid in maintaining healthy oaks in your landscape. Start by not being a stressor yourself. Avoid damaging tree limbs, trunk or roots. Prune carefully damaged or disease limbs. Remove invasives vines from the tree and monitor for insect pests or fungus. If you find something out of the ordinary affecting your oak, contact me at email@example.com or seek out a certified Arborist for advice.