Trees have evolved to adapt to disturbance and site condition for success in regeneration
Part 2: Disturbances like wildfire or windstorms that destroy many trees also create conditions to which trees have developed adaptions for successful regeneration, even for invasive species.
Most readers will be familiar with the winged seed of maple trees. Once ripe the seeds helicopter away from the parent tree to hopefully land in a suitable location to germinate. These relatively light seeds may float on streams or be blown across flooding’s and other water bodies to germinate after the water recedes far from their parent stock.
Some trees depend on help from wildlife to assist in seed distribution. Nuts and acorns are large, heavy seeds that fall directly under parent trees when ripe. These nuts and acorns are important seed sources for wildlife and although most will be consumed by the animals that come across them, enough will be moved, buried or forgotten to sustain the parent tree stands.
Bear, deer, squirrel, turkey and several other wildlife species play an important role in moving these heavy seeded species production and assist in not only regenerating the trees but also help sustain their food source.
Still other species of trees, cherry or apple for example, have fleshy fruit surrounding their seed, which also appeal to wildlife. Birds distribute many of these varieties of tree fruit seeds, however other wildlife like chipmunk, bear and raccoon feed and benefit from them as well. With fleshy fruits the bird or animal usually consumes the seed, along with the nourishing protective covering, and the seed is later deposited as it passes through the host animal’s digestive system.
Some of the seeding adaptions trees and other plants have developed prove challenging with trees we have labeled as invasive. Invasive Scots pine (Pinus sylvestris) produces seed that is remarkably hardy and able to generate in sod or grasslands that our native pines find a challenge for establishment. This encourages Scots pine to overtake areas in place of our native species.
Buckthorn and autumn olive produce abundant fleshy fruit type seeds that are attractive to a variety of wildlife. Their seeds become wildly distributed encouraging thickets of these non-native invasive species. These thickets can grow so dense that they prevent sun from getting to the soil and prevent native species from growing under their shade. A successful adaption for the exotic species that is wreaking havoc on native regeneration in many regions.
Planting trees is a popular past time and sometimes necessary, particularly if managers desire to change the species of trees growing there. Nature however has worked to adapt trees to a wide variety of growing and site conditions which, left to their own, allow trees to repopulate without human intervention.
Michigan Natural Features Inventory as part of Michigan State University Extension tracks rare and endangered species and habitat types in the state. The web site they maintain provides information on invasive species as well and is a great resource for anyone interested in finding more information on how invasives are adapted to be successful in our forests and other habitats.