The Story of a Forest
Next year Cleveland Metroparks celebrates its 100 year anniversary. Thus, the forests that were first preserved with the founding of Cleveland Metroparks are at least 100 years old. Many forests in the first reservations are even older than that (especially North Chagrin’s A.B. Williams Woods). However, it can take hundreds of years for forests to reach their “full maturity”, or “climax conditions”. Like all things in nature, forests have a life cycle as well; different stages of succession.
Forest succession loosely follows stages, but these stages depend on stable climatic conditions (temperature, precipitation, wind, etc.), soil conditions (nutrient availability, drainage, moisture levels, etc.), and the avoidance of catastrophic conditions (fires, windstorms, floods, logging, etc). Over hundreds of years it proves to be difficult to keep all three stable. In addition, there are no hard-set beginning dates and end dates for each stage. They often intertwine and blend within each other. That being said, there is a basic outline of the stages, assuming that conditions remain constant throughout succession.
At the beginning, before a forest exists, often there is a grassland. (We could go back in time before the grassland, to perhaps a wetland that is slowly accumulating soil, and before that a pond; or perhaps there was no wetland, and just rock and soil, slowly colonized by lichens, and then small grasses, then taller grasses and shrubs. For this example, we’ll begin with our grassland.) Pioneer species – species that are best adapted to spreading their seeds far distances, and colonizing new areas – will begin to inhabit the grassland first. This will include many shrubs (roses, blackberries, sumacs, etc.), and then a few tree species. Trees likely to begin colonization of a meadow include white pines, locusts, or black cherries. These trees are well adapted to thriving with lots of sunlight, and thus take advantage of growing taller and broader than the surrounding grasses and shrubs. This stage could take up to 20 years or longer – again, all depending on climactic, soul and catastrophic conditions.
The next stage could take place between the 20th year and 70th year of our grassland. This stage brings the replacement of the pioneer species – which tend to be short-lived when compared to other trees. Our new tree species – red maples, tulips, ash, and tupelo – grow up in the partial shade that was provided by the pioneer species. These tress do not fare as well in direct sunlight, and thus required the pioneer species to provide some shade in order to grow. As our second wave of tree species continues to grow, they will provide more shade, allowing for even more shade tolerant species to take root.
These species will include hardwoods like oaks, hickories, and maples. As these trees grow (over the course of 70 to over 100 years in our former grassland’s life), the canopy is now becoming more crowded. Sunlight is becoming rarer of a resource in the lower levels of the forest. When the oaks and hickories dominate the canopy, there is little sunlight making it to the forest floor. This provides the best conditions for our truly shade tolerant trees – sugar maples and beech – to begin growing, and populate the understory.
Soon, the sugar maples and beech will overtake the oaks and hickories and dominate the canopy. At this point, the canopy will have been so thick, that the understory will also be comprised of only sugar maple and beech trees. This is what is known as a climax community. The succession of this forest is “over”. However, if one of our three conditions mentioned earlier (climate, soil, catastrophe), changes, that could alter the landscape, and thus change the makeup of the forest. In addition, when large sugar maples of beech trees die and fall, they will leave a gap in the canopy allowing sunlight to once again reach the forest floor. At this point, it is a race to the top for any species that may be in the understory, or possibly lying as a dormant seed – waiting for this exact moment.
So why is this information that you should know? Understanding forest succession can tell you the story of the forest you’re hiking in. If you’re surrounded by beech and sugar maple trees - from the understory to the canopy – you’ll know that you’re in an old forest; one that took over a hundred years to reach the stage that it’s at. If in this forest, you find a patch of oak and hickory trees, that might tell you that a large beech or maple fell, allowing for sunlight to reach the forest floor, providing enough light for the oaks and hickories to grow. Being able to piece together the story of the forest around you creates a stronger sense of place, and increases the enjoyment of your hike.
So go on! Get out there and “read” your next “story”.