Natural CommunitiesEssential Knowledge for Naturalists
In Nature, Everyone is a Neighbor
Natural Communities are made up of populations of a variety of interrelated species living in close proximity and interacting with one another. While the concept of a natural community includes plants and animals, the community is generally named for the dominant plants growing in the community. This is more for convenience than out of a disregard for the animal components of the community. It is just easier to categorize and count the plants for the simple reason that they are plants; they remain still and allow themselves to be counted.
Plant communities do not always have hard boundaries, such as the edge between a field and a forest. The boundaries are generally more graduated, such as the transition between a beech-maple forest and a bottomland forest as the elevation changes. Like the plant communities, the animals that inhabit these communities do not have hard edges to their ranges. However, it is possible to say that a certain species of animal is likely to be found in a particular plant community. For example, you are more likely to find squirrels in forests with nut-bearing trees, like oaks and hickories.
Much like plants and animals grow over time and develop, so do natural communities. In the Eastern Temperate Forest ecological region, for example, areas of temporarily bare soil will naturally develop from grass and forb dominated fields to old fields with shrubs and young trees into a woodland, then a young forest, then a mature forest, then old growth forest. As the field develops, soil nutrient, light, and moisture changes also occur, which facilitates advancing to the next stage.
At each stage, a fairly predictable set of species will occur in a given ecoregion, given the right conditions. For example, pioneer species such as aspen trees, and annual forbs and grasses occur in high light, high competition environments. These are followed by perennial forbs and grasses, and trees that are longer-lived but need high light levels to grow, such as oaks. In some areas, the large-seeded, long-lived shade-intolerant trees like oaks are replaced by the shade-tolerant, fast growing trees such as maples and beeches. Beech trees and maples produce seedlings which can replace the overstory trees, because they grow in shade, whereas oaks do not. Over time, a forest made up of long-living shade-tolerant trees will be fairly stable. This stable state, where the dominants are replaced by others of the same species is known as a climax community.
While the concept of a single climax community is disfavored in some circles, it is useful as a practical matter. Just remember that calling it "the" climax community should not be construed as meaning it is the only climax condition, or that the climax community is stable. Even in a climax beech-maple forest, gaps will occur that are filled with species other than beech and maple, given the right conditions. For example, single-tree gaps may be filled with new beeches or maples, but multiple tree gaps may give rise to a stand within the forest of tulip or ash, or cherry trees, depending on the seed source, size of the gap, competition, soil nutrition, prior and future disturbances, and a good dose of chaos.
Remember, the concept of a natural community is really just an easy way for us humans to think constructively about the environment. The reality is that a plant community is a continuum, the boundaries of which are soft and subject to change, but which are determined in many ways by environmental gradients, such as moisture, soil nutrients and chemistry, seed sources, and many other variables. So, don't be surprised to see oak trees in the middle of a maple forest, or hemlocks co-dominating a stand with shag-barked hickories. Instead of being puzzled, try to use your natural curiosity to devise an explanation based on what you know and what you can surmise. Learning your natural communities and becoming literate at reading the natural landscape is as importance as literacy in the written word for those of us inextricably wound up with Nature.
Processes and factors that combine to create Natural CommuntiesMany factors influence the structure and composition of our natural communities. Check out these links to information about these processes and factors:
Natural Succession-How communities develop and change over time in Nature.
Carrying Capacity-Any natural habitat has a limit to the number of plants and animals it can sustainably support. Find out about the concept of carrying capacity, and how it relates to your life.
Competition-Although sometimes in a social context, competition has its detractors, in Nature, competition leads to stronger ecosystems, higher diversity, and healthier communities. As long as it does not get out of hand.
Stochastic Influences-Stochasticity plays an important, if not confounding, role in the world.
Dynamic Equilibrium-How Nature balances itself and maintains constancy, or homeostasis in a state of constant change.
Natural Communities of OhioOhio is blessed with a great variety of life. All of the factors discussed on this page, as well as the dynamics of nature, climate, and geological factors come together to create a robust array of interesting natural associations in Ohio.
Eventually we will provide a comprehensive guide to Ohio natural communities, but until then, check out this publication from natureserve: Ohio Subset of Plant Communities of the Midwest.