Seeing the Patterns

Plants often grow together naturally in certain combinations in certain settings. Ecologists notice these patterns, or natural communities in the landscape, and they also notice what influences the patterns.

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But not all the vegetated areas of a park are considered natural communities. What about plant communities that are not in their natural state—like pines coming up in an old field, or an abandoned homestead covered with Japanese honeysuckle and Chinese wisteria, or a manicured lawn?

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Natural Communities

Combinations of native plants often found together in particular settings are called natural communities. What sorts of factors influence these natural patterns?

  • position in the landscape,
  • type of soil or rock,
  • water supply,
  • protection from or exposure to sun, weather events, fire, and other natural processes.

Each natural community functions as essential habitat for various wildlife species. Many animals—such as wide-ranging deer and adaptable racoons—live and travel among different natural communities. Others are dependent on specific natural communities, like the beaver or kingfisher who live in floodplain forests.

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Semi-Natural Communities

Historic human manipulation—like logging or plowing—or severe natural disturbance can disrupt or destroy a natural community. As the land recovers (for decades or even centuries!), its composition differs from that of a natural community. Even when largely composed of native plants, what initially regrows are not long-standing communities, but what may be called successional or semi-natural forests. They will give way (or succeed) to other, more natural communities as natural processes take their course.

Forests regrowing in the aftermath of severe disturbance of the soil and/or vegetation display telltale signs. Ecobit: Forest Succession—Clues to the Past  As the vegetation in one of these areas changes over time, the wildlife also changes. For instance, grassland birds in an abandoned field eventually give way to woodland birds as the field succeeds to forest.

A major problem for natural communities that are disturbed in today's world is the increasing probability that they will be colonized in large or small part by non-native invasive plants. This is changing the former healthy pattern of succession of communities—what will these infested areas become with time?

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Not-So-Natural Plant Communities

Some areas in parks are neither part of a natural community, nor giving way to one. Rather, these areas are maintained in their present state by human intervention, or are so altered that restoration to a natural condition would require human intervention. Examples include: maintained meadows or lawns, forests whose understory is regularly mowed, and cattail ponds created to catch stormwater runoff.

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Ecological Systems: The Broader Landscape Context

Ecologists group natural communities that occur in similar physical settings together into groups called ecological systems. For instance, think of a large river you know well. Along that river are distinct natural communities—maybe a shady silver maple forest along one low bank, a sun-baked bouldery area with a few shrubby, stunted river birch along another stretch, an American sycamore and black walnut forest with nodding Virginia bluebells at a particular bend, and a half-submerged patch of American water-willow elsewhere. Though each community has a very different feel to it, it’s not hard to define the unifying theme—they all occur along the same river. You could trace where they collectively occur on a map. That sort of broader ecological context (such as Central Appalachian Stream and Riparian) is an ecological system.

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Next Steps

Learn about how (and why) natural communities are identified and mapped in Naming and Mapping the Patterns.

Learn how ecologists assess which natural communities and ecological systems are vulnerable to elimination, and which ones are secure. See Assessing Vulnerability.

Start exploring natural communities in a park! Go to Parks & Places, and pick a featured park.

Or, learn more about ecology in Ecology Basics.