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Community ecology is the study of interactions between multiple species in a given time and area.
Community ecologists study four main properties:
Let's put these properties to use by considering a fictional forest community.
IN CONTEXT
Let's say this community spans one square mile in the year 2015. A community ecologist would observe and record the different species in the forest community, such as squirrels, birds, trees, and shrub species. This is species composition.
The ecologist would then measure species abundance, and calculate the abundance of each species in relation to each other. The ecologist might discover that there is a large population of squirrels and a large population of nut-bearing trees, but a low number of swallow bird species.
Then the ecologist would observe the species distribution, and perhaps discover that there is a sparse but even distribution of oak trees; however, the population of a specific shrub seems to live in only one small portion of a community.
Finally, the ecologist would study the different types of relationships that the species are having, such as competition between different bird species or symbiotic relationships between microorganisms and tree roots.
We'll now delve a little deeper into the types of interactions that species can have.
There are three types of interactions:
However, in terms of interaction outcomes, there are also three possible endings for an interaction:
| Interaction | Description | Outcome | Example |
|---|---|---|---|
| Competition | Two species compete for the same food or resources |
Negative - Negative This always has a negative outcome for each species. |
Two bird species compete for available materials to build their nests, or for food for their young. |
| Predation | One species preys on or consumes another. Predation includes carnivores eating other species, herbivores consuming plants, or species laying eggs on or in another species. |
Positive - Negative This is positive for the predator and negative for the prey. |
An eagle catches and eats a snake — good for the eagle, bad for the snake. |
| Symbiosis | Two species have a mutually beneficial interaction. Symbiosis is much more common in nature than people realize. Many species, including humans, rely on symbiotic relationships to help digest their food. |
Positive - Positive This is positive on both sides. |
Humans have bacteria in their digestive tract, which allows them to digest their food better. Cows also have a symbiotic digestive relationship with bacteria. |
Ecological succession is the process of the creation of a new community, either on barren land or on highly-disrupted environments.
There are two different types of ecological succession:
EXAMPLE
If land created from an oceanic volcano became inhabited by a pioneer species, like moss and algae, and eventually by shrubs, trees, and animals, this would be primary succession.EXAMPLE
If a forest fire burned a large swath of forest, and over time, new species moved in and began growing (thus modifying the environment), this would be secondary succession. Other disturbances that can cause secondary succession are floods, fires, volcanoes, droughts, overgrazing, and human activity, such as deforestation and over-harvesting.Source: Adapted from Sophia tutorial by Jensen Morgan.
