In this lesson, we’ll be explaining what ecological succession is and the role that pioneer species play in it.
We’ll explain the pioneer community and look at an example of volcanic rock.
What is a Community?
Picture your local community. You’re probably thinking of your friends, family, maybe local businesses, or the mailman. Although, it’s a little different in biology, an ecological community is pretty similar. An ecological community is all the living things in an organism’s environment.
So, for example, in a forest community, plants, fungi, animals, and bacteria are the components of the community. Today, we’re going to look at how these communities are built from scratch. How do we transform barren rock into a thriving forest? This is the focus of our lesson today.
Ecological Succession is the development of an ecosystem over time. There are two types of ecological succession:
- Primary succession, which starts from barren rock with no life
- Secondary succession, which starts from an already existing ecosystem that has been destroyed, such as the aftermath of a forest fire.
Pioneer species are the very first species to colonize an area during primary succession. So, a community of this species would be a pioneer community. If the entire ecosystem is wiped out, you might be wondering how pioneer species get to the area in the first place. Wind carries seeds from plants and can bring them into a foreign area. In Hawaii, the volcanic mountains have different rates of succession, depending on how much wind they are exposed to.
The windward side of Kilauea volcano is teeming with thick forest. However, the leeward side, which is not exposed to wind is still mostly barren rock. Pioneer species have no way of getting to the area without wind, so there has been less primary succession.
Pioneer species are generally plants that grow quickly and are low to the ground to maximize sunlight intake. Mosses, lichen, and low-growing grasses are the first to colonize an area. These species are hearty and can withstand a harsh environment present after a disaster. For example, there may be very little groundwater on volcanic rock or little nutrients.
The sun bakes the area with little cover from other plants. Pioneer species need to be able survive these conditions to take hold.All of the pioneer species in a particular species make up a pioneer community. Pioneer species are very important to starting an ecosystem.
They break down the hard, rocky soil and make nutrients and groundwater sources available for other plants. This process may take hundreds of years before larger plant species and animals can inhabit the area. Their twisted root system prevents water runoff, leaving moisture for other plants.
They also cushion the ground, providing a substrate for other plants to grow on and a microhabitat for insects, like mites and eventually spiders.
Examples of Pioneer Communities
Next, let’s look at an example of a pioneer community in volcanic rock. A volcanic eruption occurs. Gasses, ash, and hot lava spew from the peak, rolling down into a countryside ecosystem. All of the humans are long evacuated, and grasses, trees, and animals are incinerated instantly.
As the lava cools, all the previous signs of life have vanished. There is no more fertile soil, seed, or accessible groundwater sources. This is a place for primary succession to occur.The first species to colonize the place will be small herbaceous plants, moss, and grass. At the volcanic site, Mount St.
Helens in Washington state, scientists studied primary succession over three years. The most common plant at the site was seashore bentgrass or Agrostis diegoensis. Other species included small herbs like Lupinus lepidus, which grows low to the ground, producing pretty purple flowers.Aconogonon davisiae or Davis’ knotweed, a low-growing herb also colonized the area. These pioneer species laid the groundwork for other species to take hold, like larger grasses and trees, like willows. The plants attracted insects, which provided food for birds. As the ecosystem developed, elk migrated from neighboring communities, and the ecosystem developed again.
Primary succession takes place when the entire ecosystem is wiped out and the area is left with barren rock. Pioneer species enter the area first, primarily through wind distribution of seeds. They must be hearty species like small grasses, herbs, moss, and lichen to survive in the harsh nutrient-depleted conditions. They break down the rock into useable soil, act as substrate for other plants, and hold moisture for the community.Volcanic eruptions, such as on Mt. Saint Helen’s create an area for primary succession.
In the community, small grasses and herbaceous plants took hold first, creating conditions for trees and animals to follow.