These important species are the first to colonize arid ecosystems.
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Kia Treece is an author, researcher and sustainability coach specializing in environmental policy, off-grid living, zero waste and vegan living. She owns a J.D. Diploma in Environmental Law from the University of Toledo.
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Updated October 13, 2022
A pioneer species is usually the first to colonize an arid ecosystem. These hardy plant and microbial species are also the first to return to environments devastated by events such as wildfires and deforestation. Once they arrive, the pioneer species begin to restore the ecosystem and make it more hospitable to later species. This is usually achieved through soil stabilization, nutrient enrichment, reduced light availability and wind exposure, and temperature moderation.
To survive in these conditions, pioneer species are usually:
- Rugged enough to withstand harsh environments
- Photosynthetic, due to the lack of soil nutrients.
- Capable of producing a large quantity of seeds with high dispersal rates
- Wind pollination due to lack of insects
- Can survive long latency periods.
- Precocious and dependent on asexual reproduction.
With wildfires increasing in the western United States and deforested areas expanding around the world, it is more important than ever to understand what pioneer species are and the role they play in ecosystem recovery and growth.
Pioneer species and ecological succession
ecological successiondescribes the changes in the structure of species that an ecosystem experiences over time. This is a gradual process that can occur in a previously barren environment (as in the case of primary succession) or in an area that has been deforested due to severe disturbance (as in the case of secondary succession). Pioneer species play an essential role in these processes, preparing the new or recently changed ecosystem for more complex communities.
Primary succession occurs in areas where no plants, animals, insects, seeds, or soil exist, usually where there was no previous community. However, this type of succession can technically occur even when an ancient community has been disturbed or removed, but there can be no existing organic matter to qualify as primary succession.
Fungi and lichens are the most common pioneer species in primary succession because they have the ability to break down minerals to form soil and subsequently develop organic matter. Once the pioneer species colonize the area and start accumulating soil, other species, such as B. grasses to move. The complexity of the new community increases as new species are added, including small shrubs and eventually trees.
In contrast to primary succession, secondary succession occurs after aexistthe community is disrupted or eliminated altogether by natural or man-made forces. In this case, the vegetation is removed, but the soil remains. This means that pioneer species in secondary succession can start roots and seeds in the residual soil. Alternatively, the seeds may be carried by the wind or by animals visiting neighboring communities. Grasses, alders, birches, and pines are examples of plants that initiate secondary succession.
The behavior of the community after a disturbance depends on several factors, but mainly on the nature of the ecosystem before the disturbance. However, because secondary succession begins with some remnants of the original community, change often occurs much faster than primary succession. Alder, birch, and grasses are common pioneer species in these environments because they thrive in sunny conditions.
Factors that can affect the development of a community during secondary succession include:
- soil condition:The general soil quality left after disturbance can have a significant impact on secondary succession. This can include everything from soil pH to soil density and composition.
- Residual organic matter:Likewise, the amount of organic matter remaining in the soil after disturbance affects the rate of succession and types of pioneer species. The more organic matter in the soil, the faster secondary succession occurs.
- Existing seed banks:Depending on how the community has been disturbed, the seeds may be left in the ground. This is also influenced by the area's proximity to external seed sources and may result in increased abundance of certain pioneer species.
- Remaining Organism:If roots and other underground plant structures survive the disturbance, secondary succession will occur more rapidly and in a manner that better reflects the original ecosystem.
Examples of pioneer species
Lichens, fungi, bacteria, algae, grasses, alders and willows are examples of pioneer species. Here are some common circumstances in which pioneer species have helped with succession.
Primary succession is studied less frequently and in less detail than secondary succession. However, one of the most fundamental examples of primary succession occurred in Yellowstone after the Pinedale Glacier Maximum, when the area was covered by glacial ice. After the ice removes soil and vegetation from the environment and the Ice Age ends. The area was recolonized by pioneer species that broke through the bedrock and provided soil for other plants to colonize.
After the Mount Saint Helens eruptions of 1980, the area was barren and covered in ash, and very few plants and animals survived. Despite this, some underground animals survived, as did some underground root systems of plants such as willow and black poplar. Soon after this destruction, these surviving root systems, as well as alder and fir, were able to colonize the gross debris of the landslides and lava flows.
In 1995, the flooding of the Moorman and Rapidan Rivers in Shenandoah National Park caused widespread destruction of plants and animals, many of which were replaced with gravel and boulders. Since then, plant and wildlife communities have begun to rebuild through secondary succession.
Secondary succession also occurred after the 1947 Acadia National Park wildfire, which burned over 10,000 acres of the park. After the fire, some of the previously forested land was cleared for logging and cleaning, and some logs were left behind to encourage regeneration of forest ecosystems. Secondary succession regrows forests using existing root systems, stub shoots, and windborne seeds.
Trees such as birch and poplar, which had not previously grown in the area, took advantage of the new sunny conditions and bloomed early. After these deciduous trees formed a canopy, the spruce and fir that originally thrived in the region were allowed to return, resulting in the mix of deciduous and evergreen trees that exist today.
Agriculture, especially slash and burn, can have a devastating impact on the natural environment. During the fallow periods immediately following agricultural use, secondary succession occurs when remaining seeds, root systems, weeds, and other pioneer species begin to recolonize the land. This process is similar to what happens after logging and other deforestation.
frequently asked questions
Can animals be pioneer species?
Animals are not pioneer species because they need plants (or other animals) to survive. They only arrive after the plant species have moved on.
Why are fungi and lichen common pioneer species?
Fungi and lichens are unique in that they essentially build their own soil by mining minerals in the environment. Other plants need organic material to feed themselves.
What is a pioneer community?
A pioneer community is the first community of organisms to appear in a previously ecologically dry area. Plants in a pioneer community often have short lifespans because the environment has few resources to survive.