APES Notes 2.7 - Ecological Succession

Summary

In this educational video, Mr. Smeeds explores ecological succession, a process of change in forest ecosystems. He distinguishes between primary and secondary succession, detailing how pioneer species like moss and lichen initiate growth on bare rock in primary succession, while grasses and wildflowers take the lead in secondary succession where soil already exists. The video progresses through the stages of succession, from early to late, explaining how soil depth and nutrient richness develop over time, allowing for larger, slower-growing trees like maples and oaks to eventually dominate. The video concludes with a data analysis exercise, challenging viewers to determine the successional stage of spruce trees based on a graph showing their population changes post-glacial retreat.

Takeaways

• 🌿 Ecological succession is a series of predictable changes that occur in a forest ecosystem, involving the gradual replacement of one community of plants and animals by another over time.
• 📌 There are two types of succession: primary and secondary. Primary succession starts on bare rock with no soil, while secondary succession begins in areas where soil is already present but the existing plant community has been removed by a disturbance.
• 🌱 In primary succession, pioneer species like moss and lichen colonize the area, breaking down rocks and initiating soil formation through the secretion of acids.
• 🌼 Secondary succession starts with pioneer species like grasses, sedges, and wildflowers, which are quick to grow and tolerant of full sunlight, colonizing areas where the previous plant community has been disturbed.
• 🌲 The process of succession is marked by different stages, each dominated by species adapted to the conditions of that stage, progressing from early to mid to late successional species.
• 🌳 Pioneer species are characterized by wind or animal dispersal, rapid growth, and the ability to grow in nutrient-poor conditions, such as bare rock or recently disturbed soil.
• 🌳 Mid-successional species, like shrubs and fast-growing trees, require deeper, more nutrient-rich soil and can tolerate full sunlight but take longer to grow and establish.
• 🌳 Late successional or climax community species are large, slow-growing trees that are tolerant of shade and require deep, nutrient-rich soil to anchor their roots, often taking hundreds of years to reach maturity.
• 🔍 The video emphasizes the importance of understanding the characteristics of different successional stages and species to predict and manage ecological changes.
• 📊 The practice task involves analyzing data, such as a graph showing the number of spruce trees over time, to determine whether a species is early, middle, or late successional based on its population trends.

Q & A

What is ecological succession?

Ecological succession is a series of predictable changes that occur in an ecosystem over time, involving the gradual replacement of one community of plants and animals by another.

What are the two types of ecological succession?

The two types of ecological succession are primary succession and secondary succession.

How does primary succession begin?

Primary succession begins on bare exposed rock where no soil exists. It starts with pioneer species like moss and lichen that can grow directly on rocks and break them down to form soil.

What role do moss and lichen play in primary succession?

Moss and lichen play a crucial role in primary succession by secreting acids that break down rocks, releasing nutrients needed for their growth and eventually leading to soil formation.

What is secondary succession and how does it differ from primary succession?

Secondary succession occurs in an area that already has established soil but has lost its plant community due to a disturbance. It differs from primary succession in that it starts with grasses, sedges, and wildflowers rather than moss and lichen.

What are pioneer species and why are they important in succession?

Pioneer species are the first species to colonize an area during succession. They are important because they can grow in harsh conditions, help break down rocks or enrich soil, and create conditions for other species to grow.

What are mid-successional species and what characteristics do they have?

Mid-successional species appear after pioneer species have built up the soil. They are typically faster-growing, larger plants like shrubs and small trees that can tolerate full sunlight and require deeper, more nutrient-rich soil.

How do late successional or climax community species differ from pioneer and mid-successional species?

Late successional or climax community species are the last to colonize an area. They are large, slow-growing trees that can tolerate shade and require deep, nutrient-rich soil. They indicate the end of the succession process.

Why does secondary succession occur faster than primary succession?

Secondary succession occurs faster than primary succession because it starts with established soil, which already contains nutrients and organic matter, speeding up the process of plant colonization and growth.

What is the role of disturbances in ecological succession?

Disturbances, such as wildfires, storms, or human activities, can initiate secondary succession by clearing away existing vegetation and creating space for pioneer species to colonize and start the succession process anew.

How can data analysis skills be applied to understand ecological succession?

Data analysis skills can be applied to ecological succession by examining trends in species populations over time, such as the graph showing the number of spruce trees per hectare after a glacial retreat, to determine the successional stage of a species.