Patterns and Types of Succession

Lecture Content

Introduction

• Succession is the natural process of change in species composition of communities over time.

• It follows certain patterns and can be classified into different types based on origin, causes, and habitat.

• Understanding succession patterns helps explain ecosystem development and stability.

Patterns of Succession

1. Progressive Succession

   • Leads to more complex communities with higher biodiversity.

   • Example: Bare rock → forest.

2. Retrogressive Succession

   • Leads to simpler communities with reduced biodiversity.

   • Example: Forest degraded to grassland due to overgrazing.

3. Autogenic Succession

   • Driven by changes caused by organisms themselves.

   • Example: Soil enrichment by plants leading to new vegetation.

4. Allogenic Succession

   • Driven by external factors like climate, fire, flood, or human activity.

   • Example: Vegetation change after volcanic eruption.

Types of Succession

1. Primary Succession

   • Occurs on bare surfaces without soil.

   • Example: Volcanic lava, bare rock.

   • Pioneer species: lichens, mosses.

2. Secondary Succession

   • Occurs in areas where soil is present but vegetation was disturbed.

   • Example: Abandoned farmland, burnt forest.

   • Faster than primary succession.

3. Hydrosere

   • Succession in aquatic habitats.

   • Pond → marsh → meadow → forest.

4. Xerosere

   • Succession in dry habitats.

   • Bare rock → lichens → moss → forest.

5. Lithosere

   • Succession on rocky surfaces.

6. Psammosere

   • Succession on sand dunes.

7. Halosere

   • Succession in saline habitats (salt marshes).

Ecological Importance

• Explains how ecosystems recover after disturbance.

• Shows pathways of biodiversity increase or decrease.

• Helps in conservation and habitat restoration.

• Demonstrates resilience and adaptability of communities.

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Summary / Key Takeaways

• Succession follows progressive or retrogressive patterns.

• Types include primary, secondary, hydrosere, xerosere, lithosere, psammosere, and halosere.

• Autogenic succession is driven by organisms; allogenic by external factors.

• Succession restores ecosystems, increases biodiversity, and stabilizes communities.