Succession and Biodiversity Cards

Define Succession

• long term change in the composition of a community

• explains how ecosystems develop from bare substrate into beautiful, lush biomes

• 2 types: Primary and Secondary

• divided into a series of distinct stages.  Each community in succession is called a seral stage.

Define Sere

• change in communities from the earliest community to the final community

Define Pioneer community

• first seral stage of succession

• contains hardy species able to withstand difficult conditions

Define Climax Community

• A community of organisms that is more or less stable (steady state equilibrium)

• have continuing inputs and outputs of matter and energy, but the system as a whole remains at a steady state equilibrium.

• final seral stage of succession

• more stable than earlier stages

2 types of Succession

• Primary: succession on a previously uncolonized substrate; e.g rock (e.g., new island forms in the ocean)

• Secondary: occurs in places where a previous community has been destroyed (e.g., forest fires)

Changes in energy flow due to succession

• early stages of succession => low gross productivity

• ex: energy lost through respiration is low, so net productivity is high

• Later stages of succession => high gross productivity (bc of inc consumer community)

• Gross productivity eventually becomes balanced by respiration

• => Net productivity approaches 0 and the ratio of production to respiration approaches 1

What Climax communities have

• Greater biomass

• Higher levels of species biodiversity

• More favorable soil conditions

• Better soil structure

• Taller and longer living plant species

• Greater community complexity and stability

• Greater habitat diversity

• Steady state equilibrium

Factors that interfere with ecosystem stability

• Deforestation

• Growth of animal agriculture

• Growth of monocultures

• Loss of biodiversity

• pollution /toxins that weaken organisms

Define tipping point

• the point beyond which an ecosystem becomes unstable and can no longer recover from change.

• Tipping points tend to be irreversible

Tipping points in ecosystem stability

• Anthropogenic pressures => Amazon rain-forest is losing its resilience

• The  Amazon sequesters a significant amount of carbon, so much so that it does not currently contribute to carbon emissions

• HOWEVER, recent studies have shown that parts of it are now emitting more carbon dioxide than can be absorbed

Define Keystone Species

• One which has a disproportionate impact on an ecosystem and strongly affects community structure (e.g., sea otters, elephants, prairie dogs)

• Top-down limiting factors

Resource harvesting and assessing sustainability

• Sustainability depends on the rate of harvesting of a plant or animal being lower than the rate of its replacement

• Examples:

  • Selective logging: only harvesting select trees instead of all of them

  • Maturity: mature trees have increased value–allows young trees time to mature–protects the long term value of a forest

  • Replanting: when trees are cut, saplings are planted to replace them

  • Fishing at the maximum sustainable yield

  • Using fishing techniques that do not damage marine habitats

  • Avoiding bycatch

List factors that negatively affect sustainable agriculture

• Industrial farming

• Growing of monocultures

• Eutrophication

• Bioaccumulation of pesticides, herbicides, etc

• pollution