Lecture 15 - (General Ecology) - Succession

What is a functional trait

any morpological, physiological or phenological feature that impacts an organism’s growth / reproduction or survival - includes birds, plants and invertebrates

what are response traits?

functional traits that specifically determine how a species reacts to environmental changes or stressors - e.g drought

What are effect traits?

functional traits that determine how a species influences ecosystem processes (e.g nutrient cycling)

What are multidimensional trait spaces?

a way for ecologists to represent organisms using multiple traits at once e.g diet, body size etc.

• species on the edge of these multidimensional trait spaces = show more unique traits

What idea does functional ecology have about trait variation?

species that are more closely related are more functionally similar = we can estimate trait variation

How does covergent evolution challenge the idea of functional ecology?

species can evolve to be similar over time if they live in the same place

• traits change over time - through evolution / competition

What is functional uniqueness?

a measure of how functionally distinct a species is within a community

• more vulnerable to disturbances (temporal functional insurance)

what is functional redundancy?

where multiple species perform similar or identical ecological functions = gives a species greater resilience against disturbances (temporal functional insurance)

What is succession in ecology?

the process that describes how the structure of a biological community changes over time - it is not linear, with continuous patterns of colonisation

What is autogenic succesion?

succession driven by internal changes caused by organisms themselves

• example: abandoned farmland with bare soil, where plants would eventually form a climax community (changing the environment by improving soil structure, increasing nutrient availability)

what is allogenic succession?

succession driven by external environmental forces, not caused by organisms in the community - e.g major flood depositing fresh sediment, reseting the environment

what is degradative succession?

occurs when new and degradable resources are used successively by other species, terminating when resource is used up e.g salmon carcass

What is primary succession (type of autogenic succession)?

occurs on landforms when no leftovers of a previous community exists e.g land exposed by glacial recession

What is secondary succession (type of autogenic succession)?

occurs in space opened by complete / partial removal of species, but where resources remains - e.g when a tree falls but well developed soil / seeds remain

What are the stages of succession?

1. bare ground

2. pioneer serial stage

3. seral stages

4. climax community

• Disturbance can reset any seral stage back to any other stage

What are the traits of early sucessional species?

• high growth rate

• wide dispersal

  • fast population growth AKA r selected

What are traits of late successional species?

• slow growth rate

• limited dispersal

  • slow population growth AKA k selected

What are the mechanisms driving ecological succession?

1. facilitation

2. tolerance

   1. inhibition

what is facilitation (in mechanisms driving ecological succession)?

early successional species making the environment more suitable for late successional species e.g nitrogen fixing plants = remove nitrogen from atmosphere and put into soil

What is tolerance as a mechanism driving ecological succession?

where a species doesn’t help or inhibit it’s successors

what is inhibition as a mechanism driving ecological succession

early successional species making the environment less suitable for the recruitment of late successional species

What are the beliefs of federic clements regarding succession>

thought that succession is predictable, orderly and community driven = where the environment moves towards a fixed climax community

What are the beliefs of Henry Gleason on succession?

succession is individualistic, contingent and shaped by chance and individual species traits - no single climax community

What is the monoclimax theory (Clements, 1916)?

succession is directional / predictable - resulting in a single climax controlled by the local climate = “the climatic climax”

What is the polyclimatic theory (Tansley, 1939)?

many different climax communities can arise and are controlled by soil moisture, topography, animal activities etc.

what is the climate pattern hypothesis (Whittaker, 1953)

a variation of the polyclimax idea - a continuum of climax types that vary gradually along environmental gradients

what are the human impacts on succession?

human impacts are making it difficult for species to disperse

• example: deer in the UK reduces regeneration of tree seedlings - favouring unpalatable species = can prevent establishment of climax forest