Week 1 Part 2 Flashcards
What is becoming one of the strongest forces behind community change
Human actions and we have an imperfect understanding of the consequences of those actions
What are agents of change
Acts on communities in different time and space scales
What is an example of agents of change
Coral reefs over the last few decades have expereinced slow and subtle changes like change in ph and temperature as well as catastrophic ones
What is succession
The directional change in species composition over time as a result of abiotic and biotic agents of change
What dies agents change vary in
Frequency and Intensity
If it is very high in frequency and high in intentsity no community can establish
What is primary succession
Involves the colonization of habitats devoid of life (volcanic rock)
Can be very slow and the first colonizers tend to be stress-tolerant and often transform the habitat in ways that benefit their growth and that of other speceis
What is secondary succession
Involves re-restablishent of a community in which some but not all organisms have been destroyed
Occurs after disturbances such as fires storms and logging
The legacy of the preexistitng species and their interactions with colonzing species play larger role than in primary succession
What are some competing ideas of succession
- A stable end point called climax community emerges composted of dominant species that persist over many years provide stability
- Communities from as the product of fluctuating environmental conditions acting on indvidula species
What is facilitation model
early species modify the environment in ways that benefit later species
What is the tolerance model
Early species modify the environemnt in neutral ways that neither or benefit nor inhibit later species
What is the inhibition model
assumes early species modify conditions in negative ways that hinder later successional species
Whats the best studies example of primary succession and why
Melting glacies led to a seqeunece of communities that reflect succession over many centuries the years show the extent of the glacier and the glacier is receeding oepning up new habitat for species
What increases as succcession progresses
4 things
Soil, organic matter, mositrue and nitogen concentration
What did glacier bay illustrate
Early stages showed aspects of facilitation as plants were modified the habitat in positve ways for other plants and animsals
Later species such as alders had negative effects on later sucessional species
In the spruce stage where dominance was an artificat of slow growth and long life sucession was driven by life history charcateristics a signature of the tolerance model
What is the rocky intertidal zone
Disturbance is creatly mostly by storm - waves and debris rip out the organisms
low tides expose organisms to high or low temeprature which can kill them or cause them to detach
