disturbance and ecological succession Flashcards
explain the difference between primary and secondary succession
- primary succession is ecological change in areas that have been denuded of soil (organic matter lost) -> substrate may only be bare rock
- secondary succession occurs with much less severe disturbances (more common in nature), leaves some organic matter
what environmental changes occur during succession?
- after primary succession, lichens and mosses can grow on rock
- after secondary succession, annual plants (weeds) -> perennial herbs and grasses -> shrubs -> shade intolerant trees -> final tree stage with shade tolerant trees
what is meant by expression “climax vegetation”?
climax vegetation if major species replacement no longer occurs and it is self-perpetuating (reproducing itself)
how are some ecosystems resistant or resilient?
resilient: ability to recover once perturbed to recover from changes caused by disturbances
- grasslands, in a matter of a few years it can recover from fire/drought
resistance: inertial stability, ability to remain unchanged in the face of disturbance or perturbation
- redwood forest, pine forest, tropical rainforest
what is a paradigm?
A framework of concepts, results and procedures within which subsequent work is structured. A paradigm is upset in response to an accumulation of anomalies and stresses that cannot be resolved within the framework.
definition of a niche
function or occupation of a life form in a given community
describe process of secondary succession in mid-latitude broadlead deciduous forest
- annual plants (pioneer plants, easy and broadly dispersed)
- perennial herbs and grasses (slower at growing but eventually become dominant)
- shrubs (soil gaining more organic matter and nutrients)
- shade intolerant trees (birch, softwood needle-leaf trees)
- shade-tolerant trees (hardwood trees -> broadleaf deciduous, sugar maple and beech)
describe process of secondary succession in equatorial rain forest
- too diverse to predict exact species
1. chablis (fall of tree, hole in canopy, accumulated debris, disturbance to the soil)
2. pioneer species (short-lived and unable to germinate in shade)
3. smaller trees grow into canopy
4. climax species will not be the same as original because of high seed-predation
describe process of secondary succession in boreal forest
- fire is predominant form of disturbance
- tree canopy removed -> more sunlight on soil -> melting permafrost -> soil is better for plant productivity (OM and active)
- pioneer species are forbs like fireweed
- broadleaf shade intolerant trees (birch)
- black spruce seedlings show up because they have serotinous cones (open once exposed to heat of fire)
- black spruce provides shade that decreases temperature of soil
- active layer gets thinner: restricting drainage (increase soil water content) and less nutrient availability (spruce needles are resistant to decomposition)
- cold and wet soil is favorable for mosses
- mosses compete with spruce for soil nutrients and win + make soil acidic
- organic matter of mosses is susceptible to fire during drought
which types of succession support the theory of succession leading to climax vegetation?
- broadleaf deciduous forests (mostly works in western European biomes since the idea was created there)
- tropical rainforest: hard to predict but climax species is usually a shade tolerant tree that is self-perpetuating
which examples of succession do not support the theory of succession leading to climax vegetation?
- boreal forest: climax species is moss because it competes with spruce for nutrients and the boreal forest’s succession is not self-perpetuating because it requires fire
what is chablis?
- fall of tree 2. hole in canopy 3. accumulated debris 4. disturbance to soil
what are the three zones created by chablis?
- crown gap (where the crown was before it fell)
- epicenter (where the crown fell)
- peripheral zone
what is Terra Preta?
dark rich soil, fertile soil left by settlements of early people in tropical rainforest
