lecture 3 Flashcards
what did early paradigms assume?
ssumed natural ecosystems in equilibrium -early perspective
why are models made? ex?
○ Weather-the idea of it, up to the invention of the telegraph was completely local, no way of conveying info in real time to others further away
* How we think about climate and weather changes based on our perspectives, new technology allowed us to think differently about climate
* Ecosystems are similar- if you spend time in one area, that’s your perspective, there are many other perspectives
Our everyday experience is stable, but many factors transcend lifetimes
what would a natural system in equilibrium look like?
○ Closed systems - internal recycling
○ Deterministic dynamics;; stable endpoints
○ Absence of disturbance and human influence (considered rare)
○ Equilibrium- the idea that theres some stable state that’s reached
○ Easier to study than something that fluctuates
are most systems in equilibrium? ex?
ost places are not in equilibrium
§ The system today is still experiencing the effects of events from 12 years ago-opal
how was the non equilibrium view an advancement?
past events, internal and external forces shape ecosystems
○ Maybe unbalanced inputs and outputs
○ No single stable equilibrium
Human activities and disturbance important
what are steady state equilibriums?
- Another conceptual advance; differs from equilibrium view
- Compromise between full non equilibrium model and equilibrium model
- vs Open system- an average over time driven by random factors
describe the steady state system dynamics
- Open systems, but inputs=outputs
○ No trend over time (e.g. h2o in = h2o out)
○ Can be temporal and spatial variation (e.g. plant growth varies in summer vs winter and between wet and dry years)
No long term directional tre
jenny 1941 concept? how was it an advancement?
Ecosystem structure and function governed by independent state factors and interactive controls
* 5 main state factors: set the bounds for the characteristics of an ecosystem
* Conceptual advance - emphasized controls over processes rather than descriptions of pattern
* Independent - not influenced themselves by ecosystem characteristics
what are the 5 state factors jenny
climate
topography
time
parent material (rock that gives rise to soil)
potential biota
which state factor most strongly influences?
climate
describe climate as a state factor
- The state factor that most strongly determines ecosystem structure and processes (on broad scales)
- e.g. global climate explains distribution of biomes
describe parent material as a state factor
Within a biome, parent material (rock that gives rise to soil) strongly influences the types of soils that develop and explain regional variation in ecosystem processes
describe topography as a state factor. what do slope angle, aspect, and elevation impact?
- Influences microclimate and soil development at a local scale
- Slope angle: influences drainage, erosion
- Aspect: influences temperature and precipitation
- Elevation and slope
○ Steep slope= theres a steep change in microclimate
○ Aspect: temp and precipitation based on exposure from elevation and slope
Changed elevation changes climate massively
what does potential biota influence as a state factor? where is it especially dominant?
- Governs types and diversity of organisms that will occupy a site
Especially dominant factor on island ecosystems: usually less diverse bc of differences in potential biota (new species reach islands less often)
describe time as a state factor
- Influences the development of soil and evolution of organisms over long time scales
Important component of succession, development, and change in communities and ecosystems over time
look at plant community succession
ok
Critiques of Jenny’s 5 independent state factors? (3)
- Parent material - weather depends on community of moss and lichen that secretes acids while they grow
- Ecosystem processes both respond to and control the factors that directly govern their activity
Interactive controls; factors that operate at the ecosystem scale and both control and respond to ecosystem characteristics
- Ecosystem processes both respond to and control the factors that directly govern their activity
how can jenny’s model be expanded
include microenvironment (rate of ecosystem proccesses), resources, disturbance, and biotic community
ex of why jenny’s model could be improved (3)
○ Soil fertility (resource) may control the dominant plant community that develops, but responds to weathering rates
○ Disturbance regime controls nutrient cycling, but responds to ecosystem type (availability of fuel)
Microenvironment controls decomposition rate, but responds to topography
what do state factors and interactive controls determine?
together, these state factors and interactive controls largely determine characteristics and processes
look at human activities diagram
ok
is an ecosystem linear?
- Within that, feedback in ecosystem from species interactions
Complexity of the model and non linearity
feedpacks are amplifying (positive) and stabilizing (negative) when the recip effects differ in sign
how are climate and weather different?
- Difference in temporal scale
weather refers to short-term changes in the atmosphere, climate describes what the weather is like over a long period of time in a specific area.
marco vs micro climate?
- Macroclimate: prevailing climate for a region
microclimate : small scale variation in climate caused by a distinctive substrate, location, topography, aspect, etc
