NRES 151 Exam 1
Biotic Factors Influencing Succession
(Living) Producers: get energy from sun, turns to glucose Consumers: opposite
Abiotic Factors Influencing Succession
(Non-Living) Mineral soil, water, temp, essential elements, disturbances (frequency/severity)
Dynamic Equilibrium
A state of balance between continuing processes
3 Topography Factors Influencing Soil Development
Altitude- water runs downhill Slope- soil erosion Aspect- orientation to sun
Inputs
Amount of substance entering ecosystem
Outputs
Amount of substance leaving ecosystem
Storage
Amount of substance retained in ecosystem
Steps to convert organic N to inorganic N
Bacteria eat organic N, Nematodes eat bacteria, excess N excreted as inorganic N
Factors relating to energy transfer and EE Cycling
Biological Diversity, temperature, water
3 Changes in ecosystems as they mature
Biomass increase Species richness increase (# species) Species diversity increase (# species & distribution)
CEC
Cation Exchange Efficiency: a measure of the soils ability to hold & supply essential elements. Increases with OM content, clay content, increased pH
Allogenic Changes
Caused by external factors unrelated to plant community (soil erosion, herbivory)
Autogenic Changes
Caused by organisms occupying the site (organic matter, soil pH)
Ecosystem Development
Changes over time in plant and animal communities under constraints & influences of abiotic enviornment
Ecosystem Replacement/Species Replacement
Competition, structure, growth form, etc. all change over time
How primary minerals influence soil fertility
Weathering of primary minerals releases EEs into soil. Through weathering, soil is able to retain greater amounts of EEs. Fertility increases
Primary Succession
Ecosystem development in the absence of biological legacy
Secondary Succession
Ecosystem development with biological legacy where soil stays in tact following a disturbance
Gleason's Succession Model
Ecosystem structure produced by changing interactions in environment, changes in populations of species, disturbances. Climax communities= RARE, little predictability
Laws of Thermodynamics
Energy/Heat always moves from higher to lower Energy can't be created or destroyed- just transferred Energy disperses (entropy) As temps. reach absolute zero, dispersal of energy is 0
Calculate Transfer Efficiency
Exploitation x Assimilation
Pools
Form of storage compartment within system
Liebig's Law of the Minimum
Growth is not controlled by the total resources available, but rather by the scarcest resource that is required for growth
3 Criteria for Essential Elements
If not present, organism dies element directly involved in metabolic process Can't be replaced by another element
How cycling of high demand (macro-elements) controls primary production
If the cycle is slow or disrupted there will be less primary production
How Increased Biodiversity influences Efficiency
Increases number of organisms occupying an area Increases types of organisms occupying an area Increase in number and type= Greater Utilization
How CO2 contributes to Greenhouse Effect
It traps radiation (heat) and does not allow it to escape back into space, the earth becomes warmer
Major disturbance
Large impact, ecosystem function & composition altered
Minor disturbance
Little impact, ecosystem function largely unaltered
Distribution & sources of EE in highly weathered, very old soils
Low fertility Low CEC Phosphorus Retention Majority of EEs in standing vegetation Demand of EEs met by cycling
Flux
New loss/gain from inputs & outputs
Element that commonly limits primary production
Nitrogen
Physical Weathering
No change in chemical makeup of material being weathered, increase surface area
Where majority of Carbon resides in most terrestrial Ecosystems
Organic Matter, only a function of the carbon used for growth
How pH influences activity of fungi
Populations and activity decline at high pH levels
How pH influences activity of bacteria
Populations and activity decline at low pH levels
Where Essential Elements Come From
Primary minerals weathering Accumulation & Decomposition of organic matter Atmospheric Decomposition
5 Factors influencing ecosystem recovery after disturbance
Regeneration Germination of pre-existing seed bank Sprouting Migration into area from neighboring ecosystem Resource availability
Turnover Time
Relationship between inputs & outputs
Chemical Weathering
Results in EE being released, changes in chemical makeup of materials being weathered
5 Characteristics of Species establishing on Disturbed Sites
Small size of organism Low energy requirements Many offspring produced Early maturity Individuals only reproduce once
What causes late stage communities to be more effective?
Species richness increase Energy transfer= more efficient Nutrient cycling= more efficient
Clement's Succession Model
Succession= ordered progression from 1 state to another. End state= stable community (stable, balanced, persistent, not very diverse)
2 Climate Factors influencing Soil Development
Temperature (Increase= Increase in weathering) Moisture (Increase= Increase in weathering)
Succession
The changes in community composition and associated processes following a disturbance
How pH influences EE availability/solubility
The lower the pH more soluble the soil is, the more available EEs are
How Biodiversity influences N use efficiency
The more biodiversity, the more ways N can be recycled and more sources of N, so less unused N
Assimilation Efficiency
The percentage of captured solar energy that is digested at the next trophic level
Exploitation
The percentage of energy from a primary producer that is consumed over a given period of time
Changes in soil over time
They get deeper (more) Increase in clay content CEC Increase pH decrease Organic Matter Increase Water holding capacity Increase Horizons develop
Model that Describes Litter Decomposition
Tree= Accumulation of EEs Leaf litter contains carbon & EEs Bacteria eat leaf litter Nematodes eat bacteria & release excess EE Plants take in EE & capture C from atmosphere
Sources of N
Weathering of parent material
