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Lecture 3: Earth Systems and ecosystems (Earth's Major Subsystems…
Lecture 3: Earth Systems and ecosystems
Environmental systems
Dynamic equilibrium: Stable species or ecosystems. Can have positive or negative feedback loops
Homeostasis: tendancy of a system to maintain constant internal conditions
Resistance: strength of a system's tendancy to remain constant
Resilliance: measure of how readily a system will return to its original state after disturbance
Earth's Major Subsystems
Geosphere: Ground beneath our feet
Physical and chemical foundations for life
Atmosphere: gaseous envelope
Supports life
Provides greenhouse effect
Hydrosphere: Water
Essential to life
Mass and energy transport
Biosphere: all living organisms
Small part of total environment
At convergence of other environmental spheres
Anthroposphere: Made or modified by humans for their use
Increasing at an exponential rate
Ecosystems:
Units of the biosphere
Ecosystem inputs:
Carbon
Nutrients
Water
Energy
Matter and energy
Energy
flows through an ecosystem
E.g. Net primary productivity,
see maps on slides
Matter
cycles within an ecosystem
Ecosystem Services
Ecosystems provide countire with valuable services that support both natural and human systems
Examples:
Purification of water
Formation of soil
Provision of habitat
Erosion control
Pollination of plants
Ecosystems: space and time
Natural systems and earth processes operate on a wide range of temporal and spatial scales. Some examples are illustrated on the slide
Landscape ecology
deals with broad spatial patterns and interactions among ecosystems
Movement between Reserviors
Controlled by transport mechanisms
Residences time: Average time period a chemical remains in a reservoir.
Source>Reservoir>Sink.
See slide for diagram
Geochemical Cycles
Chemical Reactions
Biogeochemical Cycles
Hydrologic cycle: Cycles from ocean> atmosphere> land> ocean
Water reservoirs: Inflow= gain, Outflow= loss
Human impact: H2O Cycle
Carbon cycle
4 Main reservoirs
Atmosphere
Oceans
Land surface
Geosphere
Human impact on Co2 cycle
3.3 Gt/yr added to atmosphere
Nitrogen Cycle
5 step biotic and abiotic process
N fixation> Nitrification> Assimilation> Ammonification> Denitrification
Human Impact N cycle
Emissions
Fertilizers
Runoff
Groundwater contamination
Phospherus cycle
Source = Geosphere, occurs only in non gaseous forms only
Human impact
Released to water surface by fertilizers and animal waste
Lost for long time periods if released to oceans
Eutrophication: Nutrient over enrichment