campbell & reece chapter 55 ecosystems & restoration ecology
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CAMPBELL & REECECHAPTER 55
Ecosystems & Restoration Ecology
Ecosystems
no matter what size; 2 processes occurring:1. energy flow2. chemical cycling
Conservation of Energy
1st Law of Thermodynamics: nrg can neither be created or destroyed, only
transferred or transformed2nd Law of Thermodynamics:
every exchange of nrg increase the entropy of the universe
lost nrg: heat
Conservation of Mass
matter can neither be created or destroyed elements not significantly gained or lost on a
global scale but can be gained or lost from a particular ecosystem
in nature most gains & losses to ecosystems small compared to amt cycled but balance between inputs & outputs determines if given ecosystem is a source or a sink for a given element
Energy, Mass, & Trophic Levels
trophic levels are based on their main source of nutrition & nrg
Primary Producers ultimately support all other levels biosphere‘s main autotrophs:
plants algae photosynthetic prokaryotes
Definitions
Detritus: nonliving organic materialDetritivores: decompsers
Global Energy Budget
every day Earth’s atmosphere bombarded by ~ 10²² joules of solar radiation
(or enough nrg to supply demands of Earth’s human population for ~25 yrs using 2009 levels)
most incoming solar radiation is absorbed, scattered or reflected by clouds & dust in the atmosphere amt that actually reaches Earth’s surface
limits the possible photosynthetic output of ecosystems
Gross & Net Production
GPP: gross primary production = amt nrg from light (or chemicals in chemoautotrophic systems) converted to the chemical nrg of organic molecules per unit time
NPP: net primary production = GPP – nrg used by primary producers for their own respiration (Ra)
NPP = GPP – Ra
NPP =/= total biomass of photosynthetic autotrophs present; NPP = amt new biomass added in given period of time
Primary Production
amt of light nrg chemical nrg by autotrophs in an ecosystem during given time
GPP: total nrg assimilated by an ecosystem in given time
NPP: nrg accumulated in autotroph biomass,
Net Ecosystem Production
total biomass accumulation of an ecosystem =
GPP – total ecosystem respirationsatellites used to study global patterns of
primary production show ecosystems vary considerably tropical rainforest highest coral reefs & estuaries high but global total
is low because only cover ~1/10th what rainforest do
Primary Production in Aquatic Ecosystems
limited by light & available nutrients
Primary Production in Terrestrial Ecosystems
globally limited by: temperature moisture
locally limited by: a particular soil nutrient
Limiting Nutrient
is the element that must be added for production to increase
in marine ecosystems it is most often N or P
Secondary Production
amt of chemical nrg in consumers’ food that is converted to their own new biomass during a given period of time
vast majority of an ecosystem’s production is eventually consumed by detritivores
Energy partitioning w/in a Link of the Food-Chain
Production Efficiency
efficiency with which food nrg is converted to biomass @ each link in a food chain
another way: Production Efficiency is the % of nrg stored
in assimilated food not used for respiration
10% Efficiency in Energy Transfers
Production efficiency =
Net secondary production x 100 Assimilation of primary production
Trophic Efficiency
% of production transferred from 1 trophic level to the next
~ 5% – 20% with 10% being typical
Pyramids of nrg & biomass reflect low trophic efficiency aquatic ecosystems can have inverted
biomass pyramids: producers grow, reproduce & are consumed so quickly there is no time to develop a large population
Biogeochemical Cycles
photosynthetic organisms essentially have unlimited supply of solar nrg but have limiting amts of chem elements atoms taken in by organism either
assimilated or wastesorganism dies: atoms replenish pool of
inorganic nutrients used by other organisms
this cycling of nutrients involving biotic & abiotic components called: biogeochemical cycles
Water Cycle: Biological Importance
water:essential to all organismsavailability influences rates of ecosystem
processes especially 1° production & decomposition in
terrestrial biomes
Water Cycle: Forms Available to Life
most water used in its liquid phaseseasonal freezing limits soil water’s
availability to terrestrial organisms
Water Cycle: Reservoirs
Water Cycle: Key Processes
main processes driving water cycle:evaporation of liquid water by solar radiationcondensation of water vaporPrecipitationTranspirationRunoff : surface or percolation groundwater
Carbon Cycle: Biological Importance
C forms framework of organic molecules essential to all living organisms
Carbon Cycle: Forma Available to Life
photosynthetic organisms utilize CO2 converting inorganic C organic C
Carbon Cycle: Reservoirs
fossil fuelssediments of aquatic ecosystemssoilsplant & animal biomassatmosphere (CO2)
Carbon Cycle: Key Processes
removing CO2 from atmosphere:photosynthesis returning CO2 to atmosphere:cellular respirationburning of fossil fuels & woodvolcanic eruptions
Nitrogen Cycle: Biological Importance
N part of a.a., proteins, & nucleic acids
Nitrogen: Forms Available to Life
plants can assimilate 2 forms of N:1. ammonium: 2. nitrate
Nitrogen: Forms Available to Life
bacteria can use both these & nitrite, NO2-
Nitrogen: Forms Available to Life
animals can only use organic forms of N
Nitrogen Cycle: Reservoirs
main reservoir of N is the atmosphere (80% free N gas)
others: soil sediments of rivers, lakes, oceans biomass
Nitrogen Cycle: Key Processes
Nitrogen Fixation:N2 forms that can be used to synthesize
organic N cpdsnatural methods:
certain bacteria or lightening man activities:
industrial production of fertilizers legume crops
Nitrogen Cycle: Key Processes
Denitrification: certain bacteria in soil organic N N2 gas (reduction of N2 )
The Phosphorus Cycle
Phosphorus Cycle: Biological Importance
P is major component of Nucleic AcidsPhospholipidsATP
Phosphorus Cycle: Forms Available to Life
plants absorb phosphate ion organic molecules
Phosphorus Cycle: Reservoirs
sedimentary rock of marine origin is largest reservoir
also in soil, dissolved in oceans & in biomassrecycling of P tends to be localized in
ecosystems
Phosphorus Cycle: Key Processes
weathering of rocks gradually adds P to soil some taken up by plants food webs
decomposition of biomass returns P to soil some runoff oceans almost no P in atmosphere
Decomposition Rates
determine the proportion of a nutrient in a particular form
is determined by same factors that limit primary production: temperature moisture nutrient availability
Decomposition in Rainforest
is rapid relatively little organic material accumulates on floor
~ 75% of nutrients in ecosystem is in woody trunks of trees ….only ~10% is in the soil
Decomposition Rates
temperate forests because decomp much slower up to 50% of all organic material in soil
decomp slower when land is either too dry for decomposers to survive or too wet to supply them with enough O2
ecosystems wet & cold (peatlands) store large organic matter (decomposers grow poorly): primary production >>decomp
Decomposition Rates in Aquatic Ecosystems
anaerobic muds: can take > 50 yearsalgae & aquatic plants usually assimilate
nutrients directly from the water so lake sediments act as nutrient “sink”
Restoration Ecology
bioremediation : use of organisms to detoxify & restore polluted & degraded ecosystems
biological augmentation: an approach to restoration ecology that uses organisms to add essential materials to a degraded ecosystem
Bioremediation
Biological Augmentation
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