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