Ecosystems & Restoration
Ecology
CAMPBELL & REECE
CHAPTER 55
Ecosystems
 no matter what size; 2 processes occurring:
energy flow
2. chemical cycling
1.
Conservation of Energy
 1st Law of Thermodynamics:

nrg can neither be created or destroyed, only
transferred or transformed
 2nd 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 material
 Detritivores: 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 respiration
 satellites 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 wastes
 organism 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 organisms
 availability influences rates of ecosystem processes

especially 1° production & decomposition in
terrestrial biomes
Water Cycle: Forms Available to Life
 most water used in its liquid phase
 seasonal 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 radiation
 condensation of water vapor
 Precipitation
 Transpiration
 Runoff : 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 fuels
 sediments of aquatic ecosystems
 soils
 plant & animal biomass
 atmosphere (CO2)
Carbon Cycle: Key Processes
 removing CO2 from atmosphere:
 photosynthesis
 returning CO2 to atmosphere:
 cellular respiration
 burning of fossil fuels & wood
 volcanic 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:
ammonium:
2. nitrate
1.
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
cpds
 natural 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
Acids
 Phospholipids
 ATP
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 biomass
 recycling 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 years
 algae & 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