Ecosystems & Restoration Ecology Campbell & Reece Chapter 55

Ecosystems no matter what size; 2 processes occurring: energy flow chemical cycling

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 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: 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 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