Ecosystem ecology studies the flow of energy and materials through organisms and the physical environment as an integrated system. a population reproduction through generations resources ?

Ecosystem ecology divides the world into pools and fluxes of materials and energy: N N N N N N N N N N N N N N N Pools are quantities of materials such as carbon & nitrogen, that are contained in certain subdivisions of the ecosystem. They are measured in g or moles per m 2. Pool of all forms of N in living plant biomass Pool of inorganic N in the soil (NO 3 and NH 4 ). N Fluxes are rates of material transfer between pools, measured in g or moles per m 2 per day or year.

water vapor release More live biomass litter O 2 release CO 2 uptake Absorbs light Water uptake Soil nutrient uptake: N,P,S,K,… root exudates (complex sugars, allelochemicals?, leached N Matter fluxes through a typical primary producer:

Matter fluxes through a typical primary consumer: C, N, H 2 O, etc. in dung C, N, H 2 O, etc. in milk C, N, H 2 O, etc. in grass C, N, H 2 O, etc. in the dead cow C, N, H 2 O, etc. in a calf C, N, H 2 O, etc. in urine O 2 of air intake CO 2 of air expelled Methane, CO 2

Scavengers: vertebrate carrion eaters, Seldom restricted to carrion. Detritivores: invertebrate consumers of organic matter. Decomposers: fungi and bacteria.

Matter fluxes through a decomposer, detritivore, or scavenger: More decomposers, detritivores or scavangers simpler organic waste CO 2 release O 2 uptake C, N, H2O, etc in dead organic matter C, N, H 2 O, etc. in the dead decomposer

Dead organic matter from carrion, litter, feces & urine Net primary production: (the biomass produced by autotrophs) Herbivores (primary consumers) Scavengers, Detritivores & Decomposers (primary consumers) Carnivores I (secondary consumers) Carnivores I (secondary consumers) Carnivores II (tertiary consumers) Carnivores II (tertiary consumers) Generalized trophic web is eaten by adds

Questions we can address only through ecosystem ecology: “Budget questions” (How do all the fluxes and the changes in pool size add up?) What happens to the portion of the nitrogen that is added to the farmers field but is not harvested with the crop? What is the fate of CO 2 expelled to the atmosphere from burning fossil fuels? How much of the annual rainfall is returned to the atmosphere via plant transpiration, soil evaporation, and how much goes to groundwater?

“Comparative questions” (Why do ecosystems differ in pool sizes and fluxes? What are the controls over ecosystem processes?) Why do ecosystems differ in the %carbon that sits in living plants versus in the soil organic matter? (E.g. : tropical forests = most carbon in biomass, tundra = most carbon in soil.) How does plant species composition and diversity affect the productivity of grasslands and forests? How will climate change (=warmer temperatures, different precipitation patterns) affect productivity and species diversity? Questions we can address only through ecosystem ecology:

Climate Vegetation Feedbacks: Vegetation amount and composition Local weather patterns Earth’s climate system Land management Changes in atmospheric composition

Energy and material cycles: Solar energy drives: The hydrologic cycle The carbon cycle The nitrogen and most other mineral cycles

Earth Energy Balance

Hydrologic cycle

The Nitrogen Cycle

Carbon cycle

Global carbon pools and residence times

Photosynthesis: The rate of carbon assimilation per area of photosynthetic area. 6H 2 O + 6CO 2 + light > C 6 H 12 O 6 + 6O 2 respiration O2O2 CO 2 root exudates new biomass

The rate of plant respiration per unit area (R p ) The rate of carbon fixation per unit area: Gross Primary Production (GPP) Net Primary Production into the trophic web Net Primary Production (NPP) Net carbon gain in biomass (= total carbon absorbed by plants (GPP) – carbon released by plant respiration R p)

NPP is primarily controlled by precipitation and temperature:

DESRT: desert TUNDR: tundra WDLND: woodland BOENL: boreal evergreen, needle-leafed BODBL: boreal decciduous, broad-leafed BODNL: boreal deciduous, needle-leafed GRSTE: temperate grassland GRSTR: tropical grassland TEDBL: temperate deciduous broad-leafed TEENL:temperate evergreen, needle-leafed TEEBL:temperate evergreen, broad-leafed TRDBL:tropical deciduous, broad-leafed TREBL:tropical evergreen, broad-leafed The major earth biomes differ in NPP with precipitation. Above-ground NPP g m -2 yr -1

Global distribution of primary productivity

Net Ecosystem Exchange (NEE) = Carbon absorbed or released by the entire ecosystem (GPP – ecosystem respiration) The rate of ecosystem respiration (R P +R s ) The rate of carbon/energy fixation: Gross Primary Productivity (GPP) Net Ecosystem Exchange This is the carbon that stays in the ecosystem.

The rate of ecosystem respiration (R P +R s ) The rate of carbon/energy fixation: Gross Primary Productivity (GPP) Net Ecosystem Exchange This is the carbon that comes out of the ecosystem. Net Ecosystem Exchange (NEE) = Carbon absorbed or released by the entire ecosystem (GPP – ecosystem respiration)

Carbon Sequestration: The long-term storage of carbon in the terrestrial biosphere or the oceans, thus removing CO 2 from the atmosphere.

(Negative fluxes indicate net CO2 uptake by the ecosystem) Data courtesy of Jim Heilman, Texas A&M and Marcy Litvak, University of New Mexico. Net Ecosystem Exchange at Freeman Ranch

Grassland site Woodland site Transition site

(Freeman Ranch is taking up carbon) Data courtesy of Jim Heilman, Texas A&M and Marcy Litvak, University of New Mexico. Cumulative ecosystem carbon gain