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UNC-Chapel Hill GEOG 110 - Chapter 19 Ecosystem Essentials

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Robert W. ChristophersonCharlie ThomsenChapter 19Ecosystem EssentialsThe space on Earth where life exist forms a sphere which extends from ocean floor to ~8km altitude into the atmosphere.Ecosystem: A self-sustaining association of living plants, animals and microbes and their nonliving physical environment. 1) Natural ecosystems are open systems with respect to energy and matter.2) Ecosystem boundaries often function as transition zone, not sharp demarcations.3) Natural ecosystems can varying significantly in sizeBiosphereEcology is the study of the relationship between organisms (human beings, plants, animals, microbes) and their environment and among the variousa) the living organisms have impacts on the environment.lichens/mosses grow on rocks  soilsgrowth of trees  add litter to soils  more fertile soilwolfs eat deer  reduce deer populationb) through altering the environment, their impacts also have feedbacks to themselves.lichens/mosses grow on rocks  soils  higher plants to grow lichens/mosses compete outWolfs eat deer  reduce deer population  less food for wolf EcologyDeforestation:  timber  economic gains  better life  more people more space for agriculture  more food  more people loss of other lives  loss of resources soil erosion  land degradation  less foodAgriculture more food  more peopleexpansion  loss of other land (grass, forest, wetland …)fertilization/pesticide  more food  pollution  diseaseUrban expansion better living  more peopleexpansion  loss of other landsFossil fuel use better living  more people global warming/pollution Humans as Most AgentsEcosystem Components and CyclesBiotic Ecosystem OperationsEcosystems, Evolution, and SuccessionEcosystem EssentialsLike any system in general, it is made up of several components, each function independently yet in concert.bioticindividuals  population  Communitiesproducers (plants), consumers (animals), decomposersAbiotic Ecosystem Components soils, light, heat (temperature), water, air As ecosystems are open systems, there are constant flow of energy and matter through the system to keep the system alive.Ecosystem ComponentsBiotic and Abiotic ComponentsFigure 19.2↑+ →+26126roplastlight/Chlo22O6OHCO6H6COSmall Leaves do the Big Job: PhotosynthesisCO2H2OLosing water is the price to pay for gaining CO2Plants also keep cool with transpirationstomaUndersideConceptsNet PhotosynthesisPlants consume energy and release CO2during the process of photosynthesis. Because photosynthesis only happens during the day time, we call this respiration as day respiration (note: this is not part of the autotrophic respiration). The net carbohydrate the photosynthesis produce is called net photosynthesis. Compensation Point The point when the day respiration and photosynthesis break even: CO2compensation point vs. light compensation pointLight Saturation PointThe point when increase of light energy on the leaves will not lead to the increase in photosynthesis rate.Stomatal Regulation1. Stoma opens when light shine on the leaf, thus opens during the day to absorb CO2and closes during night to prevent unnecessary water loss.2. Stoma closes when there is limited water in the soil.3. Stoma closes when the air is too dry, i.e. high vapor pressure deficit. 4. Stoma closes to save water when CO2concentration is high in the air.Gross Primary Production and RespirationGPP: Gross Primary Production, the amount of carbohydrate (C6H12O6) produced is called gross primary production.Plant Respiration: All living organism needs energy to stay alive. Plants do too. Plants use about 50% of GPP they produce to stay alive. The respiration is the opposite process of photosynthesis. We call this respiration as autotrophic respiration (Ra). Energy OHCOOOHC2226126++→+Autotrophic respiration is use for two purpose:(1) to keep living tissues alive, called maintenance respiration.(2) To realize growth, call growth respiration.Note: Energy is not heat energy as said in the textbook, but energy in the form plant can use, ATP (Adenosine Triphosphate)Net Primary Production NPP: Net Primary Production is the balance of GPP after plant respiration (autotrophic respiration) is taken away. NPP = GPP – RaNPP is the part of photosynthesis product that can be used for growth, includingLeavesBranchesStemsRootsPart of NPP become food resources available for the consumers ( herbivores, carnivores, humans)Photosynthesis and RespirationFigure 19.5Energy Budget of the BiosphereFigure 19.6Net Primary ProductionBiomass RemainingHerbivore consumptionEnergy Received but not fixedBiomass vs. Net Primary Production BiomassThe dry weight of the living organisms. e.g. the total dry weight of leaves, branches, stems, and roots would be the biomass of a tree, not including the dead leaves or stems on the floor.For plants, Biomass is the accumulated NPP that stays as part of the living organism. Due to litter fall and mortality, Biomass is less than the annual NPP added up. Biomass is a cumulative figure, NPP is an annual figure.For forests, the biomass eventually levels off as the addition of growth from NPP breaks even with loss of biomass due to litter fall and mortality.Net Primary ProductivityFigure 19.7Global NPP This Table is confused between Biomass and NPP. We do not have an reliable figure for global biomass. The annual NPP on land is approximately ~56 Billion tons Carbon/year, and annual NPP in the oceans is approximately 49 billion tons Carbon/year.This table is out dated!Net Ecosystem Production (NEP) NPP: Tells us how much CO2 plants suck from the atmosphere, offsetting CO2 released by fossil fuel burning.Ecosystems also releases carbon into the atmosphere:Autotrophic Respiration (Ra)Heterotrophic Respiration (Rh)Rh: Carbon released into to atmosphere by microbes (decomposers) decomposing the detritus materials.NEP= NPP- RhCarbon Sink: Taking CO2away from the atmosphereCarbon Source: Adding CO2into the atmosphereNet Ecosystem Production Kyoto Protocol (signed in Kyoto, Japan in 1997): Developed countries reduce their CO2emission by 5% at the 1990 level during 2008-2012 period.No-plan post 2012: Copenhagen will not have a binding Protocol as it was announced in APEC meeting.Carbon absorbed by forests established after 1990 can be used to offset carbon emission. These forests were later called Kyoto Forests. Potential problems


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UNC-Chapel Hill GEOG 110 - Chapter 19 Ecosystem Essentials

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