Final review1/23/13 11:02 AMEcosystemWikipedia definitionLiving and nonliving things interacting in a systemThis class talks about ecosystems at a watershed scaleLike to do this so they can define a boundaryMakes it easier to study the inputs Solar radiation, precipitation, dry depositionExports: gases, water, soilWithin boundary, interested in flow of energy and materialsAnd also internal fluxes (litter production, aka dead leaves, decomposition)

Ecosystem ecology sits in the middle of different sciencesRelated to earth science, hydrology, soil science, physiological ecology, community ecology, social and ecological stewardship

History of ecosystem ecology:Starts in 1700sPlatts and Hooke did experiments to show nutrients came from air and waterPriestley put animals in jarsWithout a plant, animal diesPut animal with a plant, itll live longer (made connection between animal and plant dependence on each other)MacBride and Priestley- found respiration leads to decompositionLate 1800s- plant systematicsFredrick Clements- idea that plant communities live like a super organism (little parts making up a bigger whole)Gleason- individualistic theory on plant communities- plants randomly dispersed to a spot and if conditions were right then they would live, also based on environmental conditionsTansley- viewed ecosystems as a physical construct- father of ecosystem ecologyChemistry and physics and biology interacting Tansley ideas:Ecosystems will remain constant or in steady state until disturbed (exogenous events, coming from outside ecosystem, abiotic)Stability and persistence (sustainability)- time compared to biomass graphOscillations in graph but if you took the mean, it would basically remain even Founded New PhytologistHis stuff wasnt grounded in actual evidence but intellectual theoryWe see how science has changed today because he never would be published without the data

Late 1800sLotka- ecosystems as an energy transforming machineFirst two laws of thermodynamics

Modern day ecologyHutchinson- cool guy, never forgot anyone, met teacher at party and remembered her a year laterLindewan (1915-1942) quantitative paper using ecosystem concepts (using Lake in Minnesota)Conversion of suns energyDescribed succession Food cycle (nutrient cycle)Combined abiotic and biotic into one to talk about ecosystem Odums- 1952- first textbook on ecology

Newer things in ecosystem ecologyNEON- National science foundation- understanding changes on different scales (global, national and local)Platform for scientists to do more research without federal grantLecture 11/23/13 11:02 AM

Basic ecosystem: Challenge to Ecosystem Ecology is to Define the Fluxes/Rates/Velocities of Mass and Energy Transfer associated with the Arrows and the Size of the Pools The Exchange is made To and FromPrimary producers: plants, autotrophsHarvest sunlight to create sugars and feed the rest of the systemSoil:Rich separate ecosystemBreak down complex organic matter into hummus and inorganic matter

Ecosystem ecology: the Baldocchi-Biometeorology PerspectivePhysics Wins, Biology is How its Donephysics sets the limits (how many plants and how big the plants can get)

Physics wins:Ecosystems function by capturing solar energyOnly so much Solar Energy can be capture per unit are of groundPlants convert solar energy into high energy carbon compounds for workgrowth and maintenance respirationPlants transfer nutrients and water down concentration/potential energy gradients between air, soil and plant pools to sustain their structure and function Ecosystems must maintain a Mass BalancePlants cant Use More Water or Carbon than has been acquiredEcosystems are Complex Systems

Biology is how its doneSpecies differentiation (via evolution and competition) produces the structure and function of plants, invertebrates and vertebrates In turn, structure and function provides the mechanisms for competing for and capturing light energy and transferring matter Gases diffuse in and out of active ports on leaves, stomata Big leaves or small leaves depending on environment (adaptations)Bacteria, fungi and other micro-organisms re-cycle material by exploiting differences in Redox Potential; they are adept at extracting chemical energy by passing electrons; Microbes are pivotal for sustaining ecosystems Reproductive success passes genes for traits through the gene pool.

Corollary to Silvers Rule: Microbes Rule the WorldThey do, given the Energy stored in Carbon Substrate, produced by Plants, eating Sunlight and Consuming CO2 All Biogeochemical Cycles come to a Halt without Microbes and their ability to Recycle Nutrients and Extract Chemical Energy All function, and indeed all life, within an ecosystem depends upon the utilization of an external source of energy, solar radiation, RL Lindeman, 1942, Ecologymicrobes may rule the world but they are still dependent on an interconnected system (they couldnt live if they didnt have things to break down)Bottom-Line: Plants and Microbes Work Together as a System, An EcoSystem

Attributes of complex adaptive systemsMany Coupled ProcessesWith Non-Linear Response to Forcing Ex: light, temperature, soil, humidity (abiotic)And Subject to Feedback Ex: transpiration, photosynthesis, respiration Hierarchal System Multiple-scalesPower Law Behavior Y = ax^nPlotting log y to log x you get a straight lineMakes it easier to diagnose data because the data you will get will most likely be on that straight lineDeterministic/Predictable Change in some component in ecosystem over change in timeSensitive to Initial Conditions Path dependency Self-Organization Scale-Emergent Properties Sum of parts does not equal the wholeResiliency and Robustness How far can you push an ecosystem before it collapses

System complexity: many interconnected ecosystem processes, with feedbacksWeather drives physiologyPhysiology is building blocks to what a plant isGrowth and allocation of plants leads to biochemistry Once you have individual plants they need to work together in a system and that leads to ecosystem dynamicsDynamics include: reproduction, dispersal, competition, disturbance, mortality, succession

Landscapes form non-linear systemsThe presence of life causes river systems to build up sediments and be non-linearWithout life, the river system will basically be straight

Non-linear biophysical processes are ubiquitous in ecologyPhotosynthesisSquare root graph, levels off at the endTranspirationRespirationLeaf temperature

Why do we worry about non-linear processesThe mean of the non-linear function does not equal the function of the mean

Ecosystems operate across a hierarchy of time and space scalesFast and small gradually to large and slow

HierarchyHierarchy is defined as the arrangement of some entity (space, time, organism) into a graded series of compartments Hierarchies are nested in that each level is made up of a group of lower levels EP Odum

Biological-ecological hierarchyOrganelles, cells, organ, organism, population, ecosystem, landscape, biogeographic region (biome), biosphere

Hierarchy of ecologically-relevant space scalesMicrobes, stomata, leaf, plant, canopy, landscape, biome/continent, globe

Super-position of fast and slow fluctuations on carbon flux time seriesLots of fluctuations

Scale emergent propertiesa cell is more than its molecules, as an organ is more than its cells, and as an organism is more than its organs, ina food web, new structure emerges at every organizational level up to and including the whole web (Cohen)ex: thought, language, creativity in humans not just a bodyex: melting ice cube vs. melting glacier are completely differentmelting glaciers are more complexof ecosystems:ex: the behavior of how photosynthesis of a leaf and canopy respond to light (leaf is square root looking graph and a canopy is linear

complexity is not the same as random, its deterministicSimple sets of Coupled Ecological or Meteorological Differential Equations (dx/dt=f(x)) can produce Complex BehaviorLord Robert May, Nature, 1974 Ed Lorenz, J. Atmos Sci, 1963

Complexity: creating order out of chaos and establishing the limits on predictabilityChaotic systems are deterministic it all depends on initial state

Example of self-organization polygons in the tundraFreezing and thawing and naturally processes led to natural made polygons

Sensitivity to initial conditions and path dependenceSoccer ball on a hill example, it can roll down one side out one water shed or down the other side and out another way and the difference is a slight difference in initial condition

Non-Linearity and Complex Systems are Robust to Perturbations, they but are subject to Regime Shifts, tooA Lesson and Warning for Unintended Consequences, when Perturbing Complex SystemsEcosystems like to stay in a state, push them too far and it could collapse

Hysteresisanother non-linear response--in EcologyThe path taken to collapse an ecosystem isnt the same path reversed to get recoveryKnow this (graph on powerpoint)

Chaos and complexity in predator-prey dynamicsHair and lynx: populations cycle together

Example: periodic crashes in the stock market, another complex systemManaging complex systems forces us to think and act differently

Ecosystems work across a hierarchy of time and space scales that span over 14 orders of magnitudeEcosystem concepts: complexity/chaos/scaling1/23/13 11:02 AM

Hubbard Brook: first watershed scale study where people tried to quantify pools and fluxes of nutrients Cut down trees in one watershed and compared to normal watershedLots of nitrogen in runoff

Discussion 1 1/281/23/13 11:02 AMPower law behavior: ecological behavior doesnt scale linearly

Allometry:Measuring complicated variables with the simple metricsMeasuring trunk of a tree to see how much wood there is/how much it would weigh when its fully grownThe study of the Relationship between Size and ShapeNon-DestructiveUse tape measure or scalePractical:Measure easy variables, like tree diameter, can infer difficult to measure quantities, like leaf area, height, and productivity

Allometry, a Tool of Ecology and Forest ManagementYou can measure trunk diameter and see the leaf massData follows trends (physics wins, you can only be so big given genes and environment)Helps with ecological analysis at larger scales

Fundamental power lawsY = ax^blog y log a b log xThe Exponent, b, equals the Slope of the Log-Log plot of x and y

Overarching ConceptsEmergent Features of Complex SystemsAllometries provide useful Rules for Ecological Assessments; they bring order of the complex diversity of ecosystems Many Biological Allometries have exponents that are multiples of 14 Are Associated with the Physics of Hierarchal Systems and Fractal Nature of Branching Systems

Ecological Power Law Scaling RulesIndividual: Leaf Mass scales w/ Tree Diameter Leaf Area scales w/ Sapwood Area Metabolism scales w/ Mass Community:Biomass scales w/ Number of Trees per unit Area Density scales inversely with Size Number of trees per unit area ~ MassBiodiversity scales with Area Physical limits to resources or availability

Fundamentals of scaling: Euclidian vs. fractal scalingEuclidian scaling relates to exterior shape power law exponents are multiples of 1/3Biological Scaling is FractalAssociated with internal shapes and networks Power Law exponents are multiples of 14

Fractal Geometry, Space-Filling Perspective, adds 4th spatial dimensionArea (a), Volume (v), Length (l), Density () Scaling: 1/4 Power Law DependencyEx: roots with mycchorizal: root takes up most the space but the mycchorizal have a lot of surface area

Fundamentals of scalingLiving things are sustained by transport of materials (water, nutrients) through networks of paths. For the network to function, it must be space filling throughout the volume the final branch is scale invariant the energy required to transport material must be minimized The hydrodynamic resistance must be minimized.

Using Scaling Laws to Infer Information on the Properties and Performance of EcosystemsMeasure upper leaves in a canopy and scale down from there to see metabolism of a whole ecosystem

Size vs Number Density transcends 9-12 orders of magnitude in an Orderly MannerPhysics Wins:You can only be so big and sustain so many individuals for the resources availableCorollary 1: You can only grow so Big and So Fast; an Ecological lessonfor the Stock Market and the Federal Reserve.Corollary 2: Dont Eat anything Bigger than your Head (Mom)You can only eat so much because your stomach is only so big and your metabolism only works so fast

Yodas Self-Thinning LawNegative slope with density (x) and average total mass (y)Negative power lawmass = a number ^-4/3, number = (mass/a)^ -3/4a forest can only sustain a few large trees, or many small trees

Kliebers lawMetabolic rate (B) of an organism scales to the power of its mass (M)B = M^3/4The Metabolic Energy needed to Sustain an organism INCREASES with Mass, to the 34 powerEx: Basal Metabolic Rate (B) of uni-cellular and multi-cellular organisms scales to the 3/4 power of their mass (M)

Metabolic Scaling of Populations of Organisms is Scale Invariant: an Emergent Property of the SystemEnergy flux of a population per unit area (Bt) is invariant with mass of the system (M):When adding scaling laws, add exponentsHelps with looking at entire ecosystem

Scaling part 21/23/13 11:02 AM

Weather & Climate MeteorsAtmospheric meteors (observable phenomena):Atmospheric radiationSolar radiation=short-waveTerrestrial radiation=long-waveTemperature, wind speed and direction, moisture and precipitation, pressure

Feedbacks between ecosystem processes and weather & climateAll those things listed above control: photosynthesis and respiration, evaporation, decomposition, ecosystem structure, and soil development and nutrients

Weather vs. ClimateWeather: day to day variability (chaotic, extreme behavior)Climate: average over a long time (30 year, century) (more stable, predictable)

Atmospheric dynamics:Prime example of a dynamic system: many + and feedbacks operating on a range of spatial and temporal scalesNon-linear feedbacksSensitivity to initial conditionsStrange (chaotic) attractorsThresholds/tipping pointsComplexities with a lot of variables that need to be considered

Edward Lorenz: Butterfly effectChaotic solutions can arise from a small predictable system of equationsDepending on initial conditionsSmall scale things creating disproportionally large effects (interconnection)Ex: glacial ages, forces shifting between different stable statesCould be normal and then greenhouse gases change and force it to a warmer stable stateTeleconnection: atmospheric phenomena at one location can impact dynamics anywhere else in the atmosphere

What controls atmosphere dynamics?Solar constant = 1366 J/m^2s or W/m^2Energy balance: driven by interactions between the sun and earths atmosphere and surface

Global energy balanceEarth-sun orientation controls seasonal climate throughout the yearLong term changes in solar radiationMilankovic cycles:Eccentricity: shape of earths orbit around the sunEccentric orbit or a more round orbitObliquity: change in the angle or Earths axis tiltAxial precession: change in orientation between Earths axis and the sunEarths axis wobbles like a topHappen on very long time scalesGlacial cycles: depend on the integrated amount of solar radiation received during the northern hemisphere summer (Milankovic theory)If the north has many years of cold summers itll kick start a new glacial ageCombination of the precession, obliquity, and eccentricity control glacial cyclesMuch of income solar radiation is reflected back to space by clouds or earths surface (albedo), energy not absorbedAlbedo: the percentage of reflected short-wave radiation from surfacesClouds and white things have highest albedoEnergy emitted by sun vs. earthSun emits much shorter wavelengths (visible) because its hotShort-wave energyEarth emits longer wavelengths in IRLong-wave energyResult of this is from Planks lawIR radiation from earth is absorbed in atmosphere and re-radiated back to earthAbsorption/re-emission of radiation in atmosphere depends on chemistry N- 78%, O2- 21%, Ar-1%, water vapor and CO2 trace gasses Trace gases ( 20% of marine microbial cells, 5% terrestrial cells

Microbial habitatsRhizosphereAggregatesMicrobial biomass decreases with depth

Microbial functional rolesNutrient reservoirsMicrobes and soil organic matterDecompositionBreakdown of dead animals, plant residues, and xenobiotic compoundsMineralization and immobilization (make new biomass)Soil pHSoil redox- exchanging electronsMicrobes can use over 50 different redox couples to drive their energy generation needsSoil Biology1/23/13 11:02 AM

Our bodies are stardust; Our lives are sunlight

Eating the Sun: Converting Solar Energy to Biomass on an Ideal Summer Day Not the Annual EfficiencyGraph: wavelength (x) energy per wavelength (y), parabola downEnergy loss:Wavelength outsides photosynthetic spectrumReflected Photochemical inefficiency PhotorespirationC4= 0C3= 6.1

Potential photosynthetic efficiencies8 photons per CO2 molecule fixed, 4 e- released with each water molecule split2%, typical maximum efficiency observed in the field

ChemotrophHeterotroph (organic)Anaerobic, aerobicLithotroph (inorganic)

Energy = workUnits: joule = newton meter = N-m = kg^2m^2/S^2Work = force x distanceForce = mass x accelerationPower = dwork/dtimeWatt = J/sEnergy flux density = W/m^2 = j/m^2s = kg/s^3

First law of thermodynamicsThe change in internal energy (U) is a function of the change in the amount of heat absorbed or lost (Q) and the change in amount of work done on the system (W)Energy cannot be created, nor destroyed; it can only be transferred from one state to another. The total amount of energy in a closed system is constant Life and Ecosystems are Open Systems

Photosynthesis has 2 photosystemsPhotosystem 1 deals with light at 700 nmPhotosystem 2 deals with light at 680 nmSunlight splits water and gives off O2 and 4 e-Electron transport chain (ADP ATP)Excess energy is lost as heat or fluorescencePhotosystem 2 comes before photosystem 1

Energy from redox, microbial batteryReduction, gain of e- (GER) (RIG)Oxidation, loss of e- (LEO) (OIL)

R: gas constant: 8.314T: absolute temperature

Energy yields from carbohydratesAerobic respiration 125 kj/e-, 3000 kj/mol C6H12O6

Solar facts:Solar constant: 1366 W/m^2Get this because sun is black body and emits energy according to planks lawSolar radiative temperature: 5770 K

As surface gets hotter, spectral peak is at shorter and shorter wavelengths

Co-evolution of atmosphere and life created ozone to protect us from UV radiation

Sun: produces short wave radiation (200-3000nm) (UV, visible, PAR, Near infrared radiation NIR)

Are under the curve of Plancks law is long wave energy lost

Terrestrial long wave radiation allows us to have water and life because without atmosphere temperature would be about 255 K

Lamberts Cosine Law: The radiation normal to a surface is a function of the projection of area normal to incident rays on a flat surfacePicture on powerpoint

What happens to photons hitting a leaf:Some reflected, some absorbed, some transmitted through leavesDont absorb green light radiationReflect as much near infrared as possible radiation as possible so they dont overheat

Albedo highest in deserts and snow

Vegetation albedo differs with canopy structureAs forests get taller, they trap more light

Energy and ecosystem ecology1/23/13 11:02 AMSnow reflectance differs with the presence and absence of trees

Form follows function: Leaves have certain sizes based on environmentSmaller in hot climates, larger in cool climateRedwood trees are so tall because they have a big base

300,000 plant specieshard to deal with them all so they try to deal with function (convergent) attributes

Diversity in functional characteristics/traits better explains differences in the acquisition of mass and energy (light, water, net primary productivity, nutrients) rather than species diversityThe contribution of each species to ecosystem performance is not equalEcosystem function is controlled by a combination of factorsDominant & Keystone Species, Ecological Engineers and Species Interactions (competition, facilitation, mutualism, predation)

Multiple Resource Limitation in EcosystemsPlants adjust resource acquisition to maximize capture of the most limiting resource Changes in Root/shoot allocation occursChanges in the environment change the relative abundance of resources, so different factors limit NPP at different times Plants exhibit mechanisms that increase the supply of the most limiting resource E.g. Symbiotic relation with N fixersDifferent resources limit different species in an ecosystem

Roles of Structure and FunctionSupporting Photosynthetic organsLeaves and plantsIntercepting sunlightLeaf size, shape, thickness, orientation and phenologyMining soil for water and nutrientsRootsIncreasing Reproductive Success Flower color, type Seed size and shape Phenology, timing of flowering and leafing Facilitating the diffusion of CO2 to ChloroplastsLeaf thickness, Photosynthetic pathway, stomatal geometry,

Important attributesPhysiognomy Grass, Herb, Shrub, Tree Broad-leaved vs. Needle-leaved Tree Fibrous vs. tap roots Life Span Annual, Biennial, Deciduous, Evergreen Pollination and Seed dispersal Insect,Wind Photosynthetic pathway C3, C4, CAM Mycorrhizal Association Endo/Ecto Tolerance Features Drought, shade, fire, nutrient, frost, freeze, heat

Leaf and Plant traitsLeaf FormSize, Thickness and Shape, Longevity, Angle, Photosynthetic Pathway, Specific Leaf Area, Carbon and Nitrogen Content, Photosynthetic CapacityPlant Growth FormLeaf area density, height, longevity, crown size, tolerance to stress

Shape and size of leavesneedles vs planar vs shootsdifferent surface areasprojected vs surface area of needles projected to total needle areaBig vs Small

Leaf size, shape and orientation affectthe properties of the leaf boundary layerthe reflectance and transmittance of light leafs energy balanceemission of hydrocarbons vs temperature is exponential graphhydrocarbons have unknown function but may be defensive compounds

form follows functionneedle leaves at the top of canopy are small thin shoots that are good at giving off heatalmost like a desert on the top of a redwood forest

Photosynthetic pathwayC3- most plants on earthCO2 interacts with rubisco and forms C3 compound before it forms sugarTrees, dicotsC4- tropical grasses (corn, soybean), higher efficienciesGo through C3 step but use different enzyme in first step CAM- desert species (cacti), open stomata at night Suck in light during the day and take up CO2 at night

Leaf Structure and Function: Emerging Ecological Rules85% of variation in photosynthesis (per unit mass) is explained by variations in leaf mass per unit area and leaf Nitrogen per unit mass

The Thicker the Leaf, More Chlorophyll for Photosynthesis; Too Thick And All Light is Intercepted and CO2 Diffusion through the Mesophyll is Inhibiting, causing a Draw-Down in CO2 and Negative Feedback on Photosynthesis

Highest Photosynthesis is with Short living, Thin leaves with high N. Lowest Photosynthesis is with Old Thick Leaves with low NPhotosynthesis increase with nitrogenPhotosynthesis per unit mass decrease with leaf thicknessPhotosynthesis decreases with ageEvergreens tend to be longer living with lower photosynthesis and nitrogen levels

Thick leaves have more photosynthesis than thin leaves based on surface area but not based on mass area

Physical Attributes of Plant CanopiesLeaf area index- amount of leaf area per ground area (m2 m-2)Plantations have high leaf area, Mediterranean have low leaf areawoody biomass area index silhouette woody biomass per unit area

Beers law-

> 500 mm/y of precipitation is a threshold for forming a closed canopy> 500 mm/y will allow you to have closed canopy if you dont youll have less leaf density

Trade-offs between shade and drought toleranceWhen light comes through, low shade tolerance. In darker forest, species are more shade tolerantThe plants that are shade intolerant tend to be drought tolerant and those shade tolerant are drought intolerantA plant that can photosynthesize at high rates and grow rapidly under conditions of high light is unable to Survive at Low-Light levels (i.e., it is shade-intolerant).A plant that is able to grow in low light (shade- tolerant plant) has a low maximum rate of growth and photosynthesis even under high light conditions

Structure and function of leaves, plants and ecosystems1/23/13 11:02 AM

Aluminum is not a nutrientPlants acquire it to lower herbivory

Hydrological Cycle and EcosystemsInputs: fog interception, rain, snowFog helps redwoods survive drought seasonsStored: soil, surface waterOutputs: evaporation, transpiration

Coupling between water cycle and nutrient cycles

Chemical Potential of WaterChemical potential quantifies the driving force for movement of water between two locationsThe chemical potential of water is related to the changein the Gibbs free energy of the system, subjected by pressure, gravity, temperature and minor constituentsUnits in pressure

Water potentialThe total water potential of a system consists of the sum of water potentials forces per unit area associated Pressure (+/-) Osmosis (-) Soil and Plant Matrix (-) Gravitation (+/-)

Turgor (pressure) potential is related to the hydrostatic pressure, as when someone is blow on or sucking on straw that is inserted in a reservoir of water. Its sign can be positive or negative.

osmotic potential The presence of solutes reduces the activity of water. Beaker with membrane. Pure water on one side and salt water on the other. Pure water has potential of 0 and water will flow into the salt water

matric potential interactions between water and solid surfaces act to reduce the activity of water. Water interacting with small soil particles

gravity Potential gravitational force is a function of the density of water, the acceleration due to gravity and the height of the water reservoir above or below a reference height: affects limits of how high trees can grow

Saturated flow, pure waterNo matric or osmotic potentialTakes Negative Pressure (suction) to lift water against gravity The Gravitational Burden of Water Overhead Imposes a Positive PressuresAll about pressure and gravitational potential

Soil-Plant-Atmosphere-Water ContinuumWater Moves UPWARD because it flows DOWNHILL EnergeticallyElectrical analogy: I (current) = voltage/resistanceI = water flux density (evaporation rate), voltage difference is water potential difference, resistance is where water is stored so the plant isnt just constantly transpiring water into the atmosphere (soil, roots, xylem, leaves)

Trees, Drought and Vulnerability to Embolism70% of 226 tree species, from 81 sites, operate within 1 MPa of Hydraulic Safety Margin for Injury.. Explains Why Drought Decline is Occurring World-Widewater adhesion breaking leads to embolism and bubblesa result of drought because pressure of water being pulled up through the plant is more than the water available

Relative Humidity: Ratio between ambient, vapor pressure, and saturated vapor pressures, es(T)water temperature increase saturated vapor pressure

evaporationEvaporation is the physical process by which a liquid or solid is converted to a gaseous state Plant canopies introduce water vapor into the atmosphere via transpiration and the evaporation of water from the soil and free water on the leaves and stems. Green water- water plants have and use and transfer to the atmosphere

Potential vs. actual evaporation

Biodiversity affects on biodiversityDepends on types of plantsThis class is stupid

Water and ecosystem ecology1/23/13 11:02 AM

Soil texture:Size class of particles in soilSand- 1mm diameter- 62.5 micrometersSilt- 62.5-3.9 micrometersClay- Mg>K=NH4>NaSoils will preferentially hold onto aluminum Cation Exchange capacity1/23/13 11:02 AMAl promotes acidity

Nitrogen cycling and nutrient cycling used synonymouslyBecause in north temperate zone they were affected by last glacial age and nitrogen is a limiting nutrient to plant growth Humans are drastically altering nitrogen cycle

Nitrogen cycleN2 gas in atmosphereFluxes into ecosystems through nitrogen fixation (turning it into NH4)Which gets further nitrified (nitrification) into NO3-Lost as NO, and N2O during nitrification or through denitrification Some of that can come back into the process (nitrogen deposition)Leaching at any step in the process

Sources of nitrogen Primary source is nitrogen fixation 10% happens abiotically, 90% bioticallyabiotic is lightning biological- symbiotic and asymbioticreduction of N2 NH3 NH4 takes a lot of energyhave to break triple bondN2 +16ATP + 8H +8e- 2NH3 + H2 + 16ADP +16Pi (inorganic phosphorous)16 ATP is a lot of energy requiredenergy comes from oxidation of carbon or from photosynthesisplants give up 25% NPP to get nitrogen also requires Mo, and Fe (micronutrients essential to nitrogen fixation)enzyme that catalyzes process is Nitrogenase requires low oxygen or else it will denaturelegumes are good nitrogen fixers

Who can do itSymbiotic- bacteria living inside specialized structures in plant rootsLive in nodules on roots5-20 gN/m^2/yearasymbiotic- free living nitrogen fixers- bacteria that live in litter layer of soil and in soilhave to find own carbon and Mo, and Fe.1-.5 gN/m^2/yearsome are phototrophs and create things to protect process from oxygenlichens- algae, cyanobacteria produce carbon and do nitrogen fixation with a fungus that provides protection

differences in N fixation rates across ecosystemsabout 1-5 kgN/ha/yearg/m^2 times 10 = kg/hahighest rates of nitrogen fixation in places with most sunlight, organic matter, where P, Mo, and Fe arent limiting, following disturbance (tree falling)after disturbance, early succession 20kgN/ha/yearisnt sustainable because of energy requirementif N availability increases in an ecosystem, nitrogen fixation will go down

constraints to nitrogen fixationN availability: as N availability increases, N fixation goes down because of energy requirementEnergyP, Mo, Fe limiting nutrientsHerbivory- herbivores tend to eat high nitrogen tissues and target nitrogen fixing plants

Nitrogen depositionNatural (background) rates are lowChiloe study- tried to find background rates of deposition when you take people away because people affect nitrogen cycle.2-.5 gN/m^2/yearwet deposition- comes in as rainfall (easier to measure)dry deposition- dust and aerosols, harder to measure depends on atmosphere, climate, location relative to oceanareas with pollution has more depositionforms of deposition:NH4+, NO3-, organic N, NH3, HNO3, NO2, NONH4 and NH3 come from natural sourcesFires, nitrogen fixation, undulates (waste of pigs)NO, NO2- nitrification, denitrification

Internal nitrogen cycleAfter you produces NH4, taken up into organisms (plants and microbes) (immobilization) Organisms decomposed by microbes and they take the organic matter and mineralize (ammonification) it into NH4 (part of immobilization process is the production of DON)As it goes from organic matter to NH4, molecules have to be soluble so it can get into the cellSmall concentration of DON in ecosystems, limiting factor, rapid fluxSome organisms can take up DON (dissolved organic nitrogen), like in the arctic where the organic matter decomposes slowly and there isnt much nitrogen fixation happening NH4 nitrification (nitrified) into NO3NH4 + 2O2 NO3- + 2H+ + H2OChemoautotrophic bacteria do thisTwo steps: NH4 NO2- by one certain group of organisms (requires oxygen) (redox reaction, energy gaining step)NO2- NO3- by another group of organisms NO3 can be immobilized and taken up by organismsNitrogen1/23/13 11:02 AMSmaller molecule, more soluble, anion, more competitive as a plant if you can use NH4 and NO3

Microbes secrete extracellular enzymes into environment to help break down complex molecules into smaller ones so they can pass into the cell Enzymes are costly to make, spend nitrogen to get nitrogen, spend energy to get energy

Carbon nitrogen ratio controls immobilization and DONCorrelated with ecosystem processes Use ratio of substrate and microbes to understand how much nitrogen is going to be tied up in organic matter and how much is recycling

Growth efficiency of microbes is about 40% (deals with NH4 part of N cycle)Assume C:N ratio of 10:1Have to maintain ratio, controls what you can and cannot metabolize Say microbes break down 100 ug of C, only incorporate 40 ug into their bodies (immobilization) and respire 60 ug carbonFor the 40 ug carbon, they need 4 ug N (10:1)For original 100 ug, C:N ratio is 25:1If there is a 30:1 ratio, the microbes keep nitrogen to themselves because they need itIf its 20:1 there will be nitrogen in the environment because they wont need all of itC:N ratios help us understand rates of mineralization

In N cycle, NH4+ NO3- (both forms are inorganic or mineral Nitrogen, most commonly used by plants (especially in tropics and temperate)In boreal, its more dissolved nitrogenMeasure availability of NH4 and NO3- through net N mineralization assays

To measure net ammonification = NH4 (at time final) NH4 (at time initial) all over time is change in ammoniumSame for net nitrification (NO3f-NO3i)/tNet mineralization = net ammonification + net nitrification Need both numbers because its switching between NH4 and NO3 so quickly The problem with this is that its graphed linearly but in real life it doesnt happen that way (non linear processes) Net mineralization is a good index of nitrogen over long periods of time

Tropical forests tend to not be limited by nitrogen Ammonification and nitrification tend to be the sameNorth temperate systems, NH4 pool is larger than NO3In dry systems, there are high rates of nitrification compared to ammonification

Gross nitrogen mineralization Use N14 (more abundant, N cycling around) and .1% N15 isotopesN15 is isotope tracer, add it to total nitrogen and ecosystem to trace them as they move around You see 15NH4 15NO3Process studied over hours to days unlike the other process above which is days to weeksThis is because you have to measure it prior to recycling

NO3- can affect ecosystemsAcidification- NH4+ uptake 1 H+Plants maintain charge balance so they spit out H+Conversion of NH4 NO3 will yield 2 H+2NH4 + 3O2 2NO3 + 2H2o + 4H+NO3 uptake net yield of 1 H+NO3 leaching means there is still 2H+ and you tend to lose a cation

Dissimilatory nitrate reduction to ammonium (NO3 NH4) (DNRA)Microbes convert NO3 back to NH4 to conserve nitrogen Low redox process, requires labile C and some NO3-Requirements for denitrification More DNRA means less nitrogen lost during denitrification Keeps nitrogen in ecosystem, anaerobic processAll soils can do this process

Nitrogen cycling part 21/23/13 11:02 AM

Nitrogen losses from the cycle:Next to nitrate leaching, gas loss is the most importantGas loss in forms of NO (nitric oxide) and N2O (nitrous oxide), and N2 (dinitrogen), NO2, and NOxNO, N2O, N2 are main componentsNitrification from NH4 to NO3 is like a hole in the pipe model As NH4 is nitrified, some of it leaks out in different forms (NO, N2O). This is .1-10% of nitrification NO flux tends to occur in drier environments after rainN2O comes out in dry and wet conditions N2O is most potent greenhouse gas, catalysts for stratospheric ozone lossOzone in troposphere is pollutantProtective layer in stratosphereDenitrification is an anaerobic process, requires NO3 and CWhen its complete it goes to N2 and completes the cyclePrimarily a microbial process and can happen anywhere (extreme deserts)Facultative anaerobes- can breathe oxygen when its there but after it rains and there is no oxygen they breathe nitrateMore NO3 you have, the more probability of N2ONitrous oxide reductase?NH3 gas also lost from ecosystemsNH4+ + OH NH3Short half life in atmosphere and gets rediposited shortly after going up into the atmosphere Stimulates nitrification when it goes into the soil and you are going to acidify the soils AnamoxAnaerobic, ammonium oxidation Take NH4 + NO2 N2NO2 comes from the middle step in nitrificationImportant in marine ecosystems

Human alterationsHuman activity has doubled rate of N fixed in the environmentN2 fixed nitrogenCauses of N fixationElectric power plants (burning fossil fuels), automobiles (fossil fuels), agriculture (synthetic fertilizer and leguminous crops)Fixed n- lightning < free living bacteria < symbiotic N fixationHuman doubling n fixation- fossil fuel combustion < fertilizer production < cultivation of N fixing cropsHaber came up with the process to break N2 bond (also boshe too)Much of this process went into bomb making (military-industrial process), and agent orangeSynthetic fertilizer being used in the tropics and this is bad because they are nitrogen rich soils already and adding it leads to more denitrification and more N2O production

Fossil fuels:Formed during the Carboniferous period in the Paleozoic Era (360-286 MYA)Anaerobic conditions, microbes arent breaking down the organic matterHydrocarbons from remains of plants and animals compacted, hardened and preservedPreserved as Coal, Oil, and Natural gasContain nitrogen that oxidize during combustion

Correlations between human population and nitrogen fertilizer useSteady increase in nitrogen use, most increase in developing countriesPeople buy more fertilizer to make more food which sustains more people

Luxury consumption- plants will keep taking up nitrogen if its available even if they dont need it

What goes up, must come downThe more nitrogen you add to ecosystems the more that is eventually in the atmosphereHuman Alteration of the Nitrogen Cycle1/23/13 11:02 AMReactive Nitrogen oxides and NH4

Wet deposition- fog and rain depositionTropics arent nitrogen limited and so increased deposition means nitrogen leaks out because its not needed

Stationary sources: coal fired electric utility plantMobile sources: automobiles, planesDry deposition: pollutants suspended as particles or gases

Nitrogen deposition monitoring programsNADP/NTN- national atmospheric deposition program/national trendsMonitors wet deposition (NH4, NO3)Urban and rural sitesPuerto rico site- nitrogen deposition increasing (NO3)Coming from across the ocean (US), developing low lands in Puerto Rico (local)CASTNet (EPA)- clean air status and trends networkMonitors dry deposition (S and N) and ozoneAreas outside urban setting

Nitrogen depositionAtmospheric nitrogen deposition initially stimulates (especially in nitrogen limiting environment) growth since N is usually limiting nutrientActs as fertilizerNegative consequences of too much nitrogenPlants use all the nitrogen they can use and it leaks outCalled nitrogen saturationLeads to an increase in N2O from denitrification and nitrificationLeaching of NO3- toxic to life and humans Seeps into ground water, blue baby syndromeKills fish and wildlifeLoss of essential cations (K, Ca, Mg)Increase H+ ions and causes other cations to leach out and declines soil fertilityReduced plant productivity and biodiversity We are seeing losses of species in US because of high N deposition for a long time Ex: sugar maple tree (starving, more sensitive to cold winters, more susceptible to pest attack)

N2O levels increasing with industrialization, global warming potentialGreenhouse gas, N2O has 290 times higher warming potential compared to CO2

3 sages of nitrogen saturation in terrestrial ecosystemsearly stages: most N used by plants increased productivitylater stages: N leaching leads to leaching of other nutrients nutrient imbalances Al toxicity (harder to leach) and Ca and Mg limitation decreased productivity graph: foliar N keeps increasing, NPP increases but then it decreases, Ca:Al and Mg:N ratios decrease

nitrate export and acidification of riverslinked to fish kills in mountain lakeswaters most affected during early season high flow events nitrogen builds up before plants take it out and then the water flushes it all out

examples of nitrogen saturation- eutrophied watersalgae blooms in Baltic Sea, Chesapeake Bay, Long Island sound

Nitrogen concentration in rivers is direct correlation to people living in water shedsFrom fertilizer use, sewage, runoff, N deposition from precipitationMississippi river: doubled since 1965Increased in northeast rivers as well

Effects of nitrogen deposition in N-rich environmentPuerto Rico siteAdd 50 kg N/ha/year since 2002This is a ton of N but because it already has a complex N cycle and other cycles, they need to add a lot to detect changeSoil carbon increased with increased N in surface soilsTrees didnt grow more so where is it coming fromMaybe trees grew more rootsMaybe a decrease in carbon respiredLabile carbon decreased (easy to break down), while recalcitrant carbon (hard to break down) increasedTurns out root biomass actually decreasedSo leading to the conclusion that soil respiration decreasedIt could be decreased root biomass lead to decrease in soil respiration (but this is a small impact)Microbial respiration declines (lab)As it gets warmer, impact is largerChanges in plant and microbial communitiesImpacted enzymes breaking down C, N, PNitrogen cycle again1/23/13 11:02 AMImpacted oxidative enzymes breaking down wood and more complex things

Nitrogen and phosphorous are linkedBoth limiting nutrients

Stoichiometry- elemental ratios C:N, N:PN:P ratios vary widely across ecosystems

Phosphorous sourcesPrimarily comes from weathering of parent materialApatite minerals (Ca-PO4 mineral), Ca breaks down and releases PSpike of P in young soils and less over time Especially when you dont have more primary minerals to weatherNo real gas phaseAtmospheric deposition- redistribution of P across ecosystemsCan be pretty significant but usually at low concentrationsComes in as dustIn low amounts but accumulates over time

P cyclingUnlike N which is mobile, P is immobile P is anion reacting with cations and forms strong bonds P + Ca hydroxyapatite with low solubility (secondary minerals that form in the soil)As it gets more basic, it becomes less solubleForms under basic conditionsIn highly weathered Fe Al soils, p reacts with Fe and AlForm under acidic conditionsOcculusion- when P goes into the internal part of mineralWeathered soils, P migrates into inner crystalline structure and doesnt go out until its weathered awaySorption potential- ability of soils to grab on to P and hold it strongly

Strategies to get PMorphological adaptations:Root hairsBiochemical adaptationsExudates that increase solubility of P in vicinity of rootCitrate, oxalate, phosphatase enzymes (increase when they are looking for P or when they are taking it up)PhysiologicalRetranslocation- Plants pull P back into plant before dropping leaves and losing P Mycorrhizal associationsMyco = fungi, rhizae = rootSymbiotic relationship between fungi and rootFungi gets carboydrates, root gets nutrients (P, N)Lots of mycorrhizal in low P soilsFungi put out lots of hyphae (thin root like structures) and increase surface area that root has access to to take up nutrients

Tropical forests on highly weathered soils are P limited Lots of Fe and Al, hot weather with a lot of rainP should be really low High NPPHow do they grow so fast and big with lots of organic matter with highly weathered soils?Direct nutrient cycling- when organic matter dies and is deposited on ground, nutrients go right back into plants and not into soils Roots invade organic matter and catch nutrients before they get into soilGrow roots from branches and stems and not just the bottom and these take up dead organic matter (arboreal roots)But this isnt enough to sustain the forests over long periods of timeFe2+ doesnt bond as strongly to P as Fe3+ so if you have more Fe2+ its easier to get P Phosphorous1/23/13 11:02 AMWhen we test soils we turn Fe2+ into Fe3+ so we think there is way less P than there really is

Three main ways nutrients get into plantsDiffusionMass flowNot as important, direct contact

Diffusion: most importantAs potassium moves into root, its creates a zone of depletion around the root where there is no potassiumThis zone creates a chemical gradient where there is a lot of K outside the zone and none insideThe K moves from high concentration outside the zone to a low concentration inside the zone and is taken up by the plantCa2+ and Mg2+ have more charge and will move more slowlyK+ and NO3- move fasterBigger sized ions move slower than smaller onesCoulombs law- F (electrostatic force) = charge/radius squaredForce between two point charges Zone of depletion depends on chargeMg2+ will have a smaller zone of depletionK+ will have larger zone of depletion

Mass flow: importantNutrients moving through water (water stream)Transpiration- movement of water through soil to roots through plants to atmosphere Important when there are high concentrations of nutrients around the root and there is a small concentration gradient Important in micronutrients Works best when there is saturated flow- water flow driven by gravity More than transpiration alone, completely connected water column in soil

Direct contact: byproduct of nutrient uptake Mass flow and diffusion arent possible without direct contact but direct contact doesnt bring nutrients near/in roots

Mycorrhizae- fungi rootsSymbiosisBalanced parasitismPlant keeps fungi in check so it doesnt damage it and it can extract nutrients from fungi. Fungi extract carbohydrates from plant without killing itIncrease soil exploration/exploitationMore surface area to take up nutrients Important for immobile nutrients (P)

Nutrient uptake:Supply rate- nutrient concentrations in soilsImportant under steady state conditions (when there isnt a disturbance) Root length- root length able to absorb When roots lignify and become woody, they are worse at absorbing nutrients This deals with newer roots Apogeotropic roots- grow towards light, against gravityGrow up, out of the soilEnvironments that are very humid so the root doesnt desiccateRoot activity

How nutrients get inside rootNutrients are higher in roots than surrounding environmentNeed to transport it away into plant so it doesnt leak outCarrier and transport proteins- helps move nutrients across soil-root interface When root takes up nutrient, they need to keep chemical balance by spitting out H+Nutrient uptake/cation uptake acidifies the soil Soil is not just constantly acidified because they take up anions as well and nutrients can leach out Area right around root isnt super acidic as you would think, microbial communities help balance pH Root exudates- stimulate microbial activity so roots can take up what the microbes dont

a tree in a nutrient/water rich environment will grow quickly and drop leaves and slough off roots into soils new tissues have higher photosynthetic ability so keeping newer leaves present and dropping the older ones will allow it to grow fasterroots lignify when they get older, new roots take up nutrients betteras growth rate falls, litter fall decreases as well where nutrients are limiting, this isnt a good strategyretranslocation- before they drop the leaf, the plant removes the nutrients from the leaf N,P,KThese relative to Ca because Ca doesnt get retranslocated as much/not at all (because it is found in cell walls)

Resource use efficiency Light use efficiency- amount of growth per unit light Water use efficiency- growth per unit water taken upNutrient use efficiency- growth per unit nutrient taken upNUE- short lived plants, An= nutrient productivity * residence time = TrAn * Tr = NUEGrams biomass/grams nutrientLong lived plants- look at the litter fall because these are proportional to rate of growth Nutrients into plants1/23/13 11:02 AMNUE = litter fall mass/litter fall nutrient content

General carbon cycleCarbon in atmosphere taken up by photosynthesis (GPP, Gross primary productivity) Used for growth and plant respirationPlant respiration fluxes carbon back into atmosphereAbout 50%From growth biomass- mortality lost into litterHarvest lost to wood products Litter supports heterotrophic respiration- microbes CO2 atmosphereSome carbon goes into organic matter which leaks CO2 out later on Litter burns in fire and leads to black carbon CO2 in atmosphere eventually

Terms and units tend to be annual on larger time scales 1 m^2 = about 70g

GPP:Vc = carboxylation = CO2 carbohydrates (C6H12O6)Photorespiration = Vo = oxygenationCO2 + rubisco C3Rubisco likes oxygen and CO2 so in the presence of oxygen in will take that up and release CO2

NPP:GPP minus autotrophic respiration (R auto)R (mass, growth, T)NPP = GPP Rauto Autotrophic respiration is respiration of the self-feeders, the plants (leaves, stems and roots)Rauto is a function of growth rate, temperature, mass of the organismRa/GPP = .5 for a wide range of mass, growth, T

NEP:Net ecosystem production= NPP heterotrophic respiration = -NEE (net ecosystem exchange) NEE = fluxes of carbon in and out of ecosystemOffice hours this Heterotrophic respiration is respiration of fungi, aerobic bacteria, invertebrates and vertebrates in the soilIt is a function of temperature, soil moisture, carbon content, its lability, and priming from recent photosynthesisHeterotrophic respiration = RhRh compared to T, exponentially increases Drier soil reduces RhIncrease in leaf area index increase Rh

Net Biome production: NBPNBP = NEP carbon loss via disturbance (Fc)Fire, herbivory, disturbance

Mauna Loa observatory measuring atmospheric CO2Isolated site, measure of CO2 in atmosphereAnnual fluxuations of CO2, general increasing trendCO2 goes up in atmosphere in winter time, more respiration than photosynthesisCO2 goes down in summer because more photosynthesis than respiration

Global carbon cycle: Gross fluxes and PoolsUnits: peta grams Pg = 10^15 g = 1 GtC (gigaton) Equivalent to a 10 micron layer of water per meter-squared across the terrestrial globe 1km^3 = 1 GtPools- 843 PgC @ 385 ppm in atmosphereVegetation is 650 PgCOceans = 38,000 PgCSoil = 3194 PgCBig stores of carbon in permafrost If you melt permafrost, C goes into atmosphereFluxes:Annual basis, global GPP = 120 PgCGlobal scale long term NPP = 60PgRh = 60 PgBalance between photosynthesis and respirationDisturbed by deforestation and fossil fuel burningDeforestation = 1.5 PgC/yearFossil fuel = 8 PgC/year

Mass of atmosphere:F = m*a = P*aMass = 5.3*10^21 g airC in atmosphere @ 393 ppm (393*10^-6)860*10^15gC 2.19 Pg/ppm

Evidence of fossil fuel combustion: 13C isotope recordPlant based Carbon has a 13C signature ~ -25 per milThis is in fossil fuel because it was taken up by plants long agoCombustion of Fossil Fuels Dilutes the Atmospheric Background so the graph is negative and dropping

Ecosystem Service:Only ~45% of CO2 emitted into the atmosphere remains thereMore carbon going into oceans, making it more acidicFx (fraction?)PgC/2.19 Pg/ppm * 47% = ppm

The amount of fuel we burn in 1 year took 175,000 years to sequesterMost Coal Deposited during Carboniferous, 300 Ma

Reservoirs containing the highest concentrations of N per mass are:petroleum (100-20,000 mg kg-1)coals (2000-30,000 mg kg-1)modern marine sediment (1772 mg kg-1 77 ) shales (600 mg kg-1),limestone (73 mg kg-1 78 )

glacial periodslow CO2 (180 ppm), low tempcarbon lost from atmosphere to cause ice ageinterglacialhigher CO2 (280 ppm), higher tempTerrestrial carbon cycle1/23/13 11:02 AM

Basic photosynthesis stoichiometry6CO2 + 6H2O + (light) (C6H12O6) + 6O2

photosynthetic pathwayC3TreesCalifornia grasses are C3 because they are Mediterranean C4Grasses, tropical/subtropical settings (Maze, sugar cane)C4 is favored under low CO2 conditions and high temperature conditionsGlacial periods with low CO2, C4 grasses expand CAMDesert species and Pineapple

Photosynthesis- balance between supply and demandBiology drives demand: Biochemical limitation: carboxylation rate Light limitation Enzyme limitation Physical limitation: delivery of CO2 to leafDiffusion through Leaf Boundary Layer Diffusion through Stomatal Pores Potential Gradient between free Atmosphere and substomatal Cavity

C3- Calvin-Benson cycleLight reactionsChlorophyll, in chloroplasts, captures photons Photons split water molecules and release electronsLight energy is used to produce chemical energy in the forms of NADPH and ATP ATP is energy source, NADPH is electron sourceOxygen is produced Dark reactionsBind CO2 with RUBP (C5 compound)C6 splits to form 2 C3 sugarsReaction catalyzed by enzyme RubiscoRubisco likes oxygen so its less efficient than C4 photosynthesis It may take up oxygen and leak CO2Rubisco accounts for about 9-25% of the N in the leaf Chemical energy (NADPH, ATP) used to generate RUBPGraph on powerpoint

Using solar energy for lifeVisible solar energy (400 to 700 nm) is absorbed by pigments This energy is converted into high energy compounds, ATP and NADPH, by photosystems II and I (PS II and I) Photosystem II uses 680 nm energy to generate ATP (non-cyclic electron transport) PS I uses 700 nm solar energy to generate NADPH (cyclic electron transport). Excess energy is lost as heat or fluorescence. 8 Photons per CO2 molecule fixed ideally- not in the real world because energy lost as heat

C4 leafContain bundle sheaths in mesophyll

C4 photosynthesis The enzyme PEP Carboxylase catalyzes a reaction between CO2 and phosophenolpyruvate (PEP) to form a C4 compound The C4 compound is transported into the specializes cells, the bundle sheaths, and is decarboxylated When it is transported, there is no oxygen in bundle sheathsExtra step but more efficient than C3CO2 is released into an environment and photosynthesis is completed via the C3 cycle Photorespiration is low; RUBISCO favors CO2 in this environment because the ratio between CO2:O2 is high

C3 vs C4Diets reflect- Americans have C4 signatures (corn), Italians have C3 signatures (pasta)Ci/Ca = .7 for C3Higher concentration of CO2 internally for C3Stomatal conductance for C3 is more than C4Ci/Ca = .4 for C4Water retention is greater in C4 than C3Ca??Light use efficiency, CO2 and temperatureC4> gunnutum yield- for every photon they absorb they take up more CO2Light vs photosynthesis graph. Linear correlationSteeper line is C4, flatter line in C3

Comparative ecophysiology chartStudy thisKrantz anatomy- C4 plants have one, because they have bundle sheaths CO2 compensation- where photosynthesis and respiration are balancesGraph of CO2 vs photosynthesis- square root curveHigher rates in C4, compensation point is NO3->Mn3+>Fe3+>SO42->CO2>H+Anaerobic respiration is much less efficient and slows down and this tends to lead to a big build up of organic matterCH4 (methane) is a byproduct of some anaerobic respiration and we care because its a greenhouse gas

Who does decompositionMostly microbesBreak down macromolecules Hang out on surface and litter layerGood at breaking down wood (lignin) More mobile than bacteriaTentacles send out to move and grab stuffDetritivores- soil invertebratesCrunch and crush, break down litter and sometimes eat itDont really decompose it because they dont really break down the macromoleculesStart the process so the microbes can break it down Earthworms are important because they are lined with microbes so there poop is decomposing rich BacteriaArent very mobile, desiccate easily Do better in variable redox conditionsFacultative bacteria- switch between redox based on conditions Important for inner soilFungi arent very good with anaerobic conditions

Controls on decomposition (most focus on top three)ClimateFaster decomposition in warmer placesWarm and wet fasterNot too wet because itll become anaerobicCold and dry slow PET = potential evapotranspiration- the amount of evaporation that wouldve occurred if there was sufficient water availableAET = actual et= amount of water removed via evapotranspirationCDI = climate decomposition index- modeling variable using monthly values of precipitation and temperatureCalculates temperature influence on decomposition Shows threshold points of very cold and very hot when microbes turn off Good on large scaleLitter quality Physical and chemical characteristics of the material being decayed Chemical factorsLignin- complex macromolecular structureMicrobes have figured out how to deal with itPlant compounds- tannins, polyphonolicsMake it hard for cells but bacteria can deal with itMake it so bugs dont eat them but its also hard on the microbes so the processes slow down Unfavorable elemental ratios (stoichiometry)EX: Ca:Al, C:NLow nutrient contentEx: N and P limitationAcross ecosystems, climate is important. Within ecosystems, litter quality is importantMicrobes exude enzymes into environment to break it down Site conditionsSoil conditionsMoisture (not precipitation)Temperature (warm faster)RedoxIf oxygen gets consumed, not a lot of decompositionNutrient availabilityMicrobes need nutrients just as plants and animalsNeed nutrients in soil to stimulate decompositionHigh in Fe, Al, Ni can be toxic to decomposersTexture- Finely textured soils (clays)- hold a lot of water so it can increase processes but too much water will slow down the processesMore surface area means more CECSorb organic matterAggregates can lock soil organic matter away from microbesUse 14C dating to see how old it isCan use these assays to study C sequestration (carbon storage/flux)Organisms DecomposersMicrobes and fungi, detritivoresHeterotrophsSo many things use carbon so its hard to figure out who does what, how, and how to manipulate them Microbial succession- during decay, you change the quality of the materialWhen the material changes, the microbes change as well and those that eat the microbes change as wellThe whole food chain cycles in microbial succession

Decomposition1/23/13 11:02 AMPlants balance needs so thats why they make woody lignin stems roots and branches even through they are worse at absorbing minerals

Decomposition = mass loss/time

Decomposition over time isnt linearPhases of decomposition1-5 years slow loss of recalcitrant (difficult) material time (x), mass loss (y)- linearly decreases in first few weeks/monthsthen it exponentially decreases from there getting less steep as time goes onLitter (at time t) = L (at time 0) e^-kt= LnLf/L0 = -KTk = decomposition constant (negative number, unitless)very few assumptions in equation

turnover of litter standing stockKl = litter fall (g/m^2/y)/litter pool (g/m^2)Requires steady state assumptionCant measure after a hurricane for months to years because system is in chaos Residence time = 1/K or 1/Kl

Take an ecosystemAbove ground NPP and below ground NPPFlux of heterotrophic respiration and leaching of dissolved organic carbonHeterotrophic respiration is flux of decomposition

Carbon exchange (y), time (x)GPP is graphed and looks like a hill. Goes up, stays flat for a little and then rolls downNEP is shorter hillGraph in book, know relationship between these

Decomposition 21/23/13 11:02 AMRsoil = R roots + Rnet

Disturbance- Important for turnover of resources and nutrientsMakes room for new organismsDisturbance severity (x), different levels

top one would be herbivory because its a small disturbance going down they could be fire (sort of severe), agricultural clearing, flooding, mining and war, glaciers and volcanoes (very severe)more severe has more organic matter removed as an index

succession- changes in plant community composition following disturbance primary- biological colonization and changes in systems that have no live plant materialproducts of ecosystems are completely removed or buriedno organic matteronly a little bit of microbes secondary- changes in organisms and the environment following a disturbance where there are still organisms alivestill life and organic matter (may not be a lot)

primary successiondisturbances- glaciers, volcanoes, meteorites (potentially), landslides (small scale), large scale flooding, human construction (roads)stages:dispersal- getting to the sitesmall seeds, spores generally get dispersed via windcyanobacteria (fix nitrogen), lichens, algae (form crusts which creates an environment that captures dust and nutrients and stabilizes ground)colonization most of the nutrients come from atmospheric depositionearly colonizers are often nitrogen fixerscombination of free living and symbiotic onesimprove environment for later organisms to invadeshade, nutrients, water, safe spots (facilitation)facilitation ex: Fern in the tropics makes stem that captures seeds that grow sometimes early colonizers make it hard for later organisms to colonizeproducing a lot of leaf litter will block seeds from making it into the soilarrested succession- when succession proceeds for a while and then kind of stops Hawaii- Myrica faya, non-native species that colonizes areas Brought by birds, nitrogen fixer, grows well in early successionCreates a lot of organic matter (because its a tree) and rapidly increases pace of primary successionEstablishment

Primary succession environments (in regards to nutrients)Time (x axis), carbon flux (y)- graph is of NPP (green), GPP (red), biomass (blue), decomposition (yellow), NEP (black)Peaks in the mid because fresh greens and new growth and towards the end its older tissues that dont sequester as much carbonIn the beginning, not a lot of nutrients available so it takes time for NPP to gear upAt some point, nutrients light and water becomes limiting

in the desert or arctic, it would look similar but over a longer period of timeyellow is decomposition- heterotrophic respiration. Lags behind NPP because there needs to be organic material available to break downat first there is hardly any organic matterNEP is going to be balance between heterotrophic respiration and NPP

Time (x), soil carbon(y) (red), CEC (blue)

slow at beginning because there arent a lot of nutrients or organic matter growth

early succession- good at holding nutrients, retranslocationinputs = outputsmid succession- dont hold onto nutrients as much, more leakyold succession- outputs > inputs

If it was primary succession, there would be no plant carbon. After disturbance during early secondary succession, ecosystem looses carbon because wood decomposes and there is a pulse of heterotrophic respiration

Slope of K (decomposition) should be negative

Death destruction and rebirth (disturbance and succession)1/23/13 11:02 AMLeaves tend to be more nitrogen rich because of RuBP and this makes them easier to break down compared to roots

1/23/13 11:02 AM

carbon into an ecosystem is NEEauto respiration fluxes out (from plants and soils)heterotrophic respiration out from soilsNEE = GPP RecosystemRecosystem = Rroot + R heterotroph

something about photosynthesis during the day

cant have negative photosynthesis, not much going on towards the lower limits of photosynthesis maybe some moss or something, not many organisms

Tropical forestsGrowing season January to December- take up light 365 days a year2% light use efficiencyforests are somewhat transparentamount of sunlight getting to soil from canopy decreases dramatically in a foresthave to take albedo into account

seasonality effectday (x), carbon flux (y)

below the line is in the growing season (photosynthesis dominating, sink), above the line respiration dominates (source)tropical forest (red), California (green)

temperature (x), respiration (y)

increased global warming means increased respiration

year to year change in photosynthesis (delta GPP) (x), year to year change in respiration (delta Respiration) (y)

decrease in photosynthesis doesnt mean increase in respiration. Things are in balance

flux of carbon largely depends on time since last disturbanceafter disturbance. Below line is source, above is sink

varies depending on where you are (bog vs chaparral) bog would take a long time to get to the zero point, chaparral would fluctuate a low because of fires

temperature (x), respiration (y)

lot of variability once the temperature warms, have to consider the other factorsCarbon 31/23/13 11:02 AMex: soil moisture, phenology, pulses of respiration from rain (microbes)

time (x), carbon (y)

slope is deltaC/deltaTderive deltaC/c = r ln C = rt take e and C(t) = C(0)e^rt

r (growth rate, y), number (x)

r = rinitial(1-N/K)as population increases, reduces r initial to get r

concentration of organisms (y), time (x)

C(t) = (K*Co*e^rt)/K + Co*e^rt-1

Law of .69.69/%growth rate (r) = when the population will double

N(t) = N(o) e^rt, divide by N(o)N(t)/N(o) = 2 for doubling time2 = e^rt, take natural log and .69/r = t

r vs. k selectionr- small adults, small offspring, many offspring at a time, reproduce early in life k- reproduce late in life, produce few offspring, produce large offspring, large adults

pulses

ex: denitirfication huge flux of N2O

switches

ex: period of dormancy to period of rapid growth (spring), fire, phenology, landslide

Temperature of soil is constant deep into ground black (2cm)blue (5cm)red (16cm)temp (y), time (x)

soil temperature lags with depth

weather physiology (respiration, photosynthesis, transpiration) biogeochemistry (light interception allocation, growth)

ecosystem dynamicsreproduction (dispersal)recruitment (baby plants succeeding in a new niche) competition (light, nutrients, water)facilitation- ponderosa pine growing under tree because it thrives in shade mortality- 1-2% mortality/year ecosystem dynamics 1/23/13 11:02 AMdisturbance and succession

Global ecology:goal: to understand fluxes everywhere all of the timestarted in 1969 with images of earth from Apollo mission Lieth- broke up earth into grid of latitude and longitude and measured temperature and precipitation

Launch of Terra satellite working on MODISHelps us see things from space

Land cover photos from space helps us understand plant functional types Dark and seasonal deciduous forestIncoming PAR- visible sunlight .4-.7 umUse light use efficiency based of others things like temperature and vapor pressure deficit

Photosynthesis (y), PAR (x)Sun leaves blue, shade leaves red

1 meter resolution from space satellitesclouds make it harder for us to see from space

Pros to satellite processingRepeated sampling, able to detect changeDisturbance, phenology, FireInterannual data

Wavelength (x), reflectance (y)

first bulge at green, dips at blue and red and the rises in the NIR

NDVI = Rnir Rred/Rnir + RredReflectance of different types of vegetation and ecosystems

GPP = Ipar*Fpar*epsilon

Global ecology and remote sensing 1/23/13 11:02 AM

specific traits: morphologicalways species show their differencesbiogeochemical processesnitrogen fixationC3 vs C4 photosynthesisDeep roots vs. shallow rootsBrowsers, grazers, pathogens

Mangaver indica (mangos)Increased soil carbon wherever it was foundSpecies that tends to flush out leaves (drop leaves) and can go through two or three flushes throughout a year

Species good at retranslocating nutrients:Ex: phosphorus. Soil will be phosphorus depleted around the plant Leading to patches of depletion around a forest

Species impact soil temperatureInsulating soil at surface because of root mats

Albedo:Fire regimes:Eucalyptus burns easily so when you introduce them into an ecosystem the ecosystem becomes more fire susceptible

Diversity in ecosystem function If number of species (biodiversity) is related to ecosystem function then maintaining diversity can be justified for the conservation of ecosystems (so we can get ecosystem services)This isnt easy (see scale below)Species richness- number of species per unit area

ScaleScale of ecosystem function and diversity differSpecies are discrete unitsFunctioning processes (nutrient cycling, succession) are measured with indexes and a rate of process Continuous and difficult to measureOther difficultiesComplex need to simplifyDetecting changes in function Most species of plants participate in most functions in fundamentally the same way (photosynthesis, nutrient uptake) (microbes however dont do things the same way)Exceptions: nitrogen fixers, C4, CAMMore focus on these because they are different How to deal with detecting problem- functional groupsDeep roots vs non deep rootsNitrogen fixers vs non nitrogen fixers Comparing one group against another Problem is functional groups vary in time and spaceRedundancy:Are there redundancy between species? Can we lose some without negative side effects? Appear to be redundant but could be important in some unknown way

Theories to look at biodiversity and system functionRate process (y), number of species (x)

black (no change in number)blue (linear, higher NPP with more species)green (asymptotic, at some point species become redundant and adding species doesnt impact function)

competition- more species, more they divide up the niche, more resources they use and more competition adaptations evolve overtime to deal with or avoid competition in nicheslife form diversity: different canopy heights lead to different life forms living at the different heights (ground, palm, tall tree, canopy)different phenologies to exploit the environment number of traits doesnt correlate with number of species competitive exclusion- competition leads to decrease in species numbers especially when one is superiorinvasive species out compete native intraspecific competition- competition within species can decrease numbers complimentary- more species more resource utilization facilitation- one species helping another speciestrees that fix nitrogen and allow other species to come inpalm in tropics catch seeds and its a good place for seeds to grow niche differentiation- sum is greater than wholespecies working together gives you more ecosystem function than the species alone sampling effect- probability of getting a certain (special) species as you increase number of species in samplewhen you have more species, your probability of having a special species is higherspecial species could be nitrogen fixer, deep rooter, species that has a disproportionate impact on function

experiment design for biodiversity and ecosystem functionDave Tillman- planted tons (200+) of small plots (1-2 meters) with different species mixtures and followed that over timeHad to weed to maintain species richnessWeeding causes disturbances of soilResults- analyzed data before and after drought Nitrate concentrations in root zone was weakly correlated to number of speciesMore diverse plots, more nitrogen fixers (sampling effect)Experimental microcosms- people create ecosystems in controlled environmentsLets people look at a different range of processes

Species effects on ecosystems 1/23/13 11:02 AMLook at data Professor Silver posts

Causes of landscape heterogeneityState factorsClimate: light, temperature, rainfall, soil moisture Geology: parent material and soils Topography: Exposure, erosion Water: rivers, lakes, tidal action (estuaries, coast) Community factorsFounder effectsSpecies influence ecosystem processes May reflect stochastic patterns of colonization Historical land-use patternsDisturbanceNatural disturbances: fire, hurricane, landslide, diseasesCreates patches of different ages and sizesHuman activity, logging, agricultural conversion, roads, urbanization, fire suppression/prescribed burningExtensification/intensificationInteractions among sources of heterogeneitySelf-Organized Criticality Scaling laws, power lawsRandom Dispersal events Sunol Hills: Roles of Topography, Water, Grazing, FireLateral Transfer of Water from Ridges to Draws Meets Greater Evaporative Demand of TreesNeed more water in tree area compared to grass areaGrass areas drain into tree areas Grazing and Fire Sustain Patterns

Patterns in Semi-Arid SystemsAlleopathy- plants exute toxic materials to prevent other things from growing close to them Resource islands- water, nutrientsFacilitation/competition Low vegetation density soil is too hot and dry low rates of colonization and recruitment low vegetation density Shading soil is important because it can account for 30-50% water loss High vegetation density shading lowers soil evaporation higher vegetation densityHigher vegetation density organic matter in soil promotes higher water infiltration higher vegetation density

Guano deposition of birds create patches of P rich area where trees can form

Boreal forests are a mosaic of time since last disturbance (fires, glaciers)

Clumped forests are resilient to fire spread

Arctic polygons: formed naturallyFreezing and thawing over and over cause shapesWetland- cold, little evaporation, positive water balance

Want to minimize energy needed to get from point a to point b and this affects landscape design and drainage network

Land fragmentationAltered environmental conditions Edge effects Increased abundance and incidence of invasive species Changed disturbance regimes Altered species interactions Pollination Seed dispersal Predation Herbivory competition Genetic deterioration

Fragments have poorer species richness

Habitat patches connected by corridorsRetained more native plants than isolated patchesDid not promote invasion by exotic species

Landscapes exhibit complex patterns that can be Geometrical and Natural Driven by limitations of resources (water, nutrients), tending to form most in arid and flooded environmentRivers form dendritic networks to minimize the energy used to transfer of water

Meandering Rivers, vs Braided Rivers, is a signal of life

Fragmentation of Landscapes Reduces Connectivity and Decreases Biodiversity Landscape patterns in ecosystem structure and function1/23/13 11:02 AM

Why modelDiagnose and understand complex interactions Cross scales Leaf and soil up to canopy and landscape Look at conditions of the past and future Ex: CO2, T, N

Light drives photosynthesis, waterModels can consider disturbance, land use change, nutrient, carbon

Model parametersSet of equations (y = ax)Driving inputPAR, ppt, TSpatial scaleTake a landscape and break it up into a gridHow do you put Fine scale information (microbes) into larger scale models Time stepCentury, or what time scaleValidateField measurements or calculationsSometimes models are better than field informationModels can help understand weaknesses in measurements Hierarchy of modelsBig leaf model Assume ecosystem is a huge green leafBucket model

Michaelic Menten equation Rate or velocity (y) is function of Vmac * C/ Km+CSquare root looking graphDeals with metabolism?

1-D turbis mediumbox with dots (leaves) randomly distributedhelps model multilayer stuff (canopy)

mean of function doesnt = function of the mean

stochasticstatistically and randomly predict where a disturbance may occur

biophysical modelSIB from nasaCLM from NCAR

Biogeochemical modelCenturyBGC- cyclingCASAPnet

Biogeography Dissociate plant functional groups and climate

Orchidaee (French) look at ice ages and see how ecosystems move and how species distributions will vary

Ecosystem modeling 1/23/13 11:02 AMTest models and validate them and they are pretty good models but not as good as they could be

Policy and sciencePeople dont want to change and its going to cost us a lot in the long runInternalize the externalities

Fallacious logicClimateGate scandal (Al Gore)Oil lobby and organizations

Global temperature recordFrom 1880 to 1960, slight increaseAfter 1980, pretty big increase

FactCO2 is increasing (Mauna Loa)Oscillating increasing since 1960Dips in northern hemisphere summer because of photosynthesisRaises in winter because of respiration CO2 absorbs infrared radiation in open IR windowsRadiation vibrates the CO2 molecules and they re admit it randomlyPeak absorption at 4.25 um, 7.2 um, 14.99 umThe window where radiation escapes is the absorption area of CO2 so when we add CO2, we make the window for escaping radiation smaller

Evidence of global warmingSea level riseTree ringsEtc..

Stable isotopes in ice, a proxy for temperature

C4 grasses outcompete C3 under low CO2 conditions so they dominate between ice ages

Natural solar forcing of climate variabilityEccentricityObliquity (tilt)Axial precession

Tree rings- grow better in warm wet years

Sea level rise- thermal expansion and melting ice

Temperature lags CO2

Feedback: climate warms ice melts CO2 solubility in ocean decreases CO2 rises climate warms

More Particles Reduce Daytime Warming from Sun

More Greenhouse Gases Reduce Nightime Cooling

leafing and flowering earlier in the year

Global Warming1/23/13 11:02 AM

Things scale from cell to leaf to organism to organisms to ecosystem to landscape to globe

3 main greenhouse gasesCO2CH4Nitrous oxide (N2O)

Other greenhouse gasesCFCs, SF6, water vapor, O3, HFC

Radiating forcing = energy change per unit area of globe measured at the top of the atmosphereAmount of energy captured per unit area per unit time (for greenhouse gases, longwave from earth)Positive is warming, negative is cooling

Global warming potentialRelative index of heat trapped by greenhouse gasesRelative because all scaled to CO2 = 1GWP (x) = something+ H = time horizonax = radiative efficiency due to increase in abundancex(t) = time dependent decayr = reference gas (CO2)GWP of CO2 = 1GWP of CH4 over 20 years = 72Over 100 years = 25Methane decreases because it decays in the atmosphere where N2O doesnt decay as quicklyGWP N2O over 20 years = 289Over 100 years = 298

Carbon cyclePhotosynthesis in, respiration outKeeling plot (mauna loa) lets us know this is happeningMore wiggle in northern hemisphere because there is more land area and more photosynthesis and respiration happening Carbon in atmosphere = 760 Pg (10^15)In plants = 650 PgTurns over every 11 years (average on global scale)Oceans = 38,000 PgSurface water = 1,000 PgStored as inorganic carbonate Marine biota = 2 Pg but cycle as much carbon as terrestrial vegetation Turnover is 2-3 weeksBiological pump- carbon is fixed and pushed to bottom of the oceanMore CO2 added to atmosphere, more CO2 entering the water and this changes acidity of waterImpacts shellfish ability to make shellsOcean cant hold as much CO2 under acidic conditions compared to neutral or basic conditions Solubility pump- linked to upwellingCO2 rich waters get transported down in northern latitudes (thermohaline circulation?)Slower cycle than biological pump Soils = 1,500-2,500 Pg CTurnover around 25 years3 poolsfast- turnover in months to yearsintermediate = years to decadesslow = decades to millennia can manage the carbon in soil and possibly can push it into the slow pool to store the carbonRocks and sediments = 10^7 Pg CTurnover slowly naturally = millions of yearsBut humans are mining fossil fuels and oxidizing it and making that turnover time fasterCO2 emissions are 77% greenhouse gas emissions Sources fossil fuel combustion (70%)Biomass burning and land use change (17%)Deforestation

Reducing CO2 emissions wont be enough to change climate change

HopeReduce emissionsGrow plants that sequester carbon Pushing carbon into rocks (CO2 injection)Risks with earthquake faults and releases of high concentrations of CO2

Methane (CH4)20% current global warmingnatural sources:wetlands, termites, tropical forestscome from archea (not bacteria) and produce methane under anaerobic conditionshuman sourceslandfills (anaerobic conditions with a lot of organic matter)enteric fermentation- cows, other live stock produce methane in their stomachs when they break down food (fiber)rice agriculture- flooded, anaerobic conditionsresidence time about 10 years (CO2 is hundreds of years)

N2O6% global warmingresidence time hundred yearsNatural sourcesTropical forests (cycling nitrogen at fast rate, denitrification)Human sourcesCow manure (feedlots, dairies) 2.1TgFossil fuel industry 1.3 TgClimate Change1/23/13 11:02 AMFertilizer and N fixing crops

More N is fixed Synthetically than Naturally > 50% of accessible fresh water is being depleted ~ 20% Marine fisheries are over exploited Extinction rates of species have accelerated Were experiencing the 6th Great Extinction Period over Earths History, the 1st caused internally. Land Use Change and Extinction Opens Niches for Invasive Species

Attributes of Global Environmental Change- Anthropocene Changing things much faster than previouslyThe time scale of this great extinction is so much smaller than in the pastChange is non-linear, hystereticChange is conditional on antecedent conditionsDown-regulation- photosynthesis response to CO2 will depend on conditions in which they are grown Change is Multi-Factorial (CO2, N, ppt, T, O3, age, invasive species, disturbance)

Ways to study ecological changeMix of observations, models, manipulations, and relate those to past environments (paleo records)

CO2 tunnelsHelp you see how photosynthesis changes with different species with different CO2 levelsFrom pre industrial levels to ice age levels to projected levels

In summer in northern hemisphere, ITCZ shifts slightly northward and so tropical areas are on the edge of the region and wont get as much water

Timing of rainfall may be as important as amounts added/subtracted Look at monthly climate drivers over annual (or at least look at both)

In Principle, Global Warming Should Accelerate and Water Cycle Increase Evaporation Increase Cloud Cover Increase Precipitation Reduce Solar Radiation Negative feedback on Evaporation

Ecosystems and environmental change1/23/13 11:02 AM

Photosynthesis vs CO2Linear/curved at the top relationship Ci = .7CaHigher and higher CO2, saturate plants

Down-Regulation of Photosynthesis based on CO2 Growth EnvironmentDont achieve as high of rates as you would otherwiseGraph on powerpointAs CO2 levels increase, stomatal conductance decreasesDont have to open up stomata as muchMore efficient water use under high CO2 conditions

Increased CO2 will increase yield and biomass but less than the theoretical amountDown-regulation

Elevated CO2: Direct and Indirect EffectsGrowth goes upCompound interest effect- small plants will grow faster with more CO2 but bigger plants grow faster than smaller onesMineralization decreasesRespiration increases

At high CO2, insects eat more leaves to get proper amount of nitrogenHerbivory increases because leaves have less nitrogen

Possible shifts with warmingIncrease in mean (hotter averages)Increase in variance (more extreme weather)Increase in mean and variance

Temperature acclimationBad effects if the temperature changes over a short time scale because plants dont have time to acclimate so more plants dieModels assume big jump in temperature and this may not be accurate Photosynthesis and acclimate in a good wayRespiration will down-regulate for warm adapted placesCold places will up-regulate respiration rates

Plants can handle a few days of heat stress but repeated days of high temperatures will cause a drastic increase in mortalityCan tolerate some stress but eventually give in

Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate.Plants will flower earlier with global warmingWhat happens when there is an unsynchronized pattern between flowers and pollinators

Increasing trends of growing season since 1980s177 days to about 187 days

disturbance and land use changeFires Deforestation/Logging Urbanization Desertification Woody Encroachment Afforestation/Reforestation Storms Invasive Species Soil Degradation

Deforestation leads to net loss of carbonResults from global change experiments 1/23/13 11:02 AMNo trends really but additions to atmosphere

Weve covered- ecosystem structure and function, water and nutrient cycles, light, chemistry and physics of plant soil atmosphere interactions, role of biotaScaling from small to globe

Humans as part of ecosystemsConsumersUse raw materials, transforming and sometimes recycling themSome stuff cant be broken down- no oxygen, no light, molecules that are hard to break down (microbes break down the easy stuff first), wont be broken down on human time scalesEverything is recycled on some time scale

Tipping point- passing a point where you no longer can recover

Ecosystem scientists contributing to policyREDD- reduced emissions from deforestation and degradation Financial market to incentivize reducing greenhouse gas emissions from deforestation Intact forest Benefits- biodiversity conservation, poverty reduction, clean water, reduced erosionEmissions from deforestation and degradation account for 12-20% of warming trendsIntact forests sequester carbon and can store them for a long period of timeWhen you remove forest and burn them and increases microbial respiration (both of which release CO2) then less CO2 is sequestered and more in the atmosphereChallengesDeforestation? Clear cutting? Selective harvesting? How much? Definitions are unclearHow large does the area need to be to be a REDD forest?Primary forests? Secondary forests? Plantations?Forest management? Thinning can increase growth Do we thin if we want to sequester carbon?Fire? Degredation- how do you quantify it? Reforestation- turning old forest land into forests again afforestation- taking non forest land (ag land) and making it forest

additionality- carbon projects, need to establish a gain in carbon above baseline conditions time (x), carbon (y) in a system that is degrading

normal in red. Blue is what you would have to show for a REDD projectyou have to show, that even though it is declining, it is still retaining more carbon than normal

leakage- carbon offset projects that result in carbon loss from another environmentREDD project- say you want to build a forest on a cow pasture, well those cows are going to go elsewhere where a forest will be cut and burned and thats the leaked carbon

Permanence- 100 years (impractical period of time)How do you fallow carbon for 100 years- only way through modelsMaybe the time period should be 20 years

GRASSLANDS:

30% global land surface, 30-50% US surface is range lands

grasslands store 1/3 of worlds soil carbon

more water loss than more water input, have to allocate resources in soil and put lots of roots in soil and store carbon

relatively stable lands

manage the lands by adding manure or compost and led to build up of carbon in ecosystems

Ecosystem management and climate treaties 1/23/13 11:02 AM

general concepts on decomposition

sampling effect- applied to concepts of biodiversity ecosystem functionprobably of finding nitrogen fixing species in a group of species is higher if you have more species

decomposition-litter chemistry: nutrient content of litterlook at N or Pamount of lignin- difficult to break downtanins, polyphenolics- distasteful or toxic to organismssecondary compounds for defense or byproductscellulose, hemi-cellulosestoichiometry- elemental ratios- C:N, N:P, Al:Ca

primary succession carbon flux (g/m^2/y) (y), time (x)npp (blue), gpp (red) (50% of carbon take up goes out as autotrophic respiration), heterotrophic respiration (green), NEP (yellow)

if it was secondary succession- steeper carbon loss (heterotrophic respiration) (dark green above) NPP would start higher, drop to almost zero and then peak above the other NPP (light blue)NEP (orange)- lots of carbon because it grows like mad after secondary succession NEP should be negative in the initial stages but I couldnt redraw it in the graph aboveEvidence grasslands are in the decline NEP wise and are loosing carbonOver time, NEP

primary succession- start from scratch, very gradual increasesecondary succession- start higher and then there is a disturbance and there is a dip

additive models, multiplicative modelshow its used, why its used