Basics in Geoecology

Keystone species

• large effect on environment (key role in ecosystem)

• critical role in maintaining structures of ecological community

• affecting other organisms

Ecosystems and dynamics can be studied on different scales

• spatial

• and temporal

a) Global ecosystem (5000km)

b) Drainage basin (10km)

c) forest ecosystem (1km)

d) endolithic ecosystem (1mm)

Non living things:

• water

• atmosphere

• soil

living things:

• plants

• animals

• decomposers

State factors:

• Climate (temperature and moisture)

• Topography (physical appearance of landscape, surface roughness)

• Parent material (weathering of rocks)

• potential biota (microorganisms)

• human activities (agriculture)

Interactive controls

Operate at the ecosystem scale and control & resoind to ecosystem caracteristics

• microenvironment (temperature - depend on climate; ph - depend on parent material) —> affect activity of organisms

• disturbance regime (fire, wind, insect outbreaks, floods and hurricanes)

• resources (support growth and maintenance of resources - air)

• functional types (species effect)

Ecosystem processes

• Disturbance

• time

• succession

• positive feedbacks

• when the reciprocal effect of each organism have the same sign (both positive or negative)

• reinforce tendencies to change

• mycorrhizal fungus, predator

• reciprocal effect differ in sign

• resist tendencies for ecosystem to change

• herbivores, plants

• Incomin SW (341 watt per square meter) solar radiation

• some is absorped by atmosphere (78), bigger amount absorbed by surface (161). The rest is reflected by clouds and atmosphere (79) or by the surface (23).

• Through evapotranspiration and albedo LW radiation is outgoing.

• Together with the reflection is it the same amount which is incoming.

• Radiation is emitted by atmosphere (lw) and absorbed by the surface (sw) through greenhouse gases which sent the radiation back

• albedo (surface reflection)

• evapotranspiration (discharge of water from surface or transpiration from plants through stomata)

  • sensible vs latent heat flux

• surface roughness —>high density of vegetation

• atmospheric gas composition

• spoil characteristics

• fire regime

• Suns energy output

• tectonics

  • change in plate positions

  • mountain building, erosions and weathering

• variation of earths orbit

  • eccentricity

  • obliquity (tilt)

  • precession

• changes in atmospheric composition

  • volcanic eruptions

  • anthropogenic inputs

Ecosystems have different budgets due to various

• albedo

• bowen ratio (ratio of sensible heat flux to latent heat flux)

• climate

• moisture availability

• transport of fine soil particles

• Parent material: physical and chemical properties of rocks and how they are weathered

• Climate: Temp, CO2, moisture and oxygen influence rates of chemical reactions (govern the rate and products of weathering)

• Topography: Influences soils through its effect on climate, moisture availability and transport of fine soil particles (erosions)

• Time: slowly

  • P availability high in early stages, but as soil develops P is lost from system or converted into forms unavailable to plants.

    • Primär: ist in mineralischer form im boden vorhanden

    • Sekundär: wurde im bodenprozess freigesetzt und kann von pflanzen aufgenommen werden

    • Okkludiert: Ist nichtmehr für die Pflanzen verfügbar durch chemische Bindung

    • Organisch: Ist in organischen Substanzen im Boden vorhanden

• Potential biota: Past and present organisms influence soil (chemical and physical properties)

• Additions to soil

  • Through precipitation; Ions and solid particles and Organic matter

  • Transformation

    • Physical, chemical and biological processes

    • Decomposition

    • Weathering

      • Physical: freeze-thaw, heating, cooling, fire, wetting drying or roots grow into rocks

      • Chemical: rock react with acidic or oxidic substances

        • Carbonic acid

• Transfer

  • Occur through leaching

  • Downward movement of water

• Losses

  • Solutions and gases

• O: Organic layer derived from plant litter

• A: contains substantial organic matter; mixed with humus

• E: maximum leaching of silicate clays, fe, al oxides

• B: maximum accumulation of iron and aluminium oxides and clay

• C: unaffected by soil-forming process, includes unweathered Parent material

• R: bedrock

• Gelisol (Tundra, bog)

• Aridisol (Desert)

• Spodosol (Acidic conifer forests)

• Mollisol (Grassland deciduous forest)

• Oxisol (tropical wet forests)

• Sand (0,05 – 2mm)

• Silt (0,002 – 0,05mm)

• Clay (<0,002mm)

• Pressure potential: generated by gravitational forces and physiological processes of organisms

• osmotic potential: presence of substances dissolved in water

• matric potential: caused by adsorption of water to surfaces

• moves from high to low water potential from soil to roots to stomata

• in arid environments

  • water moves from soil to the atmosphere on day

  • on night stomata is closed, water moves from soils at depth to dry surface soils through the root system (hydraulic drift)

• indirect controls

  • surface roughness

  • photosynthetic capacity

  • water-holding capacity

  • precipitation

• direct controls

  • aerodynamic conductance

  • stomatal conductance

  • water availability

  • net radiation /VPD

Precipitation +- Delta S = E (T) + R

• quantity of water retained by soil after gravitational water has drained

• water potential -0,03 MPa

• plant is not able to obtain water from soil

• ca. 1,5 MPa

• is greatest in ecosystems with high surface rughness

  • rough surface —> high turbulance

  • E (forest) > E (grassland)

• E (wet climates) > E (dry climates)

• E increases exponentially with air temp

• diffusion and turbulent mixing

• surface conductance determines flux of water vapour from leaf to atmosphere

• aerodynamic conductance determines flux of water vapour from air near the leaf to bulk air

• opened

  • leaves have high conductance

  • water vapour is rapidly lost

• closed

  • low conductance

  • little water will be lost

• photosynthesis

• all biological processes are possible through photosynthesis

• 50% of OM is fixed through Photosynthesis (consists of ficed C - rest O and H)

• interactive controls

  • plant functional types

  • soil resources

• direct controls

  • leaf area

  • N

  • season length

  • temperature

  • light

  • co2

• light harvest reactions

  • transforms light energy to temporary forms of chemical energy

• carbon fixing reaction

  • converts co2 into sugars

• C3 Plants: direct fixation through RuBP - Carboxylase

• C4 plants: spatial separation through PEP - Carboxylase

• CAM-plants: temporal separation through PEP-Carboxylase

• physical limitation: diffusion of co2

• biochemical limitation: Carboxylation rate

  • light and enzyme limited

• Ribulose - 1,5 - bisphosphat - carboxylase / oxygenase

• Carboxylase

  • reacts with co2 to produce sugar

  • leads to co2 fixation

• Oxygenase

  • reacts with oxygen to transform sugar to co2

  • assimilate 20-40% of fixed C

• Erste statbile product eine dreikohlenstoffhaltige Verbindung (C3 sugars)

• Fixation through Rubisco (a lot of rubisco necessary)

• 25% of nitrogen in leafs are stored in rubisco

• Further enzymatic steps:

  • Depending on light

  • Depending on co2 supply of chloroplast

  • C-fixation to generate rubisco via ATP and NADPH

• Inefficient at high temperature (high co2 in leave at closed stomata —> rubisco absorbs o2 instead of co2 —> photorespiration

Wheat, oat, rice, rye (our latitude)

• Spatial separation of fixation

• Fixation through PEP-Carboxylase to 4-kohlenstoffhaltige verbindung

• After that rubisco

• More efficient than c3 plants (more light and temp, less water or co2) – high carboxylation efficiency

• Photosynthesis at very low co2 concentration and when stomata is closed

• Requires low nitrogen

• No photorespiration

• Sensitive to cold

Zea mays

• Temporal separation of fixation (low fixation rates)

• Gain co2 in the night and save it + open stomata

• Photosynthesis at day (Rubisco driven carboxylation)

• Ananas

• gross photosynthesis - mitochondiral respiration - photoresporation = net photosynthesis

• carbon gain measured at the level of individual cells or leafs

• porometer to measure net photos

• efficiency of photosynthesis: 1-6%

• variable and most important regulation of diffusion of co2 into plants

• controls transpiration

• compromise between maximize photosynthesis and minimize water loss

• Light use efficiency

  • Light Use Efficiency (LUE) refers to the effectiveness with which a plant can use available light (photosynthetically active radiation) for photosynthesis.

• Light Limitation: At low light intensities, the photosynthetic rate is low because not enough light energy is available for photosynthesis. In this phase, the net photosynthetic rate increases rapidly with increasing light intensity.

• Light Compensation Point: This is the point where the amount of CO2 fixed by photosynthesis equals the amount of CO2 released by respiration. At this point, the net photosynthetic rate is zero.

• Light Saturation: At a certain light intensity, the photosynthesis rate reaches a plateau. More light does not lead to an increase in the photosynthesis rate because other factors (such as enzyme activity or CO2 concentration) are now limiting.

• Photooxidation: At very high light intensities, too much light can limit photosynthesis and cause damage known as photooxidation.

• Adaption (genetic adjustment)

  • Maximize leaf area (more leaves, thin and cylindrical leaves)

  • Angle of leave position

  • Leaf movement

  • Efficient use of sunflecks

  • Rejection of leaves with negative c-balance at canopy level

• Acclimation (physiological adjustment)

  • Sun leaves

    • More cell layers

    • High photosynthetic capacity

  • shade leaves

    • More light sensitive pigments

• at leave level

  • compensation of physical and biochemical limitations

• at canopy level

  • preservation of the maximum photosynthetic capacity above canopy

  • rejection of leafs with negative c-balance

• adjustment of photosynthesis capacity to soil resources

• adjustment to stomatal conductance

• adjustment to leaf area

• changes in composition of species

• leaf lifespan controls photosynthetic capacity

• conflict between lifespan and photo.. capacity

• long lifespan leafs have more non-photosynthetic active components

  • protection against herbivores

  • protection against desiccation

• short term:

  • reduction of stomatal conductance

• long term

  • reduction of leaf area —> preserves lue

• water use efficiency

• highest in dry areas (conflict between efficiency and capacity

• mechanism: longer path for co2 than for water

  • changes in stomattal conductance leads to higher consequences for water lost than for co2 gain

  • therefpre high photosynthesis capacity regard to stomatal conductance

• reduction carbon gain by reducing leaf area or photosynthetic capacity

• leading to reduced stomatal conductnace

• most control factors on leaf area are valid on stock level too

• strongest photosynthetic capacity above canopy

  • light advantage

  • young nitrogen rich leafs

Control factors:

• Leaf area

  • can be reduced by pathogens and herbivores

• length of photosynthetic season

• photosynthetc intensity of single leaf

  • capacity

  • sterss changes stomatal conductance

• major roles: plants

• c-input into ecosystems (BPP)

• c-transfer into soils (litter)

• c-lost into atmosphere (respiration)

Leaching is the rate-determining step for mass loss of plant litter when it first senesces.

Fragmentation creates fresh surface for microbial colonalization and increases the proportion of the litter mass that is accessible to microbial attack

Alteration of dead organic matter results primarily from the acticity of soil microbes or also ooccur spontaneously

• initial decomposers of terrestrial dead plant material

• together with bacteria, 80-90% of total decomposer biomass and respiration (60-90% without bacteria in foreast soils)

• network of hyphae

Mycorrhizae: symbiotic association between plant roots and fungi

• dominant in thizosphere

• dominatn in biofilms

• relatively immobile

• varying activity

• fragment and transform litter

• graze populations of bacteria

• alter soil structure

• mesofauna (0,1 - 2mm long)

• macrofauna (> 2mm long)

• environment

  • Temperature

  • moisture

• SOM

  • soil properties

  • soil disturbances

  • humus formation

• moisture mediated effects

  • evaporation rise —> water availability down (effect on microbial activity) —> oxygen rise —> microbial activity rise —> soil respiration high

  • If its warmer, more water evaporates, which decreases water availability

  • Oxygen rises because water that evaporates makes space for air

  • Soil respiration rises

• direct effects

  • microbial activity rise —> soil respiration

  • Higher temperature leads to more activity of microbes

  • Could be positive or negative, due to the effect of moisture

• nutrient mediated effect

  • weathering rise —> nutrient availability rise —> plant growth rise —> root respiration rise —> soil respiration rise

  • Higher temperature leads to more intensive weathering (temperature accelerates chemical reactions)

  • more nutrient availability

  • Increases the growth of plants which has a positive effect on root respiration and on litter quantity and quality

• range of energy gain, which element will be used first

  • o2 (Oxygen) > NO-3 (nitrate) > Mn4+ (manganese 4) > Fe3+ (Iron 3) > SO4 2- (Sulfate) > CO2 > H+ (Hydrogen ion)

• if elements are not available (bog) —> methanogenesis

  • methane (CH4) is produced through CH3COOH (essigsäure): CH3COOH —> CH4 + CO2

  • CO2 + 4H2 —> CH4 + 2H20

• net primary production

• controlled by c-requirement in plants

• resources for growth

• mainly determined by soil

  • climate controls npp through processing soil resources

  • demand on c for growth controls respiration and photosynthesis

• increases exponential with temperature rise

• increase with precipitation up to 3000 mm a year then fall

• net ecosystem production

• carbon accumulation rate in ecosystems

• total amount of carbon produced by plants (GPP) — respiration of ecosystem (R ecosy = R plants + R heterot)

• NEP is positive = storage of more carbon than losing it

NPP (Amount of carbon which is left after respiration) — R heterot

• net ecosystem exchange

• accumulation of carbon of whole ecosystem

• net - co2 exchange of entire ecosystem

• NEE = GPP — R ecosystem

• nutrient supply rate (most important)

• development of root length

  • whrn recovering following disturbances, root length strongly influences nutrient absorption and npp

• mycorrhizae

  • symbiotic relationships between plant root and fungal hyphae

  • increase the volume of soil exploited by plants

  • 80% of angiosperns, all gymnosperms are mycorrhizal

  • plants inest 4-20% of gpp in supporting mycorrhizal hyphae

• diffusion (most important)

  • diffusion sehll around roots, compensated by root growth (Dass die Nährstoffe nicht verloren gehen weil sie gehen von hoher konzentation zu niedriger konzentration)

  • nitrogen, potassium, phosphorus

• mass flow

  • movement of dissolved nutrients in flowing soil water

  • provides resources for some micronutrients (ca)

  • calcium, magnesium

• root interception (not important)

• Nitrogen fixation

  • trafe carbohydrates for nitrogen (relationship between plants and n fixing bacteria)

• plant absorb nutrients by actice transport

• 30-50% carbon budget support nutrient absorption

• Root absorption capacity increases in response to plant demand for nutrients

• Absorptions of cations: Discharge of H+ à Acifying the rizosphere

• Absorption of anions: NO 3-, PO4 3-, SO 4- à no effect on ph

• NH4+ dominates in acid soils; NO3- in base and dry soils

• Depostiotion of nutrients stimulates bacterial growth

Nutrient use efficiency

• ratio of nutrients to biomass lost in litterfall

  • highest in unproductive site (nutrients limited, plants need to be more efficient

• to maximize NUE ecosystems need

  • high productive nutrient activity

  • long residence time of nutrients

• Senescence (major avenue of nutrient loss)

  • process of plants become old

• Leaching

  • 15% of annual nutrient return from shoot to soil

  • as much as 50% of Ca and 80& of K can be leached from leaves within 24h

• herbivory

  • often returned by feces

• Disturbances

  • fire

• Nitrogen enters ecosystem —> nitrogen fixing bacteria (Phototrophic or heterotrophic)

• Process is energy consuming

• Factors constrain nitrogen fixation (P, light, energy, other nutrients)

• oxidized and reduced forms through Lightning, combustions, fertilizer production, agricultural BNF

• Human activities are the main source to deposit nitrogen in many areas of the world

• Many ecosystems have become N saturated

• Weathering of sedimentary rocks may contribute to the nitrogen budgets of some ecosystems

• Precipitation: N fixation

• Particular organic N: N in dead plants from animals

• Dissolved organic N: In Wasser gelöst und für Pflanzen verfügbar

• Microbes: change organic N to NH4+ (Ammonium) à Mineralisierung

• Nitrifiers: change NH4+ to Nitrates NO3-

• Denitrification: Process by which Nitrates changed to N gas; possible to leave for atmosphere

• Immobilization: Microbes pick up NH4+ und NO3- à fixation, to make N available for plants

• DON: If more plants absorb nitrogen, less amount of don is available for microbes to convert

• Litter quantity: High amount of dead litter leads to more Nitrogen for microbes

• Carbon quality: The higher the quality, the easier to absorb

• Microbial C:N: A low ratio of carbon to nitrogen, means that the have low amount of nitrogen to convert. They need nitrogen

• Temp and Water: High temp and water supports activity of microbes to convert N to ammonium

• Ammoniumconcentration: more ammonium leads to more nitrification

• Plant NH4+ absorption: If plants absorp more ammonium, less is available for nitrification

• Litter quantity: High amount of dead litter leads to more nitrification for microbes

• Root/microbial respiration: the higher the respiration and temperature the lower the oxygen concentration

• Soil structure: some structures are good to save water and oxygen

• Gaseous loss

  • NH3

    • Emmiting by altering of plant leaves

    • At ph value over 7 reaction of NH4+ + OH- (Hydroxidionen) = NH3 + H2O

    • Urin of animals

  • N2O, NO, N2

    • Soil nitrate content

    • SOM content

    • Soil water content

    • Weather

• Solute loss

  • In undisturbed systems, little N is lost by solute transport (as DON)

  • Disturbance may augment NO3 leaching (common following fertilization)

  • Leaching indicates N saturation

  • Leached N leaves to groundwater to lakes and rivers à lost to atmosphere

  • May be harmful to human health

• Erosional losses

• Replenishment in soil via weathering of rocks

  • Slow – old soils limited p

• Microbial biomass is important p source; mikhorrizae fungi takes p from biomass and makes it available for plants

• Phosphate is negatively charged – easily attracted to positively charged elements (iron —> unavailable for plants)

• soils with calcium or calciumcarbonate (react with phosphate), ca-phosphate precipitates, reduces p availability

• p is lost via surface runoff or soil erosion

• long-term cycle

  • tectonic uplift -> exposition of p-containing rocks

  • Dissolved P (through physical erosion and chemical weathering) in soils and inland water

  • Leaching and transport of dissolved P in rivers to oceans

  • Sedimentation of p and fixation in marine sediments

  • Subduction in earths crust and diagenesis

• Short-term cycle

  • Dissolved p taken up in soils (inland waters) through plants or microorganisms

  • P enters food web

  • Decomposition of dead om  p release

  • P reenters soil and inland waters

  • Coupled to biotic activities

• Significance

  • Essential nutrient

    • Energy carrier (ATP)

    • Genetic material (DNA, RNA)

    • Membranes, bones and dental enamel

  • No comparable process like biotic N fixation to increase p availability

  • Root exudates, mycorrhiazae and cryptogams can increase rock weathering

  • Only small part of p is bioavailable

• Biota (vegetation, animals and microbes)

• Hydrology (water level, flow, frequency)

• physiochemical environment (soil, chemistry)

• peatlands cover 3% of terrestrial surface

• 1/3 of globally stored carbon

• Eleocharis sphacelata

• accumulates organic matter