Review for Exam 1 Flashcards
Pools, Fluxes, Turnover Rates, and Turnover (residence) times
Pool: Amount of stuff per unit of space (eg g m-2)
Flux: Amount of stuff per unit of time (eg gallons h-1)
The fractional (%) turnover rate k = (Flux/Pool)
Flux = (k*Pool)
Pool = (Flux/k)
Flux and Pool Image
Modes of Heat Transfer (gain or loss): Radiation
Heat transfer through space
Modes of Heat Transfer (gain or loss): Conduction
Heat transfer by direct contact
Modes of Heat Transfer (gain or loss): Convection
Heat transfer due to moving air or water
First Law of Heat Conduction: Fourier’s Law
Q=-k*[{T2-T1/D)]
Q = (W/m2)
T = °C
D(m) = distance
k (W/m/K) = thermal conductivity (ease by which the medium transfers heat)
Rain Shadow Effect
- Air moving upward as it passes over a mountain range cools (adiabatic processes).
- Cold air holds less water vapor, so the dew point is reached and water droplets form, resulting in precipitation on the windward side of the mountain range. The leeward side is typically dry. Examples are the east sides of the Sierras, Cascades, and Rockies and the north side of the Alaska Range.
Lambert’s Cosine Law Equation
Lambert’s Cosine Law Diagram
Lambert’s Cosine Law
Light intensity (LI) at the ground is influenced by its angle of incidence, which depends on the relative height of the sun above the horizon
Light Intensity Varies With…
Latitude
Season
Time of Day
Aspect
Slope
Months vs Direct Sunlight
Solar Spectrum
- PAR = photosynthetically active radiation (the visible range, which contains the wavelengths that plants use to carry out photosynthesis).
- High rates of absorption in the visible range by chlorophylls and other pigments.
- Red and blue are the wavelengths most effectively absorbed by chlorophyll.
- The amount of energy is inversely related to the wavelength of the light.
- Water in plant cells is efficient at absorbing UV-B (280-320 nm).
Light Response Curve
Another Light Response Curve
Global Distribution of Water Pie Charts
Properties of Water
- Specific Heat
- Latent Heat
- Density
- Solvency
- Ionization
- Physical Consequences of Hydrogen Bonding
What Determines Climate
- The Coriolis effect coupled to differential solar radiation is the primary factor governing the movement of the world’s ocean currents and air movements
- The phase change of water (solid, liquid, vapor) has major effects on energy balance, and thus a host of biophysical effects on ecosystems (distribution of deserts, NPP, physiological properties of species)
Specific Heat Capacity
Specific Heat = number of calories (amount of energy) required to raise one gram of a substance from 0°C to 1°C
SH = ΔT/Mass
Latent Heat of Fusion
- Amount of energy required to convert 1 gram of a substance from solid to liquid (at its melting point)
- 80 calories for water
Latent Heat of Evaporation
- Amount of energy required to convert 1 gram of liquid to gas (at its boiling point)
- 540 degrees for water
Amount of energy to convert solid to liquid and liquid to gas (water)
Properties of Soil
- 45% Minerals
- 25% Air
- 25% Water
- 5% Soil Organic Matter
Properties of Soil: Minerals
1° Minerals = Have not been chemically altered since they crystallized from molten rock
Altered only physically
Represented by larger particles in the soil, such as stones, gravel, sand, some silt
Quartz and Mica
Properties of Soil: Minerals
2 ° Minerals = Formed by chemical alteration of 1 °minerals
Usually smaller particles, clay and some silts
Vermiculite and Kaolinite
Properties of Soil: Minerals
- More of soil volume is composed of 1° minerals, but more soil functions are controlled by 2° minerals
- Clays provide a large surface area and a large “nutrient exchange surface”
Properties of Soil: Soil Organic Matter
- Regulates the supply of N, P, and S to plants
- Provides a high surface area for nutrient and retention and exchange
- Increases storage and retention of water
- Controls soil structure
- Serves as an energy source for most microbes
- A major source for CO2 to the atmosphere
Soil Organic Matter image
Properties of Soil: Air
- The dominant process that determines the composition of soil air is respiration by roots and soil microorganisms
- CH2O → CO2 and O2→ H2O
- Composition in soil air is important because it can have a large effect on the chemistry of the soil solution
- Soil has more CO2 and less O2 than the atmosphere above the soil surface
- CO2 in soil air can be as high as 10,000 ppm, O2 as low as a few %
- CO2 combines with water to form H2CO3 (carbonic acid) . thus lowering soil-solution pH
- Carbonic acid dissolves minerals
Properties of Soil: Water
- Essential for microorganisms and other soil animals
- Many soil microbiota live in water films on the surfaces of mineral particles.
- Availability to plants depends on the amount of water in the soil and the adhesion of the water to soil particles
- Fine textured soils (clays), because of their high surface area hold water more strongly than coarser-textured soils making water availability lower for plants
Climate and Weather image
Solar Energy Image
Circular Cells and Climatic Zones Image
Regional Climates- Controlling Factors
- Topography
- Orographic Effects = those caused by the presence of mountains
- Rain shadows
- Altitude
- Orographic Effects = those caused by the presence of mountains
- Proximity to water (lakes, oceans)
- Prevailing wind directions
Rain Shadow Effect
Regional Variation in Microclimate
Vegetation Classification Biome- Why is there an empty region
Cold air cannot hold moisture, causing precipitation levels to be low
Boreal Forests
- Cold, average temperature < 5°C
- Rainfall 0.4 – 1 m; but low evapotranspiration too
- Strongly seasonal, short growing season
- Permafrost in north
- Trees – spruce and fir dominant, broad-leaf hardwoods post-disturbance
- Frequent fires
- LOTS of detritus (11% of Earth’s surface but 40% of world’s soil carbon storage)
- Slow decomposition
- Acid soils, low fertility
Hot Deserts
- Warm (avg >20°C)
- But some areas < 0° in winter
- Very low rainfall (< 25cm/yr)
- Low plant density
- Shrubs, cacti, grasses
- Highly reduced leaves, succulence
- Mineral soils, lots of sand, often impermeable (hardpan)
- 20% of Earth’s land surface!
Latitude vs. NPP
- The correlation of NPP with climate is most apparent in the Northern Hemisphere, due to its large land surface area
- The highest rate of terrestrial NPP are found in the tropics
- NPP declines in arid regions at about 25°N and S
- Oceanic NPP peaks at mid-latitudes, where zones of upwelling are found
Patterns of Primary Production
- Worldwide, terrestrial primary production increases with actual evapotranspiration (AET)
- AET is amount of water transpired plus evaporated from land
- AET increases with solar energy and precipitation
- (Potential ET (PET) increases with solar energy only)
Trophic Efficiency
- Proportion of energy transferred from one trophic level to the next
- Trophic Efficiency = (Energy trophic level x+1)/ (Energy trophic level x)
- On average, trophic efficiencies typically 1 - 20% (range is huge)
The Flow of Energy Through Ecosystems
- Energy or biomass pyramid
- Width of the structure indicates the amount of energy contained in that trophic level
Trophic Level vs. Energy Availability
10% is an important value to remember!
Ecosystem Energetics
High rates of energy metabolism usually result in low production efficiencies
Gross Production Efficiencies
- Gross Production Efficiency = (Production / Ingestion) * 100
- This is the overall energetic efficiency of biomass production within a trophic level
- Small terrestrial animals – 5%
- Large mammals – 1%
- Aquatic animals – 30%
Net Production Efficiency
- Net Production Efficiency = (Production / Assimilation) *100
- The most active animals have the lowest NPE
- Birds - 1%
- Small mammals - 6%
- Sedentary, aquatic poikilotherms - 70%
Energetics of an old-field food chain
R.L. Lindeman
- The amount of energy available at each trophic level depends on;
- 1) the net primary production at the base of the food chain
- 2) the efficiency of energy transfer from one trophic level to the next
- The production of each trophic level is approximately only 5% to 20% of the trophic level below it.
- ‘Ecological Efficiency’ – the proportion of energy transferred from one trophic level to the next (≈10% per trophic level transfer)
Decomposition- 4 Stages
- Leaching of soluble compounds
- Consumption and fragmentation by soil organisms
- Breakdown of cellulose
- Breakdown of lignin
Leaching of soluble compounds
- 10-30% of mass –
- Rapid - days rather than weeks
- salts, sugars, amino acids
- Left over? Macromolecules, lipid-soluble, some more labile contents still trapped inside cells
Consumption and fragmentation by soil organisms
- Organisms remove the easily-digested macromolecules (e.g. lipids, starch, proteins)
- Cannot digest the cellulose or lignin
- “Macrofauna” (1-50 mm length)
- Earthworms, millipedes, wood lice
- “Macrofauna” (1-50 mm length)
- Earthworms, millipedes, wood lice
- “Mesofauna” (0.1 – 1 mm)
- Mites, springtails (collembolans)
- “Microfauna” (<1 mm)
- Ciliate and flagellate protozoans, nematodes
Breakdown of cellulose (polymer of glucose)
- Some fungi
- Some bacteria
Breakdown of lignin (very slow!)
- Few organisms can break down
- Some fungi and bacteria
Decomposition vs. Mineralization vs. Latitude
Half-life
Factors that affect decomposition and nutrient cycling rates
- Temperature
- Moisture
- Chemistry of substrate
- Cellulose, lignin slow decomposition
- Secondary compounds (plant chemical defences) slow decomposition
Carbon Cycle
Carbon Dioxide Concentration: Mauna Loa Observatory
Why the fluctuations in this model?
Seasonality! Growing seasons heavily influence the fluctuations on this graph. During plant dormancy plants release CO2, but during growing season, plants take it in
The Nitrogen Paradox
- N2 makes up 79% of atmospheric gases, but N limits productivity in many biological systems across Earth
- Earth’s crust << 0.01% N, soils 0.02-0.5% N, plants 0.5-3% N
- Adequate N supply higher biomass plants and higher crop yields
Microbe-mediated N transformations
Alternative Nitrogen Cycle
Nutrient – root encounters are controlled by three principal processes:
1) Interception – root growth into pockets of high nutrient availability (Minor importance for most nutrients)
2) Mass flow – movement of nutrients dissolved in flowing water (Most important for ions with low diffusion rates, e.g., NH4 + )
3) Diffusion – movements of nutrients down a concentration gradient (Most important for mobile nutrients, especially anions such as NO3- )
New cogs in the nitrogen cycle in the taiga forests of interior Alaska
- Early succession: Advective N supply through mass flow accounts for over twice the N supply of microbially-mediated N flux
- Mid-succession: Nitrogen mineralization during shoulder seasons and winter accounts for nearly half of the annual N flux
- Late succession: Ecosystem nitrogen flux is dominated by organic forms (N turnover and N uptake)
Nitrogen Mineralization
- Organic N -> NH3 is part of decomposition process
- No change in oxidation state
- Microbes - mineralize NH4 + to get at the C in organic molecules
- Animals – mineralize N during normal protein turnover and when diet is high in protein
- Once mineralized, available to plants again
- In soil, NH3 generally present as NH4 + , clings to clay (remember cation exchange capacity?), does not readily leach
Nitrification
- Oxidation of NH4 + to NO3 - primarily by specialized groups of autotrophic bacteria
- Importance of nitrification
- Dominant process in agricultural soils
- A key pathway for N loss from terrestrial systems, because nitrate is very soluble (also it is not held on soil well)
- *Nitrate can be a major groundwater pollutant
Assimilation
- NH3 -> amino acids, nucleic acids
- In soil, NH3 generally present as NH4 +
- Assimilated by plants, bacteria, fungi
- No change in N’s oxidation state
- Plants, bacteria, fungi can assimilate NH4 + and NO3-
- But must transform NO3 - to NH3 before they can use it
- The ability to convert NH4 + -> amino acids is why plants don’t urinate!
- Some plants in far north can assimilate amino acids
- Animals must assimilate organic forms of N (amino acids, nucleic acids)
Denitrification
- Conversion of NO3 - or NO2 - to N gas
- Carried out by bacteria in the absence of oxygen
- (water-logged soils, freshwater and ocean sediments)
- Wide diversity of denitrifying bacteria
- Use NO3 as terminal electron acceptor
- Denitrification is an important source of N2O (nitrous oxide), a greenhouse gas that also catalyses the breakdown of ozone.
Atmospheric Changes with Altitude: North Facing Slope
- North Facing Slope
- Less solar energy
- Less evaporation
- Wetter, thicker soils
- Later plant flowering
- Shorter day length
- Fairbanks - permafrost
Atmospheric Changes with Altitude: South Facing Slope
- More solar energy & greater diurnal temperature changes
- More evaporation
- Drier, thinner soils
- More drought-tolerant species
- Earlier plant flowering
- In Fairbanks no continuous permafrost
- Mesic (cool, wet) conditions at toe slope
