The Physical Environment

Abiotic Factors

Climate: Temp, moisture, precipitation, wind

Weather: air in motion,

results from differential heating and global heat transfer

 

Solar Radiation (Fig. 2.1):

Solar “Constant”: energy reaching earth’s atmosphere, 2 calories/cm2

50% of solar light makes it to earth’s surface

25% reflected from clouds, atmosphere

5% reflected from earth’s surface

25% absorbed by dust, water vapor, CO2 in atm.

45% absorbed by earth as short wave radiation

29% returned to atmosphere by thermals and evaporation of surface water

Earth’s radiation is long wave (infrared-heat) 88% reflected back by CO2, water vapor: Greenhouse Effect

            Heat radiation day/night Fig 2.18

 

Spectrum of radiation changes as it reaches the earth (Fig 2.2)

Almost all UV removed by Atmosphere

Atm gases scatter short wavelengths: blue color

Water vapor scatters all wavelengths: white + shadow = gray clouds

Dust scatters long wavelengths: reds/yellows

Scattering diffuses light reaching earth:

“skylight” illuminates shadows, crepuscular periods

Infrared radiation absorbed: heat radiation

 

Albedo: reflection from earth’s surface

Water 2%

snow and ice 45-90%,   beaches

forest and grasslands 5-30%

clouds:90%

Global: 50-60% poles, 20-30% in tropics

 

Humidity: water content of air

            Absolute and Relative

            Heat absorbed by evaporative processes: latent heat of evaporation

            Air vapor has gas pressure: vapor pressure

            Saturation of water in air: temperature dependent

            1 ft3

            -34°C = 0.1 g

            4°C = 3 g

            38°C = 20 g

            Vapor pressure deficit: evaporative power

            Rain shadows: Fig 2.15

 

Heat transfer by water and air movement

Coriolis: effects of rotation on objects in motion Fig. 2.6

            Northern hemisphere: deflection to the right

            Southern hemisphere: deflection to the left

 

Circulation of air (Fig. 2.8)

            Hadley cells, convergence zones have high rainfall

            High (clockwise, downward) dry, clear

Low pressure (counterclockwise, upward) wet, cloudy

 

Ground position of the sun (Fig.2.7)

            All points on earth receive the same amount of light and dark

            But  photoperiod changes with latitude and ground position of the sun

            Intensity changes with latitude

            Effects on circulation cells (Fig. 2.9)

 

Ocean Currents (Fig. 2.10) gyres

            Polar-deep water flow

            Upwelling, Southern oscillations, Atlantic oscillations

 

Quantifying climatological regimes:  Climograph (Fig 2.13)

            Fig 2.14: evaporative power/availability of water

                        10˚ C = 20 mm rain

 

Microclimates: elevation and north-south exposures (Fig. 2.16; Fig 2.17)

            Effects of vegetation (Fig 2.25; Fig. 2.27)

Urban Climate and heat islands (Table 2.1)

Light

Temperature

Moisture

Elemental Nutrients

Abiotic factors occur in gradients: non-homogeneous distribution

Light (Fig 3.1) “visible” wavelengths

            Bees, fish see uv

            PAR is a subset, incorrect in the book

Fate of light: absorbed, reflected, transmitted

            Differences in different plant communities (Fig 3.3)

            Leaf Area Index (Fig 3.5), attenuation- extinction ceofficients

Light penetration in water: (Fig 3.4) Butterfly Fish

            Photic zone determined by light penetration:

                        Physics of light penetration in water, scattering by particles

                        Blue penetrates furthest in clear water

Clays- yellowish, green and red penetrates furthest

DOM may also limit light- humics

 

Temperature: polar to equator and altitude gradient

Heat: molecular kinetic energy: random motion of molecules

            Brownian motion, rate of dissolution, rate of chemical reactions

            Ceases at absolute zero (-273.18 °C)

Temperature: heat content and propensity to give off heat

            52°C upper limit for animals

            -60 to +60°C range for vascular plants

            Algae 73°C

            Bacteria above 100°C

Thermal energy exchange:

radiation, conduction, convection, evaporative exchange

 

Water

Freshwater aquatic (Hydric) to desert (Xeric) gradient, Mesic

            Also Freshwater to Salt, estuaries

 

Water is Polar molecule

High heat capacity “specific heat”

            Heat of fusion (must lose large amounts to freeze),

Heat of evaporation (absorb large amounts)

            Heat released upon condensation: drives global heat transfer

Viscosity: Reynolds numbers: inertia vs. viscous friction

solid less dense than liquid: ice formation as an insulator

 

Distribution of water (Fig 3.12)

            Oceans cover 71% of earth

            Freshwater is only 3% of global water

                        Lakes 60%

                        Soils 33%

                        Rivers 1%

                        Atm 6%

97% of earth’s water in oceans

0.001% of earth’s water in atmosphere = 3% of annual rain

83% of evaporation from oceans, 75% of precip returns

            Net flux of water from ocean to land

Solar energy in evaporated water released as

1) heat from condensation and

2) work as water moves back to sea level

Water Cycle:

            Rain falling to earth: Interception,

Infiltration/percolation through vadose zone to ground water, aquifers

Recharge to renewable aquifers; “Inherited” and “fossil water”

            Snowfall: snow packs, spring runoff (Prairie Gumbo; mud season)

            Overland flow or runoff; stormwater

Internal drainages.

 

Aerobic/Anaerobic

Oxidation/Reduction

When O2 depleted other compounds used as terminal electron acceptors

 

Oxidizer

Reduced product

Kcal Yield

Aerobic Respiration

O2

CO2

686

Nitrate Reduction

NO3-

N2 + CO2

649

Sulfate Reduction

SO4-2

HS- + CO2

8.9 – 97

Metha nogenesis

H2 + CO2

CH4

6.6 –8.3

 

 

Nutrients:

Discussed later under biogeochemical cycling, Chapt.25