Primary Production

1.Ecosystem concepts Production is the rate at which energy (or organic matter) is captured biochemically per unit surface area per unit time e.g.: g/m 2 /yr; kcal/m 2 /yr; j/m 2 /yr

1.Ecosystem concepts Primary production is the first level of production, usually the production of green plants. Specifically, Primary Production is the capture of energy from light or inorganic compounds. Gross PP = Net PP + Respiration Compensation Point is where instantaneous Gross PP = Respiration

1.Ecosystem concepts Biomass is the amount of organic matter (or energy) present per unit surface area. Typically kg_DryWt/m 2, or kcal/m 2 or j/m 2 Biomass = stored energy d(Biomass)/d(t) = Gross PP - Respiration - Harvest rate - Death rate

1.Ecosystem concepts Secondary Production refers to production by organisms that acquire their energy and organic matter from other organic material, dead or alive. Plants are in turn eaten by animals which are eaten by fiercer animals. Each is referred to as a trophic level. When all the linkages included = food web.

1.Ecosystem concepts Trophic levels: - Primary Producers - Primary consumers - Secondary consumers - Decomposers (or heterotrophs).

2.Ecological Efficiency The second law of thermodynamics states that the entropy always increases. This tells us that the production at one trophic level must be greater than at any higher trophic level. This does not necessarily translate to biomass, but usually does.

Typical values: PP Gross = Respiration + PP Net Long Island Oak & Pine forest: 2650 = (g/m 2 /yr) (Roughly = NC Piedmont forest) Smoky Mountain cove forest: 3500 = (Roughly = NC Piedmont pine forest) Typical forest consumes around 50% of own production as respiration

Solar maximimum = 7000 kcal/m 2 /day Only about 45% is photosynthetically active radiation (some reflected some lost as heat in reactions) NPP Efficiency is not impressive, usually < 1%: Rice 2.2 Oak-Pine 0.9 Corn 1.3 Indiv. plants < 5.0

3.Measurement of Primary Production

Measurements 1. Cut and weigh methods - Harvest: Problems = roots, insects, lost parts, perennials - Dimension analysis 2. Gas exchange: CO 2 consumption and O 2 evolution - Infrared gas analysis - light and dark bottles

4.Terrestrial patterns Limiting factors - Moisture limits because of leakage - Temperature limits chemistry, as does solar energy - Nutrients can be limiting - Relationship with Growing Season

World patterns in Net PP (g/m 2 /yr) 1) > Extremely Productive Some Marshes up to ) – Productive Forests Tropical Forest >1800 Temperate Forest 1250 Boreal Forest 800 3) Limited Production Woodlands, Shrublands, Grasslands, Cereal Crops 4) <250 - Very limited Production Semidesert, Desert, Arctic tundra

World Patterns in Biomass Highest is temperate evergreen forest Rank order very different from rank order for primary production - Forests Woodland Grassland Desert, tundra 0-2 (90% world biomass in forests; forests constitute only 33% land and 10% earth)

5. Aquatic & Marine Production. Often nutrient limited: P, N, micronutrients

Aquatic and marine production -Range same as terrestrial systems - Upwelling and coastal areas higher than open ocean -Antarctic, N Atlantic, sides (esp W) continents -Open ocean is a semidesert -Despite the fact that 70% of globe's surface = water, total NPP on land = 2X that of the oceans -Now note the extremely low biomass

ratios Production Biomass yrs g/m2/yr kg/m2 Open ocean Temperate grass Temperate forest Redwood forest

Comparison of lakes Terminology: Oligotrophic, Mesotrophic, Eutrophic

Comparison of lakes Terminology: Oligotrophic, Mesotrophic, Eutrophic Eutrophic GPP > 75 gC/m 2 /yr Cult. Eutrophic >350 gC/m 2 /yr Swamps & estuaries with allochthonous nutrients -> 3000 gC/m 2 /yr Lake Vakuru w/flamingos 4672 gC/m 2 /yr