Last weekInorganic carbon in the ocean, Individual carbon emissions,Primary productivity

TodayReview last weeks activityLimiting factors - nutrients,Controls on Productivity

The atmosphere, by volume, consists of:78% N2 atomic weight 12

21 % O2 atomic weight 16

1% Ar atomic weight 400.036% (360 ppm) CO2 atomic weight 44

 

  Using the composition of the air and the table of atomic weights above calculate the mean molecular weight of air.

Nitrogen 0.78 x 2(14) = 21.84Oxygen 0.21 x 2(16) = 6.72Argon 0.01 x 40 = 0.40CO2 0.00036 x (12 + 2(16)) = 0.016

28.98

The total mass of the atmosphere is 5 x 1021 g. Using the mean molecular mass of air calculated above determine the number of moles of air.  

5 x 1021 g / 29.98 g/mole = 1.73 x 1019 moles

If 21% of the air is oxygen (O2) (by

volume or moles, as a mole of any gas always takes up the same volume at a given temperature and pressure), calculate the number of moles of O2

in the atmosphere. 21% = a fractional amount of 0.21, so

0.21 x 1.73 x 1019 moles = 3.6 x 1018 moles of oxygen gas

Fossil fuel reserves are estimated to contain 6x1018 g carbon. At 12 grams per mole, how many moles of carbon is this?  6 x 1018 g carbon / 12 g of Carbon/mole = 5 x 1017 moles of carbon

What fraction of the atmospheric oxygen would be consumed by burning all the world’s fossil fuels? Express this as a % reduction in O2. Is this

a significant amount? How much would CO2 increase?

CH2O + O2 -----> CO2 + H2O

 Part I

For each mole of carbon in CH2O (our fossil fuel) combustion requires

one mole of O2 First we need to know how many moles of fossil fuel

carbon there are, but we already did that in question d = 5 x 1017 moles of carbon. Since the molar ratio of oxygen to carbon is 1 to 1, if we burn 10 moles of carbon we need 10 moles of oxygen; 1000 moles of carbon requires 1000 moles of oxygen.

Therefore 5 x 1017 moles of carbon requires 5 x 1017 moles of oxygen

What fraction of the atmospheric oxygen would be consumed by burning all the world’s fossil fuels? Express this as a % reduction in O2. Is this

a significant amount? How much would CO2 increase?

CH2O + O2 -----> CO2 + H2O

Part II

From Part I 5 x 1017 moles of carbon requires 5 x 1017 moles of oxygen Next we need to figure out the percentage of the total amount of oxygen in the atmosphere we would use. We know from above that we have 3.6 x 1018 moles of oxygen gas in the atmosphere. So we calculate the percentage 

5 x 1017 moles of oxygen used / 3.6 x 1018 moles of oxygen gas in the atmosphere = 14%

Burning of biomass (i.e. trees in the tropical rain forests, etc...) would also consume atmospheric oxygen. This biomass contains 600 Gtons or 6x1017 g of carbon. If, in addition to burning all the fossil fuels, we burned all the forests, would that make a significant difference in decreasing atmospheric oxygen? (No need for calculations for this question, base you answer on the calculations already done and the relative size of the reservoirs of carbon)

This one was a little tricky, but not too hard if you looked at the other questions. If fossil fuels contain 6 x 1018 g carbon and that didn’t make a huge difference, then biomass, which at 6x1017 g of carbon is only 10% of the total amount of fossil fuels probably won’t either.

Human activities including burning of biomass and fossil fuel have increased the amount of CO2 in the atmosphere from 280 ppmv (parts

per million by volume) or 0.0280% in pre-industrial times to 365 ppmv (or 0.0365%) today. How many moles of CO2 have been added to

the atmosphere? Now = 0.0365% - pre-industrial 0.0280% = an increase of 0.0085% 0.0085% (increase) x 1.73 x 1019 moles (total mass of atmosphere in moles from above)

= 1.47 x 1015 moles of CO2 added to the atmosphere

It has been estimated that humans have consumed a total 240 Gtons or 2.4x1017 g of carbon through the burning of fossil fuels. Assume that all this carbon was converted to CO2. How much would this

increase the CO2 in the atmosphere?

 2.4x1017 g of carbon / 12 g carbon/mole = 2.0 x1016 moles of carbon By how much does this differ from the value calculated above?From previous question atmospheric increase equals 1.47 x 1015

moles of CO2 - more than 10 times as much has been burned

What might explain this difference?

Photosynthesis• Primary Productivity - the amount of organic

matter produced by photosynthesis per unit time over a unit area

• CO2 + H2O + Sun Energy--> CH2O + O2

• Converts inorganic carbon to organic carbon• Removes carbon from atmosphere to organic

carbon in biomass and soil organic carbon - residence time about 10 years

• Producers or Autotrophs are the majority of biomass

Respiration• CH2O + O2 --> CO2 + H2O + Energy

• Reverse of photosynthesis • Converts organic carbon to inorganic carbon -->

releases energy• Consumers or Heterotrophs - organisms that

utilize this energy - small part of biomass (1%)• Aerobic respiration - with oxygen

Respiration, cont.

• Processes is accelerated by enzymes• Half of gross primary productivity is

respired by plants themselves• Other half is added to organic layer in soils

--> microbes - bacteria and fungi break down this organic matter

• Below the surface - Anaerobic respiration without oxygen

Marine vs. Terrestrial Carbon Cycling

• Primary Productivity takes place both in oceans and on land

• On lands - green plants

• In oceans - phytoplankton - free floating photosynthetic organisms

• What controls marine photosynthesis?

• What controls marine photosynthesis?

–Sunlight/ Energy

–Nutrients

–CO2

Map of Ocean productivity- nutrients are the key

Ocean a Source or Sink• Sinks vs. Sources• Why this

pattern?• = Nutrients and

CO2

Controls on Net Primary Productivity

Nutrients

Only about 44% of the total Electromagnetic energy reaching the earth is in the correct wavelengths for use by plants (called PAR) and only 0.5% – 3% of that is used!

Temperature is a strongLimiting factor.

Although plants in colderareas are optimized forColder conditions

Water also is a strongLimiting factor.

Much steeper curve =A much stronger positiveReaction

i.e. a little water goes a long way!

Ecosystem Type Net Primary Productivity (kilocalories/meter2/year) Tropical Rain Forest 9000 Estuary 9000 Swamps and Marshes 9000 Savanna 3000 Deciduous Temperate Forest 6000 Boreal Forest 3500 Temperate Grassland 2000 Polar Tundra 600 Desert 200

Net Primary Productivity of Different Systems

* Kilocalories are what we call “Calories” in everyday usage

Carbon Budgets: what they are and why they matter

Mike Ryan, USDA Forest ServiceRocky Mountain Research Station

Carbon Budget• Leaves make sugar from CO2 and water. • These sugars are used to support plant

metabolism and grow new leaves, wood, and roots.

• Most of the carbon that stays on site is in wood.

• Soils contain much carbon, but it changes slowly.

Objectives

• Why are carbon budgets important?

• What is the size of the components?

• What controls the process?

• How do we measure them?

• Examples: Radiata pine, Eucalyptus

Why are C Budgets Important?

• Help put wood growth in context of other processes

• There are 2 ways to grow more wood: Fix more sugars or use more of what’s there for wood

• Managing for carbon?

WOOD GROWTH

• Is a small portion of photosynthesis

• Depends on both photosynthesis and allocation

• Is very sensitive to environment

Foliage NPP Foliage Respiration

Wood Respiration

Wood NPP

Root Production + Respiration+ Exudates + Mycorrhizae

GPP

Lets look at the entire budget:

10%

20%

40%

15%

15%

What are the Processes?

• Photosynthesis

• Allocation

• Respiration

What Controls the Processes?

Photosynthesis

• Nutrients control the amount of leaf area and how well it will work

• Leaf area controls how much light is absorbed

• Humidity controls CO2 uptake during the day

• Soil water controls CO2 uptake seasonally

Respiration• Temperature controls rate• Nutrient concentration

controls amount• Closely related to

photosynthesis and growth

Over a year respiration is about 50% of photosynthesis

Allocation

• Nutrition can shift allocation from roots

• Environment: dry climate can shift allocation to roots

• Genetics

Year

1 2 3 4 5 6

0.1

0.2

0.3

ControlAlways FertilizedFertlized after year 3

Wood:GPP

Fertility can rapidly change allocation to wood

How do we Measure?Photosynthesis: IRGA, generally to measure response to environment and photosynthetic capacity. Models used to extrapolate.

How do we Measure?

Respiration: IRGA, generally to measure response to environment and growth. Models used to extrapolate.

Like measuring the flow of water into a tub from an underwater faucet (= outputs – inputs + storage change)TBCA = FS - FA + storage change

FA

TBCA

F FS E

[C C C ]S L R

Storage:

How do we Measure? Belowground Allocation

Litterfall

Soil Respiration

SoilLitterRoots

Studies use measurements of the entire C budget to measure GPP and allocation

Foliage NPP Foliage Respiration

Wood Respiration

Wood NPP

Root Production + Respiration+ Exudates + Mycorrhizae

GPP

Eucalyptus in Hawaii

January 1999, 55 months after planting

Eucalyptus Carbon Budget (Tons C ha-1 yr-1)

05

101520253035404550

Control Always Fert

Leaf ProdLeaf RespWood ProdWood RespTBCA

Fertilization increased growth and respiration (by increasing leaf area and photosynthesis and by changing allocation)

Examples:Light can limit productivity,

So can water, and

Certain nutrients too

Limiting Factors for Biological Productivity

- Plants never seem to be able to “fix”, or assimilate all

the carbon available to them – something is limiting production

- This is true both on land and in the ocean

In 1840, J. Liebig suggested that organisms are generally limited by only one single physical factor that is in shortest supply relative to demand.

Liebig's Law of the Minimum

Now thought to be inadequate – too simple!

- complex interactions between several physical factors are responsible for distribution patterns, but one can often order the priority of factors

PhosphorusIs very often limiting in freshwater systems

What is happening here?Why doesn’t the line keepGoing up?

As we’ve seen in the ocean, nutrients are often limiting.

Why nutrients?

Needed for enzymes, cellular structures, etc.

Pretty much analogous to vitamins for humans

Soon as you meet the requirements for one, anotherends up being limiting

Nutrient elements needed for all life

C HOPKINS Mg CaFe run by CuZn Mo

Hydrogen

Carbon

Zinc

Molybdinum

OxygenCopper

Calcium

Phosphorus

Magnesium

Iron

Iodine

Potassium

NitrogenSulfur

Order of Importance of Nutrient Elements in Different Environments

On Land In Freshwater In the Ocean

1) Nitrogen 1) Phosphorus 1) Iron

2) Phosphorus 2) Nitrogen 2) Phosphorus

3) Potassium 3) Silica 3) Silica

As we’ve seen, nutrients are often limiting.

Why nutrients?

Needed for enzymes, cellular structures, etc.

Pretty much analogous to vitamins for humans

Soon as you meet the requirements for one, anotherends up being limiting

In addition to primary productivity being a major sink for atmosphericCO2, it is also the base of the food chain and allows humans and allOther creatures to live, and…

It takes a lot of primary production to support higher trophic levels!

Data from Whittaker, R.H. 1961. Experiments with radiophosphorus tracer in aquarium microcosms. Ecological Monographs 31:157-188

1. Carbone, C. & Gittleman, J.L. A common rule for the scaling of carnivore density. Science, 295, 2273 - 2276, (2002). 2.Enquist, B.J. & Niklas, K.J. Global allocation rules for patterns of biomass partitioning in seed plants. Science, 295, 1517 - 1520, (2002).

Every Kg of predator needs 111KgOf prey living in the same area for the System to stay stable

OK, so we need to know what control productivity both forGlobal climate and for organisms that live here (including humans!)

We saw that water and temperature are very important, and that thereIs a huge response to small change in water. But what about theNutrients we talked about on Tuesday? What affect do they have?

PhosphorusIs very often limiting in freshwater systems

What is happening here?Why doesn’t the line keepGoing up?

Multiple or co-limiting factors – often it is more Complex than Liebig’s Law of the minimum

Look what happens with the addition of N

Multiple or co-limiting factors – often it is more Complex than Liebig’s Law of the minimum

This is real live data from a real live experiment

Nutrient Inputs to Ecosystems

Important nutrients for life generally enter ecosystems by way of four processes:

(1). Weathering

(2). Atmospheric Input

(3). Biological Nitrogen Fixation

(4). Immigration

Red means humans have a huge impact on these processes

Nutrient Outputs from Ecosystems

Important nutrients required for life leave ecosystems by way of four processes:

(1). Erosion

(2). Leaching

(3). Gaseous Losses

(4). Emigration and Harvesting

Red means humans have a huge impact on these processes

In well functioning ecosystems relatively small amounts ofNutrients enter or leave.

Most of what is needed comes from internal recycling!(true for all systems not just aquatic)