Ecosystem Type Net Primary Productivity (kilocalories/meter 2 /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

Controls on Net Primary Productivity Nutrients

In addition to primary productivity being a major sink for atmospheric CO 2, it is also the base of the food chain and allows humans and all Other creatures to live, and… It takes a lot of primary production to support higher trophic levels! Data from Whittaker, R.H Experiments with radiophosphorus tracer in aquarium microcosms. Ecological Monographs 31:

1. Carbone, C. & Gittleman, J.L. A common rule for the scaling of carnivore density. Science, 295, , (2002). 2.Enquist, B.J. & Niklas, K.J. Global allocation rules for patterns of biomass partitioning in seed plants. Science, 295, , (2002). Every Kg of predator needs 111Kg Of prey living in the same area for the System to stay stable

OK, so we need to know what control productivity both for Global climate and for organisms that live here (including humans!) We saw that water and temperature are very important, and that there Is a huge response to small change in water. But what about the Nutrients we talked about on Tuesday? What affect do they have?

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 CO 2 rarely limits productivity

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 strong Limiting factor. Although plants in colder areas are optimized for Colder conditions

Water also is a strong Limiting factor. Much steeper curve = A much stronger positive Reaction i.e. a little water goes a long way!

If plants have enough water, enough sunlight, and are bathed in CO 2, why don’t they “fix” more carbon, or grow more efficiently, faster, larger?

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

Phosphorus Is very often limiting in freshwater systems What is happening here? Why doesn’t the line keep Going up?

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

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

As we’ve seen in the ocean and on land, 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, another ends up being limiting

Nutrient elements needed for all life C HOPKINS Mg CaFe run by CuZn Mo Hydrogen Carbon Zinc Molybdinum Oxygen Copper Calcium Phosphorus Magnesium Iron Iodine Potassium Nitrogen Sulfur

Order of Importance of Nutrient Elements in Different Environments On LandIn FreshwaterIn the Ocean 1) Nitrogen1) Phosphorus 1) Iron 2) Phosphorus2) Nitrogen 2) Phosphorus 3) Potassium3) Silica 3) Silica

Eucalyptus Carbon Budget (Tons C ha -1 yr -1 ) Fertilization increased growth and respiration

Eucalyptus in Hawaii January 1999, 55 months after planting

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

INPUTS Weathering Atmospheric Input Biological Nitrogen Fixation Immigration OUTPUTS Erosion Leaching Gaseous Losses Emigration/Harvesting Nutrient flux in Ecosystems

In well functioning ecosystems relatively small amounts of Nutrients enter or leave. Most of what is needed comes from internal recycling! (true for all systems not just aquatic)

Excess Nitrogen Deposition – Too much of a good thing! Because Nitrogen often limits plant growth humans have gone to great lengths to use it as fertilizer It is also a by product of all types of combustion The net result is that we have altered the natural way that Nitrogen cycles more than we have any other element -including Carbon

In an undisturbed nitrogen cycle the element cycles very Efficiently – it is valuable so not readily given up by biota

In an undisturbed nitrogen cycle the element cycles very Efficiently – it is valuable so not readily given up by biota But humans add HUGE amounts of Nitrogen to the ecosystem 160

Nitrogen containing Compounds N 2 – nitrogen gas NO 3 – nitrate NO 2 - nitrite NH 4 – ammonium NH 3 – ammonia N 2 O – Nitrous Oxide Organic Nitrogen – Living and dead plants And animals