2.3 Flows of Energy and Matter

Significant Ideas  Ecosystems are linked together by energy and matter flows.  The Sun’s energy drives these flows, and humans are impacting the flows of energy and matter both locally and globally.

Knowledge and Understanding SEE YOUR TEXTBOOK OR ESS SYLLABUS

Applications and Skills 1. Analyze quantitative models of flows of energy and matter. 2. Construct quantitative model of flows of energy or matter for given data. 3. Analyze the efficiency of energy transfers through a system. 4. Calculate the values of both gross primary productivity (GPP) and net primary productivity (NPP). 5. Calculate the values of both gross secondary productivity (GSP) and net secondary productivity (NSP) from given data. 6. Discuss human impacts on energy flows, the carbon, and nitrogen cycles.

Energy Flows, Materials Cycle Almost all ecosystems are driven by energy from the sun. Energy (heat) continually flows through systems Matter (nutrients, oxygen, carbon dioxide, water) are cycled and recycled. Biosphere systems are dependent on amount of energy reaching the ground.  Affected by time of day, season, cloud cover, etc. Most solar energy is not used to power living systems; it is reflected or reradiated (lost) as heat (infrared).

THE FATE OF SOLAR RADIATION  Roughly 60% of solar radiation is intercepted by the atmosphere.  Of the light that does reach the surface of the Earth, 35% is reflected back into space by ice, snow, water and land. Only 1-4% of light is available to Plants. Plants capture 0.06%.

Pathways of Energy in an Ecosystem Transformation of light energy into chemical energy (photosynthesis). The only way to turn solar energy into food is through photosynthesis. Transfer of chemical energy from one trophic level to another with varying efficiencies (moving up the food chain/food web)

Terminology Productivity: The conversion of energy into biomass over a given period of time. (g m -2 y -1 ) or (j m -2 y -1 ) Biomass: Living mass of an organism or organisms (sometimes referred to as dry mass). (g m -2 ) Gross: Refers to the total amount of something Net: Refers to the amount left over after deductions.  Gross Income: $60,000 per/year  Net Income: $50,000 per/year after taxes, etc.

Types of Productivity

Gross vs. Net Productivity (These are General Terms) Gross Productivity: Total gain in energy or biomass per unit area per unit time.  Biomass that can be gained before any deductions/loss  But all organisms have to respire to stay alive so some energy is used up to stay alive instead of used to grow. Net Productivity: Gain in energy or biomass per unit area per unit time that remains after deductions due to respiration.

Gross Primary Productivity (GPP) - Plants All light energy fixed by plants is converted to sugars We can estimate plant’s energy uptake by measuring amount of sugar produced, oxygen released or by carbon dioxide uptake: Gross Primary Productivity. Measuring sugar produced is difficult because it is used almost as soon as it is produced. Easier to measure Net Primary Productivity (NPP)

Net Primary Productivity (NPP) - Plants NPP: An ecosystem’s NPP is the rate at which plants accumulate dry mass (actual plant material). Measured in grams per square meter. It is a measure of potential food for consumers in the ecosystem. Calculation for NPP: GPP – R, where GPP is Gross Primary Productivity (production of sugar) and R is respiratory loss.  In theory, any glucose that’s left over after photosynthesis and respiration (life processes) should be material deposited in and around cells to form new plant matter.  NPP is Biomass (stuff)

Net Primary Productivity (NPP)

GENERAL RULES The Amount of Biomass Produced Varies: Spatially: some biomes have much higher NPP rates than others (Tropical Rainforest vs. Tundra) Temporally: Many plants have seasonal productivity linked to changes in light, temperature, water, etc.

Therefore… The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients.  Example biome:_______________ The most productive ecosystems are those with high temperature, lots of water light and nutrients.  Example biome:__________________

Gross Secondary Productivity (GSP) The total food ingested including the food not used for energy (excreted as waste).

Net Secondary Productivity (NSP) Dry mass of plants that is stored in new tissue (the tissue of an animal) Calculate: NSP = GSP – R GSP is equal to food eaten minus energy in waste (feces and urine) R is respiratory loss

Maximum Sustainable Yield Equivalent to the NPP or NSP of system. Important number for farmers who are trying to predict how much money they will get for their product. Farmers are often paid by how much biomass (often measured by weight/acre) that their crop yields. Modern agricultural economists spend many months predicting yields which drives prices of the food you buy.  Corn Futures are a good example. People bet on how much corn will be grown in a particular year…even before it is ever planted!

Photosynthesis Process where plants use sunlight energy to create chemical energy Photosynthesis: equation  6CO 2 + 6H 2 O --> C 6 H 12 O 6 + 6O 2 Inputs: light energy, water, carbon dioxide Outputs: oxygen gas, sugar Energy transformations: Light to Chemical

Cellular Respiration Process by which animals create energy through consumption of organic molecules (sugars) Respiration:  C 6 H 12 O 6 + 6O 2 --> 6CO 2 + 6H 2 O Inputs: oxygen gas, organic molecules (sugars) Outputs: carbon dioxide, energy in ATP, waste heat Energy transformations: chemical to heat

The data in the table below relate to the transfer of energy in a small clearly defined habitat. The units in each case are in kJ m -2 yr -1 energy flow model Construct an energy flow model to represent all these data – Label each arrow with the appropriate amount from the data table above. Use boxes to represent each trophic level and arrows to show the flow of energy Net Productivity Calculate the Net Productivity for  NPP for Producers  NSP for 1°Consumers, 2°Consumers, 3°Consumers  NSP for Decomposers Trophic Level Gross Production Respiratory Loss Loss to decomposers Producers ° Consumer ° Consumer ° Consumer 741 Respiratory loss by decomposers

ProducersHerbivores 1st.CarnivoresTopCarnivores Decomposers R= R= R= R=4 1 R=3120 ENERGY FLOW MODEL

Assimilation and Productivity Efficiencies We don’t need to know the equation for efficiency. For an animal raised for meat, these questions involve: 1. How much grass than an animal eats can it assimilate into its body? Farmers need to know this. 2. How much of what is assimilated is used for productivity (turned into meat)?

Trophic Efficiency The efficiency of transfer from one trophic level to the next (ratio of secondary productivity to primary productivity consumed) is roughly 10%. Trophic efficiencies generally range from 5% - 20%. 5-20% of primary producer biomass consumed is converted to biomass. Trophic efficiencies vary according to the type of organism (warm blooded, cold blooded, etc.)

Flows of Energy & Cycling of Matter Energy Flows Through Systems Matter Flows and Cycles Through and In Ecosystems How Much?Infinite solar radiationFinite When?OnceCycles and recycles repeatedly OutputsAll organisms give out energy (heat) during respiration. All organisms release waste nutrients, carbon dioxide, and water. QualityDegrades from higher to lower quality energy (light to heat). Entropy increases. Matter is neither created nor destroyed but changed from one form to another. Doesn’t degrade. Storages (Sinks) Temporarily stored as chemical energy. Is stored long and short term in chemical forms.

Matter Flow and Cycling Matter flows through ecosystems linking them together. The flow of matter involves transfers and transformations. The Biogeochemical Cycles While energy flows in one direction in an ecosystem (solar radiation → heat), chemical nutrients circulate through ecosystems. There are about 40 elements that cycle through ecosystems.

The Carbon Cycle Carbon flows through ecosystems through feeding, death and decomposition, photosynthesis, respiration, dissolving, and fossilization. Carbon is stored in organisms and forests, the atmosphere, soil, fossil fuels, and in the oceans. Places where carbon is stored are called Carbon Sinks The oceans are the largest carbon sinks, holding many times more carbon than all the forests on earth combined. Climate change is affecting how much carbon the oceans can hold.

Summary of the Carbon Cycle FLOWSSTORAGES Consumption (Feeding)/Assimilation/Absorption Organisms and forests (organic) Death and DecompositionThe Atmosphere Photosynthesis and RespirationSoil Dissolving in water/oceansFossil Fuels Fossilization and Formation of Fossil Fuels

Nitrogen Cycle Nitrogen flows include nitrogen fixation by bacteria and lightning, absorption, assimilation, consumption, excretion, death, decomposition, and denitrification by bacteria in water-logged soils. Nitrogen is stored in organisms, soil, fossil fuels, atmosphere, and bodies of water. Places where nitrogen is stored are called Nitrogen Sinks

The atmosphere is 78% Nitrogen Gas Lightening can also create soil nitrates. Fertilizer runoff can allow nitrates into waterways. Nitrous oxide from fossil fuels falls as nitric acid in rainwater.

Summary of the Nitrogen Cycle FLOWSSTORAGES Consumption (Feeding), Assimilation, Absorption Organisms and forests (organic) Death and DecompositionThe Atmosphere Nitrogen Fixation by bacteria & lightening. Denitrification by bacteria in water-logged soils. Soil Dissolving in water/oceansFossil Fuels Excretion in WastesBodies of Water

How Do Humans Impact the Carbon & Nitrogen Cycles? Human activities are substantially modifying the global carbon and nitrogen cycles. The global carbon cycle is being modified principally by the burning of fossil fuels, and also by deforestation; these activities are increasing the carbon dioxide concentration of the atmosphere and changing global climate. The nitrogen cycle is being modified by the production of nitrogen fertilizer, the planting of legumes and the combustion of fossil fuels (nitrous oxides); these activities are altering the rate of fixation of nitrogen and contributing to the unbalanced productivity and acidification of ecosystems.