Biogeochemical Cycles Ecosystems Biogeochemical Cycles

KEY CONCEPT 1 Ecosystems consist of nonliving (abiotic) and living (biotic) components.

KEY CONCEPT 2 An ecosystem survives by a combination of energy flow and matter recycling.

KEY CONCEPT 3 Earth is a Closed System! Biosphere Carbon cycle Phosphorus Nitrogen Water Oxygen Heat in the environment Heat

BIOGEOCHEMICAL CYCLES: ABIOTIC CYCLES GLOBAL RECYLING - A closed pathway where matter cycles from the nonliving environment to living and then back again for reuse. Key feature- nutrients recycle through the earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. The overall rate of nutrient movement is limited most by decomposition. The rate of nutrient loss is a key characteristic in any ecosystem.

Overview of Nutrient Cycling Plants Consumption Overview of Nutrient Cycling Herbivore Assimilation Feces or urine Death Death Detritus Uptake Soil nutrient pool Decomposer food web Loss to erosion or leaching into groundwater

Water Cycle Condensation Transpiration Evaporation Precipitation Rain clouds Transpiration Evaporation Precipitation to land Transpiration from plants Precipitation Precipitation Evaporation from land Evaporation from ocean Surface runoff (rapid) Runoff Precipitation to ocean Infiltration and Percolation Surface runoff (rapid) Groundwater movement (slow) Ocean storage

Water Cycle Causes wind currents There are strong forces of attraction between molecules of water. Water exists as a liquid over a wide temperature range. Liquid water changes temperature slowly. It takes a large amount of energy for water to evaporate. Liquid water can dissolve a variety of compounds. Water expands when it freezes. Water Cycle Water has greatest influence of all non-living components

Effects of Human Activities on Water Cycle We alter the water cycle by: Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Polluting surface and underground water. Contributing to climate change.

Carbon Cycle Combustion: Photosynthesis and Cellular respiration: Burning- CO2 Fossil fuels –hydrocarbons Volcanic Action Forest Fires Photosynthesis and Cellular respiration: O2   CO2 Erosion: CaCO3  shells  limestone

Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation faster than it is replaced. Figure 3-28

Greenhouse gases Carbon dioxide Water Methane Nitrous oxide Sulfur hexafluoride

Most Important Greenhouse Gases GHGs Source Examples Water: H2O Oceans, rivers, plants, soil Carbon Dioxide: CO2 Combustion of fossil fuels, plant respiration, oceans, volcanoes Methane: CH4 Mining operations, combustion, animals, wetlands, landfills Other GHGs : Nitrous oxide (N2O), Ozone (near surface), Learn more about GHGs: http://www.epa.gov/climatechange/emissions/index.html Source: U.S. EPA 2005 http://www.for.gov.bc.ca

Nitrogen Cycle Availability of Nitrogen is a limiting factor for primary productivity 78% N gas in atmosphere unusable

Nitrogen Cycle Ammonification Decomposition by bacteria during decay Bacteria can “fix nitrogen” which means they break apart nitrogen gas and convert it into ammonia or ammonium. Assimilation Absorption and incorporation of nitrogen by plants These nodules are called rhyzomes. They are where the nitrifying bacteria reside. They have a symbiotic relationship with the plant Nitrification Ammonia to nitrates and nitrites by bacteria Then can be assimilated by plants Denitrification Denitrifying bacteria convert nitrates back into N2

Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

Phosphorous Cycle No gaseous component (from land to sediment and back to land only) Erosion releases phosphate soil plants Decomposers phosphate  soil Deposited in oceanic sediment  unavailable for years Fertilizers, run off containing animal wastes, and sewage aquatic ecosystems

The Phosphorous Cycle

Effects of Human Activities on the Phosphorous Cycle We remove large amounts of phosphate from the earth to make fertilizer. We reduce phosphorous in tropical soils by clearing forests. We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

The Sulfur Cycle

Effects of Human Activities on the Sulfur Cycle We add sulfur dioxide to the atmosphere by: Burning coal and oil Refining sulfur containing petroleum. Converting sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

Acid Precipitation Rain, snow or fog that has a pH value of less than 5.6 because of the carbon dioxide from air dissolved in it Any rainfall has a pH value less than 5.6 is defined as acid rain

Acid Precipitation When gas pollutants e.g. sulfur dioxide, nitrogen dioxide dissolve in rain water, various acids are formed. CO2 + H2O  H2CO3 (carbonic acid) SO2 + H2O  H2SO3 (sulphorous acid) NO2 + H2O  HNO2 (nitrous acid) + HNO3 (nitric acid)

CAUSES OF ACID RAIN